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

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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
Page 1 and 2: THE FLORIDA STATE UNIVERSITY COLLEG
Page 3 and 4: TABLE OF CONTENTS List of Tables…
Page 5 and 6: 5. Case study…………………
Page 7 and 8: LIST OF FIGURES Figure 2-1 The Evol
Page 9 and 10: LIST OF ABBREVIATIONS Abbreviation
Page 11 and 12: PSS Portable Subscriber Station 89
Page 13 and 14: CHAPTER ONE 1. Introduction The cel
Page 15 and 16: Table 1-1 Cont. 802.3an 2006 10GBAS
Page 17 and 18: 2.1. Introduction CHAPTER TWO 2. 3G
Page 19 and 20: 2.3. Development 3G has been in dev
Page 21 and 22: 2.5. Conclusion WAP (Wireless Appli
Page 23 and 24: IEEE 802.11n is the newest standard
Page 25 and 26: Table 3-3 Cont. 10 2.457 X Y Y Y Y
Page 27: 3.3.1.2. PLCP and PMD The physical
Page 31 and 32: Figure 3-5 CCK Modulation HR-DSSS P
Page 33 and 34: other problem is inter-carrier inte
Page 35 and 36: Tab ble 3-5 OFDDM Modulaation and D
Page 37 and 38: and contains DSSS, CCK, PBCC (Packe
Page 39 and 40: 3.3.2. MAC Layer 3.3.2.1. Introduct
Page 41 and 42: Virtual channel sensing he other me
Page 43 and 44: SIFS (Short InterFrame Spacing) Fig
Page 45 and 46: Figure 3-20 WEP Frame and Operation
Page 47 and 48: 3.4.2. MIMO (Multiple-Input/Multipl
Page 49 and 50: 4.1. The background of IEEE 802.16
Page 51 and 52: The working groups of WiMax Forum a
Page 53 and 54: Table 4-1 Thee Basic Datta of IEEE
Page 55 and 56: Figure 4-1 The Layer Structure of I
Page 57 and 58: codes ( (CTC) and low densityy pari
Page 59 and 60: 4.3.1.2.2. AAS (Advanced Antenna Sy
Page 61 and 62: Best-effort service (BE) This schem
Page 63 and 64: Encryption Figure 4-4 PKM Protocol
Page 65 and 66: 4.3.2. IEEE 802.16e-2005, the newes
Page 67 and 68: transmiission, the aadjacent cellls
Page 69 and 70: the uplink bandwidth periodically f
Page 71 and 72: Figure 4-7 Coverage and Capacity fo
Page 73 and 74: CHAPTER FIVE 5. Case study This cha
Page 75 and 76: increased bandwidth, fixed connecti
Page 77 and 78: Figure 5-3 Landis Green Figure 5-4
Page 79 and 80:
Table 5-2 Xirrus XS-3700 AP Technol
Page 81 and 82:
• Automatic Tx power selection
Page 83 and 84:
Table 5-4 Cont. 71
Page 85 and 86:
5.1.3. Analysis The FSU wireless ne
Page 87 and 88:
since the January 2006. The populat
Page 89 and 90:
Table 5-5 Parameters of WLAN and Me
Page 91 and 92:
Table 5-6 Features of Nortel Wirele
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• -101 dBm typical @ 1 Mbps Recei
Page 95 and 96:
Operating environment specification
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uilding density, high population de
Page 99 and 100:
epeater r is developping and it wil
Page 101 and 102:
Figure 5-17 WiBro Features The data
Page 103 and 104:
Figure 5-19 U-RAS Premium Figure 5-
Page 105 and 106:
In KT’s recent report, 60% of sub
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Figure 5-21 An Example Application
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Name Parameters Standard Table 5-10
Page 111 and 112:
WiFly used Wi-Fi to cover 60% of th
Page 113 and 114:
BIBLIOGRAPHY [01]. IEEE 802.11 offi
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[37]. Sun, Y.; "Bandwidth-efficient
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[88]. Mineno T.; Babji T.,"Issues a
Page 119 and 120:
[117]. Yun Z.; Yuguang F., "Securit
Page 121 and 122:
Network Operations and Management S
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