A comparison of wi-fi and wimax with case studies - Florida State ...

THE FLORIDA STATE UNIVERSITY
COLLEGE OF ENGINEERING
A COMPARISON OF WI-FI AND WIMAX WITH CASE STUDIES
By
Ming-Chieh Wu
A Thesis submitted to the
Department of Electrical and Computer Engineering
in partial fulfillment of the
requirements for the degree of
Master of Science
Degree Awarded:
Fall Semester, 2007

The members of the Committee approve the Thesis of Ming-Chieh Wu defended on October 30 th ,
2007.
Approved:
Bruce A. Harvey
Professor Directing Thesis
Ming Yu
Committee Member
Simon Y. Foo
Committee Member
Victor DeBrunner, Chair, Department of Electrical and Computer Engineering
Ching-Jen Chen, Dean, FAMU-FSU College of Engineering
The Office of Graduate Studies has verified and approved the above named committee members.
ii

TABLE OF CONTENTS
List of Tables…………………………..………….………………………………………..……vi
List of Figures………………………………….…………………………………………….…vii
List of Abbreviations……………………..………….………………………………………….ix
ABSTRACT……………………………………………..……………………………………...xii
CHAPTER ONE
1. Introduction …………………………………………………………………………………....1
CHAPTER TWO
2. 3G…………………………………..…………………………………………………………..5
2.1. Introduction………………………………………………………………………...…..5
2.2. Technologies…………………………………………………………………………...5
2.2.1. WCDMA……………………………….………………………………………..5
2.2.2. CDMA2000………………………………………………………………….…..6
2.2.3. TD-SCDMA……………………………………………………………….…….6
2.3. Development…………………………………………………..……………………….7
2.4. Cases………………………………………………………………..…………….…….8
2.5. Conclusion……………………………………………………………………….……..9
CHAPTER THREE
3. IEEE 802.11, Wireless LAN…………………………………………………...……………..10
3.1. The background of IEEE 802.11…………………………………………….………10
3.2. Capacity……………………………………………………………………….….….11
3.3. The Physical Layer and MAC Layer…………………………………………...……14
3.3.1. The Physical Layer………………………………………………..……….….14
3.3.1.1. Introduction……………………………………………………….……14
3.3.1.2. PLCP and PMD…………………..………………………...……….……15
3.3.1.3. CS/CCA………………………………………………………….……….15
3.3.1.4. IEEE 802.11b, DSSS and HR-DSSS…………………………..…...…..16
3.3.1.4.1. Theory and Transmission method…………………………………16
3.3.1.4.2. Against interference……………………..…………………………17
3.3.1.4.3. PLCP and PMD of DSSS…………………….......................……..17
3.3.1.4.4. HR-DSSS and CCK…………………………………………..……18
3.3.1.4.5. PLCP and PMD of HR-DSSS………..……………....……………19
3.3.1.5. IEEE 802.11a and OFDM…………………………………………….…20
3.3.1.5.1. Background…………………………………………………..…….20
3.3.1.5.2. Principles…………………………………………………………..20
3.3.1.5.3. The IEEE 802.11a’s OFDM and its PLCP and PMD……………..22
3.3.1.6. IEEE 802.11g and the Physical Layer……………………………………24
3.3.1.6.1. Background and Backward Compatibility………….……...……24
3.3.1.6.2. ERP-OFDM and DSSS-OFDM………………………………..…..25
3.3.2. MAC Layer………………………………………………………………..…….27
3.3.2.1. Introduction……………………………………………...….……………27
3.3.2.2. DCF and PCF…………………………….……………………………..27
iii

3.3.2.3. Hidden node and CSMA/CA……………………………......……………28
3.3.2.4. Fragmentation………………………………………………………….30
3.3.2.5. Interframe spacing………………………………………………………..30
3.3.2.6. Power saving………………………………..…………………………….31
3.3.2.7. Security…………………………………….……………………………..32
3.4. The next generation standard…………………………………………………………..34
3.4.1. IEEE 802.11n…………………………………………..………………………..34
3.4.2. MIMO (Multiple-Input/Multiple-Output)………………….………………...…35
3.5. Limitation………………………………………………………..……………………..35
CHAPTER FOUR
4. IEEE 802.16, Wireless MAN………………………………………………………...……….37
4.1. The background of IEEE 802.16……………………………………...….………….37
4.2. Capacity of the IEEE 802.16 family………………………………………...…………39
4.2.1. IEEE 802.16………………………………………………………………….….39
4.2.2. IEEE 802.16a………………………………………………………………..…..39
4.2.3. IEEE 802.16c…………………………………………………………..………..39
4.2.4. IEEE 802.16-2004.……………………………………………...…...………….39
4.2.5. IEEE 802.16e-2005…………………………………………………………..….40
4.2.6. IEEE 802.16f, IEEE 802.16g and IEEE 802.16h……………….…………….40
4.3. The Physical Layer and MAC Layer…………………………….......…...……………42
4.3.1. IEEE 802.16-2004……………………………………………….………..…..42
4.3.1.1. Physical Layer…………………………………………….…………....42
4.3.1.1.1. Four transmission mode: SC, SCa, OFDM and OFDMA…………44
4.3.1.1.2. AMC (Adaptive Modulation and Coding)….…………………...44
4.3.1.1.3. Channel-quality Measurement……………………………………..45
4.3.1.1.4. OFDM in WiMax……………………...………….……………….45
4.3.1.2. MAC Layer……………………………………………………….…..…..46
4.3.1.2.1. Three sublayers: CS, CPS and SS…………...…….………………46
4.3.1.2.2. AAS (Advanced Antenna Systems)………………….…...……..47
4.3.1.2.3. QoS……………………………………………………..………….47
4.3.1.2.4. Security…………………………………………………………….49
4.3.1.2.4.1. Overview……………………………………...……………49
4.3.1.2.4.2. Overall Analysis………………….……………...………..52
4.3.2. IEEE 802.16e-2005, the newest standard…………………………………….....53
4.3.2.1. OFDMA-PHY………………………………...………………………..53
4.3.2.1.1. Background…………………..…………………………………….53
4.3.2.1.2. Frame structure…………………….………………………………53
4.3.2.1.3. Various Subcarrier Allocation Modes……………………………..54
4.3.2.2. MAC Layer…………..…………………………………………………..56
4.3.2.2.1. QoS…………………….…………………………………………..56
4.3.2.2.2. Power-saving………….………………………………………...…57
4.3.2.2.2.1. Sleep Mode…………….……………………………………57
4.3.2.2.2.2. Idle Mode……...…………………………………………….58
4.4. The future of WiMax…………………………….……………..……………………58
CHAPTER FIVE
iv

5. Case study…………………………………………………………………………………….61
5.1. FSU wireless network………………………………………………………………….61
5.1.1. Introduction………………………………………………………………...……61
5.1.2. Implementation…………….……………………………………………………62
5.1.3. Analysis…………………………………………………………….…………73
5.1.4. Conclusion…………….……………………………………...…………………74
5.2. WiFly in Taipei……………………………..………………………………………….74
5.2.1. Introduction………………………..…………………………………………….74
5.2.2. Implementation………………………………………………………………….75
5.2.3. Analysis…………………………....………………………………………….83
5.2.4. Conclusion……………………….…………………………………………....86
5.3. Wibro in South Korea…………………………….……………………………………86
5.3.1. Introduction…………………………….………………………………………..86
5.3.2. History…………………………………………………………………….…..87
5.3.3. Implementation……………………………………………….......................…..88
5.3.4. Analysis……………………………………………………………………...….92
5.3.5. Conclusion……………………………..…………………….……………….....93
5.4 . Overall analysis………………………...………………………..……………..………94
5.5. Other developing wireless network………...……………………………….……….95
CHAPTER SIX
6. Conclusion…………………………………………………..…………………….………..98
BIBLIOGRAPHY……………………………………...…………………………….………..101
BIOGRAPHICAL SKETCH…………………………………………………………………110
v

LIST OF TABLES
Table 1-1 802.3 Family……………………………………………………..…………..……….2
Table 3-1 Family of IEEE 802.11……………..……..……………………..…………………11
Table 3-2 Capacities for 802.11a/b/g……………….……...…………….………………………12
Table 3-3 IEEE 802.11b/g Channel Used for Different Countries……….……...………………12
Table 3-4 IEEE 802.11a Channel Use for North America…………….……………............13
Table 3-5 OFDM Modulation and Data Rate…………………...…………………..………..23
Table 4-1 The Basic Data of IEEE 802.16………………………………………...….41
Table 4-2 Modulation and Coding Supported in WiMax……………..…………..…..45
Table 4-3 OFDM Parameters Used for WiMAX…………………..…………..…….46
Table 4-4 Service Flows in WiMax……………………...……………………..…….48
Table 4-5 DL Distributed Subcarrier Permutation (FUSC)………….………..………55
Table 4-6 UL-DL Adjacent Subcarrier Permutation ………………………….………….……..56
Table 5-1 The Basic Information of FSUWIN………………………………………...…66
Table 5-2 Xirrus XS-3700 AP Technology Data………….……………………………....66
Table 5-3 Foundry Networks IP250 Technology Data……………...……….…….......….66
Table 5-4 Vivato 2.4 GHz Indoor & Outdoor Wi-Fi Switch Technology Data…...…..…68
Table 5-5 Parameters of WLAN and Mesh Network……………………….....………..70
Table 5-6 Features of Nortel Wireless Mesh Network………………..….…………..77
Table 5-7 The Numbers of Subscribers………………...……………..…………………79
Table 5-8 The Comparison of WiBro and WiMax……………………...….……………..92
Table 5-9 The Basic Data of FSUWIN, WiFly and WiBro…………..…………………96
Table 5-10 Current Internet Access Technologies……………….……..…………..……..97
Table 6-1 3G, Wi-Fi and WiMax Overall Comparison………………………….………..98
vi

LIST OF FIGURES
Figure 2-1 The Evolution of 3G………………………………...………...…………..7
Figure 3-1 OSI Model………………………………………..…………..…………..14
Figure 3-2 802.11 PLCP, PMD and MAC Structure…………..………………..……15
Figure 3-3 DSSS Transmission………………………………..…………………...…16
Figure 3-4 DSSS PLCP………………………………………..………………..……18
Figure 3-5 CCK Modulation…………………………………..……………………..19
Figure 3-6 HR/DSSS PLCP Framing…………………………..…………………….19
Figure 3-7 FDM and OFDM…………………………………..……………………..20
Figure 3-8 CP and PP………………………………………..…….…………………21
Figure 3-9 OFDM Modem……………………………………..….…………………22
Figure 3-10 Constellations Diagram…………………………..……………………..23
Figure 3-11 OFDM PLCP Structure………………………….………………………24
Figure 3-12 DSSS-OFDM PSDU Format………………………..…..………………26
Figure 3-13 DSSS-OFDM Long Preamble Structure……………..…………………..26
Figure 3-14 DSSS-OFDM Short Preamble Structure……………………..…………..27
Figure 3-15 The Hidden Node Problem………………………..………...……………28
Figure 3-16 CDMA/CA………………………………………..…………….………29
Figure 3-17 Virtual Channel Sensing…………………………..……………………..29
Figure 3-18 A Fragment Burst…………………………………..…………………....30
Figure 3-19 Frame Interval for IEEE 802.11…………...………..…………………..31
Figure 3-20 WEP Frame and Operation…………………………..…………………..33
Figure 3-21 The WEP Encryption Process………………………….………………..33
Figure 4-1 The Layer Structure of IEEE802.16……………………..………...………43
Figure 4-2 A Spatial Multiplexing MIMO System…………………....………………44
Figure 4-3 PKM Authorization Process and Parameters………………..…………….50
Figure 4-4 PKM Protocol Messages Exchange Process and Parameters…….....……………..51
Figure 4-5 Encryption Frame Structure and Process……………………..…….……..52
Figure 4-6 OFDMA Frame Structure……………………………………..…………..54
Figure 4-7 Coverage and Capacity for Different Wireless Access Techniques…..….....59
Figure 5-1 The Coverage of FSU Wireless Network………….…..……………………….62
Figure 5-2 Fisher Lecture Hall………………………..………..…………………….64
Figure 5-3 Landis Green………………………………………..…..………………..65
Figure 5-4 Shores Library……………………………………..………………….….65
Figure 5-5 Stadium……………………………………………..……………………66
Figure 5-6 Xirrus XS-3700 AP…………………………………………………………..67
Figure 5-7 Foundry Networks IP250……..………………………..………...…………..69
Figure 5-8 Vivato 2.4 GHz Indoor & Outdoor Wi-Fi Switches………..……………..72
Figure 5-9 FSUWIN Login System……………………………………..…………….74
Figure 5-10 Wireless Mesh Network Structure I……………...………..…………….76
Figure 5-11 Wireless Mesh Network Structure II………………….…..…………….76
Figure 5-12 Wireless Access Point 7220………………………………..….………..77
Figure 5-13 Nortel Wireless Mesh Network Solution Example…………..…………..80
Figure 5-14 The Relationship Between WiMax and WiBro……...……..……………..87
Figure 5-15 The Network Structure of WiBro……………………..……..……………87
vii

Figure 5-16 The Operation Band of WiBro……………………………………..………...…….88
Figure 5-17 WiBro Features………………………...…………………..…………..……89
Figure 5-18 MAC Layer Model…………………………………………..……….……..90
Figure 5-19 U-RAS Premium……………………………………………..…….………91
Figure 5-20 ACR Basic Data……………………..……………………………………….91
Figure 5-21 An Example Application of 3G, Wi-Fi and WiMax…………………..……..95
Figure 6-1 Cooperation of WiMax and Wi-Fi………………………………………...…100
viii

LIST OF ABBREVIATIONS
Abbreviation Full Name Page
3G Third generation of mobile phone standards and technologies 5
3GPP 3 rd Generation Partnership Project 5
AAS Advanced Antenna Systems 42
ACK Acknowledgement 26
AGC Automatic Gain Control 21
AMC Adaptive Modulation and Coding 40
AP Access Point 32
APEC Asia Pacific Economic Cooperation 93
ARPA Advanced Research Projects Agency 1
BE Best-effort service 44
BER Bit Error Rate 20
BS Base Station 29
BTC Block Turbo Codes 40
BWA Broadband Wireless Access 34
CCK Complementary Code Keying 16
CDMA/CA Carrier Sense Multiple Access/Collision Avoidance 25
CDMA/CD Carrier Sense Multiple Access/Collision Detection 26
CDMA2000 1X
Evolution-Data Only 6
EV-DO
CID Connection Identifier 42
COFDM Coded OFDM 20
CP cyclic prefix 19
CS/CCA Carrier Sense/Clear Channel Assessment 14
CT Communication Technology ix
CTC Convolution Turbo Codes 40
CTS Clear To Send 23, 26
DBPSK Differential Binary Phase shift Keying 15
DCF Distributed Coordination Function 25
DECT Digital-Enhanced Cordless Telephony 34
DIFS DCF InterFrame Spacing 28
DL Downlink 48
DQPSK Differential Quadrature Phase shift Keying 15
DSSS Direct Sequence Spread Spectrum 14
EIFS Extended InterFrame Spacing 28
ERP Extended Rate PHY 22
ertPS Extended Real-Time Polling Service 51
FCC Federal Communications Commission 11
FDD Frequency Division Duplexing 35
FDM Frequency Division Multiplexing 18
FDMA Frequency Division Multiple Access 47
FEC Forward Error Correction 40
FFT Fast Fourier Transform 19
ix

FOMA Freedom of Mobile Multimedia Access 8
FSUWIN Florida State University Wireless Integrated Network 55
FUSC Fully Used Subchannelization 48, 49
GPRS General Packet Radio Service 5
GSM
Global System for Mobile Communications/Pan-European digital
5
cellular land mobile telecommunication system
ICI inter-carrier interference 19
ICV Integrity Check Value 29
IEEE Institute of Electrical and Electronic Engineers 1
IFFT inverse Fast Fourier Transform 19
IMT International Mobile Telecommunication 5
ISI Inter-symbol interference 19
ISP Internet Service Provider 33
IT Information Technology ix
ITU International Telecommunication Union 5
IV Initialization Vector 29
KT Korean Telecoms Industry 86
LDPC Low Density Parity Check 40
LMDS Local Multipoint Distribution Systems 34
LOS Line of Sight 34
MAC Media Access Control 25
MIMO Multiple-Input/Multiple-Output 31
MMDS Multichannel Multipoint Distribution Services 34
MMS Multimedia Message Service) 5
MPDUs MAC Protocol Data Units 13
MS Mobile Station 28
MSDUs MAC Service Data Units 41
NAV Network Allocation Vector 23, 26
NLOS Non-Line of Sight 35
nrtPS Non-real-time polling service 43
OFDM Orthogonal Frequency Division Multiplexing 9, 19
OFDMA Orthogonal Frequency Division Multiple Access 47
OSI Open System Interconnection 12
OTC Office of Telecommunications and Networking 55
PBCC Packet Binary Convolution Coding 22
PCF Point Coordination Function 25
PIFS PCF InterFrame Spacing 28
PKM Privacy and Key Management 44
PLCP Physical Layer Convergence Protocol 13
PMD Physical Medium Dependent 13
PN Codes Pseudorandom Noise Codes 15
PP cyclic postfix 19
PPDU PLCP Protocol Data Unit 13
PRNG Pseudorandom Number Generator 29
PSDU PLCP Service Data Unit 13
x

PSS Portable Subscriber Station 89
PUSC Partially Used Subchannelization 48, 50
QAM Quadrature Amplitude Modulation 20
QoS Quality of Service 42
RAS Radio Access Station 89
RCF Request to Send 26
RS-CC Reed Solomon – Convolution Code 40
rtPS Real-time polling services 43
SA Security Associations 44
SDUs Service Data Units 51
SIFS Short Inter-Frame Space 23, 28
SKT South Korea Telecom 8
SS Subscriber Station 44
STBC Space-Time Block Coding 32
TCP/IP Transmission Control protocol/Internet Protocol 3
TDD Time Division Duplexing 35
TDM Time Division Multiplexing 35
TD-SCDMA Time Division - Synchronized Code Division Multiple Access 5
UGS Unsolicited grant services 43
UL Uplink 48
UMTS Universal Mobile Telecommunications System 5
VoIP Voice over IP 32
WCDMA Wideband Code Division Multiple Access 5
WEP Wired Equivalent Privacy 29
WiBro Wireless Broadband Access Service 86
Wi-Fi Wireless fidelity 31
WiMax World Interoperability for Microwave Access 35
WISP Wireless Internet Service Provider 34
WLAN Wireless Local Area Network 9
WLL Wireless Local-Loop 34
WMAN Wireless Metropolitan Area Network 35
WWW World Wide Web 3
xi

ABSTRACT
Currently over 50% of the world’s population check their e-mails everyday. Collecting
information from the Internet is a routine. In the early 21 st century, wireless communication has
become a hot topic in IT (Information Technology) and CT (Communication Technology), as
evidenced by the growth of wireless technologies such as 3G, Wi-Fi and WiMax. 3G is a cellular
technology developed in conjunction with the cellular phone network. Wi-Fi is a wireless local
area network technology. WiMax is designed for the wireless metropolitan area network. Today,
people not only want the fixed wireless access to the Internet, but also want the mobile wireless
access as well. They want a ubiquitous connection, even when in a train, a cab, or the subway.
This demand is resulting in increasing competition between the leading wireless technologies.
3G, Wi-Fi and WiMax all appear to have the potential to feed the demand, but still have issues
that need to be addressed. The future direction of wireless Internet access is uncertain, including
whether these three technologies will operate cooperatively or competitively. This thesis is
going to predict the future direction by analysis of 3G, Wi-Fi and WiMax technologies and the
evaluation of three wireless access case studies.
This thesis will begin with an introduction to the history of Internet and will then continue
with a discussion of the technical aspects of 3G, Wi-Fi and WiMax. After the technology
introduction, this thesis will evaluate three current implementations of wireless Internet access as
case studies to verify the capabilities of Wi-Fi and WiMax, and to discuss the feasibility of
building a city-wide wireless network. Finally, a reasonable prediction of the future
implementation of a city-wide wireless Internet structure will be presented.
xii

CHAPTER ONE
1. Introduction
The cellphone company Nokia uses the slogan of “connecting people” in its advertising
campaign. That means that technologies should be based on demand and humility. In the field of
the Internet, the basis of all research and innovation is geared towards making transmission of
communication more efficient. The network technology that would eventually evolve into “the
Internet” was initially developed by the military requisition called ARPANET, during late 1960s.
ARPA is the acronym for Advanced Research Projects Agency an agency of the Department of
Defense. This network was the pioneer of the “packet switch” type network. Little did the
originators of ARPANET realize that this network would eventually lead to a method that could
connect every PC in the world for sharing and exchanging information. The two most significant
features of ARPANET were the concept of network routing and the use of packet for data
transfer. In ARPANET, each computer was a node and it received the data and then routed it to
next node. ARPANET was also the first network using packet switching to transmit data. Each
node could send each packet to its destination by different paths, so it could improve the
transmission to become more efficient and more reliable. In the beginning, this project only
included four locations, Stanford Research institute, UCLA, UC Santa Barbara and Utah
University. After it was initiated successfully in 1969, the locations extended to the east coast the
following year including MIT, Harvard, Beranek and Newman. This was the world’s first WAN
(Wide Area Network).
In 1973, the Xerox Corporation, located in California, developed the LAN (Local Area
Network) for connecting PCs within a local area. Therefore, the Ethernet was formed. The DIX
alliance (DEC, Intel and Xerox) was the first pusher of Ethernet and then transferred the patent
right to IEEE (Institute of Electrical and Electronic Engineers). This move made Ethernet
become popular very quickly. In 1982, DIX published Ethernet Version 2 (EV2) and later on
IEEE published IEEE 802.3 CDMA/CD standard which was based on EV2 in 1983. Today, the
IEEE 802.3 series is the most well-known Ethernet standard. The IEEE 802.3 is a big family that
is presented in table 1-1[67][86]. They can support speeds from 10 Mbps to 1 Gbps. The
increased technology causes the Internet to continually speed up.
Communication technology continues to develop and an increasing number of
communication technologies have been implemented. However these technologies may not be
compatible with each other. The ARPANET researchers developed a set of protocols called
TCP/IP (Transmission Control protocol/Internet Protocol) to integrate networks that may be
based on differing communications technologies and protocols. Internet research was not only
conducted in U.S., but also in other places such as Europe, Asia, Canada and so on. Competing
1

protocols such as the X.25 protocol from Europe were developed, but eventually TCI/IP became
accepted as a world-wide standard and the world-wide Internet was formed.
Ethernet
Standard
Experimental
Ethernet
Ethernet II
(DIX v2.0)
Table 1-1 802.3 Family
Date Description
1972 2.94 Mbit/s (367 kB/s) over coaxial cable (coax) cable bus
1982
10 Mbit/s (1.25 MB/s) over thin coax (thinnet) - Frames have a Type field. This
frame format is used on all forms of Ethernet by protocols in the Internet
protocol suite.
IEEE 802.3 1983
10BASE5 10 Mbit/s (1.25MB/s) over thick coax - same as DIX except Type
field is replaced by Length, and an 802.2 LLC header follows the 802.3 header
802.3a 1985 10BASE2 10 Mbit/s (1.25 MB/s) over thin Coax (thinnet or cheapernet)
802.3b 1985 10BROAD36
802.3c 1985 10 Mbit/s (1.25 MB/s) repeater specs
802.3d 1987 FOIRL (Fiber-Optic Inter-Repeater Link)
802.3e 1987 1BASE5 or StarLAN
802.3i 1990 10BASE-T 10 Mbit/s (1.25 MB/s) over twisted pair
802.3j 1993 10BASE-F 10 Mbit/s (1.25 MB/s) over Fiber-Optic
802.3u 1995
100BASE-TX, 100BASE-T4, 100BASE-FX Fast Ethernet at 100 Mbit/s (12.5
MB/s) w/auto negotiation
802.3x 1997
Full Duplex and flow control; also incorporates DIX framing, so there's no
longer a DIX/802.3 split
802.3y 1998 100BASE-T2 100 Mbit/s (12.5 MB/s) over low quality twisted pair
802.3z 1998 1000BASE-X Gbit/s Ethernet over Fiber-Optic at 1 Gbit/s (125 MB/s)
802.3-1998 1998 A revision of base standard incorporating the above amendments and errata
802.3ab 1999 1000BASE-T Gbit/s Ethernet over twisted pair at 1 Gbit/s (125 MB/s)
802.3ac 1998
Max frame size extended to 1522 bytes (to allow "Q-tag") The Q-tag includes
802.1Q VLAN information and 802.1p priority information.
802.3ad 2000 Link aggregation for parallel links
802.3-2002 2002 A revision of base standard incorporating the three prior amendments and errata
802.3ae 2003
10 Gbit/s (1,250 MB/s) Ethernet over fiber; 10GBASE-SR, 10GBASE-LR,
10GBASE-ER, 10GBASE-SW, 10GBASE-LW, 10GBASE-EW
802.3af 2003 Power over Ethernet
802.3ah 2004 Ethernet in the First Mile
802.3ak 2004 10GBASE-CX4 10 Gbit/s (1,250 MB/s) Ethernet over twin-axial cable
802.3-2005 2005 A revision of base standard incorporating the four prior amendments and errata.
2

Table 1-1 Cont.
802.3an 2006 10GBASE-T 10 Gbit/s (1,250 MB/s) Ethernet over unshielded twisted pair(UTP)
802.3ap 2007
Backplane Ethernet (1 and 10 Gbit/s (125 and 1,250 MB/s) over printed circuit
boards)
802.3aq 2006 10GBASE-LRM 10 Gbit/s (1,250 MB/s) Ethernet over multimode fiber
802.3ar
On
Hold
Congestion management
802.3as 2006 Frame expansion
802.3at
exp.
2008
Power over Ethernet enhancements
802.3au 2006 Isolation requirements for Power Over Ethernet (802.3-2005/Cor 1)
802.3av
exp.
2009
802.3aw 2007
802.3ax
802.3ay
802.3ba
exp
2008
exp
2008
exp.
2009
10 Gbit/s EPON
Fixed an equation in the publication of 10GBASE-T (released as 802.3-2005/Cor
2)
Move Link aggregation out of 802.3 to IEEE 802.1
Maintenance to base standard
Higher Speed Study Group. 40 Gb/s over 1m backplane, 10m Cu cable assembly
(several pairs) and 100m of MMF and 100 Gb/s up to 10m or Cu cable assembly,
100 m of MMF or 40 km of SMF respectively
For creating a common information sharing space to physicists, Tim Berners-Lee (1955- ,
British) designed the World Wide Web (WWW). At that time he was in the European Laboratory
for Particle Physics, CERN (Conseil Européen pour la Recherche Nucléaire, European Council
for Nuclear Research), and wanted to create a simple way to share and cooperate with other
physicists around the world. Now WWW becomes another name for the Internet.
In the 1990s, data transmission went into the wireless era. Wireless transmission includes
Bluetooth, Infrared, RF, IEEE 802.11, IEEE 802.16 and 3G. Currently there are several
competing communication technologies for providing wireless Internet access. The primary
competitors are 3G, Wi-Fi (IEEE 802.11) and WiMax (IEEE 802.16). 3G is a cellular technology
and is currently evolving into all-IP network. Wi-Fi is a wireless local area network technology
designed for home and small area implementations. WiMax is a wireless metropolitan area
network technology which can cover larger area and support mobile Internet access at speeds up
to 120km/hr. Each individual technology is designed for a particular application, but their
capabilities at least partially overlap. WiMax is a newer technology that promises longer ranges
and mobile access. Wi-Fi has been used for ten years, but has recently been implemented in
campus-wide and city-wide networks. Moreover 3G is trying to increase its market share in
3

Internet access using the wide availability of the cellular telephone networks. These factors make
it really difficult to predict the future of wireless Internet access.
In this thesis, the focus is primarily implementations of IEEE 802.11 and IEEE 802.16. In
chapter 2, 3G will be discussed briefly, but the low data rate of current 3G implementations limit
it’s applicability for general wireless Internet access. And for clarifying the capabilities of Wi-Fi
and WiMax, this thesis will include three case studies. The case studies are the FSU (Florida
State Univ.) campus Wi-Fi network, the city-wide Wi-Fi network in Taipei, Taiwan, and the
city-wide WiMax network in Seoul, Korea. By comparing these three cases, the design problems
and operation difficulties can be identified. Taipei and Seoul are both the first complete citywide
wireless network in the world. The current statuses of their networks reflect the capabilities
of WiMax and Wi-Fi. By study these case studies, this paper is going to evaluate the feasibility
of building a Wireless Networked City using WiMax and/or Wi-Fi.
4

2.1. Introduction
CHAPTER TWO
2. 3G
3G stands for “third generation of mobile phone standards and technologies”. It was
developed under the IMT-2000 program (IMT, International Mobile Telecommunication) by the
International Telecommunication Union (ITU). 3G has three standards, WCDMA (Wideband
Code Division Multiple Access), CDMA2000 and TD-SCDMA (Time Division - Synchronized
Code Division Multiple Access). Also, 3G’s network is a wide area cellular telephone network.
It can provide internet access and video telephone. Compared to 2G, the 3G has higher
bandwidth and faster speed. With this advantage, 3G can provide varieties of service. 3G
supports both fixed and mobile environment and is also backward compatible with 2G.
[68][69][136] – [138]
When doing vocal transmission, 3G can use Circuit Switch Mode for voice and video phone;
for internet access/data transmission, 3G uses Packet Switch Mode. In this mode, users pay for
how much they used, for example 0.099 cents per packet. Multimedia Message Service (MMS)
is an important application of 3G. Although MMS has been applied to General Packet Radio
Service (GPRS) as the 2.5G major application, with 3G’s advantages, wireless communication
companies can provide more choices (video, audio, pictures and text) with MMS.
2.2. Technologies
2.2.1. WCDMA
WCDMA was developed by an organization called 3GPP (3 rd Generation Partnership
Project, December 1998) and also a part of IMT-2000 program. The WCDMA is based on GSM
(Global System for Mobile Communications/Pan-European digital cellular land mobile
telecommunication system) and GPRS. GSM is based on Circuit Switch Mode and GPRS is
based on Packet Switch Mode. In Europe, WCDMA is called Universal Mobile
Telecommunications System (UMTS). This technology came from the early third generation
wireless network studies in Japan and Europe. Since the GSM was such a success, Europe began
actively working on developing 3G. In 1995, Europe established Advanced Communications
Technologies and Services (ACTS) for research and development of 3G. Also, in Japan the
Association of Radio Industries and Businesses (ARIB) was established in 1993 as a committee
for studying and developing Japan’s 3G technology. The WCDMA has several versions, R99, R4,
R5 and the following ones. [69][139] – [141]
5

R99 was introduced in 1999 and could support 64 kbps circuit switching payload and up to
2Mbps packet switching payload. It is also compatible with GSM and GPRS services. The core
network structure has two layers, Circuit Switch Layer and Packet Switch Layer. Circuit Switch
Layer used GSM network and Packet Switch Layer used GPRS network. R99 inherited services
and features of GSM and GPRS. The commercialized WCDMA network in the world are all
based on this WCDMA Release 99 version. [69]
R4 was finalized in March 2001. Comparing with R99, the network structure did not change.
The most different parts were in interface setup and functions improvements. One major change
was in MSC (Mobile Switching Center). R4 split it into two parts MSC service and MGW
(Media Gateway). The idea behind this was to separate control and payload. The other major
change was introducing IP transmission to Circuit Switch Layer. R4 is an important step to All
IP network. [69]
R5 was stopped upgrading in September 2002. It is a starting point of all-IP network of
WCDMA network. R5 supports IP transmission and services. The most important component of
R5 was IMS (IP Multimedia Subsystem). This subsystem can provide multimedia service based
on the Internet. It is the bridge to integrate cellular system and the Internet. [69]
2.2.2. CDMA2000
CDMA2000 is the trade mark of TIA-USA (Telecommunication Industry Association) and
which developed by 3GPP2. There were several versions of CDMA, CDMA2000 1X,
CDMA2000 1X EV-DO. [69][142][143]
The evolution direction was the same with WCDMA, All IP network. Therefore, in CDMA-
LMSD (Legacy MS Domain), the separation of control and payload was introduced. There are
four phases in the CDMA2000 evolution. In phase 0, the main issues were to improve the present
system. In phase 1/2 were to upgrade the system to become the All IP network system. In phase
3, the All IP network was formed and MMD (Multimedia Domain) started to show in the system.
[69]
2.2.3. TD-SCDMA
This standard was individually developed by China and co-work with 3GPP. Future
development is still ongoing. [69] [144]
6

2.3. Development
3G has been in development for couple years already. During this period of time, the
telecommunication industry almost crashed in Europe. 3G is a promising technology, but the
over-expectation made the European telecommunication industries spend too much money on
the license of band operation, set up infrastructures and marketing. The result was that many
companies cannot recoup their profits, and many of them had to give up the license and projects
in order to lower the debt or litigate with government. These facts caused the development of 3G
slowed down greatly in Europe. The most successful case in Asia is Japan. There are two
companies running the business, NTT DoCoMo and KDDI. The NTT DoCoMo uses WCDMA
and KDDI uses CDMA2000. Taiwan initialed the 3G service in 2005. In North America 3G is in
sprout stage. Around the world, there are total 29 countries has 3G network so far. Figure 2-1
shows the evolution steps of 3G. [69][77]
Figure 2-1 The Evolution of 3G
The popularization of 3G has several factors, such as the user’s habits, market positioning,
applications, and infrastructures. 3G has two opponents which are Wi-Fi and WiMax. They
could be partners or enemies and it all depends on applications and market positioning. These
wireless standards have their own advantages. 3G has bigger coverage and support mobility, but
has lower data rate, and Wi-Fi has higher data rate, but smaller coverage and does not support
7

mobility. On the other hand, WiMax has the biggest coverage, highest data rate and also support
mobility. [69][78]
The applications of 3G partially overlap with Wi-Fi and WiMax. 3G is a mobile phone
technology, so its main stage is in the cell-phone market; internet access is only an additional
benefit. 3G’s signal will fade out fast when there are too many people in the nearby area tring to
access the Internet at the same time. 3G’s interface is mainly onthrough the cell-phone.
Considering the operation convenience, it is tolerable for checking or sending e-mail, time tables,
or MMS. However for high throughput applications, 3G appears to be not as good as the other
two standards. The cell-phone’s inborn limitation, keyboard and screen size, makes it unsuitable
for internet access. Moreover, 3G’s data rate and bandwidth are not fast enough for internet use.
2.4. Cases
Japan is a successful case for 3G development and mobile Internet access and there are
some unique reasons for this. Japanese 3G service was started in late 2001 called FOMA
(Freedom of Mobile Multimedia Access) by NTT DoCoMo. FOMA is the brand name of NTT
DoCoMo’s 3G service. As the network coverage rate became higher and higher, most Japanese
started to get used to checking and sending e-mail as well as getting daily information by phones.
This phenomenon especially happens during rush hours in mass transit systems. Teenagers also
like to share secrets, pictures and gossip by e-mail and MMS. Therefore, FOMA has become part
of life and Multimedia service is the major applications of 3G. The most popular service in Japan
now is called i-mode, it was in 2G and then upgrade to 3G. [69][76] – [78]
The 3G service in Korea is called JUNE. It is pushed by SKT (South Korea Telecom) in
November 2002 and based on CDMA2000 1X EV-DO. Similar to Japan, it is also focused on
multimedia service. In August 2003, just 8 month later, the users already increased to one million.
JUNE has a music channel, video channel, MMS service and NOUL (Korean Idol). It is the first
service which realizes the commercial video phone-call. [69]
In Taiwan, 3G cell-phones have become the main stream and the system also has upgraded
completely. However, because of Wi-Fi and WiMax, telecommunication industries are still
seeking where the business and balance point are. It is a true struggle in the communication
market. Varieties of websites and software fit users’ different demands on the Internet. But with
cell-phones, internet service is only provided by telecommunication industries and is very
limited and not universal. In addition, because the cell-phones’ specifications are not unified,
such as in the revolution of screen resolution and numbers of buttons, it is more difficult to
design web pages as well as to promote the service. In Japan, the cell-phones are more unified,
so it is easier to popularize mobile Internet access service. [69][76] – [78]
8

2.5. Conclusion
WAP (Wireless Application Protocol) is the previous model of mobile Internet access
service, but it did not become as popular as “i-mode”. Poor contents and costly usage rate are
two major reasons. 3G may revive it again, but it is an important lesson about the relationship
between people and mobile Internet access service. Do people really need to use cell-phones to
access the Internet? This is one of the key points for 3G’s future. And then after the final goal of
3G network is done, the All IP network, what will be the impact of the tele-market will be an
important observation point.
Video phone-call is the major selling point of 3G. However there is a problem: who wants
to be seen on thea phone call? Who wants to be awakened when the boss calls in the morning
and be seen on the phone? Privacy is very important issue for everyone, but video phone-call has
potential risk to break it. Therefore, it may take a long time for people to get used to it. In
Taiwan, it has taken five years to get people used to the idea of pulling over to make a phone call
and talking on the street. Currently, 99.9% population in Taiwan have a cell-phone. 3G still has a
long way to go, because it takes time to change life styles and in most places in the world 3G has
just arrived.
9

3.1. The background of IEEE 802.11
CHAPTER THREE
3. IEEE 802.11, Wireless LAN
When, IEEE published the standard 802.11Wireless Local Area Network protocol in 1997, it
caused a revolution in methods of communication. People started to get rid of the constraint of
wires and began to enjoy the freedom of unlimited space for getting information. It changed the
way that people entertain themselves, get information, communicate and so on. IEEE 802.11 has
many members in its family, and there are some of them that are widely used such as 802.11 a,
802.11b, and 802.11g. The newest incoming standard is 802.11n. The other name for 802.11 is
called Wi-Fi. [01] - [03][22]
The first practical standard in the 802.11 family is 802.11b and it came out in 1999. The
earlier standard 802.11 was too slow. Due to its sluggish speed, users could not experience the
advantages of wireless communication. However, 802.11b was still very successful. Its speed
may be only 5.5 Mbps and 11 Mbps [04]-[06], but it was fast enough to satisfy the basic
requirement for browsing the Internet. In the past two years, this standard has become extremely
popular. As a result, a PC which can support this protocol becomes a fundamental requirement.
Approximately around the same time when 802.11b came out, IEEE published another
standard, 802.11a. These two standards used different operation bands and were not compatible.
[07][08] 802.11a can reach the speed 54 Mbps and has more channels in its band to improve the
bandwidth capacity for users. However, because of higher cost and the shorter transmission
distance, this standard was only used by certain groups. [09][15]
The standard 802.11g was developed based on 802.11b and combined with OFDM
(Orthogonal Frequency Division Multiplexing, used in 802.11a). Theoretically, its speed could
reach 54 Mbps. This standard was published in the summer of 2003.. [10][20] Compared to the
previous two standards, it was faster than 802.11b and had longer transmission distance and
lower cost than 802.11a. It had the advantages of 802.11a and had backward compatibility with
802.11b. [09][11][15]
In the business field, rebuilding is always the last choice. 802.11b has existed in the market
for a long time making it unwise to replace 802.11b with 802.11g. Therefore, the best method is
to produce a device which can support both standards. Because they are compatible and operate
in the same band, this is a more cost efficient option. For example Intel’s “Centrino” and
“Sonoma” uses this type of production. [12] – [14] Meanwhile, the 802.11a has its unique
advantages and was still used in certain areas. A device that supports a/b/g standards is also
currently available. [08][09]
10

IEEE 802.11n is the newest standard of WLAN (Wireless Local Area Network) next
generation. In January 2006, Hawaii, IEEE passed a draft of the 802.11n standard. However the
official 802.11n universal standard is still in discussion. There are two main groups working on it,
TGn Sync and WWiSE. In order to complete the standard earlier, these two groups composed a
team called IPT (joint proposal team). [02]
The following section is going to introduce the capabilities of IEEE 802.11a/b/g theses three
standards. Table 3-1 shows the IEEE 802.11 standard family members. [01][86]
Table 3-1 Family of IEEE 802.11
Protocol Release Date Op. Frequency
11
Throughput
(Typ)
Data Rate
(Max)
Legacy 1997 2.4 GHz 0.9 Mbps 2 Mbps
802.11a 1999 5 GHz 23 Mbps 54 Mbps
802.11b 1999 2.4 GHz 4.3 Mbps 11 Mbps
802.11g 2003 2.4 GHz 19 Mbps 54 Mbps
802.11j 2004 4.9 - 5 GHz 23 Mbps 54 Mbps
802.11h 2004
5,15 – 5,35 indoor
5,47 – 5,725 indoor/outdoor
23 Mbps 54 Mbps
802.11n Sept, 2008 (est.) 2.4 GHz/5 GHz 74 Mbps 248 Mbps
802.11y March, 2008 (est.) 3.7 GHz 23 Mbps 54 Mbps
3.2. Capacity
As shown in the Table 3-2 [16], although the operation band of 802.11b is in 2.4 GHz, the
FCC (Federal Communications Commission) is only allowing it to carry a certain level of
frequency. Therefore for the U.S. the available WLAN channels are from 1 to11. This rule is also
used on 802.11g. When building a WLAN, the interference is a very important factor. To avoid
interference between channels in one area, the channels should not be overlapped and the
interval of the frequency must be at least 25MHz. [04][05][16] That means, when selecting a
channel, the number has to be five numbers apart from each other, for example, 1, 6 and 11.
Thus, for 802.11b, the maximum bandwidth capacity is 3*11 = 33Mbps and for 802.11g is 3*54
= 162 Mbps. [11][14][17] - [20]
The UNII is the initial for ‘Unlicensed National Information Infrastructure’. This band is
only free in certain countries, such as the U.S. and Taiwan. Table 3-3 [16] In the U.S., this band
is divided into three sub-bands and then each sub-band is split up into four non-overlap channels.
Therefore, the total available channels for 802.11a are twelve. Since the 5 GHz band is not
commonly used, it has a lower level of interference. When using 802.11a to build a WLAN, one

area can have a maximum of eight non-overlap channels to use, so the overall bandwidth
capacity is 8*54 = 432 Mbps. [08][09]
Term
Standard
Table 3- 2 Capacities for 802.11a/b/g
802.11a 802.11b 802.11g
Band 5 GHz 2.4 GHz 2.4 GHz
Available channels 12 11 11
Bandwidth capacity 432 Mbps 33 Mbps 162 Mbps
Coverage 75 ft. 125 ft. 155 ft.
Datarate 54 Mbps Max. 11Mbps 54 Mbps
Modulation OFDM DSSS
Channel Number
Table 3-3 IEEE 802.11b/g Channel Used for Different Countries
Frequency
(GHz)
Japan
12
North
America
Country Name
ERP-OFDM
DSSS-OFDM
Europe France Spain
1 2.412 X Y Y X X
2 2.417 X Y Y X X
3 2.422 X Y Y X X
4 2.427 X Y Y X X
5 2.432 X Y Y X X
6 2.437 X Y Y X X
7 2.442 X Y Y X X
8 2.447 X Y Y X X
9 2.452 X Y Y X X

Table 3-3 Cont.
10 2.457 X Y Y Y Y
11 2.462 X Y Y Y Y
12 2.467 X X Y Y X
13 2.472 X X Y Y X
14 2.484 Y X X X X
Table 3-4 IEEE 802.11a Channel Used for North America
Band (GHz) Frequency (GHz) Channel Number
5.15 – 5.25
UNII Lower Band
5.25 – 5.35
UNII Middle Band
5.725 – 5.825
UNII Upper Band
5.180 36
5.200 40
5.220 44
5.240 48
5.260 52
5.280 56
5.300 60
5.320 64
5.745 149
5.765 153
5.785 157
5.805 161
802.11b/g is the most widely used standard for WLAN. Because of the different operation
band, 802.11a cannot cooperate with b/g standard. Also, there are some other problems, such as
its high cost for equipments. The working band is also not free for all countries, and has a lower
transmission distance. However it is still used currently, because it is fast, stable, and has high
capacity. Also, some people think that the lower transmission distance makes the network more
13

difficultt
to be hhacked;
theerefore,
it is populaar
for somme
industriies.
To immprove
thee
competitiveness
off
802.11a, rresearchers
invent a tripple
frequenncies
chip foor
a/b/g. Someone
whoo
works iin
the officee
with 802.111a
can then n walk out to a public place and gget
on the Innternet
withh
802.11bb/g.
The neew
productss
make cerrtain
that thhese
three sstandards
caan
be opera ated in onee
buildingg.
[7] – [9] [14]
3.3. TThe
Physiccal
Layerr
and MA AC Layer
3.3.1. The Phyysical
Layyer
3.3.1.11.
Introduuction
The e Physical llayer
is the first layer oof
the OSI ( (Open Systeem
Interconnnection)
mmodel,
figuree
3-1. It is at the boottom
of thhe
model. TThis
layer iis
responsibble
for deciding
the tr ransmissionn
methodd,
bandwidthh,
mediums,
bit synchronization,
mmodulation
and so on. MMost
physic cal set up iss
completted
in this layer. It is the first layer
of the nnetwork
strructure.
It pprovides
a mechanical m ,
electrical
and alsoo
proceduraal
flattop be etween the transmissioon
mediumm.
The mosst
importantt
missionn
of the phyysical
layerr
is the flueency
of dataa
streams. TThis
sectionn
is going to t introducee
several technologiees
used for 802.11 prottocols
and wwill
discuss how they wwork
in this layer.
FFigure
3-1 OOSI
Model
14

3.3.1.2. PLCP and PMD
The physical layer contains two sublayers, PLCP (Physical Layer Convergence Protocol)
and PMD (Physical Medium Dependent), figure 3-2. These two layers communicate with each
other by SAP (Service Access Point). Different transmission methods will add different
preambles and headers to their own PLCP and PMD. [04] – [07][09][21]
PLCP
The function of PLCP is to prepare MPDU’s (MAC Protocol Data Units), also called PSDU
(PLCP Service Data Unit), for communicating with the MAC layer. It transfers the incoming
frames from mediums to the MAC layer. The PLCP is located between the PMD sublayer and
the MAC layer so that it can help PMD transmit frames without communicating with the MAC
layer in advance. For this purpose, PLCP will map the MPDUs into PMD frames before
transmission. MPDU’s contain a unique preamble and header in the physical layer, which
includes the information of PHY transmitters and receivers. These kind of composited frames are
called PPDU (PLCP Protocol Data Unit).
PMD
This sublayer is right under the PLCP. It controls the transmission and reception of the
physical layer data units from stations via mediums. PMD is the interface of a layer and a
physical medium. It connects with wireless mediums (RF, … etc.) directly. Frames are also
modulated and demodulated in this sublayer.
3.3.1.3. CS/CCA
Figure 3-2 802.11 PLCP, PMD and MAC Structure
No matter what kind of network it is, there is one problem in common. That is how to
improve effective transmission. For solving this problem, 802.11 applied CS/CCA technologies
during transmission process. CS/CCA is the initial of Carrier Sense/Clear Channel Assessment.
15

CS/CCA can detect the state of a medium and report it to the transmitter. It is activated when
the receiver and transmitter are on but no data streams are currently passing. It determines the
channel state before transmitting. If the channel is busy, it will wait for a period of time, and then
detect it again. CS/CCA also can detect whether a signal can or cannot be received by a receiver.
[04][05][21][23]
3.3.1.4. IEEE 802.11b, DSSS and HR-DSSS
3.3.1.4.1. Theory and Transmission method
DSSS (Direct Sequence Spread Spectrum) was first added to the 802.11 standard in 1997. At
that time the speed was only 1 Mbps and 2 Mbps. But soon, it was found that DSSS has potential
to run faster. The next standard 802.11b with new DSSS came out in 1999 and ran at 5.5 Mbps
and 11 Mbps. Although these four speeds are often combined together as one standard, they
actually belong to two different standards.
The principle of DSSS is to transmit a signal over a wide frequency band, by spreading the
RF energy across a wide band precisely. Then a receiver can get the transmitted signal by
operating the correlation process.
Figure 3-3 DSSS Transmission [17]
For transmitting a signal, first a spreader has to flatten the amplitude of the narrowband
radio signal and spread its RF energy to a wide band. This step includes a lot of mathematical
calculations. After this process is complete, the signal will look like a RF low level noise. Then
when the receivers monitor the wide frequency band and locate the noise-like signal, they can
identify it as the transmitted signals/data. The received noises will be recovered by a correlator
which can invert the spreading process. Since the true noise can not affect the whole band, the
correlator can spread it out without damage the original signal.
When modulating the DSSS data streams, 11-chips will be added to the transmitted signals.
A chip is a binary number and it is just only a part of encoding and transmission process. Chips
do not carry any data. The chipped streams have another name called PN Codes (Pseudorandom
16

Noise Codes). The most powerful consumptions of the DSSS-PHY are to generate chipped data
streams and recover data streams from chipped streams. [24] – [28][16]
“Spreading ratio” is an important parameter used to decide how many chips are needed for
one bit. The improper spreading ratio will cause the waste of bandwidth. Although to increase
the spreading ratio does help the ability of recovering data, it will also require higher chipping
rate and larger frequency band. And there are prices to pay for increasing the chipping rate. First
is the hardware, the costly high frequency RF components and second is the cost of enlarging
frequency bandwidth.
The modulation method used for DSSS are DBPSK (Differential Binary Phase shift Keying)
for 1 Mbps and DQPSK (Differential Quadrature Phase shift Keying) for 2 Mbps. The encoding
method is Barker code. [24] – [26][16]
3.3.1.4.2. Against interference
To avoid interference and guarantee the fluency of the data streams, the two channels,
according to 802.11 rules, must be at least 25 MHz away. The overlapped channels will cause
more interference and damage the transmitted frames. By using DSSS transmission the
interference problem have been improved to a certain extent. During transmission, because chips
have been added to the data streams, they can get protection from chips. It is exactly like the
function of armor. Even if the chips are damaged, the data is still safe. However, if the
interference is really strong, it can still hurt the data very badly, and then nothing can be
recovered. [27][28]
3.3.1.4.3. PLCP and PMD of DSSS
The DSSS-PLCP adds six parts in the DSSS-PPDU. The first two parts are PLCP preamble
and the other four are headers. The structure is showed in Figure 3-4[21]. The data rate of DSSS-
PLCP is 1 Mbps and 2Mbps. This preamble is also called a long preamble. The function of the
preamble is to help a receiver to synchronize to the incoming frame. The header contains the
information of the frame.
The DSSS-PMD is used to operate transmission and reception between stations. It is also in
charge of modulating and de-modulating the PPDUs. The relationship between PLCP and PMD
is like a brain and a body. PMD is response for action and PLCP gives an order. [04] –
[06][16][21]
17

3.3.1.4.4. HR-DSSS and CCK
Figure 3-4 DSSS PLCP
The original modulation method (Barker code) used in DSSS, for 802.11, only achieved the
speeds of 1 and 2 Mbps. For commercial use, this is not an acceptable amount. In the data stream,
each barker word carries one or two bits depending on the data rate. To improve the speed, it is
necessary to increase the capacity of each symbol. That means more complicated phase angle
changes. For example, the DQPSK receiver could at least detect four cycle phase differences.
More cycle phase differences will cause the smaller phase changes. It ends up with the need of a
highly accurate and costly receiver.
Therefore, the next standard 802.11b had a different modulation method known as
Complementary Code Keying (CCK). This method splits the data stream into code symbols
composed with 8 bits. By a complex mathematic procedure, the CCK can encode four or eight
bits per code word with 8-bit code symbols. Also, this procedure can help receivers to identify
different codes easily, even in interference or a multipath fading environment. By using the CCK
process, the speed can reach 5.5 Mbps or 11 Mbps.
The process of CCK is quite similar to the DS chipping process. Figure 3-5[17]. The
difference between them is that CCK does not use the static repeating code word, as for example,
Barker Code. The code word is converted from the data. These code words are used to transmit
data and spread the signal. Phase angle also plays an important role here, but this time it will not
cost as much as DQPSK.
18

Figure 3-5 CCK Modulation
HR-DSSS PHY is defined as the data rate equal to 5.5 or 11 Mbps. It also contains two
parts, PLCP and PMD. PLCP is in charge of framing and PMD is response for transmission.
3.3.1.4.5. PLCP and PMD of HR-DSSS
The structure of HR-DSSS PLCP is show in Figure 3-6[17]. It is very similar to DSSS-
PLCP, the only difference being in preamble. Its preamble is called short preamble. This kind of
preamble could improve the efficiency of PLCP framing.
For backward compatibility, the HR-DSSS PMD can support both low (1, 2 Mbps) and high
(5.5, 11 Mbps) transmission. The only difference is low speed must uses long preamble while
high speed uses short one. In addition, for high speed, the framed data will be encoded by CCK
modulation before transmitting. At 5.5 Mbps, each symbol has four data bits and at 11 Mbps,
each symbol has eight data bits.
Figure 3-6 HR/DSSS PLCP Framing
19

3.3.1.5. IEEE 802.11a and OFDM
3.3.1.5.1. Background
Because there are lots of non-802.11 signals that also existed in the 2.4 GHz band, this band
is often very crowded. For achieving higher speed and capacity, 802.11 Task group A (TGa)
came out with a new standard. It used a 5 GHz un-licensed band and a different transmission
method (OFDM). Although this standard was published in 1999, the practical hardware was not
available until the end of 2001. At first, 802.11a used the UNII band and was specified for the
U.S. only. Later, two similar standards were published. 802.11h is for Europe and 802.11j is for
Japan. [08][30][31][43][44]
OFDM (Orthogonal Frequency Division Multiplexing) was developed in the late 1960s. It is
not a new theory however, because of the wireless technology it revived again. OFDM has
several features. First, it uses multiple subcarriers to do a single transmission. Second, for
simplifying equalization at receiver, it transforms scattered channels into parallel narrowband
subchannels. Third it is based on simple mathematics. OFDM is related with FDM (Frequency
Division Multiplexing), that both divide bandwidth into divisions which is called carriers or
subcarriers and use them for transmitting information. [08][17][29][33][36]
3.3.1.5.2. Principles
When transmitting data, OFDM chooses channels which overlap in frequency domain, but
will not disturb with each other. Figure 3-7[17] These overlapping subcarriers are defined by
mathematical calculation, therefore, they can travel individually, and this relationship is called
orthogonal. With this feature, OFDM can increase capacity in the fixed bandwidth. Thus the
overall performance is improved. [08][17][29]
Figure 3-7 FDM and OFDM
Although OFDM has better performance, there is still a cost. Inter-symbol interference (ISI)
is a common problem when transmitting data. It mainly occurs when the delay that happens in
different paths is too large and causes a later copy to shift onto a previously arrived copy. The
20

other problem is inter-carrier interference (ICI). When several subcarriers transmit in a channel
and one of them shifts slightly then the interference between subcarriers would be occurred.
To avoid these problems, scientists came out with several methods. The first method was to
add a “guard time” between each subcarrier. A guard time is a silent period between two
subcarriers, however this method wastes bandwidth and once the delay is too large then the
orthogonality would be destroyed. The other way to avoid interference is using “cyclic prefix
(CP)” and “cyclic postfix (PP)”. Figure 3-8[51] CP is a guard interval between the signal N and
the signal N-1. PP is an interval in signal N+1 and N. The idea of CP is to extend the time range
of signal N longer, so that even if interference happened it will not affect FFT block which is the
information section of a signal carried. However, sometimes the problem not only comes from
the previous signal, therefore, the guard interval will have two parts “cyclic prefix” and “cyclic
postfix”. Here are some other studies about OFDM and interference: [30] – [40]
Figure 3-8 CP and PP
OFDM modem is based on block-by-block structure. The transmitter first converts the signal
into N subcarriers and then uses IFFT (inverse Fast Fourier Transform) to modulate them into
orthogonal waveforms. The receiver reverses the process by using FFT (Fast Fourier Transform).
It will remove CP first and find the FFT block. Then it starts using FFT to demodulate the signal
that has received. Finally, the information is recovered. Figure 3-9[51]
OFDM has higher capacity and is more reliable than some of other methods. The
mathematics of OFDM is FFT and IFFT; and they are not complicated. With FFT, the operation
number in each signal is on the order of NlogN. This can be done easily by a program. That is
the reason that OFDM is broadly used in wireless technology. [34][36] - [39]
21

Figure 3-9 OFDM Modem
3.3.1.5.3. The IEEE 802.11a’s OFDM and its PLCP and PMD
OFDM is a good transmission technology, but TGa did not use the full version. They
modified their own one.
When building an OFDM network, there are some important parameters which are
bandwidth, delay and bit rate. The bandwidth is fixed for 802.11a. When considering delay, it is
necessary to have guard time. Usually the ratio of guard time and delay is two to four times as
big. And the symbol time is five times of the guard time. Thus TGa chose 800 ns as guard time
and 4 µs as symbol time. The bandwidth of an operation band is 20 MHz and the theoretical
highest speed is 54 Mbps. Higher capacity could have higher throughput. However it will
decrease the number of operation channels. Therefore, how to achieve a reasonable balance is an
important design issue. [17][29] - [31][39]
The modulation technology for OFDM is shown in Table 3-4[17]. To reach a higher speed,
TGa has not only changed the transmission method, but also used another modulation technology
QAM (Quadrature Amplitude Modulation). Figure 3-10[55] For preventing the BER (Bit Error
Rate) increase which caused by certain channel’s signal fading, the error correction code is
added to the all sub-channels. The error correction code is called “Convolutional Code”, and this
kind of OFDM sometimes is named COFDM (Coded OFDM). Here is the related research:
[36][39][40] – [42]
22

Tab ble 3-5 OFDDM
Modulaation
and Daata
Rate
Figure 3-10
Constellaations
Diagrram
The e OFDM-PLLCP
structuure
is shownn
in Figure 3-11[21]. TThe
preamblle
contains 12 symbolss
and is uused
to synnchronize
with w a receivver.
The duration
time of an OFDDM
preamb ble is 16 µs.
There aare
two parrts
of the prreamble;
shhort
trainingg
sequence (the first tten
symbols s) and longg
trainingg
sequence ( (the rest tw wo symbols) ). The short one is usedd
to create AAGC
(Auto omatic Gain n
Controll),
timing annd
initial freequency
offfset
estimatiion
of the carrier
signaal.
The long one is used d
23

for the channel, timing and fine frequency offset estimation. The Head contains two parts, the
signal and data’s service section. The head is 40 bits long (signal is 24 bits plus service 16 bits).
The signal field is always transmitted with BPSK at 6 Mbps.
Figure 3-11 OFDM PLCP Structure
In the OFDM-PMD sub-layer, to maintain the speed 6, 12 and 24 Mbps is required. An
operation channel (20 MHz bandwidth) is divided into 52 sub-channels (sub-carriers). Four of
them are pilot carriers; the rest of the 48 sub-channels are used to transmit data. The data will be
divided and modulated into sub-channels, then transmitted parallel. [17][21][29]
3.3.1.6. IEEE 802.11g and the Physical Layer
3.3.1.6.1. Background and Backward Compatibility
As 802.11b became more and more popular, people started to notice the convenience of
wireless LAN. At that time, 802.11b could only provide a maximum 11Mbps. Compared to
Ethernet, this was not a good performance – it was just barely acceptable. When 802.11a started
to join the market, end users also wanted 802.11b to become faster. In fact, 54 Mbps really was
not very fast and most of the time, in a wonderful environment, the performance could only
achieve 50% of the possible speed. However WLAN has its own advantages and “wireless” has
become a trend gradually. Under these conditions, 802.11g is the answer. It has the same speed
with 802.11a, but it has a longer area of coverage. Moreover, it operates in the 2.4 GHz band.
According to 802.11g clause, this standard is not a “new” standard. It is an integrated
standard using many existing technologies. Its physical layer is called ERP (Extended Rate PHY)
24

and contains DSSS, CCK, PBCC (Packet Binary Convolution Coding) and OFDM. It supports
the speed:
ERP-DSSS: 1, 2, 5.5 and 11 Mbps
ERP-PBCC: 22 and 33Mbps
ERP-OFDM: 6, 9, 12, 18, 24, 36, 48 and 54 Mbps (6, 12 and 24 Mbps are mandatory)
For backward compatibility, these methods have some slight changes, but are pretty much the
same original standard. An 802.11g stationary must have the ability to communicate with both
old 802.11b stations and other 802.11 stations. For that reason, the ERP-DSSS and ERP-CCK
were added.
A problem of backward compatibility is that the 802.11g can receive and decode 802.11b
signals, but the converse is not true. Therefore a protection has to be added to the 802.11g
standard. The first part of the protection is that when doing transmission with 802.11b stations,
the Beacon frames cannot be transmitted higher than 11 Mbps. The second part is to avoid
network interference between 802.11b and 802.11g. When 802.11g is transmitting data, in order
to avoid disturbing 802.11b, it will send CTS (Clear To Send) frames to notify the 802.11b
stations and update the NAV (Network Allocation Vector).This process is called CTS-self
Protection. To make sure every station in the network can receive and process the CTS frames,
they have to be sent under 802.11b protocol. The protection is controlled by the ERP information
element in Beacon frames and will limit the data rate of 802.11g. [13][14][17][20][21][29]
3.3.1.6.2. ERP-OFDM and DSSS-OFDM
The ERP-OFDM is very similar to the OFDM used in 802.11a with only a slight difference.
The PLCP is shown in Figure 3-12[21]. When comparing these two OFDM-PLCP, the difference
is the “signal extension” field. This 6µs extra time is used to prepare and decode the 802.11a
frames. 802.11a uses 16 µs SIFS (Short Inter-Frame Space) which is different form 802.11b 10
µs SIFS. 802.11g chooses 10 µs because of backward compatibility, therefore, it adds 6 µs after
a frame to match timing and frame with 802.11a. Beside the PPDU structure, the transmission
method is exactly the same with 802.11a.
25

Figure 3-12 DSSS-OFDM PSDU Format
DSSS-OFDM is a composite framing technology. Its PPDU structure is shown in Figure 3-
13[21] and Figure 3-14[21]. The preamble and head are framed by HR-DSSS mode, and the
PSDU is the ERP-OFDM PPDU. The preamble has long and short formats. With this method,
the protection is not required. The data rate of DSSS-OFDM preamble and head is the same with
DSSS. [13][14][17][20][21][29]
Figure 3-13 DSSS-OFDM Long Preamble Structure
26

3.3.2. MAC Layer
3.3.2.1. Introduction
Figure 3-14 DSSS-OFDM Short Preamble Structure
In the human world, laws are the tools to avoid arguments and accidents and it is the same
with networks. Wireless transmission has many problems such as interference, fading, collision,
and security. In the MAC (Media Access Control) layer, the 802.11 working group, established a
variety of rules and functions to improve system performance and solve these problems.
3.3.2.2. DCF (Distributed Coordination Function) and PCF (Point
Coordination Function)
DCF is the core of CSMA/CA and most of the transmissions using 802.11 standards are
based on it. With DCF, there is no central control. Stations have to compete for the use of
channels. Any transmissions using CSMA/CA (Carrier Sense Multiple Access/Collision
Avoidance) belongs to DCF type transmission. The other mode, PCF, is a central control type.
With PCF, a base station controls all transmission orders; therefore there is no competition and
collisions in this mode. The base station will poll other stations to see if they have frames to send.
The polling frequency and order are decided by a polling list, which is not equaled. Any station
will be added to the list after connecting to the base station. [17][55]
27

3.3.2.3. Hidden node and CSMA/CA
When a station is communicating with another station, there is an existing risk that the
packets may collide. It is due to the hidden node problem. Each station has limited coverage, so
stations may not be aware of the other nearby stations. Thus if there are more than two stations
that try to transmit a signal to the same station at the same time, and then the collision will
happen. In Figure 3-15, station A and C are hidden nodes to each other. If station A is sending a
signal, station C cannot be aware of it. Since most stations are half-duplex (cannot transmit and
listen at the same time), the collision is difficult to be detected. In Figure 2-17, it shows that only
station B knows collisions happened. [17][55]
Figure 3-15 The Hidden Node Problem
To deal with this problem, 802.11 WG uses a different method from Ethernet. With wired
transmission they use CSMA/CD (Carrier Sense Multiple Access/Collision Detection), but since
the wireless transmission has very limited resource and is not as reliable as Ethernet, 802.11 WG
turns to use collision avoidance (CSMA/CA).
There are two technologies used in CSMA/CA, physical channel sensing and virtual channel
sensing. [17][55]
Physical channel sensing
When a station wants to send signals, for example, it senses the channel first. If the channel
is idle, it just sends. During the transmission, it will not sense the channel at the time, but keeps
sending signals. However if the channel is busy, it will wait until the channel is idle and then
start the transmission. Once a collision occurs, the stations will wait for certain time, by using the
Ethernet binary exponential back off algorithm, and then try again later. [17][55]
28

Virtual channel sensing
he other method, virtual channel sensing, is shown in figure 3-16 [55] and figure 3-17[55].
When station A wants to send signals to station B, it will send a RTS (Request to Send) frame to
the station to occupy a channel first. If the channel is idle, station B will send CTS (Clear to Send)
frame back. When station A receives CTS, it will start to transmit a signal. When the process is
initiated, an important “timer” is including in RTS and CTS frame which called NAV (Network
Allocation Vector). The information that is included in NAV is how long the channel will be
occupied. One operation contains RTS, CTS, data frames and ACK (Acknowledgement). NAV
will set how long it will take including the last ACK frame. Therefore, since station D is within
the range of station A, it will receive RTS and then stop completely from occupying the channel
until NAV counter becomes zero. It is the same with station D. Station C will receive CTS, so it
will also wait until the operation is completed. However, before the ACK is received by station
A, the NAV is expired. Then the operation has to run again. [17][55]
Figure 3-16 CDMA/CA
Figure 3-17 Virtual Channel Sensing
29

3.3.2.4. Fragmentation
In most occasions, the frames from the upper layer maybe longer than the fragmentation
threshold. In this situation, the frames have to be fragmented before transmitting. The advantages
for using fragmentation are that it can improve throughput and reliability. By fragmenting frames,
the interference only destroys small pieces of frames, but not the entire frames. Thus the overall
effective transmission is improved. Also, only the destroyed pieces need to be retransmitted,
therefore, the reliability is also improved.
The transmission process of fragmented frames is called fragmentation burst. In the clause,
there are no rules for fragmentation threshold. It depends on network designers. During the
transmission, each fragment has the same frame sequence number and an increasing fragment
number for recombination. To keep occupying the channel for completing fragmentation burst,
each fragment will reset the NAV for next fragment including ACK. Figure 3-18[55]. [17][55]
3.3.2.5. Interframe spacing
Figure 3-18 A Fragment Burst
Interframe spacing is a very important protocol for coordinating medium access. There are
four different intervals which are shown in figure 3-19[55]. To avoid collision, stations wait a
certain period of time until channels are idle before transmission. These different intervals decide
the priority for different types of transmission. High priority transmissions wait a shorter amount
of time, so it can occupy the channel first. [17][55]
30

SIFS (Short InterFrame Spacing)
Figure 3-19 Frame Interval for IEEE 802.11
This is the shortest interval and mainly used for high priority transmission; including a
receiver sends CTS back to a transmitter, a receiver sends an ACK for a fragment or a full frame
and a transmitter of a fragmentation burst send the next fragment without sending RTS again.
PIFS (PCF InterFrame Spacing)
This interval is used for competition-free transmission by PCF. If the SIFS interval passed
and no stations occupy the channel, after PIFS, the base station will send a poll frame or a
beacon frame. Any stations which have data or fragment sequence waiting for transmitting can
start to send after PIFS without disturbance or competition.
DIFS (DCF InterFrame Spacing)
After DIFS, every station can start to compete for earning the channel usage and then the
winner takes all. The all transmission rules and Ethernet binary exponential back off algorithm
are applied.
EIFS (Extended InterFrame Spacing)
This is only used when a mistake has happened during a transmission.
3.3.2.6. Power saving
To extend the battery’s life of the MS (Mobile Station), the 802.11 MAC layer provides a
power management protocol. A base station can direct a MS to go into the sleep mode and buffer
frames for it. Later the MS could be awakened by a base station which sends a beacon frame or a
31

user. The awakened MS will send a PS-Poll frame to the base station to get the buffered frames.
The base station can choose either immediate response or deferred response to the MS. [17][55]
The immediate response means the BS (Base Station) will send the buffered frames to MS
after SIFS interval. If the BS chooses a deferred response, it will send an ACK frame back to MS
first, and then transmit data frames later. After sending the PS-Poll frame, the MS must stays
awake until the whole process is over. The BS notifies the MS for buffered frames by sending a
beacon frame. The buffered frames may be fragmented for transmission. [17][55]
3.3.2.7. Security
This is a very important part for the whole MAC layer design. So far the most widely used
security procedure for wireless communication is WEP (Wired Equivalent Privacy). WEP uses
RC4 cipher to encrypt data. The RC4 cipher is a kind of symmetric stream cipher; it generates a
keystream and then uses the XOR algorithm to mix with data to produce the ciphertext stream.
The receiver will use the same XOR algorithm to recover original data. To encrypt the data, the
secret key has to be chosen first and then extended to the same size of data by PRNG
(Pseudorandom Number Generator). This extended secret key is called keystream. For
recovering data, both transmitters and receivers must have the same secret key and PRNG, and
how to distribute the secret key is an important issue; sometimes it may be preloaded by system
designers or manufacturers. The other issue is “key to keystream expansion” of RC4 stream
cipher, because the safety is dependent upon on how random it is. [17][55]
The communication security has three major properties: confidentiality, integrity and
authentication. Confidentiality is needed to protect data from being stolen by unauthorized
people. Integrity is used to make sure the data has not been changed during transmission. This
part is dependent on CRC code. Finally, authentication is the foundation of all security
procedures. For transmitting data, the users must be trusted and the source must be reliable.
Otherwise, authorization and access control will not be allowed. [17][55]
RC4 shared secret key is composed by 40-bit shared secret and 24-bit IV (Initialization
Vector) usually called 64-bit WEP and the other one is 128-bit WEP. When framing a frame,
WEP will generate an ICV (Integrity Check Value) which is a hash value to combine with
payload as an original data. This ICV can use to protect data from unauthorized changes. After
entering the original payload, secret key and IV, WEP can generate an encrypted frame for
transmission in either secure or not secure network. Figure 3-20[17] shows the frame structure
and operation of WEP. Figure 3-21[55] shows the encryption process. [17][55]
32

Figure 3-20 WEP Frame and Operation
Figure 3-21 The WEP Encryption Process
However there is no perfect encryption in the world. There are some problems that exist in
WEP; key management, reusing the keystream, and IV. WEP has been thought of as a very
secure way to protect wireless communication. However, a study from University of California,
Berkeley called ISAAC (Internet Security Applications, Authentication and Cryptography)
showed the defects of WEP design [56]. Also a method for breaking WEP has already been
published [57].
33

The reason that WEP was safe was because the secret key was not easily broken. However
in some cases, the network designers use the same shared key for all users. That means that
people can read each other’s packets. That is not good for security. If it is a small network, trying
to use the different keys for each user should not be a big problem, but if it is a big network, for
security reasons, if a secret key changes once in a period of time, it is a huge job. How to
distribute a secret key and how to assure it is not repeated are very important issues at this point.
Moreover, IV is another potential risk. The WEP protocol recommends that the IV value should
be different for every packet to avoid the keystream attack. If IV is not a random value, the
encryption will be broken easily. Unfortunately some wireless network cards set the initial IV as
0 and increase the number by one for each packet sent. With this kind of IVs, to break the
encryption is way too easy. Unless the secret key is changed often or assuring the use of random
and different IV for each packet, the risk will remain high. If a hacker collects enough packets
with repeated IV from the same user, the cipher will be broken. [17][55]
3.4. The next generation standard
3.4.1. IEEE 802.11n
IEEE 802.11n is the standard of WLAN for next generation which also called Wi-Fi
(Wireless fidelity). This standard was initiated in 2004 by TGn. The goal of this standard was to
improve the net transmission speed up to 100 Mbps. In the beginning, there were six proposals
that had been posted. After many discussions, there were only two proposals left and they were
from TGnSync and WWiSE. These two groups have their own support from chip makers.
TGnSync has Athero, Agere, Marvell and Intel, while WWiSE has Airgo, Broadcom, Conexant
and Texas Instruments. The first draft was approved in March 2006 and draft 2.0 was approved
in March 2007. Since the demands from the market are becoming higher, Wi-Fi Alliance decided
to start to certifying IEEE 802.11n products based on the draft 2.0 in summer 2007. Now, these
pre-n products are already in stores, such as routers and network cards for desktops or notebooks.
The official approval of IEEE 802.11n standard had been delayed many times because TGnSync
and WWiSE kept fighting for their own proposal to become the official standard. However, they
finally agreed to propose a merged proposal to speed up the birth of official IEEE 802.11n
standard. Therefore, the IEEE 802.11n standard may be finally approved in early 2008. [17] [65]
[66]
Actually, the ideal of these two groups have may be different, but the technologies are the
same. TGnSync emphasizes on improving the peak data rate and WWiSE wants to ameliorate
the MAC-layer. Both of them can reach the goal, or even much better than that. The common
points are they both use MIMO-OFDM as the transmission function and support the bandwidth
for both 20 MHz and 40 MHz. IEEE 802.11n PHY-layer is extended from IEEE 802.11a PHYlayer.
So it is also an OFDM-based PHY-layer and just introduced MIMO technology to increase
the speed. [17] [61]-[66]
34

3.4.2. MIMO (Multiple-Input/Multiple-Output)
Usually, the IEEE 802.11 air-interface only transmits data with single antenna. Although
some systems use two antennas, systems that only use the one have the best performance.
Therefore, no matter how many antennas that systems has, there is only one used to transmit and
receive data, and there is only one input chain and one output chain.
The basic operation of MIMO is to distribute the RF chain to every system antenna and each
RF chain can do simultaneous transmission and reception. This can enormously increase
throughput. Moreover simultaneous receiver processing can solve multipath interference and
improve the quality of the received signals. A frame can be split, multiplexed and then
transmitted by more than one spatial stream. The antenna configuration of MIMO usually
express as “YxZ “format. For example, in both TGnSync and WWiSE proposals require “2x2”
operation, which means there are two transmit chains, two receiving chains and two spatial
streams. That is mandatory mode in both proposals and there is optional mode included. [17]
When setting up hardware, the BS and end users may have different numbers of antenna.
For example, a BS has three and the end user has two. Usually BS has more antennas, because of
saving power and cost for the end users. In this situation, 2x3 is for uplink and 3x2 is for
downlink. Two spatial streams are distributed to three antennas. One spatial stream is transmitted
by multiple antennas; this is called STBC (Space-Time Block Coding). This method is also used
in IEEE 802.16 PHY-layer. [17] [61]-[66]
3.5. Limitation
As the Internet goes into the wireless stage, internet access seems become more and more
convenient. Wired Internet access, such as ADSL, can provide at least 100 Mbps data rate, and
Wi-Fi, with the g standard, can achieve 54 Mbps, and it depends on the air-interface conditions
however, if Wi-Fi wants to share the ADSL market, it still has a long way to go. Wi-Fi is strict to
the operation environment and sensitive to channel fading, so reliability is a big issue. Since Wi-
Fi is designed for small area not BWA, such as home or office, VoIP (Voice over IP), video
service and a large file download are heavy duty for it. If a business building wants to install a
wireless network for the whole building, every floor may need an individual AP (access point) or
even more than one, depending on the location structure. This is because the signals suffer the
short transmission range, channel fading and interference, therefore the installation cost and
complexity will be high.
The other problem of Wi-Fi is the market share. This is caused by fundamental
infrastructure, completion rate users’ behavior patterns and technologies maturity. What is Wi-
Fi’s market positioning? And who is the major customer group? The answers of these two
questions are the key to the future of Wi-Fi. If Wi-Fi wants to take VoIP, for example, as the kill
35

application, its biggest opponent will be 3G. Or if Wi-Fi wants to take broad area wireless
network as the goal, the WiMax is blocking its way. Compared to 3G, Wi-Fi is faster, but the
signal is not as stable. And compared to WiMax, Wi-Fi is slow, has small-coverage and is
unreliable. In this difficult situation, Wi-Fi should not keep thinking its killer application or try to
occupy market share of other wireless technologies. The future of Wi-Fi should be cooperation
not competition.
Since Intel integrates Wi-Fi with laptop computers, it speeds up the demand of wireless
access. The laptop has come into the main stream in the IT industry. People can carry their PC
with them, but they cannot carry the ADSL. Therefore, it is the reason why a wireless network is
desirable. Generally, most people believe that businessmen are the one who need wireless access
everywhere. However, the major Wi-Fi users or the potential users should be home workers and
students. Observing the behavior patterns, it is easy to find out that people want to get rid of
annoying wires and use the Internet access in different rooms at home, and students need to
access the Internet for information, online games or entertainment in different indoor hotspots at
any time. Another important fact from the behavior patterns is there is no killer application for
Wi-Fi. People access the Internet for enjoying ubiquitous service not just for a single purpose.
Thus, with the new coming standard IEEE 802.11n, Wi-Fi should focus on how to get involved
to meet the demands of home users and students. That means to provide ubiquitous access.
Therefore, the next problem is if the ISP (Internet Service Provider) wants to build the
public Wi-Fi network. Is it possible and what are the issues behind it? This topic will be
discussed in chapter five.
36

4.1. The background of IEEE 802.16
CHAPTER FOUR
4. IEEE 802.16, Wireless MAN
The IEEE 802.16 standard is the second generation of BWA (Broadband Wireless Access).
The standard group was formed in 1998 and its purpose was to develop an air- interface standard
for BWA. At the beginning of the project, the group focused on a LOS-based (Line of Sight)
point-to-multipoint wireless broadband system operated in the 10 GHz – 66 GHz band. The
complete standard was finished in December 2001. The evolution of IEEE 802.16 can be split
into four stages: 1. Narrowband wireless local-loop systems, 2. First-generation line-of-sight
broadband systems, 3. Second-generation non-line-of-sight broadband systems, and 4.
Standards-based broadband wireless systems. [50][60]
Narrowband wireless local-loop systems
The First system is related to the wireless voice telephony. The WLL systems (Wireless
Local-Loop) were successful in many developing countries such as China, India and Brazil.
There are two major technologies used in these WLL systems digital-enhanced cordless
telephony (DECT) and code division multiple access (CDMA). To stay competitive, WLL
systems started to join the Internet service market in 1993. In February 1997 AT&T developed a
wireless access system for 1900 MHz PCS (Personal Communications Service) and ended the
service in December 2001 due to high costs and poor take-rate. During the same time, some
small companies focused on wireless internet service. These WISP (Wireless Internet Service
Provider) companies set up the system in license-exempt bands, 900 MHz and 2.4 GHz and
needed customers’ permission to install antennas either on the rooftop or top of the building. At
this time the range, capacity, and speed were limited. [50][87] – [90]
First-generation line-of-sight broadband systems
Since wired internet service can provide higher and more stable service, wireless systems
needed to evolve to be competitive. There are two major systems called local multipoint
distribution systems (LMDS) and multichannel multipoint distribution services (MMDS). LMDS
mainly supported SOHO (Small Office, Home Office), business centers, and small corporations.
This system only had short success in the late 1990s. MMDS was once used to provide wireless
cable broadcast video service in rural areas where no cable TV service was available. When
satellite TV came out, the wireless cable business crashed. The operators sought an alternative
way to use this band (2.5 GHz). In September 1998 FCC relaxes rules for the MMDS band to
allow two-way communication. After these changes in regulations some companies such as MIC
WorldCom and Sprint, bought licenses to use the MMDS spectrum and began to develop high
37

speed fixed wireless broadband service for this band. These first-generation broadband systems
used towers which were several hundred feet tall and had LOS coverage up to 35 miles with high
power transmitters. The users had to install outdoor antennas high enough to receive a signal
and pointed toward the tower for the clear LOS path. This LOS equipment was soon considered
an impediment. And because towers were difficult to set up, the service was quite limited.
[50][91][92]
Second-generation non-line-of-sight broadband systems
The second-generation broadband systems had potential to solve the LOS problem and had
the ability to provide more capacity and higher speed. This was because they used cellular
architecture and advanced-signal processing technology. With these methods, the link and
system performance was improved under multipath conditions. These new second-generation
systems also perform well in NOLS (Non-Line of Sight) environment by using OFDM, CDMA
and multiantenna processing. Some of them can even be operated without setting an antenna
outside. [50]
Standards-based broadband wireless systems.
IEEE 802.16 standard was approved officially on December 2001 and the formal name was
wireless metropolitan area network (WMAN). This first standard only focused on the10 GHz –
66 GHz band and can only do LOS transmission. In PHY-layer, it used single-carrier modulation
and in the MAC-layer, it had time division multiplexing (TDM) structure which supported FDD
(Frequency Division Duplexing) and TDD (Time Division Duplexing). [50]
In order to maintain a competitive advantage, the IEEE 802.16 standard group developed a
series of extended standards to improve WMAN performance. The IEEE 802.16 family members
include IEEE 802.16, IEEE 802.16a, IEEE 802.16c, IEEE 802.16-2004, IEEE 802.16e-2005,
IEEE 802.16f, IEEE 802.16g and IEEE 802.16h. [60]
WiMax Forum
This is a Non-Profit Organization formed in April 2001. The initial members included Intel,
Fujistu, and Nokia among others. The major mission of this forum is to assure the unity and
compatibility of BWA products produced by any manufacturer. In the beginning, the
certification was only between IEEE 802.16 standard and ETSI HiperMAN standard (European
Telecommunications Standards Institute, High Performance Metropolitan Area Network). As the
technologies of the 802.16 become more mature, many industries started to pay attention to it.
Therefore, more companies around the world joined and established several working groups to
promote the standard. Because of this forum, WiMax (World Interoperability for Microwave
Access) became the second name of IEEE 802.16. [59]
38

The working groups of WiMax Forum are CWG (Certification Working Group), TWG
(Technical Working Group), RWG (Regulatory Working Group), MWG (Marketing Working
Group), SPWG (Service Provider Working Group), NWG (Network Working Group) and AWG
(Application Working Group) [59]
4.2. Capacity of the IEEE 802.16 family
4.2.1. IEEE 802.16
This initial standard is fixed air-interface BWA. Because it operated in a high frequency
band, it can only do LOS transmission. In addition, since IEEE established this unified clause,
manufacturers can produce compatible equipment by following the standard. This was a big step
for realizing WMAN. [45][50] [60][93][96]
4.2.2. IEEE 802.16a
This standard was approved in January 2003. The NLOS transmission was added. The IEEE
802.16 TGa extended the operation band to 2 – 11 GHz licensed and licensed-exempt band. This
frequency had a longer wavelength, thus performs NLOS transmission very well. The maximum
coverage was 30 miles and minimum was 6 miles. The other key technology called OFDM was
also added in PHY-layer at this time. OFDM proved (in IEEE 802.11) that it was the solution for
the multipath issue. These two were the major changes in PHY-layer. In the MAC-layer, the
IEEE 802.16a provided QoS system the ability to support voice and video real time service.
[46][50] [60]
4.2.3. IEEE 802.16c
This standard is just an improved standard of the initial IEEE 802.16 standard. This one
established more detailed rules of how to run a system in 10 – 66 GHz band. [47][50] [60]
4.2.4. IEEE 802.16-2004
This standard was the first practical standard of the IEEE 802.16 family. It is also known as
fixed-WiMax. It integrated the previous standards and re-edited PHY and MAC-layer contents to
improve the system performance and compatibility. Therefore it can support various business
uses. IEEE 802.16-2004 was a fixed air-interface of BWA, and it supported 2 – 11 GHz licensed
and licensed-exempt band and 10 – 66 GHz band. That meant it can do both LOS and NLOS
39

transmission. The complete edition of IEEE 802.16-2004 was approved in December 2004.
[48][50] [60]
4.2.5. IEEE 802.16e-2005
In 2003, the 802.16 standard group started another mission. The TGe began to combine
mobility and BWA together. The result was IEEE 802.16e and it was formally published in
February 2006. This standard introduces scalable OFDMA in PHY-layer and modifies the MAClayer
for supporting high speed mobility. The goal is to support end users moving in cars and
giving them the ability to access the BWA without any problems. It has backward compatibility
with IEEE 802.16-2004. Because of its mobility, it is also referred to as mobile-WiMax. [49][50]
[60]
4.2.6. IEEE 802.16f, IEEE 802.16g and IEEE 802.16h
These standards are still under discussion. So far only drafts are available. [50][60] Table 4-
1[50] is the basic information of IEEE 802.16 family.
40

Table 4-1 Thee
Basic Datta
of IEEE 802.16
41

4.3. The Physical Layer and MAC Layer
In the following section, the IEEE 802.16-2004 and IEEE 802.16e-2005 will be discussed.
IEEE 802.16e-2005 inherits the fixed-BWA ability from IEEE 802.16-2004 and re-edits the
PHY and MAC layer to combine fixed-BWA with mobility. According to the WiMax forum,
there are four usage scenarios: nomadic, portable, simple mobility and full mobility. The
applications of IEEE 802.16-2004 are to provide an air-interface for fixed and nomadic
transmission, while IEEE 802.16e-2005 is to provide an air-interface for portable and mobile
transmission. [50][59][94] – [96]
Nomadic
The user can use his/her devices with a local fixed service and reconnect to a different fixed
service in another place.
Portable
Provide service for 3G-phones, PDA or notebook.
Simple mobility
Allowed the end users move in the speed up to 60 km/hr with less than 1 second
interruptions.
Full mobility
Provide up to 120 km/hr mobility service with less than 50 ms latency and less than 1%
packet loss.
4.3.1. IEEE 802.16-2004
4.3.1.1. Physical Layer
There are several key technologies used in IEEE 802.16-2004 (fixed-WiMax). The fixed-
WiMax is based on OFDM-PHY. It has a strong ability to protect against multipath fading and
support multipath and NLOS transmission. The blueprint of the operation theory is derived from
the 802.11a. The 802.16 WG changed some parameters to fit its own demands. The figure 4-1
shows the fundamental structure of IEEE 802.16 bottom layers.
42

Figure 4-1 The Layer Structure of IEEE802.16
The other key technology used in WiMax is multiple-antenna techniques. This technology is
also referred to as MIMO. Through OFDM, WiMax can achieve frequency diversity and by
multiple –antenna techniques, WiMax can have spatial diversity. The term spatial diversity
means using two or more antennas at the receiver and/or transmitter to do transmission. During
the procedure the spatial multiplexing and the STBC is required. The idea of spatial multiplexing,
figure 4-2[50], is to create multiple parallel channels to carry one data stream. The advantages of
MIMO are that it increases system reliability, data rate, system capacity, and coverage, and
decreases the required transmit power. The theory of MIMO was introduced in section 3.4.2.
[50][95] – [101]
43

Whhere
y = H. .X + n
Figuree
4-2 A Spaatial
Multipllexing
MIMMO
System
4.3.1.11.1.
Fouur
transmmission
mode:
SC, SCa, OFDDM
and OOFDMA
In IIEEE
802.16-2004
PHYY-layer,
SCC
(Signal Laayer)
is respponsible
forr
the 10 – 666
GHz band d
and SCCa
is used ffor
the 2 – 11GHz baand.
The coore
of this standard iss
the OFDM M/OFDMAA
modulaation
and ussed
in the 2 – 10 GHz band. Thiss
method haas
many advvantages
annd
has beenn
widely used for maany
wirelesss
technologies.
[50]
4.3.1.11.2.
AMMC
(Adapptive
Mod dulation aand
Codinng)
Wi ith AMC, WWiMax
can support va arious kindss
of modulaation
and foorward
error r correctionn
(FEC) ccoding.
This
method allows
modu ulation scheemes
to be cchanged
forr
each persoon
based onn
channell
conditionss.
AMC is very effecttive
on opttimizing
ovverall
channnel
capacity y in a time-
varyingg
channel. TTherefore
uusers
can bee
provided with the poossible
highhest
data raate
which iss
allowedd
by the ISPP
and link conditions.
The T theory iis
that whenn
the channeel
condition ns are good; ;
then it transmits aas
high dataa
rate as poossible.
Whhen
the cha annel condiitions
are poor,
then itt
transmiits
at a lowwer
data ratee
to avoid eexcessive
ppackets
beco oming lost. Lower dat te rates and d
higher date rates ccan
be achi ieved by ussing
differeent
modulattion,
such aas
QPSK an nd low-ratee
error-coorrection
coodes
for loww
speed, aand
64-QAMM
and lesss
robust errror-correctioon
for highh
speed. [ [50]
In both IEEE 802.16-20006
and IEEEE
802.16ee-2005
PHYY,
the RS- CC (Reed Solomon –
Convoluution
Code) ) is the requuired
codingg
mode andd
block turbo
codes (BTTC),
convol lution turboo
44

codes ( (CTC) and low densityy
parity cheeck
(LDPC) ) codes aree
optional mmodes.
Sincce
the IEEEE
802.16 clause did nnot
set up thhe
bandwiddth
and moddulation
method,
differrent
configuurations
willl
end up with different
speeds. Thus with AMC, the system cann
have the mmaximum
uusage
of thee
channell.
Table 4-2[50]
shows the modulaation
and cooding
suppoorted
in WiMMax.
[50]
4.3.1.11.3.
Chhannel-quality
Meaasurement
The e channel-qquality
meassurement
sccheme
is thee
fundamenntal
of downnlink
and upplink
powerr
control processes aand
modulattion
and code
rate adapptation.
A MMS
is requirred
to send the channell
quality feedback (CCQI)
includding
RSSI ( (Received SSignal
Stren ngth Indicattor)
and SIN NR (Signal-
to-Interrference-pluus-Noise
Raatio)
to BS for f evaluatinng
channel conditions. With this innformation,
BS can: : [50]
Change moodulation
annd/or
coding g rate for thee
transmissiion
Change thee
power leveel
of the asssociated
DLL
or UL trannsmissions.
4.3.1.11.4.
OFFDM
in WWiMax
Table 4-22
Modulatioon
and Codiing
Supportted
in WiMaax
In fixed-WiMa f ax, the FFTT
size is onlly
256. Therre
are 192 ssubcarriers
used for ca arrying data; ;
8 for pilot p subcarrriers
and thhe
rest are guard subccarriers.
Be ecause the FFFT
size is s fixed, thee
subcarrier
intervall
is related to the channnel
bandwwidth.
With larger banndwidth,
thee
subcarrierr
intervall
increases, but the symmbol
time ddecreases.
TThat
means a larger pieece
of fram mes needs too
be alloccated
properrly
to overccome
delay spread. The
table 4-3[ [50] shows the OFDM parameterss
used fo or WiMAX. The OFDMM-PHY
of WiMax has
a wide raange
of guaard
times, th herefore thee
networkk
designerss
can make e fitting traade-offs
bettween
specctral
efficiency
and de elay spreadd
robustnness.
When using a 255
percent guuard
time, iit
can deal with the mmaximum
delay d spread d
45

obustnness
which iis
up to 16µ µs in a 3.5 MMHz
channnel
and 8µs in a 7 MHHz
channel. [50][102] –
[106]
Tablee
4-3 OFDMM
Parameterrs
Used for WiMAX
4.3.1.22.
MAC LLayer
4.3.1.22.1.
Three
sublayers:
CS, , CPS andd
SS
The e MAC layyer
is an innterface
bet tween the hhigher
layerr
and the PPHY.
It also o processess
packetss
for the uppper
layer called MSDDUs
(MACC
Service DData
Units) ) and mapss
them intoo
MPDUss
for transmmitting
in PPHY.The
IIEEE
802.16
standard splits the MAC-layer r into threee
sublayeers,
figure 22-22,
conveergence
subblayer
(CS) , common part sublayyer
(CPS) aand
securityy
sublayeer
(SS). CS is an interfaace
betweenn
MAC-layeer
and higheer
layer prootocol
such as a ATM, IPP
and so on. CPS prrovides
MA AC manageement,
ARQQ
(Automattic
Repeat QQuest)
scheeduling
andd
assembly
of MAC PDUs. SS iis
in chargee
of encryptiion.
[50][1007]
46

4.3.1.2.2. AAS (Advanced Antenna Systems)
Multiantena is a good way to improve system performance. However it includes some
problems such as transmit diversity, beamforming, and spatial multiplexing.. The AAS is a
solution for them. [50][113][114]
Transmit diversity
Transmit diversity requires at least two transmitting antennas and one receiving antenna. For
this type of transmission, WiMax defined STBC scheme, for example the 2x1 antenna system
with Alamouti codes. The advantage of it is the same as with MIMO. The MS or end users will
not have a complex set up and the cost is lower.
Beamforming
Beamforming has great ability to quard against interference and improve the coverage range,
capacity, reliability, and received SINR. The idea is to use multiple antennas to transmit the same
signal in the direction of the receiver. To operate using this method, the signal must be weighted
properly for each antenna and the transmitter has to have accurate knowledge of the channel.
WiMax supports beamforming for both uplink and downlink.
Spatial multiplexing
Spatial multiplexing means using multiple antennas to transmit multiple independent
streams. When both receiver and transmitter have more than one antenna, by performing the
STBC scheme, the streams can be split. The purpose of this method is to improve the data rate or
capacity of the system. The increasing ratio is linear with the number of antennas. For example, a
2x2 MIMO system will double the capacity. If the MS only has one antenna, the spatial
multiplexing is still supported. However, spatial multiplexing only works under good SINR
conditions.
4.3.1.2.3. QoS
QoS (Quality of Service) is a basic function of the WiMax MAC-layer. By using
connection-oriented MAC structure, the QoS control is robust. All the uplink and downlink
connections are controlled by the BS. Before transmission, a BS and a MS set up a unidirectional
logical link called “connection”. This link is between two MAC layers and every connection is
verified by a 16-bit connection identifier (CID). [50]
To ensure the QoS, WiMax defines a scheme named “service flow”. It is a one way flow of
packets that includes a special set of QoS parameters and is verified by a 32-bit service flow
identifier (SFID). These parameters are used to support different kind of QoS of different tasks.
47

There aare
varies of
parameterrs.
[50] The e SFID is isssued
and mmapped
to CCIDs
by the e BS. Theree
are fouur
types of scheduling g services ffor
providinng
the best performannce
of data transfer off
various applicationns.
[50] Tabble
4-4[50][ 108] – [1122]
UGGS
is designned
to suppoort
real-timee
fixed-sizee
packets peeriodic
transsmission
at constant bitt
rate (CBBR),
for exaample
T1.
Thi is scheme iss
designed tto
support rreal-time
unnfixed-size
ppackets
perriodic
transmmission.
Ann
example
is MPEG video. Thiss
service allows
BS to provide unnicast
pollinng
opportun nities for thee
MS to rrequest
banddwidth.
Unsolicitedd
grant servi ices (UGS)
Real-time ppolling
services
(rtPS)
Non-real-timme
polling service (nrttPS)
Table 4-4 Service Floows
in WiMMax
Thi is one suppoorts
delay-ttolerant
dataa
streams wwith
unfixed-size
packetts,
like FTP P. The nrtPSS
and rtPPs
are similar.
The diffference
is tthat
a MS can use coontention-baased
polling g or unicastt
polling opportunitiies
in the upplink
to requuest
bandwiidth
in nrtPSS
service.
48

Best-effort service (BE)
This scheme is used only for service that does not require strict QoS, such as web browsing.
The MS uses merely contention-based polling opportunities to request bandwidth and sends data
whenever channels are available.
4.3.1.2.4. Security
4.3.1.2.4.1. Overview
The security of IEEE 802.16 is called the privacy sublayer at the bottom of the MAC layer.
It is mainly used to provide access control and confidentiality of the data link. The configuration
of the IEEE 802.16 security has five components and will be introduced in the following.
[50][52][115] – [119]
Security Associations (SA)
This component is mainly concerned about connection. IEEE 802.16 has two types of SA;
data SA and authorization SA. Only data SA has a clear definition. The data SA is used to
protect transmit connections between SS (Subscriber Station) and BS (Base Station).
The authorization SA is a state which is shared between two particular SS and BS. The BS
uses authorization SAs to configure data SAs on the SS.[52]
For securing a transmit connection, a SS first uses a “create-connection” request to initiate a
data SA. The standard will let several connection IPs share a SA to support multicast. On
network entry, the standard automatically establishes a SA for the secondary management
channel. Thus, a SS may have two or three SAs, one for the secondary management channel,
others for uplink and downlink connections. Each multicast group requires a SA to share with
group members.
X.509 certificate profile
This is used to identify communication parities and 802.16 does not define its extensions.
This standard defines two types: manufacturer certificates and SS certificates. There are no
certificates of BS. A manufacturer certificate is used to identify the manufacturer of an IEEE
802.16 device. It can be self-signed or issued by a third party. An SS certificate can identify a
particular SS and also its MAC address. The SS certificates are created and signed by
manufacturers.
The BS uses the manufacturer certificate’s public key to confirm the SS certificate and also
verify the device. The SS must take care of the private key corresponding to its public key to
prevent intrusion from attackers.
49

PKM (Privacy and Key Management) authorization
This protocol is used to send an authorization token to an authorized SS. And it contains
three communication steps between SS and BS. Figure 4-3[52] The first two steps are sent by SS
for verifying itself with BS and the third one is used for response from BS to SS.
Privacy and Key Management
Figure 4-3 PKM Authorization Process and Parameters
PKM is used to establish data SAs between SS and BS. This protocol can have two or three
steps of message exchange between SS and BS. Figure 4-4[52] The first step is optional. It
depends on whether that BS requests rekeying or not. The second one, SS uses it to initiate the
protocol and BS reply with the third one.
50

Encryption
Figure 4-4 PKM Protocol Messages Exchange Process and Parameters
The DES-CBC (Data Encryption Standard-Cipher Block Chaining) encryption enciphers a
plaintext MPDU, but not the MPDU GMH or CRC. Figure 4-5[52]
51

4.3.1.2.4.2. Overall Analysis
Figure 4-5 Encryption Frame Structure and Process
Learning from the experience from IEEE 802.11, the IEEE 802.16 working group faces
security threats both in the MAC and PHY levels. 802.11 only has protections in the MAC level
cannot present against attacks from PHY-Level. 802.16 progression has many good functions,
however it also brings with it an increase of threats to users
The initial standard IEEE 802.16-2001 requires an attacker to put real equipment between
SS and BS and also operate at a frequency of 10 to 66 GHz. The IEEE 802.16e adds mobility to
the standard; however it creates a security risk. Now, an attacker’s physical position is not really
constrained and the management messages are much weaker than IEEE 802.11.
With radio transmission, there is a great risk. Anyone who has a proper well located receiver
can intercept the channel. So the designers have to establish a safety mechanism. The other threat
is that anybody who has a correctly configured radio transmitter can access the wireless network.
Through this weakness, an attacker can make up or modify frames from authorized organizations.
Therefore there must be a procedure to protect the transmitting data. Furthermore, the
interference and distance may also give attackers a chance to intrude the system or two systems
which cannot connect to each other directly. Thus, how to protect a system and examine the
received data are also very important to designers.
52

4.3.2. IEEE 802.16e-2005, the newest standard
4.3.2.1. OFDMA-PHY
4.3.2.1.1. Background
OFDMA (Orthogonal Frequency Division Multiple Access) is the main difference of
802.16e from other 802.16 standards. Most of new improvements and design are based on it.
This method is deeply related with FDMA (Frequency Division Multiple Access). By using
FFT/IFFT, FDMA can divide and combine the baseband in an orthogonal way. In OFDMA-PHY,
the subchannels are a minimum frequency resource-unit assigned by a base station. Thus
different subchannels can be allocated to different users as a multiple-access mechanism. The
IEEE TGe introduces scalability to OFDMA which can help provide best performance in a
channel with bandwidth between 1.25MHz to 20MHz. for both fixed and mobile service. Also it
can lower the cost of system. [50][53]
The FFT size in OFDMA-PHY is scalable from 128 to 2048. When the bandwidth increases,
the FFT size is increased too, but the subcarrier interval is fixed as 10.94 kHz. This also keeps
the OFDM symbol duration fixed. The 10.94 kHz interval is the best choice for balancing
between the delay-spread and Doppler spread requirements for operating in fixed and mobile
environments. This interval allows the delay-spread up to 20µs and mobility speed up to 125
kmph in 3.5 GHz band. The FFT size 128, 512, 1024 and 2068 are used when the channel
bandwidth are 1.25, 5, 10 and 20 MHz, respectively. The 256 bits OFDM is included in the
OFDMA-PHY, so the mobile-WiMax is backward compatible with fixed-WiMax, when the FFT
size is 256. [50][53][106][120] – [123]
Table 4-3 is the recommended scalability parameters for system.
4.3.2.1.2. Frame structure
OFDMA supports many different frame sizes to fit the need of various applications and
models. There are three types of OFDMA subcarriers: [53][102][103][124] – [126]
1. Data subcarriers for data transmission.
2. Pilot subcarriers for various estimation and synchronization purposes.
3. Null subcarriers for no transmission at all, used for guard bands and DC carriers.
In different subcarrier allocation modes, the pilot allocation is performed differently. For DL
(Downlink) Partially Used Subchannelization (PUSC) and all UL (Uplink) modes, the set of
subcarriers of data and pilot is first sliced into subchannels, and then the pilot subcarriers are
allocated by each subchannel. For DL Fully Used Subchannelization (FUSC), the pilot
53

subcarriers will be assigned first and then the rest of subcarriers are partitioned into data
subchannels. FUSC has one set for pilot subcarriers, but each subchannel in PUSC has its own
set for pilot subcarriers.
Figure 4-6[53] is the frame structure of OFDMA-TDD. This kind of frame is sliced into DL
and UL two subframes. The DL and UL subframes are separated by Transmit/Receive Gap and
Receive/Transmit Gap (TRG and RTG).The DL subframe starts with FCH (Frame Control
Header) and then a DL-MAP and a UL-MAP. In DL-MAP BS will tell MS which subcarriers are
going to assign for it. The UL-MAP includes which subcarriers that MS can use to transmit on.
Figure 4-6 OFDMA Frame Structure
4.3.2.1.3. Various Subcarrier Allocation Modes
OFDMA supports subchannelization to effectively allocate subchannels for both DL and UL.
In WiMax, each user is allocated blocks of subcarriers, not individual subcarriers. This method
can decrease the complexity of the subcarrier-allocation algorithm and make the mapping
message easier. There are two main types of subcarrier permutations; distributed and
adjacent.[50][53] Generally speaking, the distributed subcarrier permutation has very good
performance in mobile applications and improves frequency diversity and robustness. Adjacent
subcarrier permutation is good at fixed, portable or less mobility surroundings and increases
multiuser diversity.
DL Distributed Subcarrier Permutations: Fully Used Subchannelization (FUSC)
All subchannels and full channel diversity are well utilized in this method by dispensing the
allocated subcarriers to subchannels and a permutation mechanism is used here. During
54

transmiission,
the aadjacent
cellls/sectors
mmay
hit each other by ceertain
possibbility,
becauuse
of usingg
the samme
subcarrieers.
This meechanism
reeuses
subcaarriers
to minimize
thee
probabilityy
of hits. In n
additionn,
fast fadinng
of mobilee
surroundinngs
would llower
the sy ystem performance.
Buut
frequencyy
diversitty
can minimmize
it.
Tabble
4-5[53] is the summmary
of subbcarrier
alloocation
struucture.
In DDL-FUSC
th here are twoo
kinds of
sets of piloot;
variable and fixed ssets.
The fixxed
one is uused
in all OOFDM
symbbols
and thee
variablee
one is divvided
into subsets s useed
in odd annd
even syymbols
alterrnatively.
Itt
makes thee
tradeofff
of channell
estimationn
appropriate
between aassigned
powwer
and freequency
diversity.
In OOFDMA
sppecificationn,
the OFDMMA
DL andd
UL subfraames
must bbegin
with DL D and ULL
mode. IIn
DL PUSCC,
all subchhannels
willl
be sliced aand
assigneed
to three ssegments,
an nd it can be e
allocateed
to sectoors
of the same cell. [53] Thiss
method utilizes u fulll-channel
ddiversity
byy
dispenssing
the alloocated
subcaarriers
to suubchannels.
. [53] A perrmutation
mmechanism
is i also usedd
here too
minimizee
the probaability
of hhits
and uusing
frequuency
diverrsity
to miinimize
thee
performmance
degraadation.
Table 4-5 DL Distribuuted
Subcarrrier
Permuutation
(FUSSC)
DL and ULL
Distributed
Subcarrieer
Permutatiion:
Partiallly
Used Subbchanneliza
ation (PUSC C)
Optional DDL
and ULL
Adjacentt
Subcarrieer
Permutattion:
Advannced
Moduulation
andd
Coding (AMMC)
55

Adj djacent subccarriers
are used u by thiss
method too
form subchhannels.
AMMC
can quiickly
elect a
modulaation
and cooding
combiination
per subchannell,
when it iss
used with fast feedbaack
channel.
The subbchannels
of AMC ccan
use thee
“water-poouring”
typpes
of algorrithms,
and d it can bee
combinned
with an AAAS
optionn.
Tabble
4-6[53] is the summmary
of the AMC subcaarrier
allocaation
parammeters.
4.3.2.22.
MAC LLayer
4.3.2.22.1.
QooS
Table
4-6 UL-DDL
Adjacennt
Subcarrieer
Permutatiion
(optionaal
AMC)
The e functions of the QoSS
of the IEE EE 802.16-22005
includde
the old foour
schemess
and a neww
one schheme,
extennded
real-timme
polling service (errtPS).
This scheme is only defined
in IEEEE
802.16ee-2005
MAAC-layer.
It combines tthe
advantagges
of UGSS
and rtPS. This methood
allocatess
56

the uplink bandwidth periodically for MS and with this feature ertPS can coordinate data services
which the bandwidth requirements change with time. [50][121][127][128]
4.3.2.2.2. Power-saving
How to extend the battery life is a very important issue of mobility. Therefore power
management is a fundamental requirement of a mobile wireless network. The IEEE 802.16e-
2005 defines two modes to operate power saving. [50][129] – [132]
4.3.2.2.2.1. Sleep Mode
This mode is an optional mode of WiMax power management. The MS is defined by two
statuses, sleep window and listen window. The sleep window is defined as when a MS
temporarily disconnects to the BS for a predetermined period of time. The listen window is
following the sleep window, during which the MS reconnects to the BS. The lengths of each
sleep and listen window depend on the power-saving classes and is negotiated between the MS
and BS. When the MS is in sleep window, this period is called unavailability interval. During the
unavailability interval, the MS cannot receive any DL transmission and send any UL
transmission. During the availability interval when the MS is in listen window, the MS can
receive DL transmission and send UL transmission as normal. BS will not send any DL
transmission to MS when it is in sleep window, therefore the MS can turn off one or more
physical components for saving power. The BS buffers the SDUs (Service Data Units) for MS
and transmits them later to the MS during availability interval.
For different services, there are three power-saving classes:
1. Power-saving class type 1
Class type 1 is used for BE or nrtPS connections. In this class, the listen window size is
fixed and followed by a sleep window. Each sleep window size is twice the size of the previous
sleep window, but not bigger than the final sleep window size. The size of the initial sleep
window and the final sleep window are notified to the MS by the BS before the power-saving
class type 1 begins. During the sleep mode, the BS can reset the window size to the initial sleep
window size at any time. For UL allocations, the reset process happens under the request from
the MS. And for DL allocations, it happens when the BS finds out that the number of listen
window is not enough for the traffic.
2. Power-saving class type 2
57

This class is used for UGS or rtPS connections. The sleep windows and listen windows are
all fixed-length and cross each other one by one in order. The BS tells the MS the window size
before entering this power-saving mode.
3. Power-saving class type 3
This mode is used for multicast traffic or MAC management traffic. Different from other
classes, it has only a single sleep window. Before entering this mode the BS decides the window
size and the start time; then notifies the MS. The power-saving operation is inactive, after the
sleep window has passed.
4.3.2.2.2.2. Idle Mode
Idle mode is also an optional scheme of WiMax power management, and it can save more
power than sleep mode. With this scheme, several BS’s are assigned to a paging group and a MS
can move within this area and receive broadcast DL transmission from a BS without switching or
registering to the network. When a MS is in idle mode, it listens to the network periodically for
determining in which paging group it is and running the paging group update. MS also notifies
the network of its appearance while running the paging group update. When a BS needs to
connect with the MS in idle mode, all the BSs in the paging group, where the MS is, have to join
the paging process. Once the MS receives the paging message, it will end the idle mode and start
to connect to the network.
In idle mode, a MS has two statuses;, MS paging-unavailable interval and MS paging-listen
interval. When a MS is in MS paging-unavailable interval, it cannot be paged but can power
down or run other operations not related with connection with BS, such as scanning. In the MS
paging-listen interval, the MS listens to the serving BS for broadcast paging message to see
whether it is paged or not. If it is paged, it ends the idle mode and if not, it goes into next MS
paging-unavailable interval.
4.4. The future of WiMax
The new member of 802.11, 802.11n, is on the way. 3G is also becoming more popular.
Therefore, WiMax definitely has to cooperate with them on a some certain level. WiMax is a
wide range wireless communication; Wi-Fi is short range and 3G is also wide range but with
narrower bandwidth. Figure 4-7[54] Since they are all wireless communication type systems, the
market will be overlapped partially. The services demanded most from end users are e-mail,
sharing files, video and/or audio transmission and etc…. [54]
58

Figure 4-7
Coverage
and Capacity
for Diffferent
Wireeless
Accesss
Technique es
Bas sically, thee
applications
of themm
are different,
althouugh
they hhave
some features in n
commoon.
WiMax is develooped
for MANs; M Wi-Fi
is for LANs andd
3G is tthe
cellularr
commuunication
staandard.
Thuus,
the relaationships
aamong
themm
should bbe
of coope eration, nott
competition.
The sservices
of 33G
are phon ne service aand
limited internet serrvice
in a lo ow mobility y
environnment.
Wi-FFi
providess
broadband d wireless sservice
in a fixed envvironment,
most likelyy
indoorss.
WiMax iis
going to provide a large rangge
broadbannd
wireless service in a fixed orr
mobility y environmment.
They can
cover eaach
other’s ddrawbacks.
[54][133]
In an urban arrea,
IEEE 8802.16
has sseveral
commpetitors
suuch
as DSL, , cable, or ffiber.
Thesee
wired cconnectionss
have highher
speed aand
are moore
stable. MMost
of timme,
they ha ave alreadyy
existed when a buuilding
was built. Evenn
through wwireless
commmunicationn
has been improved a
lot; wirred
communnication
is sstill
more reeliable
and safer. The maximum speed that WiMax W cann
reach iss
about 70 Mbps, but with fiber, it can achieve
at least t 1 Gbps! TTherefore,
users u wouldd
choose wired ratheer
than wirelless.
[58]
Annother
probllem
is the ttopography.
. In a highlly
developeed
city, thesse
tall builddings
wouldd
interfere
with the ttransmissionn
of radio. For high frequency
miicrowaves,
it requires a clear pathh
to reachh
the terminnal;
otherwise
the base station musst
set on a bbuilding
thaat
is higher tthan
others.
On the other hand, , lower-freqquency
micrrowave
usinng
non-linee-of-sight
(NNLOS)
tech hnology still l
has a pr roblem; a signal
is diff ficult to locck
on becauuse
of manyy
reflectionss
off mason nry walls. Inn
59

an urban area, there are still several problems remaining to be solved for wireless communication.
That is the task of WiMax. [58]
In smaller cities and suburban areas, wireless communication has better performance. This is
because the competition between wireless and wired is less and the topography is more favorable.
It is not worth installing fiber or DSL in this kind of area. Population distribution of these areas
is usually scattered, so it will cost more to wire the whole network in this situation. And the
numbers of users may be a problem too, thus wireless could be a better choice. Especially when
lower-frequency microwave with (NLOS) is more suitable. [58]
Wireless communication has the best performance in rural areas. Not only because of the
lack of competition, but also the more friendly geography. It however still has challenges. How
to and where to set up stations are two major problems. Distance and population distribution
must be considered as well. [58]
When moving in a vehicle, mobile-WiMax can support wireless access. Unlike 3G, mobile-
WiMax can provide not only mobility but also BWA. For example, when taking a train for long
distance trip, people can use mobile-WiMax to access the Internet for news, video entertainment,
or online-game to entertain themselves. However, since the mobile-WiMax is still not
commercialized, besides in Korea, the practical operation will continue to be on hold..
60

CHAPTER FIVE
5. Case study
This chapter will discuss and compare three individual cases using Wi-Fi or WiMax to build
up the public wireless network. These cases are located in the cities of Tallahassee, Fl, USA,
Taipei, Taiwan and Seoul, South Korea. The network located at Florida State University in
Tallahassee, Fl, USA uses 802.11b/g to build an indoor and partial outdoor wireless network.
That allows students and faculties to use wireless access in any building. Taipei initiated their
public wireless network project in September 2004. This project is contracted by Q-ware
communications, Inc. The operation was officially started in December 2005. The service area
covers 90% of the population of Taipei City. Installation was officially finished in September
2006 and was named WiFly. South Korea is the first country operating the commercial WiMax
network. It is not the only country that uses the fixed-WiMax technology. They are the only
country that also combines it with mobile-WiMax. This project is developed by the Korean
telecoms industry. The main coverage area is located in its capital, Seoul. The network was
launched in June 2006.
Florida State University located in Tallahassee, Florida is the easiest one to gather data,
because it is nearby. And by interviewing the related staff [147], more precise and detailed
information could be collected. Because the information and business news concerning WiFly
are written in English and Chinese, they are easy to read and collect. However because of the
time factor, only one interview was conducted concerning WiFly. Most of the data was gathered
from the Internet and books. Although it is easy to find the newest information on the Internet, it
require cross validation to ensure its validity. This is the most important issue when doing a case
study of Wifly. WiBro is the most difficult one of data collection and analysis in case studies. it
is because of language barrier. The WiBro official website has an English version, but not for all
documents. Most of them are written in Korean. Thus the information is limited and makes the
analysis more difficult.
The following sections will introduce these three cases and their implementation. Each
section contains analysis and small conclusion. The last section is the overall analysis.
5.1. FSU wireless network
5.1.1. Introduction
The wireless network solution of FSU (Florida State University) is called FSUWIN. WIN
means Wireless Integrated Network. This network is based on the existed wired network and
provides a more flexible and convenient internet service on campus. With FSUWIN, students
61

and faculties can use their NB’s to access the Internet everywhere on campus. This wireless
network follows the IEEE 802.11 standard and covers major buildings and most public areas.
Figure 5-1[70]. The department which is in charge of FSUWIN is OTC (Office of
Telecommunications and Networking). It is also responsible for maintenance and network
security. The first wireless network at FSU was started in 1999, and at that time it was only an
experimental network. There was no plan for building a campus-wide network. In 2002, OTC
got the funding they needed to install the wireless network at FSU. The goal is to provide an
indoor/outdoor wireless public network for all students and faculty. [147]
5.1.2. Implementation
Figure 5-1 The Coverage of FSU Wireless Network
The reason why FSU used WLAN to extend the campus network instead of wired LANs is
because it is cheaper and more flexible. The implementation was started from upgrading the
existing wired network. The construction and installation were conducted in two parts. First part
was Building-to-Building Connectivity (Bridges), and second part was Intra-Building
Connectivity (AP). [70] Table 5-1 shows the basic information of FSUWIN.
Part I contains three phases. In phase I, the goal was to install wireless network equipment in
6 buildings and support 89 users. The operators took 4 buildings and created two domains in two
connectivity points of the FSU network. After creating these two domains, the network could
simply be enlarged by adding additional buildings into each domain. The operators also
62

increased bandwidth, fixed connectivity issues, and hid antennas through upgrading in this phase.
The total cost was within $6,000 but if using fiber, it would cost at least $10,000. [70]
In phase II, the operators tracked the outside campus usage and wanted to install wireless
network to these small groups or departments. They located the outside campus connections. The
goal was to renovate these networks in the FSU extended campus. After evaluating these
connections, the operators found out that they could establish connections to these places
wirelessly and retrieved many modem lines. Eventually, the operators removed 37 dial-up
connections in 5 buildings and then they had more dial-up resources for other users. These
buildings used hubs to connect each PC and then used wireless bridges/gateway to connect back
to main campus network. In the middle, there is no wired network; it is totally wireless. [70]
In this last phase, operators added 8 additional buildings into the FSU wireless network. The
problems of these buildings were that they were either too far away from campus (1.5 miles
away) or too expensive to install fiber for each user (spanned city street). By applying the
wireless solution, the operators spent around 15,000 dollars without recurring costs or permits.
[70]
The Building-to-Building Connections covered 19 buildings with 207 users and 22 bridges.
(Document in 09/2006) [70]
Part II contained two phases and mainly focused on the inner connections of a building. In
phase I, the operators estimate the areas on the campus where the WLAN was highly needed.
These places included three libraries and Student Union. The Student Union is a place where
vendors are and students and employees hand-out together. [70]
Phase II was to help the departments which requested an intra-building network to install
and setup the FSUWIN network. The process included implementation, integration, optimization
and installation. They would make sure the departments did not have any problems when using
the WLAN. For achieving maximum efficiency, the operators not only installed and maintained
the network, but also evaluated future extensions for the departments. The installation process is
documented for future improvement. The departments which have FSUWIN service are the
College of Law, Registrar’s Office, College of Business, School of Social-Work, and
Mathematics. (Document in 09/2006)[70]
The APs and switches used by FSUWIN are produced by many different companies, such as
Vivato Networks, Xirrus and Foundry Networks. The technology details are shown in figure 5-
6[145], figure 5-7[146] And figure 5-8[71]; table 5-2[145], table 5-3[146] and table 5-4[71].
Comparing the Vivato solution to regular AP, it is easy to find that Vivato has longer coverage
and could support more users. In the survey “Vivato Switch Evaluation”[70], there are five
scenarios had been defined: Fisher, Landis, Shores, Sliger and Stadium. This survey shows that
only 1 or 2 pieces of Vivato equipment are needed to cover an area. In the scenario one, Fisher
Lecture Hall takes 6 regular APs, three at each side, to cover the whole area, but the Vivato
63

solution needs only one. Figure 5-2[70]. In scenario two, Landis Green needs 3 regular APs, but
just one Vivato switch is enough for this area. Figure 5-3[70]. In scenario three, Shores Library
total needs five regular APs to cover the whole floors. There are two in the basements, one in the
first floor and two in the second floor. In this case Vivato solution needs two switches to cover
this area, one in the basement and the other on second floor. Figure 5-4[70]. Scenario four is not
available in the survey. The last scenario is Stadium. In this case it takes at least nine regular APs
to cover the area and the complex is also high. For Vivato solution, it simply needs only one in
the indoor place where there was already power. The Vivato switches are mainly used in the
outdoor scenario, and for indoor scenarios, the other types of APs, Xirrus and Foundry Networks,
are used.
For ensure the quality of signal strength and maximum capacity, each AP is directly
connected to the backbone network; and no more than 20 users for a single AP. If there is a high
usage in a certain area, the operators would install more APs to share the throughput. The critical
locations of FSUWIN installation were libraries, Student Union and other common public places,
because FSUWIN is a public campus network. [147]
Figure 5-2 Fisher Lecture Hall
64

Figure 5-3 Landis Green
Figure 5-4 Shores Library
65

Figure 5-5 Stadium
Table 5-1 The Basic Information of FSUWIN
Terms Parameters
Standard IEEE 802.11 a/b/g
Official Initial date 2002
Coverage
66
Outdoor 70 ~ 75%
Indoor 10%
Maximum Users per AP 20 (Design Issue)
Average User per Month 2500 ~ 3000
AP model Vivato, Xirrus, Foundry Networks
Data Rate 1 ~ 26 Mbps (actually speed)
Network Type Direct to Backbone network

Table 5-2 Xirrus XS-3700 AP Technology Data
802.11a/b/g Radios 4
802.11a Radios 4
Total Number of Radios 8
Number of Integrated Switch Ports 8
Uplink Ethernet Ports 2 Gigabit
Maximum Wi-Fi Bandwidth 432 Mbps
Integrated Wi-Fi Threat Sensor Yes
Maximum Number of Users per Radio 64
Maximum Number of Users per Array 512
Number of Voice Calls per Array 84
Number of Video Streams per Array 21
Figure 5-6 Xirrus XS-3700 AP
67

Table 5-3 Foundry Networks IP250 Technology Data
AP And Network Features • Fragmentation Threshold Setting
• Multi-Country Support • Idle Timeout (set at 30 minutes)
• Mounting Bracket for Wall, Ceiling, and
Tabletop
68
• Layer 2 Roaming-802.11f IAPP
• Integrated AP Locking Mechanism Wireless Data Encryption
• LEDs For Status, Link, Radio a, Radio
b/g
• RC4 64-bit/128-bit/152-bit Wired
Equivalent Privacy (WEP)
• Auto-sensing 10/100BASE-T PoE Port • Temporal Key Integrity Protocol
(TKIP)
• Power Over Ethernet (PoE) Support-
802.3af
• Advanced Encryption Standard (AES)
• 802.11a, 802.11b, 802.11g Standards • Pairwise Master Key Security
Association (PMKSA)
• 802.11a Turbo Mode • WPA2 mixed-mode AES/TKIP
• Simultaneous Dual Radio Support 2.4-
GHz and 5-GHz
• Integrated Antenna Support For
802.11a/b/g
• External Antenna Support for
802.11a/b/g
Wireless Quality Of Service
• 802.1p tag mapping to priority queue
• Source/Destination MAC-address
mapping to priority queue
• Plenum Rated UL 2043 AP Housing • Ethertype mapping to priority queue
• Automatic Channel Assignment • Spectralink voice prioritization
• Adjustable Power Levels • AP Load Balancing
• AP Load Balancing Radio Support
• Maximum Speed Setting • Simultaneous Dual Radio Support
2.4GHz and 5GHz
• Broadcast/Multicast Rate Limiting • 802.11g protected mode
• VLAN Support-64 VLANs • Automatic channel select

• Automatic Tx power selection
• Maximum station data rate
• Multicast data rate
• Antenna type
• Antenna diversity
• Fragmentation length
Table 5-3 Cont.
Figure 5-7 Foundry Networks IP250
69

Table 5-4 Vivato 2.4 GHz Indoor & Outdoor Wi-Fi Switch Technology Data
70

Table 5-4 Cont.
71

Table 5-4 Cont.
Figure 5-8 Vivato 2.4 GHz Indoor & Outdoor Wi-Fi Switches
72

5.1.3. Analysis
The FSU wireless network is a very convenient system. It allows all students and faculty to
have more freedom to access the Internet without a strict location limitation. The connection is
robust and the signal is stable. However there are still complaints and technical problems that
exist. Mr. Clint Ringgold, Network Administrator of OTC, said that the primary complaint is
about the coverage of the indoor area. At the beginning of the project, the FSUWIN installation
was focused on the outdoors, especially for public areas, and had very limited budget. Therefore,
if it is not a public area, the installation would be only under the request of the departments.
Hence sometimes the coverage is only a half of the building or very small area of the building.
That is why users may get a signal on one side of the building, but no signal on the other side of
the building. [147]
Concerning this technical problem, Mr. Clint Ringgold mentioned two future goals. One is
handoff and the other is the central controller. Mr. Phillip M. Callahan, Assistant Director of
OTC, said that installing a central controller is their future direction and it should be the
university issue. It is very expensive equipment and the OTC is still waiting for funding.
Meanwhile the other issue is to shift the current technology to fit the controller. The function of
this controller is to connect to the APs around the campus and monitor the status of each AP, so
that the OTC can control the network efficiently. A single controller can connect at least 500
APs. Concerning the other goal, Mr. Clint Ringgold indicated that the current FSUWIN does not
support roaming, so users cannot move between two hotspots and maintain a connection. This
can be done either by switching to another technology or growing the network. Mr. Ringold
described it as a design issue.
The network security is guarded by the FSUWIN login system. Figure 5-9[70]. Every user
needs to register a FSUID in order to login to the system to establish a connection. To maintain
network reliability, OTC has the right to control the traffic load and RF devices are used for
avoiding congestion and interference to wireless signals. The terrain of the FSU campus is
favorable to signal transmission, because it does not have high buildings and the density of
buildings is low. Therefore multipath fading is not serious to the signal.
Mr. Phillip M. Callahan said that OTC faces several difficulties while installing the network
concerning policy and technology issues. Addressing policy, he mentioned ownership and
funding. The OTC has skill and management duty, but does not always own the equipment. For
example, if a department asks the OTC to install FSUWIN for them and they buy the equipment
themselves, then the problem is who is responsible for the cost of maintenance, upgrade and
replacement in the future. They need FSU to set a policy for this issue. For technical difficulties,
Mr. Clint Ringgold indicated that most of the time there is no data-wires in the location where
they want to install an AP, so they need to wire it by themselves or change the planned location.
Users complain about the speed and service quality, but it depends on the radio interference,
such as distance from the AP, microwave and cell-phone. There is another technical problem that
73

Mr. Phillip M. Callahan mentioned. He said that sometimes people buy their own devices and
just plug them in without reporting them to the OTC. They can cause interference and security
problems. He said it may be cheaper to buy an AP in local store, but this would cause security
vulnerability in the end.
5.1.4. Conclusion
Figure 5-9 FSUWIN Login System
FSU campus is a relatively small area, so it is suitable for Wi-Fi. The network structure is
also designed very well. It is a successful wireless network model. The next step of FSUWIN is
to install a central controller, upgrade the network for roaming and extend coverage for more
indoor environments. So far, the OTC does not have any plans to upgrade the system to IEEE
802.11n or IEEE 802.16, said Mr. Phillip M. Callahan. FSUWIN does not have many serious
problems. The technical problems can be solved by new technologies and the policy issues are
dependent on FSU. Beside these issues, FSUWIN is a stable and convenient wireless public
network. In the future, if a small town, a village or other smaller areas want to upgrade its existed
wired network to wireless public network, FSU is a good example to follow.
5.2. WiFly in Taipei
5.2.1. Introduction
WiFly is part of the Mobile Taiwan Applications Promotion Project. This project started in
2004 and its goal is “to bring out communication industries growth and stronger of national
competitiveness based on complete broadband network infrastructure.” [74] WiFly is based on
Wi-Fi standard (IEEE 802.11 a/b/g). The WiFly has officially operated for one and a half years
74

since the January 2006. The population coverage is more than 90%, but the geographic coverage
is only about 50%. The total number of APs are about 4200.
5.2.2. Implementation
The WiFly infrastructure installation was split in three stages. The first stage was to cover
the 30 MRT (Mass Rapid Transit) stations and the surrounding areas, including the underground
shopping streets. This stage was finished in May 2005. The second stage included 42 main city
arteries, shopping districts, coffee shops, and the rest of MRT stations and so on. There were
about 2000 APs that were installed in this stage. In the third stage, there were 9 city hospitals, 53
libraries, 12 Taipei administrative buildings and 600 7-11s (chained convenient stores) included.
The final stage was finished in July 2006. More than 4200 APs were used, and up to 90% of the
population was covered. This was a brand new world record. [72]
The WiFly uses Nortel Wireless Mesh Network as its fundamental model. Two components,
Wireless Gateway 7250 and Wireless Access Point 7220, were used for this model. In this
network, the connection between APs is 802.11a and the connection between AP and end users
is 802.11b/g. Since there is no need to wire every AP in the network, the cost of installing wired
network from gateway to AP and AP to AP can be eliminated. [72]
The Nortel Wireless Mesh Network is a solution of installing the outdoor and indoor Wi-Fi
network. It is scalable and secure. An ISP can use it to provide wireless internet service and
companies can use it to build inner private networks. The network contains three components; a
wireless access point, wireless a gateway and a wireless mesh management platform. Figure 5-
10[75], Figure 5-11[75], Table 5-5[75]
There are two models of APs, Wireless AP 7220 and Wireless AP 7215. The WAP 7220 is
an outdoor and indoor-type AP and the WAP 7215 is an indoor-type AP. Figure 5-12[75]. The
WAP 7220s can be connected together to cooperate for improving system performance. WAP
7215 only works in indoor locations. It can connect to either wired or wireless networks. WAP
7220 and WAP 7215 also can cooperate together to form the wireless mesh network. The
wireless gateway has two models as well; Wireless Gateway 7250 and Wireless Gateway 7240.
The WG 7250 can support 10/100 Ethernet interface and 120 WAPs. The WG 7240 also has
10/100 Ethernet interface but only supports 10 WAPs. The Wireless Mesh Management System
provides a communication interface for Nortel’s wired and wireless network products. [75]
75

Figure 5-10 Wireless Mesh Network Structure I
Figure 5-11 Wireless Mesh Network Structure II
76

Table 5-5 Parameters of WLAN and Mesh Network
Figure 5-12 Wireless Access Point 7220
The advantage of the mesh network is that all APs can share the connections among the
network. Therefore the reliability and stability of the network can be improved. If any AP in the
network is malfunctioning, the transmission route is not going to fail. Other APs will form an
alternative path to keep the network functional. The other advantage is that for places that wired
network is difficult to install or cannot be installed; this type of network is a nice alternative
solution. [75]
77

In the AP operation system, Nortel developed a critical scheme called Nortel’s Adaptive
Mesh Management Protocol. This protocol can simplify the deployments and optimize the
overall performance of the mesh network. There are several important functions in this protocol:
auto-discover the neighbor APs, auto-configuration and system synchronization, radio resource
management, smart antenna management, dynamic mesh routing, and fast fault recovery. With
these technologies, the Nortel Wireless Mesh Network can solve many technical problems such
as interference, security, system scalability and reliability, QoS, simplifying installation and
lower the cost. [75] Table 5-6[75] is the features of Nortel Wireless Mesh Network.
While dealing with interference, Nortel uses three schemes, Nortel’s Adaptive Mesh
Management Protocol, smart antenna mechanism, and dual radio design. The dual radio design
uses different spectrums for transmission and reception to avoid self-interference. Nortel’s
Adaptive Mesh Management Protocol can sense the status of nearby channels to achieve the
maximum usage of channels. With the smart antenna mechanism, data is transmitted in a
beamform and directional way, so the data streams do not affect or be affected by other beams.
[75]
In the security field, because the wireless network is easier to be attacked by hackers than
wired network, to enhance this defect, Nortel’s mesh network adopts WEP/WAP/WAP2 and
IPSec (IP Security Protocol). IPSec is derived from VPN (Virtual Private Network) technology.
It uses a firewall to filter the incoming data stream before entering the wired network. For
extending the network capacity, the mesh network allows the network designers to add new
WAPs into the network at any locations in the covered area. This is the scalability of the Nortel
Wireless Mesh Network. With the Nortel’s Adaptive Mesh Management Protocol, a new WAP
can auto-discover the surrounding WAPs and establish the new optimized transmission path.
Similarly, when an AP or more APs are malfunctioning, the Nortel’s Adaptive Mesh
Management Protocol can re-route a substitute path to keep the network functional. [75]
Nortel’s Wireless Mesh Network solution can be integrated with WiMax BS. With the
indoor/outdoor APs and the mesh network features, this solution gives network designers a lot of
freedom to build up a low-cost and network that is also fairly simple. [75]
78

Table 5-6 Features of Nortel Wireless Mesh Network
79

Figure 5-13 Nortel Wireless Mesh Network Solution Example [75]
The following section is the data of AP and gateway. [73]
Wireless Access Point 7220
Technical Specifications
Wireless AP 7220 Access Link 802.11b/g (2.4 GHz) Radio System
Center frequency
• 2417 MHz to 2457 MHz (i.e., North America)
Data rate: 54 Mbps max
• Supports 1, 2, 5.5, 11 Mbps (IEEE 802.11b)
• Supports 6, 9, 12, 18, 24, 36, 48 and 54 Mbps (IEEE 802.11g)
• IEEE 802.11b/g standard rates
Access antenna options
• Co-linear whip, 5 dBi nominal antenna, SMA connectors
• PIFA integrated antenna, 0 dBi nominal SMA connectors
Radiated EIRP
• +26 dBm typical
Receive Sensitivity 802.11b (11Mbps)
• -95 dBm typical @ 11 Mbps
• -96 dBm typical @ 5.5 Mbps
• -98 dBm typical @ 2 Mbps
80

• -101 dBm typical @ 1 Mbps
Receive Sensitivity 802.11g (54 Mbps)
• -80 dBm typical @ 54 Mbps
• -82 dBm typical @ 48 Mbps
• -86 dBm typical @ 36 Mbps
• -90 dBm typical @ 24 Mbps
• -92 dBm typical @ 18 Mbps
• -95 dBm typical @ 12 Mbps
• -95 dBm typical @ 9 Mbps
• -96 dBm typical @ 6 Mbps
Wireless AP 7220 Transit Link 802.11a (5 GHz) radio system
Center frequency
• 5740 MHz to 5840 MHz
Data rate: 54 Mbps max
• Supports 6, 9, 12, 18, 24, 36, 48 and 54 Mbps
• IEEE 802.11a standard rates
Antenna system gain from radio module card inside the unit
• 8.4 dBi nominal
Radiated EIRP
• +28 dBm typical @ 54 Mbps
• +30 dBm typical @ 48 Mbps
• +32 dBm typical @ 6-36 Mbps
Receive Sensitivity (

• Wired network interface: Auto sensing 10/100BaseT Ethernet, 1.5kV surge
protection per IEC60950
• Power input nominal: 100V - 240V AC (45Hz – 65Hz)
Power consumption
• Operating: Indoor or outdoor > 0°C = 8W typical Outdoor < 0°C = 8W – 14W (-
40°C)
• Startup: Indoor or outdoor > 0°C = 8W typical Outdoor < 0°C = 24W (short
duration) 8W– 14W (- 40°C)
Dimensions (without mounting brackets or antennas)
• 265mm (10.5 inches) tall x 200mm (8 inches) diameter
• Weight: 2.4 kg (5.3 lbs)
• Color: Gray
Optional accessories
• Mounting brackets (right-angle or straight horizontal attachment)
• 5m, CAT5 Ethernet indoor/outdoor rated cable for network access point (NAP)
operation
• Street light photo-electric control power tap 'luminaire' 120/208/240 V
• 13dBi, 18dBi and 23dBi TL external antennae
Wireless Gateway 7250
Technical Specifications
Standard:
• 128 MB memory
• Processor - 850 MHz
• PCI expansion slot - one (available for additional Ethernet interface or hardware
accelerator card)
• LAN/WAN interfaces
Two 10/100 BaseT Ethernet
Management/console (DB9)
Optional:
• One additional 10/100 BaseT Ethernet interface (provides additional LAN/WAN
connectivity, if required by network design)
• 128 MB RAM upgrade
• Hardware encryption accelerator card
Physical specifications:
• Length: 21 in. (53.3 cm)
• Width: 17.25 in. (43.8 cm)
• Height: 3.5 in. (8.9 cm)
• Weight: 10.0 lb. (4.5 kg)
82

Operating environment specifications:
• Electrical: 90-264 VAC, 2.0 @ 90 VAC, 47-63 Hz
• Temperature: 32°-104° F (0°-40° C)
• Relative humidity: 10-90% non-condensing
5.2.3. Analysis
The WiFly has been in operation for about 21 months. As of the end of August 2007, there
were one hundred and fifty thousand registered customers with an average of six thousand users
per month. The population coverage is 96% (two million six hundred thousand people) and the
number of APs are 4600. [72] This is the biggest wireless network construction in the world.
However, there were many complaints since the first day of service. There are several reasons.
First, the signal is unstable with too many dead spots. Second, coverage is concentrated in
metropolitan areas; the geographic coverage is only 50%. Third, the signal path is too
unpredictable. This is because of the multipath fading and signal reflection. Forth, the price is too
high and lacks service applications. These problems can be classified as two parts, mechanical
and marketing. The mechanical part includes signal stabilization, AP coverage and security; the
marketing part contains service applications and pricing rate. [76] – [78][85]
Compared with the population coverage, the numbers of user is very low. Table 5-7. This
project spent a total of approximately thirty million dollars, but ended up facing a low usage
situation. Taiwan has a strong manufacturing background and in the 1980s and 1990s, MIT
(Made in Taiwan) became a well known mark around the world. With this ability, the
infrastructure installation is not a difficult job at all. WiFly is a first city-wide wireless network
project; therefore since there is no precedent to learn from, WiFly has to learn through trial and
error. [76] – [78][85]
Date
Terms
Table 5-7 The Numbers of Subscribers
Registered Users Active Users Industry Customer
2006/6 45,000 20,000 N/A
2007/1 110,000 35,000 70
2007/8 150,000 6,000 (monthly) N/A
In the mechanical problem part, the signal is the first problem. It is what most customers
complain about. This problem is caused by many factors, such as the number of users, weather,
environment, AP locations, and RF interference. This is a common difficulty of all wireless
83

communications. Taipei is a busy city with many office buildings. It is a “concrete jungle”,
especially in the metropolitan area. This kind of area is very unfavorable to signal transmission
and it will cause serious multipath fading. Thus, the end users may scan the signal, but cannot
establish a connection, or even have no signal at all. The other problem is AP. It includes
numbers of user and locations. Most of APs are located outdoor, such as wire poles and street
lights. Because APs are exposed outside and Taiwan is hot and humid, the failure rate will be
high. Moreover these kinds of AP locations also have big security issues. There are 4600 APs in
Taipei, management and maintenance is a big challenge. And since the AP installation is focus
on population coverage, most suburb residents do not have WiFly signal.
The Q-ware does not limit the numbers of user on an AP. Therefore it may cause congestion
and channel overlapping problems. For channel allocation and reallocation, Linda Yeh, the
Account Manager in Sales & Customer Service Dep. of Q-ware Systems & Services Corp. [148],
said the company has a control platform to manage each AP’s operation channel. In a high
density area, if there is congestion or channel overlapping the network engineers can use this
platform to switch the operation channel for each AP to release the situation. However, the
platform cannot solve the problem completely. In most high usage areas of WiFly, after
switching channels, the problem still exists. She said this is because there are only three channels
that can be used in one area. It is Wi-Fi’s inherent limitation. [148]
The maximum data rate for each user was 512 kbps for both Uplink and Downlink. In
January 2007, Q-ware upgraded to 1Mbps for Downlink and 512 kbps for Uplink. This speed is
not a shearing speed, which means it will not be changed even if the users increased. [148] To
avoid heavy traffic, Linda indicated that they have a flow control scheme to monitor the traffic
flow for APs. The detail of flow control scheme is trade secret, thus she cannot provide more
information for it. Channel overlapping and congestion are two major problems of signal
transmission. There are several methods to solve the congestion issue, such as, hop-by-hop
congestion control and multihop congestion control. [149][150] The main idea of these methods
is to send a congestion feedback packet to slow down the source speed to release the congestion.
The congestion control has been studied for years. Here is some related researche. [151] – [153]
For improving signal stability, end users can install bridge or high power wireless network
cards. These two methods can solve most signal instability. Q-ware also has to install more APs
or use high power APs in high usage areas. Since WiMax licenses have been issued in Taiwan. It
can also be a solution for signal stability and extending geographical coverage. About security
vulnerability, Q-ware said that the wireless connection must be authorized before established and
the user account needs two identifications to apply. However there is no one hundred percent
security scheme. Users still have to protect their account information and PC from spy-programs.
The responsibility is upon both WISP and the users.
The Nortel Wireless Mesh Network solution is a suitable model for WiFly. However, no
matter how perfect the model is, Taipei still has its intrinsic limitations, such as high office
84

uilding density, high population density, humid and hot weather, and unfavorable wired
network infrastructure. Because the Nortel Wireless Mesh Network solution adopts mesh
structure (APs and Ethernet communicate through Gateways), it decreases the difficulty while
installing APs. Nevertheless, the APs’ power supply is still a big issue. And even through APs
are not necessary to connect to Ethernet, the Gateways have to. One Gateway can support 120
APs, so 4600 APs need at least 39 Gateways. Considering the connection status, usage and AP
locations, it is impossible to use just 39 Gateways to handle the whole network and it will cause
serious congestion problem. Therefore, where to install the Gateways and how to wire the
Gateways are other important issues. According to Linda Yeh, so far the company does not have
an efficient way to solve channel overlapping and congestion problems completely. To install a
booster to increase the signal power can be a good solution for these problems, but the National
Communications Commission (NCC) has strict rules for signal power. Therefore, Q-ware does
not have plans to install it. These problems are still pending. [148]
The marketing problem is another big issue waiting to be solved. When WiFly first came out,
it guarantees to provide ubiquitous connection to every citizen. However it was plagued with
serious mechanical problems and that is not the only reason for low numbers of users. The WiFly
did not meet the needs of end users.
Before WiFly, Wi-Fi had been available in stores for years, such as McDonald’s and some
coffee shops. This company was called Yaw Jenq Technology and the service was called “Easy-
Up”. At that time the project was cooperated with Intel. It was the first WISP in Taiwan, but
ended up in.bankruptcy in May 2005. Easy-Up brought new Internet access to people. This
project officially began in May 2003. At that time the wireless interface is NB with built-in
centrino platform. With Easy-Up, access internet in McDonald’s or other chain stores was slowly
becoming a trend. Currently, sitting in a Starbucks, having a cup of coffee and browsing the
Internet has become a very common activity.
With regards to the service policy, Linda Yeh said that the indoor APs are used for mobile
devices users and the outdoor APs are mainly for fixed users. The indoor APs are most installed
in coffee shops, chain restaurants and other public areas, such as airports. In these places, the
signal is more stable and the connection quality is better than outdoor. The outdoor APs are used
to provide service to fixed users such as home and industries. These users can use bridges or
antennas to receive WiFly signal. However because of many external factors, such as RF
interference, weather and transmission path, the signal quality is not as good as the indoor APs.
[148] In WiFly’s official website, there is a search engine for WiFly hotspot, but they do not
provide AP location search. If a customer wants to know if are there any APs nearby, they need
call Q-ware directly. [148]
Wireless Internet access is definitely a business point. WiFly also has the ability to occupy a
high market share. But the wrong market positioning and unfriendly pricing rate makes the usage
much lower than the prediction. WiFly can never replace the ADSL at home. Therefore it is an
85

auxiliary of extending the ADSL to end users in short range. Unless there is a unique application
that only WiFly can do; otherwise keep seeking new service to increase users is still no help.
ADSL and WiFly are like roads and bridges, but if WISP tries to use bridges to replace roads;
then there is no future for WiFly. Taipei’s city government and Q-ware now are trying to use
new VoIP service (Taipei easy call) and WiFly cube to attract more users. [76] – [78][85]
However the fundamental problem is why WiFly. There are other choices for indoor wireless
internet service, such as Hinet-WLAN and 3G wireless.
It is like selling a game station without games and the price is also way too high. For
temporary users, $3.20 for one day access is too expensive; not to mention carrying the NB and
looking for signal. WiFly’s unique feature is its ubiquitous connection, but if the feature cannot
be used stably and conveniently; then it is still useless.
5.2.4. Conclusion
WiFly tries to provide make people’s lives more convenient. However, it still has
fundamental problems to be conquered. How to provide end users more stable connection and
higher speed should be the current mission of WiFly. And the customers have to find out
whether they need WiFly or not. Taiwanese network market is already saturated and has many
competitors, so if WiFly wants to take the market share it will be not easy. Since Wi-Fi has some
limitations and the original design is for home use; thus it is difficult to use as the last mile of the
network and the city-wide coverage. Since the mother company of WiFly, FAREASTONE, has
gotten the operation license of WiMax; the next step of WiFly should be the WiMax
infrastructure installation. By adopting WiMax, WiFly may be able to have much better
performance and show its real value.
5.3. Wibro in South Korea
5.3.1. Introduction
WiBro (Wireless Broadband Access Service) is a WBA technology. It is a standard extended
from 802.16-2004 and 802.16 2005 and uses many techniques the same with them. Figure 5-
14[79]. It has better coverage and stronger mobility than WLAN and higher data rate than 3G.
However, 3G has better coverage than WiBro and WLAN has higher data rate than 3G.
Therefore WiBro’s position is just in the middle. It can fix their weaknesses, but cannot replace
them. This standard was developed by KT (Korean Telecoms Industry) and standardized by TTA
(Telecommunications Technology Association) later on.
The manufacturers who are contracted to produce WiBro devices are Samsung, LG,
POSDATA and so on. For extending transmission range and decreasing dead spot, the TDD
86

epeater r is developping
and it will have two
versionn,
optical reppeater
and RF repeaterr.
Figure 5-
15[79] shows the nnetwork
struucture
of WWiBro.
The related
workks
: [134][1335]
5.3.2.
History
Figure 5-14
The Relat tionship Beetween
WiMMax
and WiBBro
Figuure
5-15 Thhe
Network Structure off
WiBro
Thi is project wwas
initiateed
by manu ufacturers ( (Samsung aand
LG) aand
telecom mmunicationn
industriies
(KT andd
SKT). It sstarted
fromm
2003 to 20005.
They tootal
investeed
approximmately
thirtyy
six milllion
dollars in this projject.
The first
stage staandardizatioon
was commpleted
by TTA T in latee
87

2004. It was a very big delay since WiMax was well developing at that time. November 2004
was the critical timing for WiBro. Intel started to get involved in WiBro’s development. It
cooperated with LG and KT to help develop WiBro’s equipments and ensure that WiBro can be
compatible with WiMax. In April 2005, Samsung was elected as a member of WiMax Forum
board, so the integration of WiMax and WiBro was speeded up. Therefore, WiBro became a
worldwide standard, little by little. U.S. and Japan both had plans to use WiBro to build their
WiMax network. In January 2005, three companies got the operation license, KT, HTI (Hanaro
Telecom, Inc.), and SKT. And KT and SKT were selected to run the WiBro business. The
system installation was initiated in early 2006. The project has three stages. First stage is to
finish installation in 20 major cities at the end of 2006. Second is to finish 18 medium scale
cities installation in 2007. And finally finish the 46 remote areas’ installation in 2008. [76] –
[78][84][85]
5.3.3. Implementation
The operation band of WiBro is between 2.3 GHz to 2.4 GHz. This band is divided into 9
channels. These channels are not overlapped but adjacent and every 3 channels have one guard
band, figure 5-16[79] – [82]. WiBro PHY-layer is based on OFDMA for against multipath fading
and interference. WiMax supports both TDD and FDD scheme, but WiBro only supports TDD.
This is for having biggest spectrum usage. In modulation field, WiBro supports QPSK, 16QAM
and 64QAM. And for coding, WiBro uses CTC and other optional method, such as BTC, RS-CC
and FEC. Figure 5-17[79] – [82] shows the goal and features of WiBro.
Figure 5-16 The Operation Band
88

Figure 5-17 WiBro Features
The data rate of Wibro is asymmetric, for a RAS (Radio Access Station) the maximum
downlink speed is 18 Mbps and uplink speed is 6 Mbps; for a PSS (Portable Subscriber Station)
the maximum downlink speed is 3 Mbps and uplink speed is 1 Mbps. Under mobile conditions,
WiBro can only support under 60 kmph movement. It is lower than 3G which is support at least
120 kmph, but much better than Wi-Fi. The coverage of a RAS is defined in three levels, Pico,
Micro and Macro. Pico can cover a radius of100 meters area. Coverage of Micro is 400 meters
and Macro is 100 meters. This design would make installation of RAS more flexible. [79] – [82]
WiBro also has QoS. It contains three schemes, rtPS, nrtPS and BS; not including UGS. For
saving power, WiBro provides sleep mode for end users to extend the battery life. In order to
improve the system performance, WiBro introduces scheduling algorithm for transmission
service and AMC for coding and modulation. WiBro also supports ARQ/H-ARQ (Hybrid
Automatic Request) as well as WiMax. This scheme can effectively re-send the packet, if it is
damaged by interference or channel fading. The handoff break time between two RASs is less
than 150 ms, it is a very good performance comparing with other wireless algorithm, such as
PHS. [79] – [82]
There are still other optional technologies used in WiBro, for example MIMO, AAS and
SDCA(Space Time Coding Adoption). The purpose is to extend the coverage and against
interference. Table 5-8[79] – [82] contains the PHY specification of WiBro. Figure 5-18[79] –
[82] shows the MAC-layer structure.
89

- Transformation of
external network data
into MAC SDUs;
- Payload header suppression
- System Access
- Bandwidth Allocation
- Connection set-up
- Connection maintenance
-QoS
- Authentication
- Secure key exchange
-Encryption
Figure 5-18 MAC Layer Model
Samsung is the major manufacturer producing the ACRs and RASs. In June 2007, Samsung
won the WiMAX World Europe 2007 Award by U-RAS Premium Base Station in System
Design. Figure 5-19[83] is the technology data and the picture for U-RAS Premium Base Station.
Figure 5-20[83] is the information for ACRs. Table 5-8 is the comparison of WiBro and WiMax.
90

Figure 5-19 U-RAS Premium
Figure 5-20 ACR Basic Data
91

Terms
Table 5-8 The Comparison of WiBro and WiMax.
Standards
Operation Band
Bandwidth
WiMax
(IEEE 802.16-2005)
2 – 11 GHz for fixed
10 – 66 GHz for mobile
1.75 MHz, 3.5 MHz, 7 MHz,
14 MHz, 1.25 MHz, 5 MHz,
10 MHz, 15 MHz, 8.75 MHz
92
WiBro
2.3 – 2.4 GHz
10 MHz
Multiplexing Burst TDM/TDMA/OFDMA OFDMA
Duplexing TDD and FDD TDD
Modulation QPSK, 16-QAM, 64-QAM
QPSK, 16-QAM, 64-
QAM
Channel Coding CC, CTC, RS, LDPC CTC
Data Rate 1 – 75 Mbps
QoS mode
5.3.4. Analysis
UGS, rtPS, nrtPS, BS;
ARQ/H-ARQ
UL: 6.1 Mbps
DL: 18.4 Mbps
rtPS, nrtPS, BS;
ARQ/H-ARQ
Power Saving Sleep Mode, Idle Mode Sleep Mode
Coverage Maximum 10 km Urban 1 km
Mobility 120 km/hr 60 km/hr
Other Techs AAS, AMC, MIMO AAS, AMC, MIMO
WiBro has been in use for one year. However the number of users is not as high as predicted.
At the end of June 2007, there were twenty thousand registered users and the goal is two hundred
thousand by the end of 2007. If WiBro wants to reach this goal, it has to increase by 170,000
users in half year! According to a recent study from IDC Korea, the subscribers will reach
130,000 at the end of 2007, 600,000 in 2008, 1.4 million in 2009 and 3.9 million in 2011. If there
are various supplemental applications and devices available in the market, the number will grow
to 800,000 in 2008 and 5 million in 2011. This prediction may be too optimistic compared to the
current situation. [84][85]

In KT’s recent report, 60% of subscribers are between 30 and 40 and 20% are college
students in their 20s. They also find that these customers are satisfied with service and price but
upset about the prices and availability of devices. KT has to pay subsidization to laptops, WiBrophone
and USB-modem buyers about one hundred to two hundred and sixty dollars. However,
after subsidizing, the NB (model # NT-Q35) still costs $1750 to $2400, not including accessories.
Until June 2007, the WiBro-related products include two pc-cards, two cell-phones, two mobile-
PCs and one notebook. The choices are very limited. [76] – [78][84][85]
The coverage of WiBro so far is still restricted in Seoul and certain nearby areas. The speed
is fast but the signal is not stable. Although the mobility is available in a bus or subway, the
operation environment is not friendly to use a mobile-PC or NB, not to mention the connection is
not stable. People need a seat to operate them. Since 3G also can provide mobile internet service
and is more reliable, WiBro really faces a very difficult situation in South Korea. Mobility is the
most important feature of WiBro. If subscribers cannot feel the advantages, it would be difficult
to increase numbers. Therefore in technical field, WiBro has to not only improve signal quality
and coverage, but also the mobility. The device problem, sooner or later, will be solved. It is just
a matter of time. When mechanism becomes mature, the price will goes down and products will
be more varied.
In marketing field, KT WiBro proposed six applications: Wonder-Eye (Personal Multimedia
service, Push-Pull on Demand), Wonder-Media (Video Streaming), Wonder-Media (MMS),
Wonder-Phone (Video-Phone), Wonder-Net (Wireless Internet Service), Wonder-Tour (3-D tour
of APEC). These applications contain multimedia and internet service. WiBro is an interface
between users and network. And it can be found out that these applications are overlapped with
3G and Wi-Fi. Thus WiBro has to provide better system performance; otherwise it is difficult to
take marketing share from other two standards. After all, they are not kill applications. For
WiBro’s long term development, KT and SKT should put more effort on technical problems.
5.3.5. Conclusion
KT, SKT and Samsung still believe in the future of WiBro. With the extension of coverage
and new available devices, the subscribers are going to increase. But prices and service contents
are the real problems waiting to be solved. If WiBro is not the essential requirement and there are
alternative choices available and better for internet access, WiBro is difficult to increase the
market share. Therefore considering the occasions which WiBro is used, mobility and stable
signal are the only way for it to keep going.
93

5.4. Overall analysis
Table 5-9 is the basic information of FSUWIN, WiFly and WiBro. FSU and Taipei use the
same standard; Taipei and Seoul belong to the same area. In technical field, Taipei should use
WiMax not Wi-Fi, because it is not designed for metropolitan area. Even if WiFly upgrades to
the IEEE 802.11n in the future, the overall performance is not going to improve too much. It is
like carrying seven people in car with four seats; it can work, but not very well. So the best way
is to replace the system to WiMax or combine with WiMax. In Seoul, WiBro’s major problem is
mobility and it is also the selling point. Using WiMax to cover a city is a suitable way. It is what
WiMax designed for. Even though WiBro’s overall performance is not as good as expected so
far, the technical issues are solvable by new devices and technologies. As for cost and service
problems, it is the same road and bridge issues with WiFly. Both WiFly and WiBro are WISPs
and the best way for them to survive in future Internet market is to integrate with ISPs.
FSUWIN is the most successful case within these three cases. In the future, after installing
the central controller, OTC can easily monitor the network status and provide more reliable
service. FSUWIN reached its goal and does a good job. One more factor of FSUWIN’s success
is no financial burden. It is not a commercial network and is supported mainly by tuition. Thus it
does not have to worry about users and application issues. This feature makes its operation
simpler than other two systems. In short, it is a good solution for smaller and local area.
So far WiFly and WiBro are still seeking their marketing positioning. 3G, Wi-Fi, WiMax
and wired internet service where the balance point for these technologies is an important issue to
industries, manufactures and researchers. Table 5-10 is the basic information for internet access
methods. The service providers and WISP should not only focus on providing content but also
have to think about the demand of wireless network users.
Based on the patterns of people’s behaviors accessing the Internet, these technologies should
be coexisted. Figure 5-21 is an example for using these technologies. When a man wants to go to
a state park and has the Internet access all the way, he has to bring his phone and NB. At home
he can use Wi-Fi to collect the information of the state park. During transportation, he can access
the Internet by mobile-WiMax. And then, when he arrives the state park, he can still check his email
by fixed-WiMax service. If he wants to take a rest, he can stay in the state park service
center where Wi-Fi is available. Moreover, all the way, he can make a video phone call
anywhere at any time. It is one possibility for future development.
WiFly and WiBro were just commercialized. They have to learn from mistakes, because
they are the pioneers of public wireless network. The technical issues they have right now are all
solvable. WiBro can showed its real capacity only after the mobility is truly functional and
devices price is acceptable. WiFly can adopt WiBro’s technologies to improve its signal and
coverage issues. The wireless city story has not finished yet, and WiFly and WiBro still have a
chance for success.
94

Figure 5-21 An Example Application of 3G, Wi-Fi and WiMax
5.5. Other developing wireless network
In U.S., Sprint Nextel has announced to cooperate with Samsung, Motorola and Intel will
build a national-wide 4G broadband mobile network. They are going to invest $1 billion in 2007
and between $1.5 billion and $2 billion in 2008. In China, they are developing their own 4G
standard, McWill. It is not an international standard and has a worse performance than WiMax.
The Chinese government set many restrictions on WiMax and wants to develop their own
standard, so in short term, WiMax is not going to develop in China. In Europe, England started
to install fixed-WiMax since 2005. There are two companies in the projects, Telebria and
Community Internet (CI). Japan issued three WiMax licenses at the end of 2006. They are KDDI,
NTT DoCoMo and Yozan. Taiwan issued six WiMax licenses and split into two area, North
district and South district. The test service will be launched in 2008.
95

Service Name
Parameters
Table 5-9 The Basic Data of FSUWIN, WiFly and WiBro
FSUWIN WiFly WiBro
Standard IEEE 802.11 b/g IEEE 802.11 a/b/g IEEE 802.16e
Location
FSU, Tallahassee,
FL, USA
96
Taipei
Taiwan
Seoul
South Korea
Operator FSU, OTC Q-ware KT, SKT, Samsung
Launch date 2003 ~ 2004 January 2006 July 2006
Band 2.4 GHz ISM 2.4 GHz ISM 2.3 ~ 2.4 GHz
Data rate ~ 25 Mbp UL/DL:512 kbps
Coverage
Indoor: 600 m
Outdoor: 7200 m
UL:6.1 Mbps
DL:18.4 Mbps
N/A Urban ~ 1 km
Overall Coverage 75% of campus 90% of population N/A
Mobility X X 60 km/hr
Hand-Off Ability X X Low
Subscribers
All students and
faculty
150,000 (6/2007) 24,000(7/2007)
Users per device 100 N/A N/A
AP model
Operation
environment
Applications
Vivato, Xirrus,
Foundry
Networks
Nortel AP 7220 Samsung RAS
Campus Metropolitan area Metropolitan area
Internet access
FSU campus life
WiFly cube
Taipei easy call
N/A
(VoIP will not be
supported)

Name
Parameters
Standard
Table 5-10 Current Internet Access Technologies
3G Wi-Fi WiMax
WCDMA
CDMA2000
IEEE 802.11
a/b/g/n
Supporter ITU Wi-Fi Alliance
Band
2100MHz ~
2200MHz
2.4 GHz
Coverage 1 ~ 5 km 100m ~1000m
Hand-Off
Ability
Data rate 384 kbps
97
IEEE 802.16
d/e
WiMax
Forum
2 – 11 GHz
for fixed
10 – 66 GHz
for mobile
Maximum
10 ~ 50 km
Wired
Internet
Ethernet
N/A
N/A
Largest
Highest Low Low N/A
54 Mbps (a/g)
200Mbps (n)
70 Mbps
100 Mbps ~
1Gbps
Mobility 100 km/hr < 20 km/hr 120 km/hr N/A
Devices Cell-phone
Current
application
FOMA (Japan),
JUNE (Korea),
i-mode (Taiwan)
Cell-phone/
PC/NB
WiFly (Taipei,
Taiwan)
PC/NB PC/NB
WiBro
(Seoul,
Korea)
ADSL/Cable

CHAPTER SIX
6. Conclusion
Wireless communications have been available for more than ten years. Today, 3G, Wi-Fi
and WiMax are the most popular and widely discussed standards. Telecommunication industries
hope that 3G can bring them new fortune, because 3G has improved enough to support e-mail
and small data download. Therefore telecommunication industries want to occupy more of the
market share of wireless Internet access by using 3G technology. But compared to Wi-Fi and
WiMax, it is still too slow. Moreover, with the new coming Wi-Fi standard, IEEE 802.11n,
WLAN becomes more powerful than before and can overcome many past limitations, such as
coverage, stability and speed. It is slowly catching up with the capacities of wired networks. A
Wired network’s advantage is its reliability, but its biggest disadvantage is path design. In a city,
to wire a line to a house or a building is easy; however in remote or rural areas it is a huge issue.
Thus WiMax is emerging as a possible solution.
Parameters
Table 6-1 3G, Wi-Fi and WiMax Overall Comparison
Standard
3G Wi-Fi WiMax
Coverage (a single tower) 2 (< 1 km) 3 1 (1 ~ 5 km)
Data Rate 3 (< 300 kbps) 1 (~ 25Mbps) 2
Throughput 3 2 1
Mobility and hand-off 1 3 (WiFly) 2 (WiBro)
1: Very good, 2: Good, 3: Bad
Table 6-1 is a comprehensive result of Table 5-11 and 5-12. 3G, Wi-Fi and WiMax. They
have individual and unique fundamental technologies, but their capacities are partially
overlapped. 3G can be a way to access the Internet and Wi-Fi and WiMax can provide VoIP
service as an alternative for the traditional phone-call. However in Table 6-1, it can be found that
for Internet service, 3G is too slow for real-time service, such as downloading larger files or
watching online-TV. For phone-call service, VoIP’s quality is not as good as 3G; it is because of
the design issue. 3G is telecommunication technology and Wi-Fi and WiMax are Internet
technologies. They were designed for different purposes. Even though these technologies are
overlapped in the application field, it is impossible for them to replace each other at this point.
The overlap can be treated simply as a backup. It is better to let a cell-phone just be a cell-phone.
98

WiFly used Wi-Fi to cover 60% of the city including all metropolitan areas. It takes 4200
APs to do it. If it is replaced by WiMax, it will not take that much. And for FSU campus, if
WiMax is applied, just one or two base stations are enough to cover the whole campus. However,
two towers are not enough to take care of the daily usage. Moreover, it is always difficult to
receive a signal from the outside in a concrete building. Therefore it needs a bridge or a gateway
to direct a signal into a building. Wi-Fi may have low coverage, but it can be fixed by using
more APs in a hotspot. The advantage is that it can not only extend the coverage but also reduce
the flow rate for each AP.
To build a city-wide wireless network is going to be a trend and it is feasible, but if a
network only uses Wi-Fi or WiMax, it would suffer cost, coverage, signal and mobility issues.
The best way would be for them to be used in combination with each other. So far there is no
single technology can feed all different needs. In local area Wi-Fi has strong capability and
WiMax is designed as the extension of ADSL or cable. The combination of these two standards
can form a most efficient wireless network. Therefore the future of the wireless technologies
should be created with the cooperation and integration of these technologies.
There is a new standard IEEE 802.11u is based on this idea. It tries to make Wi-Fi interwork
with other different types of networks. [154] The IEEE 802.11u allows devices to interwork with
external networks. For this purpose, interworking refers to MAC layer enhancements. It allows
the higher layer functionality to provide the overall end to end solution. Instead of telling it what
to do, the IEEE 802.11u only helps upper layers to establish an end to end connection with
external networks. It provides a “virtual point of presence” for many different networks via a
single AP. IEEE 802.11u assists the advertising and connection to remote service beyond the DS
and provides information to the STA about the external network prior to association. In fact, the
IEEE 802.11u is an amendment to the IEEE 802.11 standard. The final approval of IEEE
802.11u is expected to be September 2009. [154] the Figure 6-1 shows the possible
implementation of the future network.
99

Figure 6-1 Integration of WiMax and Wi-Fi
100

BIBLIOGRAPHY
[01]. IEEE 802.11 official website (http://www.ieee802.org/11/)
[02]. Vaughan-Nichols, S.J, "Will the New Wi-Fi Fly?", Computer, Volume 39 , Issue 10,
page(s): 16 - 18, Oct. 2006
[03]. Reinwand, Cole C.; "Municipal Broadband - The Evolution of Next Generation Wireless
Networks", Radio and Wireless Symposium, 2007 IEEE, Pages: 273 - 276, Jan. 2007
[04]. IEEE Std 802.11-1997 (http://standards.ieee.org/getieee802/802.11.html)
[05]. IEEE Std 802.11-1999 (http://standards.ieee.org/getieee802/802.11.html)
[06]. IEEE 802.11b-1999 (http://standards.ieee.org/getieee802/802.11.html)
[07]. IEEE 802.11a-1999 (http://standards.ieee.org/getieee802/802.11.html)
[08]. Kapp, S.; "802.11a. More bandwidth without the wires", Internet Computing IEEE,
Volume 6 , Issue 4, page(s): 75 - 79, July-Aug. 2002
[09]. Doefexi, A.; Armour, S.; Beng-Sin Lee; Nix, A.; Bull, D.; "An evaluation of the
performance of IEEE 802.11a and 802.11g wireless local area networks in a corporate
office environment", Communications, 2003. ICC '03. IEEE International Conference on,
Volume 2, page(s): 1196 - 1200, May 2003
[10]. IEEE 802.11g-2003 (http://standards.ieee.org/getieee802/802.11.html)
[11]. Clincy, V.; Sitaram, A.; Odaibo, D.; Sogarwal, G,; "A Real-Time Study of 802.11b and
802.11g", Systems and Networks Communication, 2006. ICSNC '06. International
Conference on, page(s): 69 - 69, Oct. 2006
[12]. Intel Corporation (http://www.intel.com/)
[13]. Sunghyun Choi; del Prado Pavon, J.; "802.11g CP: a solution for IEEE 802.11g and
802.11b inter-working", Vehicular Technology Conference, 2003. VTC 2003-Spring.
The 57th IEEE Semiannual, Volume 1, page(s): 609 - 694, April 2003
[14]. Wang, S.-C.; Chen, Y.-M.; Tsern-Huei Lee; Helmy, A; "Performance evaluations for
hybrid IEEE 802.11b and 802.11g wireless networks", Performance, Computing, and
Communications Conference, 2005. IPCCC 2005. 24th IEEE International, page(s): 111 -
118, April 2005
[15]. Mahasukhon, P.; Hempel, M.; Ci, S.; Sharif, H.; “Comparison of Throughput
Performance for the IEEE 802.11a and 802.11g Networks”, AINA, pp. 792-799, 21st
International Conference on Advanced Networking and Applications (AINA '07), 2007
[16]. Wei-Min S. Studio, Book, "Networking Essentials", 2006, In Chinese.
[17]. Gast S. M., Book, “802.11 Wireless Networks: The Definitive Guide”, Second Edition,
2005
[18]. Heusse, M.; Rousseau, F.; Berger-Sabbatel, G.; Duda, A.; "Performance anomaly of
802.11b", INFOCOM 2003. Twenty-Second Annual Joint Conference of the IEEE
Computer and Communications Societies. IEEE, Volume 2, page(s): 836- 843, April
2003
[19]. Paruchuri, R.C.; Agrawal, P.; "Interference Study of 802.11b Networks for Proactive
Performance Management", Network Operations and Management Symposium, 2006.
NOMS 2006. 10th IEEE/IFIP, 2006
[20]. Vassis, D.; Kormentzas, G.; Rouskas, A.; Maglogiannis, I.; "The IEEE 802.11g standard
for high data rate WLANs", Network, IEEE, Volume 19, Issue 3, June 2005
[21]. 802.11 PHY Layers
101

(http://searchmobilecomputing.techtarget.com/searchMobileComputing/downloads/CWA
P_ch8.pdf)
[22]. Crow, B.P.; Widjaja, I.; Kim, L.G.; Sakai, P.T.; "IEEE 802.11 Wireless Local Area
Networks", Communications Magazine, IEEE, Volume 35, Issue 9, Sept. 1997
[23]. Qi, Y.; Li, H.; Hara, S.; Kohno, R.; "Clear Channel Assessment (CCA) with multiplexed
preamble symbols for impulse Ultra-wideband (UWB) communications", Ultra-
Wideband, The 2006 IEEE 2006 International Conference on, Sept. 2006
[24]. Vermeer, V.; "Wireless LANs; why IEEE 802.11 DSSS?", WESCON/97. Conference
Proceedings, Nov. 1997
[25]. Spasojevic, Z.; Burns, J.; "Performance comparison of frequency flopping and direct
sequence spread spectrum systems in the 2.4 GHz range", Personal, Indoor and Mobile
Radio Communications, 2000. PIMRC 2000. The 11th IEEE International Symposium on,
Volume 1, Sept. 2000
[26]. Wiegandt, D.A.; Zhiqiang Wu; Nassar, C.R.; "High-performance, high-throughput IEEE
802.11 DSSS WLAN via carrier-interferometry chip-shaping", Broadband
Communications for the Internet Era Symposium digest, 2001 IEEE Emerging
Technologies Symposium on, Sept. 2001
[27]. Barman, K.; Malipatil, A.V.; "ICI equalizer in a CCK based DSSS communication
system", TENCON 2003. Conference on Convergent Technologies for Asia-Pacific
Region, Volume 4, Oct. 2003
[28]. Chang-Joo Kim; Hyuck-Jae Lee; Hwang-Soo Lee; "Adaptive acquisition of PN
sequences for DSSS communications", Communications, IEEE Transactions on, Volume
46 , Issue 8, Aug. 1998
[29]. Roshan, Pejman., Book, “802.11 Wireless LAN fundamentals”, 2004
[30]. Singh, G.; Alphones, A.; "OFDM modulation study for a radio-over-fiber system for
wireless LAN (IEEE 802.11a)", Information, Communications and Signal Processing,
2003 and the Fourth Pacific Rim Conference on Multimedia. Proceedings of the 2003
Joint Conference of the Fourth International Conference on, Volume 3, Dec. 2003
[31]. Shenghao Yang; Yuping Zhao; "Channel estimation method for 802.11a WLAN with
multiple-antenna", Communications, 2004 and the 5th International Symposium on
Multi-Dimensional Mobile Communications Proceedings. The 2004 Joint Conference of
the 10th Asia-Pacific Conference on, Volume 1, 29 Aug.-1 Sept. 2004
[32]. Wiegandt, D.A.; Nassar, C.R.; "High-performance 802.11a wireless LAN via carrierinterferometry
orthogonal frequency division multiplexing at 5 GHz", Global
Telecommunications Conference, 2001. GLOBECOM '01. IEEE, Volume 6, 25-29 Nov.
2001
[33]. Hongwei Yang; "A road to future broadband wireless access: MIMO-OFDM-Based air
interface", Communications Magazine, IEEE, Volume 43, Issue 1, Jan. 2005
[34]. Xianbin Wang; Wu, Y.; Chouinard, J.-Y.; Hsiao-Chun Wu; "On the design and
performance analysis of multisymbol encapsulated OFDM systems", Vehicular
Technology, IEEE Transactions on, Volume 55, Issue 3, May 2006
[35]. Gerakoulis, D.; Salmi, P.; "An interference suppressing OFDM system for ultra wide
bandwidth radio channels", Ultra Wideband Systems and Technologies, 2002. Digest of
Papers. 2002 IEEE Conference on, 21-23 May 2002
[36]. Zou, W.Y.; Yiyan Wu; "COFDM: an overview", Broadcasting, IEEE Transactions on,
Volume 41, Issue 1, March 1995
102

[37]. Sun, Y.; "Bandwidth-efficient wireless OFDM", Selected Areas in Communications,
IEEE Journal on, Volume 19, Issue 11, Nov. 2001
[38]. Maharatna, K.; Grass, E.; Jagdhold, U.; "A 64-point Fourier transform chip for highspeed
wireless LAN application using OFDM", Solid-State Circuits, IEEE Journal of,
Volume 39, Issue 3, March 2004
[39]. Ye Li; Chuang, J.C.; Sollenberger, N.R.; "Transmitter diversity for OFDM systems and
its impact on high-rate data wireless networks", Selected Areas in Communications, IEEE
Journal on, Volume 17, Issue 7, July 1999
[40]. Zhengdao Wang; Giannakis, G.B.; "Complex-field coding for OFDM over fading
wireless channels", Information Theory, IEEE Transactions on, Volume 49, Issue 3,
March 2003
[41]. Agrawal, D.; Tarokh, V.; Naguib, A.; Seshadri, N.; "Space-time coded OFDM for high
data-rate wireless communication over wideband channels", Vehicular Technology
Conference, 1998. VTC 98. 48th IEEE, Volume 3, 18-21 May 1998
[42]. Zhiqiang Liu; Yan Xin; Giannakis, G.B.; "Space-time-frequency coded OFDM over
frequency-selective fading channels", Signal Processing, IEEE Transactions on [see also
Acoustics, Speech, and Signal Processing, IEEE Transactions on], Volume 50, Issue 10,
Oct. 2002
[43]. IEEE 802.11h-2003 (http://standards.ieee.org/getieee802/802.11.html)
[44]. IEEE 802.11j-2004 (http://standards.ieee.org/getieee802/802.11.html)
[45]. IEEE 802.16 (http://www.ieee802.org/16/)
[46]. IEEE 802.16a (http://www.ieee802.org/16/)
[47]. IEEE 802.16c (http://www.ieee802.org/16/)
[48]. IEEE 802.16-2004 (http://www.ieee802.org/16/)
[49]. IEEE 802.16e-2005 (http://www.ieee802.org/16/)
[50]. Andrews. J. G., Ghosh A., Muhamed R., Book, “Fundamentals of WiMax”, 2007
[51]. Liu H., Li G., Book “OFDM-Based Broadband Wireless Networks ”, 2005
[52]. Johnston D., Walker, J., “Overview of IEEE 802.16 security”, Security & Privacy
Magazine, IEEE, Vol. 02, Issue 3, May-June 2004
[53]. Yaghoobi H., "Scalable OFDMA Physical Layer in IEEE 802.16 WirelessMAN.", Intel
Technology Journal. Vol. 8, issue 3, 2004
[54]. Liangshan Ma, Dongyan Jia, “The Competition and Cooperation of WiMAX, WLAN and
3G”, Mobile Technology, Applications and Systems, 2005 2nd International Conference
on 15-17 Nov. 2005 Page(s):1 – 5
[55]. Tanenbaum A. S., Book “Computer Network”, 4 th edition, 2002
[56]. Borisov N., Goldberg I., Wagner D., "Intercepting Mobile Communications: The
Insecurity of 802.11" , http://www.isaac.cs.berkeley.edu/isaac/wep-faq.html
[57]. Borisov N., Goldberg I., Wagner D., "Intercepting mobile communications: the insecurity
of 802.11." MOBICOM 2001, pp180–189.
[58]. Sweeney D., Book “WiMax operator's manual : building 802.16 wireless networks ”,
2006
[59]. WiMAX Forum - WiMAX Home < http://www.wimaxforum.org/home/>
[60]. IEEE 802.16 http://www.ieee802.org/16/
[61]. Xiao Y., “IEEE 802.11n: enhancements for higher throughput in wireless LANs”,
Wireless Communications, IEEE [see also IEEE Personal Communications], Volume
12, Issue 6 ,Dec. 2005
103

[62]. Lorincz, J. Begusic, D., “Physical layer analysis of emerging IEEE 802.11n WLAN
standard”, Advanced Communication Technology, 2006. ICACT 2006. The 8th
International Conference, Volume 1, 20-22 Feb. 2006
[63]. Abraham, S. Meylan, A. Nanda, S., “802.11n MAC design and system performance”,
Communications, 2005. ICC 2005. 2005 IEEE International Conference on, Volume 5,
16-20 May 2005
[64]. Cai, L.X. Xinhua Ling Xuemin Shen Mark, J.W. Hua Long, “Capacity Analysis of
Enhanced MAC in IEEE 802.11n”, Communications and Networking in China, 2006.
ChinaCom '06. First International Conference on, 25-27 Oct. 2006
[65]. 簡永懿(Yung Yih Jian) , “IEEE 802.11n 技術提案摘之研究-PHY Layer Frame
Format”, May 3 2005, Information and Communications Research Labs, Industrial
Technology Research Institute, in Chinese.
[66]. 郭俊均(Chun Chun Guo), “IEEE 802.11n 合併提案之研究-目前合併提案中 PHY 的
內容與分析 (IEEE 802.11n merge study-PHY study and analysis)”, December 15 2005,
Information and Communications Research Labs, Industrial Technology Research
Institute, in Chinese.
[67]. IEEE 802.3 (http://www.ieee802.org/3/)
[68]. ITU (http://www.itu.int/net/home/index.aspx
[69]. Jhih-Jiang J., Book, “3 rd Generation Mobile Telecommunication Technology”, 2006, In
Chinese.
[70]. FSU - OTC (http://otc.fsu.edu/Networking/NetMenu.html)
[71]. Vivato Networks Inc. (http://www.vivato.net/)
[72]. WiFly (http://www.wifly.com.tw/Wifly6/tw)
[73]. Nortel Networks (http://www.nortel.com/)
[74]. M-Taiwan (http://www.mtaiwan.org.tw/mp.asp?mp=3)
[75]. Nortel Networks, “Solution Brief Wireless Mesh Network”,
(http://media.govtech.net/Digital_Communities/Nortel/WirelessMesh_SolutionBrief.pdf)
[76]. CNET, Business News, In Chinese, (http://taiwan.cnet.com/)
[77]. DIGITALWALL, Business News, In Chinese, (http://www.digitalwall.com/)
[78]. DIGITIMES, Business News, In Chinese, (http://www.digitimes.com.tw/)
[79]. WiBro (http://www.wibro.or.kr/)
[80]. Soon-Young Y., “Introduction to Wibro Technology”, Telecom R&D Center Samsung
Electronics Co, Ltd., September 2004,
(http://www.itu.int/ITU-D/imt-2000/documents/Busan/Session3_Yoon.pdf)
[81]. Balaji S. H., Manoj C., Taewon K, “South Korea Plans for ‘WiBro’”, Samsung
Electronics Co., December 2004
(http://www.cewit.org.in/docms/ws3/Wimaxwsbalajih.pdf)
[82]. MIC, “Wireless Internet Access : WiBro”, Korea, July 2005
(http://www.telecomnetworks.ru/datadocs/doc_350tu.pdf)
[83]. Samsung Electronics Co. (http://www.samsung.com/us/)
[84]. WiMax.com, Business News (http://www.wimax.com/)
[85]. AsiaMedia, Business News (http://www.asiamedia.ucla.edu/)
[86]. Wikipedia (http://www.wikipedia.org/)
[87]. Sung Ki P.; Pyeong-Jung S.; Geun Sik B.; “Joint optimization of radio repeater location
and linking in WLL systems with 2.3 GHz frequency band”, Communications, 1999. ICC
'99. 1999 IEEE International Conference on, Volume 3, page(s): 1617 – 1621, June 1999
104

[88]. Mineno T.; Babji T.,"Issues and challenges of implementing a wireless local loop (WLL)
based telephone access network", Personal Wireless Communications, 1997 IEEE
International Conference on, page(s): 366 - 370, Dec. 1997
[89]. Noerpel A.R.; Yi-Bing L., "Wireless local loop: architecture, technologies and services",
Personal Communications, IEEE [see also IEEE Wireless Communications], Volume 5,
Issue 3, page(s): 74 - 80, June 1998
[90]. Haiying Z.;Boucher L.M.; Wachira M., "Technology comparisons in wireless local loop",
Personal, Indoor and Mobile Radio Communications, 2001 12th IEEE International
Symposium on, Volume 1, page(s): A-46 - A-50, Oct 2001
[91]. Seidel S.Y., "Radio propagation and planning at 28 GHz for local multipoint distribution
service (LMDS)", Antennas and Propagation Society International Symposium, 1998.
IEEE, Volume 2, page(s): 622 - 625, June 1998
[92]. Schellenberg J., "Designing the digital MMDS network for maximum benefit:
technological considerations in service, coverage and subscriber issues", Broadcasting
Convention, 1997. IBS 97., International (Conf. Publ. 447), page(s): LP1 - LP5, Sept.
1997
[93]. Ghosh A.; Wolter D.R.; Andrews J.G.; Chen R., "Broadband wireless access with
WiMax/802.16: current performance benchmarks and future potential", Communications
Magazine, IEEE, Volume 43, Issue 2 page(s): 129- 136, Feb. 2005
[94]. Eklund C.; Marks R.B.; Stanwood K.L.; Wang, S., "IEEE standard 802.16: a technical
overview of theWirelessMANTM air interface for broadband wirelessaccess",
Communications Magazine, IEEE, Volume 40, Issue 6, page(s): 98-107, Jun 2002
[95]. Dong-Hoon C.; Jung-Hoon S. ;Min-Su K.; Ki-Jun H., "Performance analysis of the IEEE
802.16 wireless metropolitan area network", Distributed Frameworks for Multimedia
Applications, 2005. DFMA '05. First International Conference on, page(s): 130- 136, Feb.
2005
[96]. Carl E., "The IEEE 802.16 Standard for Broadband Wireless Access"
(http://www2.ing.unipi.it/ew2002/proceedings/pmp002.pdf)
[97]. Schwingenschlogl C.; Dastis V.; Mogre P.S.; Hollick M.; Steinmetz R., "Performance
Analysis of the Real-time Capabilities of Coordinated Centralized Scheduling in 802.16
Mesh Mode", Vehicular Technology Conference, 2006. VTC 2006-Spring. IEEE 63rd,
Volume 3, page(s): 1241 - 1245, 2006
[98]. Nuaymi L.; Noun Z., "Simple Capacity Estimations in WIMAX/802.16 System",
Personal, Indoor and Mobile Radio Communications, 2006 IEEE 17th International
Symposium on, page(s): 1 - 5, Sept. 2006
[99]. Juan L.; Haggman S. G., "Performance of IEEE802.16-2004 Based System in Jamming
Environment and its Improvement with Link Adaptation", Personal, Indoor and Mobile
Radio Communications, 2006 IEEE 17th International Symposium on, page(s): 1 - 5,
Sept. 2006
[100]. Christian H., "Analysis and performance evaluation of the OFDM-based metropolitan
area network IEEE 802.16", European Wireless 2004 Conference, Volume 49, Issue 3,
Pages 341-363, 19 October 2005
[101]. Bo H.; Weijia J.; Lidong L., "Performance evaluation of scheduling in IEEE 802.16
based wireless mesh networks", Computer Communications, Volume 30, Issue 4, Pages
782-792, 26 February 2007
105

[102]. Koffman I.; Roman V., "Broadband wireless access solutions based on OFDM access in
IEEE802.16", Communications Magazine, IEEE, Volume 40, Issue 4, page(s): 96-103,
Apr 2002
[103]. Baxley R.J.; Kleider J.E.; Zhou G.T., "Pilot Design for IEEE 802.16 OFDM and
OFDMA", Acoustics, Speech and Signal Processing, 2007. ICASSP 2007. IEEE
International Conference on, Volume 2, page(s): II-321 - II-324, April 2007
[104]. Yanxin Y.; Tomisawa M.; Yi G.; Yong Liang G.; Gang W.; Choi Look L., "Joint timing
and frequency synchronization for IEEE 802.16 OFDM systems", Mobile WiMAX
Symposium, 2007. IEEE, page(s): 17 - 21, March 2007
[105]. Al-Gharabally M.; Das P., "Performance analysis of OFDM in frequency selective timevariant
channels with application to IEEE 802.16 broadband wireless access", Volume 1,
page(s): 351 - 356, Oct. 2005
[106]. Jisang Y.; Kanghee K.; Kiseon K., "Capacity evaluation of the OFDMA-CDMA ranging
subsystem in IEEE 802.16-2004", Wireless And Mobile Computing, Networking And
Communications, 2005. (WiMob'2005), IEEE International Conference on, Volume 1,
Page(s):217 - 223, 2005
[107]. de Moraes L.F.M.; Maciel P.D.Jr.; "Analysis and evaluation of a new MAC protocol for
broadband wireless access", Wireless Networks, Communications and Mobile Computing,
2005 International Conference on, Volume 1, page(s): 107- 112, June 2005
[108]. GuoSong C.; Deng W.; Shunliang M., "A QoS architecture for the MAC protocol of
IEEE 802.16 BWA system", Communications, Circuits and Systems and West Sino
Expositions, IEEE 2002 International Conference on, Volume 1, Page(s):435 - 439, 29
June-1 July 2002
[109]. Haitang W.; Bing H.; Agrawal, D.P., "Admission Control and Bandwidth Allocation
above Packet Level for IEEE 802.16 Wireless MAN", Parallel and Distributed Systems,
2006. ICPADS 2006. 12th International Conference on, Volume 1, 12-15 July 2006
[110]. Cicconetti C.; Erta A.; Lenzini L.; Mingozzi E., "Performance Evaluation of the IEEE
802.16 MAC for QoS Support", Mobile Computing, IEEE Transactions on, Volume 6,
Issue 1, Page(s):26 - 38, Jan. 2007
[111]. Lin J.; Sirisena H.; "Quality of Service Scheduling in IEEE 802.16 Broadband Wireless
Networks", Industrial and Information Systems, First International Conference on,
Page(s):396 - 401, 8-11 Aug. 2006
[112]. Sun J.; Yanling Y.; Hongfei Z.; "Quality of Service Scheduling for 802.16 Broadband
Wireless Access Systems", Vehicular Technology Conference, 2006. VTC 2006-Spring.
IEEE 63rd, Volume 3, Page(s):1221 - 1225, 2006
[113]. Soong A.C.K., "Technological enablers of the IEEE wireless metropolitan area network
(IEEE 802.16)", Quality of Service in Heterogeneous Wired/Wireless Networks, 2005.
Second International Conference on, 22-24 Aug. 2005
[114]. Piechoclri, R.J.; Tsoulos, G.V., "A macrocellular radio channel model for smart antenna
tracking algorithms", Vehicular Technology Conference, 1999 IEEE 49th, Volume 3,
Page(s):1754 - 1758, 16-20 May 1999
[115]. Hamid Z.; Khan Shoab A., "An Augmented Security Protocol for WirelessMAN Mesh
Networks", Communications and Information Technologies, 2006. ISCIT '06.
International Symposium on, Page(s):861 - 865, Oct. 18 2006-Sept. 20 2006
[116]. Sen X.; Manton M.; Chin-Tser H., "Security issues in privacy and key management
protocols of IEEE 802.16", ACM Southeast Regional Conference, Pages: 113 - 118, 2006
106

[117]. Yun Z.; Yuguang F., "Security of IEEE 802.16 in Mesh Mode", Military
Communications Conference, 2006. MILCOM 2006, Page(s):1 - 6, 23-25 Oct. 2006
[118]. Sen X.; Chin-Tser H.; Matthews M., "Secure multicast in various scenarios of
WirelessMAN", SoutheastCon, 2007. Proceedings. IEEE, Page(s):709 - 714, March 2007
[119]. Ginley M.; Sen X.; Chin-Tser H.; Matthews M., "Efficient and Secure Multicast in
WirelessMAN", Wireless Pervasive Computing, 2007. ISWPC '07. 2nd International
Symposium on, 5-7 Feb. 2007
[120]. Moiseev S.N.; Sergey N. M.; Filin S.A.; Kondakov M.S.; Alexandre V. G.; Garmonov
A.V.; Andrew Y. S.; Savinkov A.Y.; Yun Sang P.; Seok Ho C., "Optimal Average
Number of Data Block Transmissions for the ARQ Mechanism in the IEEE 802.16
OFDMA System", Personal, Indoor and Mobile Radio Communications, 2006 IEEE 17th
International Symposium on, Page(s):1 - 5, Sept. 2006
[121]. Gowda H.; Lakshmaiah R.; Kaur M.; Mohanram C.; Singh M.; Dongre S., "A slot
allocation mechanism for diverse QoS types in OFDMA based IEEE 802.16e systems",
Advanced Communication Technology, The 9th International Conference on, Volume 1,
Page(s):13 - 17, 12-14 Feb. 2007
[122]. Wang F.; Ghosh A.; Love R.; Stewart K.; Ratasuk R.; Bachu R.; Sun Y.; Zhao Q., "IEEE
802.16e system performance: analysis and simulations", Personal, Indoor and Mobile
Radio Communications, 2005. PIMRC 2005. IEEE 16th International Symposium on,
Volume 2, page(s): 900- 904, 11-14 Sept. 2005
[123]. Sen I.; Wang B.; Matolak David W., "Performance of IEEE 802.16 OFDMA Standard
Systems in Airport Surface Area Channels", Integrated Communications, Navigation and
Surveillance Conference, 2007. ICNS '07, Page(s):1 - 12, April 30 2007-May 3 2007
[124]. Hongxiang L.; Hui L., "An Analysis on Uplink OFDMA Optimality", Vehicular
Technology Conference, 2006. VTC 2006-Spring. IEEE 63rd, Volume 3, Page(s):1339 -
1343, 2006
[125]. Esli C.; Delic H., "Performance Analysis for OFDMA in the Presence of Tone
Interference", Communications, IEEE Transactions on, Volume 55, Issue 5, Page(s):845
- 849, May 2007
[126]. Kivanc D.; Hui L., "Subcarrier allocation and power control for OFDMA", Signals,
Systems and Computers, 2000. Conference Record of the Thirty-Fourth Asilomar
Conference on, Volume 1, Page(s):147 - 151, 29 Oct.-1 Nov. 2000
[127]. Hui-Juan Y.; Geng-Sheng K., "An Integrated QoS-Aware Mobility Architecture for
Seamless Handover in IEEE 802.16e Mobile BWA Networks", Military Communications
Conference, 2006. MILCOM 2006, Page(s):1 - 7, 23-25 Oct. 2006
[128]. Kuo G. S.; Yao H. J., "A QoS-Adaptive Admission Control for IEEE 802.16e-based
Mobile BWA Networks", Consumer Communications and Networking Conference, 2007.
CCNC 2007. 2007 4th IEEE, Page(s):833 - 837, Jan. 2007
[129]. Vatsa Omanand J.; Raj M.; K Ritesh K.; Panigrahy D.; Das D., "Adaptive Power Saving
Algorithm for Mobile Subscriber Station in 802.16e", Communication Systems Software
and Middleware, 2007. COMSWARE 2007. 2nd International Conference on, Page(s):1 -
7, 7-12 Jan. 2007
[130]. Zhang Y.; Fujise M., "Energy management in the IEEE 802.16e MAC", Communications
Letters, IEEE, Volume 10, Issue 4, Page(s):311 - 313, Apr 2006
[131]. Xiao Y., "Energy saving mechanism in the IEEE 802.16e wireless MAN",
Communications Letters, IEEE, Volume 9, Issue 7, Page(s):595 - 597, July 2005
107

[132]. Mukherjee S.; Leung K.K.; Rittenhouse G.E., "Protocol and control mechanisms to save
terminal energy in IEEE 802.16 networks", Communications, Computers and signal
Processing, 2005. PACRIM. 2005 IEEE Pacific Rim Conference on, Page(s):5 - 8, 24-26
Aug. 2005
[133]. Jee-young S.; Hyun-ho C.; Hyun-dae K.; Sang-wook K.; Dong-ho C.; Hong-sung C.;
Geunwhi L.; Jun-hyung K., "Performance comparison of 802.16d OFDMA, TD-CDMA,
cdma2000 1xEV-D0 and 802.11a WLAN on voice over IP service", Vehicular
Technology Conference, 2005. VTC 2005-Spring. 2005 IEEE 61st, Volume 3,
Page(s):1965 - 1969, 30 May-1 June 2005
[134]. Yuexing P.; Hongzhong Y.; Young il K.; Yong Su L.; Wenbo W., "Performance of
Convolutional Turbo Coded High-speed Portable Internet (WiBro) System", Vehicular
Technology Conference, 2007. VTC2007-Spring. IEEE 65th, Page(s):730 - 734, 22-25
April 2007
[135]. Taesoo K.; Howon L.; Sik C.; Juyeop K.; Dong-Ho C.; Sunghyun C.; Sangboh Y.; Won-
Hyoung P.; Kiho K., "Design and implementation of a simulator based on a cross-layer
protocol between MAC and PHY layers in a WiBro Compatible.IEEE 802.16e OFDMA
system", Communications Magazine, IEEE, Volume 43, Issue 12, Page(s):136 - 146, Dec.
2005
[136]. Xiao Y.; Pan Y.; Li J., "Design and analysis of location management for 3G cellular
networks", Parallel and Distributed Systems, IEEE Transactions on, Volume 15, Issue 4,
Page(s):339 - 349, April 2004
[137]. Derryberry R.T.; Gray S.D.; Ionescu D.M.; Mandyam G.; Raghothaman B., "Transmit
diversity in 3G CDMA systems", Communications Magazine, IEEE, Volume 40, Issue 4,
page(s): 68-75, Apr 2002
[138]. Proctor T.K., "Evolution to 3G services: provision of 3G services over GERAN
(GSM/EDGE radio access network)", 3G Mobile Communication Technologies, 2003.
3G 2003. 4th International Conference on (Conf. Publ. No. 494), Page(s):78 - 82, 25-27
June 2003
[139]. Rikkinen K.; Wildey C., "WCDMA scenarios for the 2.5 GHz IMT-2000 extension band
supporting asymmetric frequency allocations", 3G Mobile Communication Technologies,
2003. 3G 2003. 4th International Conference on (Conf. Publ. No. 494), Page(s):294 - 298,
25-27 June 2003
[140]. Goransson B.; Hagerman B.; Petersson S.; Sorelius J., "Advanced antenna systems for
WCDMA: link and system level results", Personal, Indoor and Mobile Radio
Communications, 2000. PIMRC 2000. The 11th IEEE International Symposium on,
Volume 1, Page(s):62 - 66, 18-21 Sept. 2000
[141]. Suryanegara M.; Hutabarat E.R.; Gunawan D., "The Interference on WCDMA System in
3G Coexistence Network", Personal, Indoor and Mobile Radio Communications, 2006
IEEE 17th International Symposium on, Page(s):1 - 5, Sept. 2006
[142]. Liangchi H.; Cheng M.W.; Niva I., "Evolution towards simultaneous high-speed packet
data and voice services: an overview of cdma2000 1/spl times/EV-DV",
Telecommunications, 2003. ICT 2003. 10th International Conference on, Volume 2,
Page(s):1313 - 1317, 23 Feb.-1 March 2003
[143]. Becker G.E.; Rudrapatna R.; Sowlay S.; Wong K.N.; Wu J.R., "Integrated Network and
Element Management System for the 3rd generation CDMA2000 wireless network",
108

Network Operations and Management Symposium, 2000. NOMS 2000. 2000 IEEE/IFIP,
Page(s):953 - 954, 10-14 April 2000
[144]. Chen H. H.; Fan C. X.; Lu W. W., "China's perspectives on 3G mobile commuunications
and beyond: TD-SCDMA technology", Wireless Communications, IEEE [see also IEEE
Personal Communications], Volume 9, Issue 2, Page(s):48 - 59, April 2002
[145]. Xirrus High Performance Wi-Fi (http://www.xirrus.com/)
[146]. Foundry Networks (http://www.foundrynet.com/)
[147]. Interview From FSU-OTC, 10/08/2007, Mr. Clint Ringgold, Network Administrator of
OTC and Mr. Phillip M. Callahan, Assistant Director of OTC.
[148]. Interview From Q-WARE SYSTEMS & SERVICES CORP., 11/06/2007, Ms. Linda Yeh,
Account Manager of Sales & Customer Service Dep.
[149]. Tan K.; Feng J.; Qian Z.; Xuemin S., "Congestion Control in Multihop Wireless
Networks", Vehicular Technology, IEEE Transactions on, Volume 56, Issue 2, March
2007
[150]. Yung Y.; Shakkottai, S., "Hop-by-hop Congestion Control over a Wireless Multi-hop
Network", Networking, IEEE/ACM Transactions on, Volume 15, Issue 1, Feb. 2007
[151]. Zhou, H.; Hoang, D.; Nhan, P.; Mirchandani, V., "Introducing feedback congestion
control to a network with IEEE 802.11 wireless LAN", Wireless Telecommunications
Symposium, 2004, 14-15 May 2004
[152]. Weirong L.; Jianqiang Y.; Dongbin Z.; Wen, J.T., "A Smooth Control to Avoid
Congestion for Wireless Network", Networking, Sensing and Control, 2006. ICNSC '06.
Proceedings of the 2006 IEEE International Conference on, 23-25 April 2006
[153]. Seungcheon K.; Jamalipour, A., "Congestion control for best-effort services in wireless
access network", ATM (ICATM 2001) and High Speed Intelligent Internet Symposium,
2001. Joint 4th IEEE International Conference on, 22-25 April 2001
[154]. IEEE 802.11u ( http://www.ieee802.org/11/Reports/tgu_update.htm)
109

BIOGRAPHICAL SKETCH
Ming-Chieh Wu was born in Tainan, Taiwan, in 1978. He entered Tang Kong University in
Taiwan, in 1998 majoring in Aerospace Engineering.. His interest at that time was navigation. In
senior year, he joined a project called “Regional Aircraft Design” with another classmate. In this
project, the group did not need to build a real airplane, but they had to run a simulation that had a
reasonable solution to make sure this aircraft could fly. At the end of the project, the group
received an “A.” Mr. Wu graduated in 2002 and joined the Air Force for two years. After his
military service, he started to apply to graduate school in the U.S. and was accepted by Florida
State University. In graduate school, he changed his major to Electrical Engineering. After his
first semester, he found that his true interest was in wireless communication. After that, he
started to take communication related classes. After graduating from FSU, Mr. Wu would like to
design wireless communication networks because he believes that it will be the future trend.
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