Aspects of WINNER+ Spectrum Preferences - Celtic-Plus
Aspects of WINNER+ Spectrum Preferences - Celtic-Plus
Aspects of WINNER+ Spectrum Preferences - Celtic-Plus
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Project Number:<br />
Project Title:<br />
Document Type:<br />
CELTIC / CP5-026<br />
Wireless World Initiative New Radio – <strong>WINNER+</strong><br />
I (Internal)<br />
Document Identifier: D3.2<br />
Document Title:<br />
Source Activity:<br />
Editor:<br />
<strong>Aspects</strong> <strong>of</strong> <strong>WINNER+</strong> <strong>Spectrum</strong> <strong>Preferences</strong><br />
WP3<br />
Matthias Siebert<br />
Authors:<br />
Anne-Lyse Bouaziz, Jean-Philippe Desbat, Jean-Marc Kelif, Horst<br />
Mennenga, Albena Mihovska, Werner Mohr, Miia Mustonen,<br />
Matthias Siebert<br />
Status / Version: 1.0<br />
Date Last changes: 26.05.09<br />
File Name:<br />
D3.2_<strong>WINNER+</strong><strong>Spectrum</strong><strong>Preferences</strong>_v1.0.doc<br />
Abstract:<br />
This deliverable covers selected items on <strong>WINNER+</strong> spectrum<br />
preferences. A large part <strong>of</strong> this work is dedicated to spectrum<br />
aggregation issues covering scheduling aspects, transceiver<br />
concepts and an analysis <strong>of</strong> deployment scenarios as discussed<br />
within ITU and 3GPP. Further, Femto-Macro coexistence is<br />
investigated as an exemplary Intra-Operator sharing scenario,<br />
complemented by some multi-operator resource sharing<br />
considerations.<br />
Keywords: <strong>Spectrum</strong> Aggregation, <strong>Spectrum</strong> Sharing, Femto-Macro<br />
Coexistence, Multi-Operator <strong>Spectrum</strong> Usage, Scheduling,<br />
<strong>Spectrum</strong> Usage Scenarios, Transceiver Concepts<br />
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<strong>WINNER+</strong> D3.2<br />
Table <strong>of</strong> Contents<br />
1. Introduction............................................................................................ 5<br />
2. <strong>Spectrum</strong> Regulation and Demand ...................................................... 5<br />
2.1 Worldwide Standardisation & Regulation .............................................................................. 5<br />
2.2 European Standardisation & Regulation................................................................................. 7<br />
2.3 <strong>Spectrum</strong> Estimation Methodologies ...................................................................................... 8<br />
2.4 <strong>Spectrum</strong> Requirement Estimation ......................................................................................... 8<br />
3. <strong>Spectrum</strong> Sharing and Co-Jointly Usage ............................................ 9<br />
3.1 Intra-Operator Femto-Macro coexistence ............................................................................... 9<br />
3.1.1 Scenario 1: Interference between femtocells ................................................................. 11<br />
3.1.1.1 Assumptions.......................................................................................................... 11<br />
3.1.1.2 Interference between femtocells: SINR results ..................................................... 12<br />
3.1.1.3 Interference between femtocells: Throughput results............................................ 16<br />
3.1.1.4 Scenario 1 conclusion............................................................................................ 18<br />
3.1.2 Scenario 2: Interference between femto and macrocells................................................ 20<br />
3.1.2.1 Assumptions.......................................................................................................... 20<br />
3.1.2.2 Interference between femto and macro cells: SINR results................................... 22<br />
3.1.2.3 Interference between femto cells: Throughput results........................................... 24<br />
3.1.2.4 Scenario 2 conclusion............................................................................................ 26<br />
3.1.3 Scenario 3: Interference between femto and macrocells................................................ 28<br />
3.1.3.1 Assumptions.......................................................................................................... 28<br />
3.1.3.2 Interference between femto and macro cells: SINR results................................... 30<br />
3.1.3.3 Interference between femtocells: Throughput results............................................ 31<br />
3.1.3.4 Scenario 3 conclusion............................................................................................ 31<br />
3.2 Multi-Operator Resource Sharing Scenario in the Context <strong>of</strong> IMT-A Systems.................... 32<br />
3.2.1 <strong>Spectrum</strong> Aggregation Requirements ............................................................................ 33<br />
3.2.2 Hypotheses for System and <strong>Spectrum</strong> Resource Usage................................................. 34<br />
3.2.3 Intra-and Inter-Operator Sharing <strong>Aspects</strong>...................................................................... 34<br />
3.2.3.1 Intra-Operator Sharing Considerations.................................................................. 34<br />
3.2.3.2 Inter-Operator Considerations............................................................................... 36<br />
4. <strong>Spectrum</strong> Aggregation ........................................................................ 37<br />
4.1 <strong>Spectrum</strong> Aggregation with Multi-Band User Allocation over Two Frequency Bands........ 38<br />
4.1.1 Problem Statement......................................................................................................... 38<br />
4.1.2 General Multi-band Scheduling <strong>Spectrum</strong> Sharing as a General Assignment Problem 39<br />
4.1.2.1 Pr<strong>of</strong>it Function....................................................................................................... 39<br />
4.1.2.2 Resource Allocation .............................................................................................. 40<br />
4.1.2.3 Differences between the 2-GHz and 5-GHz frequency bands............................... 41<br />
4.1.3 Suboptimal Multiband Allocation Algorithm ................................................................ 41<br />
4.1.4 Results ........................................................................................................................... 41<br />
4.2 Basic Transceiver Concepts for aggregated <strong>Spectrum</strong>.......................................................... 41<br />
4.2.1 Approach........................................................................................................................41<br />
4.2.2 Brief Investigation <strong>of</strong> Several Topics Affecting the System Design ............................. 44<br />
4.2.2.1 Frequency Dependent Path Loss ........................................................................... 44<br />
4.2.2.2 Doppler Frequency and Doppler <strong>Spectrum</strong>........................................................... 45<br />
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4.2.2.3 Effective Noise Power........................................................................................... 46<br />
4.2.2.4 Receiver Input Signal ............................................................................................ 46<br />
4.2.2.5 Nonlinearities in the Analogue Receiver Components.......................................... 47<br />
4.2.2.6 Image Rejection..................................................................................................... 47<br />
4.2.2.7 Receiver Performance (Desensitization, Blocking, Intermodulation) ................... 49<br />
4.2.2.8 Reciprocal Mixing and Receiver Noise Figure ..................................................... 49<br />
4.2.2.9 Band Pass Filters and Filter Slope for Stop-band Attenuation .............................. 51<br />
4.2.2.10 Maximum Input Signal........................................................................................ 53<br />
4.2.2.11 Sampling Theorem for Both Receiver Versions.................................................. 54<br />
4.2.2.12 A/D-Converter Dynamic Range and Output Data Rate ...................................... 54<br />
4.2.2.13 A/D-Converter Performance Development......................................................... 55<br />
4.2.3 Conclusions.................................................................................................................... 56<br />
4.3 Actual discussions in 3GPP and ITU-R on the implementation <strong>of</strong> identified frequency<br />
spectrum in WRC 2007 ....................................................................................................................... 57<br />
4.3.1 Frequency arrangements in the ITU-R WP5D meeting in Geneva, Switzerland, from<br />
February 10 – 17, 2009 ................................................................................................................ 57<br />
4.3.2 Status <strong>of</strong> discussion on the implementation <strong>of</strong> identified additional IMT frequency<br />
bands in the 3GPP TSG-RAN meting in Athens, Greece, in February 3 – 13, 2009 ................... 59<br />
4.3.3 Conclusions.................................................................................................................... 68<br />
5. References ........................................................................................... 69<br />
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<strong>WINNER+</strong> D3.2<br />
1. Introduction<br />
This deliverable covers spectrum aspects as considered within <strong>WINNER+</strong>.<br />
Starting with a summary on worldwide, European and national regulation activities and fora in<br />
Section 2, sharing options for single- and multi-operator environments are discussed in<br />
Section 3. A large part <strong>of</strong> this deliverable finally is dedicated to spectrum aggregation as<br />
addressed within Section 4.<br />
2. <strong>Spectrum</strong> Regulation and Demand<br />
This section gives an overview <strong>of</strong> national as well as international groups and authorities being concerned<br />
with spectrum. The presentation is chosen to be top down as illustrated in Figure 2-1, starting with<br />
worldwide fora followed by associations on a European level.<br />
Level <strong>of</strong><br />
participation<br />
Standardization organizations / results<br />
Regulatory<br />
Organizations<br />
Results<br />
World<br />
-wide<br />
ISO/IEC<br />
ITU<br />
Recommendation<br />
International Standard<br />
reference<br />
Conferences<br />
ITU-Plenipotentiary<br />
ITU-Administrative<br />
Voluntary<br />
Standard<br />
International<br />
convention<br />
Regulations<br />
ETSI<br />
EN<br />
TCAM<br />
Europe<br />
CEN/CENELEC<br />
EN/ENV<br />
reference<br />
reference<br />
European<br />
Council<br />
European<br />
Commission<br />
Harmonised<br />
Norm<br />
Directive<br />
Decisions<br />
National<br />
(Germany)<br />
DIN/DKE<br />
TBETSI<br />
DIN Standard<br />
reference<br />
Federal<br />
Government<br />
(BMWi / BNetzA)<br />
Acts<br />
Ordinances<br />
Ordinances<br />
Regulations<br />
Figure 2-1: Relation between the fields <strong>of</strong> voluntary standardization and regulatory activities<br />
2.1 Worldwide Standardisation & Regulation<br />
There are three organisations which take care about worldwide standardisation, see also Figure 2-1:<br />
- ISO: International Organization for Standardization (General)<br />
- IEC: International Electrotechnical Commission<br />
- ITU: International Telecommunication Union<br />
ITU is the leading United Nations agency for information and communication technology issues, and the<br />
global focal point for governments and the private sector in developing networks and services. For nearly<br />
145 years, ITU has coordinated the shared global use <strong>of</strong> the radio spectrum, promoted international<br />
cooperation in assigning satellite orbits, worked to improve telecommunication infrastructure in the<br />
developing world, established the worldwide standards that foster seamless interconnection <strong>of</strong> a vast<br />
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range <strong>of</strong> communications systems and addressed the global challenges <strong>of</strong> our times, such as mitigating<br />
climate change and strengthening cyber security.<br />
ITU is committed to connecting the world.<br />
– Membership: 191 Member countries and over 700 companies and organisations;<br />
– Provides the international regulatory framework within which the various<br />
communication services can be operated<br />
The ITU has three Sectors:<br />
– Telecommunication Development (ITU-D)<br />
– Telecommunication Standardization (ITU-T)<br />
– Radiocommunication (ITU-R),<br />
The main task <strong>of</strong> International Telecommunication Union Radiocommunication sector (ITU-R) is to<br />
manage international radio-frequency spectrum and satellite orbit resources. ITU-R develops standards<br />
for radiocommunication systems to ensure the effective use <strong>of</strong> the radio-frequency spectrum and carries<br />
out studies concerning the development <strong>of</strong> radiocommunication systems. Furthermore, ITU-R carries out<br />
studies for the development <strong>of</strong> radiocommunication systems used in disaster mitigation and relief<br />
operations. ITU-R consists <strong>of</strong> five Study Groups (SG) two <strong>of</strong> which are <strong>of</strong> main interest to the Winner+<br />
project and are briefly described below.<br />
Study Group 1 <strong>of</strong> ITU-R deals with issues related to spectrum management. Study group 1 is responsible<br />
for the overall development <strong>of</strong> principles and techniques for spectrum management and long-term<br />
strategies for effective spectrum use. SG 1 is divided into three Working Parties (WPs). Working Party<br />
1A (WP 1A) is responsible <strong>of</strong> spectrum engineering techniques, WP 1B <strong>of</strong> spectrum management<br />
methodologies and economic strategies, and WP 1C <strong>of</strong> spectrum monitoring. WP 1B is responsible <strong>of</strong> the<br />
World Radio Conference 2011 (WRC-11) agenda item 1.19 concerning s<strong>of</strong>tware-defined radio and<br />
cognitive radio systems (an overview about the WRC agenda items is provided later in this section).<br />
Study Group 5 is called terrestrial services and it deals with systems and networks for fixed, mobile, radio<br />
determination, amateur and amateur-satellite services. The responsibility <strong>of</strong> WP 5A are land mobile<br />
services excluding International Mobile Telecommunications (IMT); amateur and amateur-satellite<br />
service WP 5A is responsible <strong>of</strong> providing technical input to WP 1B concerning the WRC-11 agenda item<br />
on s<strong>of</strong>tware-defined radio and cognitive radio systems. The main focus <strong>of</strong> the Winner+ project and its<br />
predecessor EU-projects WINNER I and II is WP 5D (before WRC-07 WP 8F), which is concentrated on<br />
IMT systems. WP 5D is at the moment in the process <strong>of</strong> evaluating IMT-Advanced proposals. WP 5D is<br />
also responsible for developing band plans for frequency bands identified for IMT in WRC-07.<br />
The ITU WRC, which convenes every three to four years, is at the core <strong>of</strong> the international spectrum<br />
management process and constitutes the starting point for national practices. WRC reviews and revises<br />
the Radio Regulations, an international treaty establishing the framework for the utilization <strong>of</strong> radio<br />
frequencies and satellite orbits among ITU member countries, and considers any question <strong>of</strong> a worldwide<br />
character within its competence and related to its agenda.<br />
WRC-07<br />
The WRC-07 has identified the following new spectrum bands for IMT systems, some <strong>of</strong> which Region 1<br />
specific:<br />
• 450-470 MHz globally,<br />
• 698-806 MHz in Region 2 and nine countries in Region 3,<br />
• 790-862 MHz in Region 3 and part <strong>of</strong> Region 1 countries,<br />
• 2.3-2.4 GHz globally,<br />
• 3.4-3.6 GHz in a large number <strong>of</strong> countries in Regions 1 and 3.<br />
1 Region 1: Europe, the Middle East and Africa (EMEA)<br />
Region 2: North- and South America (Americas)<br />
Region 3: Asia Pacific (APAC)<br />
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The intention is that the bands previously identified in the Radio Regulations for IMT-2000 are now<br />
identified for IMT. The WRC’07 allocations are used as the starting point in the considerations <strong>of</strong><br />
preferred spectrum use in <strong>WINNER+</strong>.<br />
A considerable amount <strong>of</strong> work on preferred spectrum use has been done in WINNER II. In [WIN2D591]<br />
TDD / FDD inter-mode operation is investigated, whereas in [WIN2D592] and [WIN2D593] scenarios<br />
for wide area, metropolitan, and local area are considered.<br />
WRC-11<br />
There are three agenda items (AI) in WRC-11 that could be considered the most interesting ones from<br />
Winner+ perspective:<br />
• AI 1.17 to consider results <strong>of</strong> sharing studies between the mobile service and other services in<br />
the band 790-862 MHz in Regions 1 and 3, in accordance with Resolution 749 [COM4/13]<br />
(WRC-07), to ensure the adequate protection <strong>of</strong> services to which this frequency band is<br />
allocated, and take appropriate action;<br />
• AI 1.19 to consider regulatory measures and their relevance, in order to enable the introduction<br />
<strong>of</strong> s<strong>of</strong>tware-defined radio and cognitive radio systems, based on the results <strong>of</strong> ITU-R studies, in<br />
accordance with Resolution 956 [COM6/18] (WRC-07);<br />
• AI 1.25 to consider possible additional allocations to the mobile-satellite service, in accordance<br />
with Resolution 231 [COM6/21] (WRC-07);<br />
The proposals for action items to the WRC-15 can be made via the following action item:<br />
• AI 6 to identify those items requiring urgent action by the Radiocommunication Study<br />
Groups in preparation for the next world radiocommunication conference<br />
2.2 European Standardisation & Regulation<br />
There are three organisations which take care about European standardisation:<br />
- CEN: European Committee for Standardization (General)<br />
- CENLEC: European Committee for Electrotechnical Standardization<br />
- ETSI: European Telecommunications Standards Institute<br />
The European Telecommunications Standards Institute (ETSI) is an independent, non-pr<strong>of</strong>it,<br />
standardization organization in the telecommunications industry (equipment makers and network<br />
operators) in Europe, with worldwide projection. ETSI has been successful in standardizing the GSM cell<br />
phone system and the TETRA pr<strong>of</strong>essional mobile radio system.<br />
ETSI is developing telecommunication standards (EN) for Europe. The part <strong>of</strong> the EN which contains the<br />
regulatory requirements may be published in the <strong>of</strong>ficial journal <strong>of</strong> the European Commission, after that<br />
the EN will be known as Harmonized Standard (HN).<br />
For the frequency related requirements ETSI works together with the European Conference <strong>of</strong> Postal and<br />
Telecommunications Administrations (CEPT). CEPT and ETSI have created a Memorandum <strong>of</strong><br />
Understanding (MoU) to solve this task.<br />
CEPT: Conference <strong>of</strong> 48 European Post and Telecommunication Administrations<br />
CEPT is a body <strong>of</strong> policy-makers and regulators for:<br />
• establishing a European forum for discussions on sovereign and regulatory issues in the<br />
field <strong>of</strong> post and telecommunications issues<br />
• influencing, through common positions, developments within ITU and UPU (Universal<br />
Postal Union) in accordance with European goals<br />
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<strong>WINNER+</strong> D3.2<br />
Table 2-1: Some national regulators <strong>of</strong> European countries<br />
National <strong>Spectrum</strong> Authority Body (Regulator)<br />
Denmark<br />
National IT and Telecom Agency<br />
France ANFR Agence Nationale des Fréquences<br />
Germany BNetzA Bundesnetzagentur für Elektrizität, Gas, Telekommunikation,<br />
Post und Eisenbahnen (The Federal Network Agency for<br />
Electricity, Gas, Telecommunications, Post and Railway)<br />
Netherlands<br />
Agentschap Telecom<br />
United Kingdom Ofcom Office <strong>of</strong> Communications<br />
ECC: Electronic Communications Committee<br />
The ECC is the main group <strong>of</strong> the CEPT. Its tasks are related to:<br />
• Development <strong>of</strong> European radiocommunications policies<br />
• Harmonisation <strong>of</strong> the frequency usages within the CEPT area<br />
• Coordination <strong>of</strong> frequency management aspects and regulation matters<br />
• Providing <strong>of</strong> guidelines regarding cooperation with the ITU<br />
• ECC PT1 is making the European preparation for ITU-R WP 5D<br />
ECC PT1 is responsible for the overall system aspects <strong>of</strong> IMT. Currently the work in ECC PT1 includes<br />
developing appropriate ECC Deliverables on the designation and frequency arrangements for the<br />
spectrum bands 3.4-3.6 GHz and 790-862 MHz. The sharing and compatibility issues on all these bands<br />
will be considered and reported in ECC Recommendations and Reports. ECC PT1 is also going to address<br />
the band 3.6-3.8 GHz for IMT. Additionally, ECC PT1 will co-ordinate positions on the ITU process for<br />
the development <strong>of</strong> IMT-Advanced as well as the compatibility studies and frequency arrangements for<br />
other bands identified for IMT in WRC-07.<br />
EU Regulations<br />
The European Commission had set up a Group (Telecommunications Conformity Assessment and Market<br />
Surveillance Committee, TCAM) which handles the requirements concerning the R&TTE Directive.<br />
<strong>Spectrum</strong> related activities were handed in the Radio <strong>Spectrum</strong> Committee (RSC) and Radio <strong>Spectrum</strong><br />
Policy Group (RSPG)<br />
2.3 <strong>Spectrum</strong> Estimation Methodologies<br />
The methodology for calculating the spectrum requirements for IMT has been developed in ITU-R WP<br />
8F, and most parts <strong>of</strong> the methodology originate from the EU-project WINNER. The methodology<br />
accommodates a complex mixture <strong>of</strong> services from market studies with service categories having<br />
different traffic volumes and QoS constraints. The methodology is to apply a technology neutral approach<br />
to handle emerging as well as established systems. A detailed description <strong>of</strong> the methodology is provided<br />
in [WIND6.2] and [WIND6.5]. A summary <strong>of</strong> the methodology with the main steps and parameters can<br />
be found in [WIN2D5.10.2]. This methodology is implemented into a tool (SPECULATOR) calculating<br />
the predicted spectrum needs for 2010, 2015 and 2020. The spectrum calculation tool has been developed<br />
in the WINNER project and it has been also adapted as an <strong>of</strong>ficial ITU-R tool. A detailed description <strong>of</strong><br />
the tool can be found in [WIND6.5] and a brief guide to the usage <strong>of</strong> the tool can be found in<br />
[WIN2D5.10.2].<br />
2.4 <strong>Spectrum</strong> Requirement Estimation<br />
Based on the methodology, an estimation <strong>of</strong> the additional spectrum needed for IMT by the year 2020 has<br />
been calculated to be 1280 - 1720 MHz for lower and higher market setting, respectively [WIN2D5.10.2].<br />
Including the spectrum identified in WRC-07 the total amount <strong>of</strong> spectrum for IMT is still left far below<br />
the spectrum prediction for lower market setting in all <strong>of</strong> the ITU regions as illustrated in Table 2.1. This<br />
indicates that additional spectrum would be needed in the future to provide the predicted services.<br />
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However, there is not an agenda item for WRC-11 identification <strong>of</strong> additional spectrum for IMT and<br />
therefore at earliest additional spectrum can be allocated for IMT in WRC-15.<br />
Identified<br />
before WRC-<br />
07 [MHz]<br />
693 whole region<br />
120, partially<br />
392<br />
Table 2-2: Amount <strong>of</strong> spectrum in different ITU Regions<br />
Region 1 Region 2 Region 3<br />
Identified in<br />
WRC-07<br />
[MHz]<br />
Total<br />
[MHz]<br />
Identified<br />
before<br />
WRC-07<br />
Identified in<br />
WRC-07<br />
[MHz]<br />
Total<br />
[MHz]<br />
Identified<br />
before<br />
WRC-07<br />
Identified in<br />
WRC-07<br />
[MHz]<br />
whole<br />
region 813,<br />
partially<br />
1085<br />
[MHz]<br />
723 whole region<br />
228<br />
whole<br />
region 951<br />
Total<br />
[MHz]<br />
[MHz]<br />
749 whole region whole<br />
192, partially region 941,<br />
484 partially<br />
1233<br />
3. <strong>Spectrum</strong> Sharing and Co-Jointly Usage<br />
Mobile network operators are now preparing for the next generation <strong>of</strong> mobile communication systems.<br />
This is a transformation <strong>of</strong> cellular telephone networks into ubiquitous wireless broadband, which will be<br />
based on a new technology, called International Mobile Telecommunications Advanced (IMT-A) [ITU-<br />
CL 2008]. Affordable, high-bandwidth mobile access improves the quality <strong>of</strong> experience for users,<br />
enabling them to get more out <strong>of</strong> existing services, and opens up opportunities for new mobile broadband<br />
services. By delivering more capacity through faster radio access technologies (RATs), a universally<br />
accessible broadband infrastructure will improve the value <strong>of</strong> these services. The standardization <strong>of</strong><br />
IMT-A technologies for preferred spectrum use in frequency bands announced by WRC-07 is, however,<br />
still a challenge to overcome [WRC’07]. The existing highly fragmented radio frequency spectrum does<br />
not match the actual demand for transmission and network resources, and there is a need for a revolution<br />
on how regulators manage spectrum. Mobile devices that implement various RAT standards (i.e.,<br />
multiband devices) increase the complexity <strong>of</strong> coordination, reuse <strong>of</strong> resources and interference<br />
management.<br />
Mobile operators might be forced to aggregate spectrum <strong>of</strong> two or more separated sub-bands for downlink<br />
(DL) and uplink (UL) bands.<br />
<strong>Spectrum</strong> aggregation can be performed in the same or in different bands. It can appear when the<br />
operator’s dedicated DL or UL band is not contiguous but split into two or more parts. In addition,<br />
spectrum aggregation can happen in scenarios, in which an operator accesses both dedicated band and a<br />
spectrum sharing band, which is separated in frequency from the dedicated operator’s band. <strong>Spectrum</strong><br />
aggregation has been proposed for Long Term Evolution-Advanced (LTE-A) [3GPP]. This process is<br />
investigated here also in relation to other IMT-A candidate systems, such as the WINNER system. The<br />
provided results are based on the preliminary investigations reported in [WIN+D1.2], [WIN+D3.1].<br />
A mobile transmission system’s ability to support a wide range <strong>of</strong> services lies across all elements <strong>of</strong> the<br />
network (i.e., core, distribution and access), and across all layers <strong>of</strong> the OSI model [WIN+D3.1]. This<br />
becomes challenging in a scenario <strong>of</strong> dynamic spectrum use (e.g., spectrum aggregation) where<br />
information is required about how to aggregate contiguous parts <strong>of</strong> the highly fragmented spectrum for<br />
the use <strong>of</strong> a single operator and how to achieve this when access is available to a dedicated and a shared<br />
band separated by frequencies. Currently, there is no information available yet about how to cope with<br />
multiple bands and what are the added complexities both at the network managing and at the user<br />
equipment (UE) level.<br />
Section 3 investigates the aspects related to intra-and inter-operator sharing in the above context.<br />
3.1 Intra-Operator Femto-Macro coexistence<br />
In this section, the study focuses on the three following general scenarios:<br />
• Interference between femtocells,<br />
• Interference between femtocells and femto plus macrocells,<br />
• Interference between macrocells and femto plus macrocells,<br />
This aim <strong>of</strong> this study is to known if a femtocell network can be deployed on the same frequency band as<br />
a macrocell network and to deduce dimensioning aspects like cell size in femto LTE. For additional<br />
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coexistence scenarios e.g. Femto-Macro interference in a close-access scenario, please refer to<br />
<strong>WINNER+</strong> D1.2 Chapter 4.<br />
Figure 3-1: Representation <strong>of</strong> the femtocell concept<br />
In the given three scenarios, we assess the impact <strong>of</strong> various parameters on interference factor, SINR and<br />
throughput. These parameters are:<br />
• the femtocell transmitting power in mW,<br />
• the macro cell transmitting power in mW,<br />
• the cell load,<br />
• the pathloss,<br />
• the distance between the serving cell and the MS (=UE),<br />
• the number <strong>of</strong> walls between the serving cell and the MS,<br />
• the mean number <strong>of</strong> walls between the interfering cells and the MS,<br />
The location configurations are defined by: The number <strong>of</strong> walls between the serving cell and the MS and<br />
the mean number <strong>of</strong> walls between the interfering cells and the MS, as represented in Figure 3-2. As<br />
illustrated, the number <strong>of</strong> walls between the serving femtocell and the MS varies from 0 to 3 and from 1<br />
to 4 between the others femtocells and the MS.<br />
Figure 3-2: Different location configurations<br />
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3.1.1 Scenario 1: Interference between femtocells<br />
The scenario 1 focuses on the assessment <strong>of</strong> the interference caused in between femtocells for particular<br />
location configurations. Indeed in this scenario, the impact <strong>of</strong> the number <strong>of</strong> walls between the serving<br />
HBS (Home Base Station) and the MS and the impact <strong>of</strong> the number <strong>of</strong> walls between the interfering<br />
HBS and the MS are assessed.<br />
3.1.1.1 Assumptions<br />
In this scenario, we assume that all the femtocells transmit at the same power and we use the ITU indoor<br />
pathloss model from Recommendation ITU-R P.1238-2 [INDOOR]:<br />
L<br />
dB<br />
= 20log10 ( f<br />
MHz<br />
) + 28log10<br />
( rm<br />
) − 28 + N<br />
walls<br />
× 12 .<br />
This leads in linear to:<br />
2 2.8 1.2 N walls − 8 η<br />
Llinear = f × r × 10 2. = Kr ,<br />
where N walls is the number <strong>of</strong> walls.<br />
The SINRs are calculated as follows:<br />
SINR =<br />
F<br />
F<br />
OMNI<br />
( η − 2)<br />
Nother<br />
η<br />
OMNI<br />
+<br />
1<br />
,<br />
Noise<br />
2 × π × ρ BS × K Nown × r<br />
2−η<br />
η<br />
Thermal Noise K Nown r<br />
Noise<br />
⎡<br />
2−<br />
× ×<br />
+ =<br />
( 2Rc<br />
− r) − ( R − r)<br />
⎤ +<br />
× K ⎢⎣<br />
⎥⎦<br />
P<br />
femto<br />
η<br />
,<br />
where r represents the varying distance between the serving femtocell and MS, η the exponential pathloss<br />
factor, ρ BS the BS's density, 2Rc the distance between two interfering femtocells (Figure 3), R the<br />
network's size in meters and P femto represents the femtocells transmitting power in mW. We define K Nown<br />
and K Nother as a function <strong>of</strong> N walls for the serving femtocell and the others femtocells, respectively. The<br />
general formula is:<br />
2 1.2 N walls −2.8<br />
K<br />
N<br />
= f × 10 .<br />
Validation <strong>of</strong> the use <strong>of</strong> these formulas has been assessed and counterchecked with comparison with<br />
system simulations developed within Orange. The carrier frequency is set to 2.6 GHz. The distance<br />
between two interfering HBS is about 56.4 meters.<br />
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Figure 3-3: Input parameters<br />
Figure 3-4: Symbolisation <strong>of</strong> the 1 st ring <strong>of</strong> femtocells<br />
3.1.1.2 Interference between femtocells: SINR results<br />
We start the study by the assessment <strong>of</strong> the SINR, we focus on DL transmission. In this study simulation<br />
parameters are shown in Figure 3-3. Figure 3-5 shows the SINR in different configurations, considering<br />
interference from only the first ring <strong>of</strong> femtocells as symbolically represented in Figure 3-4. Figure 6<br />
shows the SINR in different configurations, considering interference from the entire network (N other is the<br />
number <strong>of</strong> walls between the interfering cells and the MS and N own is the number <strong>of</strong> walls between the<br />
serving femtocell and the MS).<br />
From Figure 3-5 we can say that, if there is one wall between the interfering cells and the MS and no wall<br />
between the serving femtocell and the MS, the user experiences an SINR <strong>of</strong> about 34 dB when he is at 6<br />
meters from his serving HBS.<br />
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100<br />
Plot <strong>of</strong> SINR<br />
80<br />
Plot <strong>of</strong> SINR<br />
80<br />
60<br />
60<br />
40<br />
40<br />
dB<br />
20<br />
dB<br />
20<br />
0<br />
0<br />
-20<br />
-20<br />
-40<br />
0 5 10 15 20 25 30<br />
Distance between the serving femto cell and the MS in meters<br />
Figure 3-5: 1 st ring <strong>of</strong> cells<br />
-40<br />
0 5 10 15 20 25 30<br />
Distance between the serving femto cell and the MS in meters<br />
Figure 3-6: The entire network<br />
The most important result to notice is that interference mainly comes from the 1 st ring <strong>of</strong> cells. From<br />
Figure 3-5 and Figure 3-6, it clearly appears that the best SINRs are obtained for the best location<br />
configurations. Indeed, when there is no wall between the serving HBS and the MS and 3 walls between<br />
the interfering femtocells and the MS (which corresponds to N other =3 N own =0), the SINR reaches 55.9 dB<br />
when the MS is at 5 meters from its serving HBS (Figure 3-5).<br />
Whereas, when there are 3 walls between the serving HBS and the MS and one wall between the<br />
interfering femtocells and the MS (which corresponds to N other =1 N own =3), the SINR reaches 0.44 dB<br />
when the MS is at 5 meters from its serving HBS (Figure 3-5).<br />
Another important result to notice is that, as expected, some location configurations are equivalent.<br />
Indeed, it is due to the ratio calculation:<br />
K<br />
K<br />
Nown<br />
Nother<br />
=<br />
2600<br />
2600<br />
MHz<br />
MHz<br />
× 10<br />
× 10<br />
1.2Nother<br />
−2.8<br />
1.2Nown<br />
−2.8<br />
= 10<br />
1.2<br />
( Nother<br />
−Nown<br />
)<br />
.<br />
This leads to four equivalences as symbolized in Figure 3-7:<br />
• N other =1 N own =2 ≡ N other =2 N own =3,<br />
• N other =1 N own =1 ≡ N other =2 N own =2 ≡ N other =3 N own =3,<br />
• N other =1 N own =0 ≡ N other =2 N own =1 ≡ N other =3 N own =2,<br />
• N other =2 N own =0 ≡ N other =3 N own =1.<br />
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Figure 3-7: Equivalent configuration for SINR calculation<br />
In the following analysis we set an SINR threshold which depends on the number <strong>of</strong> users in the cell and<br />
on the requested service as can be seen in Table 3-1. As the targeted services in LTE need high<br />
throughput performance, this study focuses on a 5 Mbps service.<br />
Table 3-1: SINR threshold for a requested service <strong>of</strong> 5 Mbps<br />
SINR threshold<br />
1 user using the whole bandwidth (50RB/TTI) 1 dB<br />
5 users using 10RB/TTI 13.9 dB<br />
These SINR threshold values are obtained from some throughput performance curves generated by a<br />
system simulator for an Indoor A 3km/h channel (6 paths) (see Table 3-2) in a 2x2 MIMO with spatial<br />
multiplexing configuration which is a classical LTE configuration.<br />
Table 3-2: ITU Indoor A 3 km/h channel<br />
Tap Channel A Doppler<br />
Rel. Delay (nsec) Avg. Power (dB) <strong>Spectrum</strong><br />
1 0 0.0 CLASSIC<br />
2 50 -3.0 CLASSIC<br />
3 110 -10.0 CLASSIC<br />
4 170 -18.0 CLASSIC<br />
5 290 -26.0 CLASSIC<br />
6 310 -32.0 CLASSIC<br />
This result has been validated with a 3GPP document [3GPP1]. Under these thresholds the link quality is<br />
not good enough to satisfy the users.<br />
These thresholds are represented in Figure 3-8 by the red and black dashed lines. From these figures, we<br />
notice that, as above: the smaller the number <strong>of</strong> walls between the serving HBS and the MS is and the<br />
higher the number <strong>of</strong> walls between the other HBSs and the MS is, the greater is the SINR. This is<br />
because, as the desired signal, the interference suffers from fading.<br />
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Plot <strong>of</strong> SINR<br />
Cdf plot <strong>of</strong> SINR<br />
80<br />
60<br />
1<br />
0.9<br />
0.8<br />
1user<br />
40<br />
0.7<br />
0.6<br />
5 users<br />
dB<br />
20<br />
0<br />
-20<br />
0.5<br />
0.4<br />
0.3<br />
0.2<br />
0.1<br />
0 5 10 15 20 25 30<br />
Distance between the serving femto cell and the MS in meters<br />
0<br />
-20 0 20 40 60 80<br />
dB<br />
Figure 3-8: SINR and CDF <strong>of</strong> SINR with thresholds<br />
In Table 3-3, we can see in which location configurations a femtocell network can achieve at least the<br />
SINR threshold corresponding to a 5 Mbps service (HBS density =0.0004m -2 ).<br />
Table 3-3: Summary <strong>of</strong> the possible configurations<br />
SINR Thresholds<br />
1 dB 13.9 dB<br />
N other =3 N own =0 User is always satisfied. Users are always satisfied.<br />
N other =2 N own =0<br />
≡<br />
N other =3 N own =1<br />
N other =1 N own =0<br />
≡<br />
N other =2 N own =1<br />
≡<br />
N other =3 N own =2<br />
N other =1 N own =1<br />
≡<br />
N other =2 N own =2<br />
≡<br />
N other =3 N own =3,<br />
N other =1 N own =2<br />
≡<br />
N other =2 N own =3<br />
N other =1 N own =3<br />
User is always satisfied.<br />
User is always satisfied.<br />
User is satisfied if he is NOT further<br />
than 26.2 meters from the serving<br />
HBS.<br />
User is satisfied if he is NOT further<br />
than 11.8 meters from the serving<br />
HBS.<br />
User is satisfied if he is NOT further<br />
than 4.9 meters from the serving<br />
HBS.<br />
Users are always satisfied.<br />
Users are satisfied if they are NOT further<br />
than 24.9 meters from the serving HBS.<br />
Users are satisfied if they are NOT further<br />
than 11.1 meters from the serving HBS.<br />
Users are satisfied if they are NOT further<br />
than 4.5 meters from the serving HBS.<br />
Users are satisfied if they are NOT further<br />
than 1.7 meters from the serving HBS.<br />
From Table 3-3, we can conclude that a femtocell network <strong>of</strong> 400 HBS in 1km 2 , on a dedicated frequency<br />
band can be deployed. Indeed, when there is only one user requesting a 5 Mbps service all spatial<br />
configurations are satisfying, except the more pessimistic N other =1, N own =3, which is an improbable<br />
configuration. For five users the same results are observed. As expected, when users are closer to the<br />
interfering HBSs than to their HBS, the interference is too strong.<br />
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Considering the entire network, it is<br />
reasonable to think that the average<br />
number <strong>of</strong> walls between the interfering<br />
HBS and the MS is about 2. For this<br />
reason the following parts <strong>of</strong> the study will<br />
focus on this spatial configuration.<br />
Figure 3-9 is an example <strong>of</strong> a dense<br />
internet box deployment in which each<br />
logo <strong>of</strong> France Telecom represents an<br />
internet box equipped with an HBS.<br />
Figure 3-9: Example <strong>of</strong> internet box deployment<br />
3.1.1.3 Interference between femtocells: Throughput results<br />
In this section we focus on the throughput performance for a 2x2 MIMO configuration with spatial<br />
multiplexing. We choose what is seen as the most realistic deployment scenario for LTE. The simulation<br />
has been done with the following parameters:<br />
• Downlink OFDM LTE, Carrier frequency 2.6 GHz,<br />
• Indoor A 3km/h channel (6 paths),<br />
• Channel bandwidth 10MHz<br />
• DTxAA MIMO scheme (spatial multiplexing, the highest MCS used is 64 QAM, code rate 5/6),<br />
• Maximum transmit power 15 dBm,<br />
• Without shadowing,<br />
• BER=0.01,<br />
• 1 user in the cell (using 10RB).<br />
The link curve has been generated by a system simulator calibrated for 3GPP studies in Orange labs for<br />
an Indoor A 3km/h channel (6 paths) and it has been validated by comparing the obtained throughput<br />
performance curves to simulations done by a NEC 3GPP contribution [3GPP2]. As the curve does not go<br />
under 0.5 dB, smaller values have been extrapolated.<br />
Figure 3-10 shows the maximum throughput that<br />
can be achieved when the total system bandwidth<br />
is used.<br />
60<br />
50<br />
Throughput per TTI<br />
40<br />
Mbps<br />
30<br />
20<br />
As expected, the greatest total throughput is<br />
achieved by the best location configuration (N other<br />
=2 N own =0), as the throughput is calculated from<br />
the SINR. Another important result to notice is<br />
that the slope <strong>of</strong> the curve increases as the<br />
number <strong>of</strong> walls increases. Indeed, when there is<br />
no wall between the user and his serving HBS,<br />
the throughput per TTI decreases from about 8.5<br />
Mbps between 16 meters and 26 meters.<br />
10<br />
0<br />
0 5 10 15 20 25 30<br />
Distance between the serving femto cell and the MS in meters<br />
Figure 3-10: Throughput performance for the whole<br />
bandwidth (50 RB/TTI)<br />
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Number <strong>of</strong> satisfied users N other<br />
= 2 Service=5 Mbps<br />
10<br />
Whereas, when there are 3 walls between the user<br />
and his serving HBS, the throughput per TTI 9<br />
decreases from about 42.3 Mbps between 2<br />
8<br />
meters and 12 meters. Furthermore, in this<br />
configuration the user must not be further than 13<br />
N<br />
7<br />
ow n<br />
=0<br />
meters.<br />
N ow n<br />
=1<br />
The same observation is done for the number <strong>of</strong><br />
satisfied users shown in Figure 3-11. Indeed,<br />
when there are 3 walls between the user and his<br />
serving HBS, the number <strong>of</strong> satisfied users<br />
decreases dramatically. When there are 3 walls<br />
between the user and his serving HBS, the<br />
number <strong>of</strong> satisfied users decreases from 10 users<br />
at 1 meter from the serving HBS to 2 users at 5<br />
Number <strong>of</strong> users satisfied<br />
6<br />
5<br />
4<br />
3<br />
2<br />
1<br />
N ow n<br />
=2<br />
N ow n<br />
=3<br />
0<br />
meters. 0 5 10 15 20 25 30<br />
Distance between the serving femto cell and the MS in meters<br />
Figure 3-11: Number <strong>of</strong> satisfied users<br />
The impact <strong>of</strong> the number <strong>of</strong> walls is easily seen on average total throughput <strong>of</strong> the cell given in Table<br />
3-4.<br />
Space configurations<br />
• Table 3-4: Average total throughput and average number <strong>of</strong> satisfied users<br />
Average total throughput<br />
Average satisfied users<br />
requesting 5 Mbps<br />
Average satisfied users<br />
requesting 10 Mbps<br />
N other =2 N own =0 53 Mbps 9.4 4.7<br />
N other =2 N own =1 28.5 Mbps 4.9 2.3<br />
N other =2 N own =2 9 Mbps 1.2 0<br />
N other =2 N own =3 1.4 Mbps 0 0<br />
Table 3-4 also shows the average number <strong>of</strong> users satisfied depending on the requesting service and on<br />
the location configurations. From all the results shown above, it appears that to be at 3 walls from his<br />
serving HBS (which will not be a common situation) does not satisfy users requesting high data rate<br />
services. However, this configuration allows basic low data rate services (VoIP…).<br />
We also imagined a pretty dense scenario in which the internet box would have an impressive success.<br />
The following figures (12, 13 and 14) show that almost the same performances are achieved when there<br />
are three times more HBS (1200 HBS in 1km 2 ) which means that the distance between two interfering<br />
HBS is about 32 meters. The throughput performances are very similar. However the cell size is reduced,<br />
but still acceptable.<br />
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60<br />
Throughput per TTI<br />
50<br />
40<br />
30<br />
N other<br />
=2 N ow n<br />
=0<br />
N other<br />
=2 N ow n<br />
=1<br />
N other<br />
=2 N ow n<br />
=2<br />
N other<br />
=2 N ow n<br />
=3<br />
50<br />
40<br />
N other<br />
=2 N ow n<br />
=0<br />
N other<br />
=2 N ow n<br />
=1<br />
N other<br />
=2 N ow n<br />
=2<br />
dB<br />
20<br />
Mbps<br />
30<br />
N other<br />
=2 N ow n<br />
=3<br />
10<br />
20<br />
0<br />
-10<br />
10<br />
-20<br />
0 2 4 6 8 10 12 14 16 18<br />
Distance between the serving femto cell and the MS in meters<br />
Figure 3-12: SINR as a function <strong>of</strong> the distance.<br />
Table 3-5: Average total throughput and average number <strong>of</strong><br />
satisfied users.<br />
Space<br />
configurations<br />
N other =2<br />
N own =0<br />
N other =2<br />
N own =1<br />
N other =2<br />
N own =2<br />
N other =2<br />
N own =3<br />
Average<br />
total<br />
throughput<br />
Average<br />
satisfied<br />
users<br />
requesting 5<br />
Mbps<br />
Average<br />
satisfied<br />
users<br />
requesting<br />
10 Mbps<br />
52.6 Mbps 9.4 4.7<br />
28 Mbps 4.8 2.3<br />
8.7 Mbps 1.2 0<br />
1.3 Mbps 0 0<br />
Number <strong>of</strong> users satisfied<br />
0<br />
0 2 4 6 8 10 12 14 16 18<br />
Distance between the serving femto cell and the MS in meters<br />
Figure 3-13: Throughput performance for the whole<br />
bandwidth (50 RB/TTI).<br />
10<br />
9<br />
8<br />
7<br />
6<br />
5<br />
4<br />
3<br />
2<br />
1<br />
Number <strong>of</strong> satisfied users N other<br />
= 2 Service=5 Mbps<br />
N ow n<br />
=0<br />
N ow n<br />
=1<br />
N ow n<br />
=2<br />
N ow n<br />
=3<br />
0<br />
0 2 4 6 8 10 12 14 16 18<br />
Distance between the serving femto cell and the MS in meters<br />
Figure 3-14: Number <strong>of</strong> satisfied users<br />
3.1.1.4 Scenario 1 conclusion<br />
The most important result to notice is that interference mainly comes from the 1 st ring <strong>of</strong> cells. All results<br />
shown above lead to the conclusion that a femtocell network on a dedicated frequency band (here<br />
10MHz) can be deployed.<br />
As seen on Figure 3-15, for a femtocell<br />
network <strong>of</strong> 400 HBS in 1km 2 (which means<br />
that the distance between two interfering HBS<br />
is about 56.4 meters), if a user wants to have a<br />
guaranteed throughput <strong>of</strong> 10 Mbps (HDTV +<br />
other services):<br />
• he can be further than 28.2 meters from<br />
his serving HBS when the MS is in<br />
the same room,<br />
• he must not be further than 28.2 meters<br />
from his serving HBS when there is 1<br />
wall between the serving HBS and<br />
the MS,<br />
• he must not be further than 14.3 meters<br />
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from his serving HBS when there are<br />
2 walls between the serving HBS and<br />
the MS,<br />
• he must not be further than 5.7meters<br />
from his serving HBS when there are<br />
3 walls between the serving HBS and<br />
the MS.<br />
•<br />
Figure 3-15: Size <strong>of</strong> a femtocell depending on the<br />
spatial configuration.<br />
As can be seen on Figure 3-16, for a femtocell<br />
network <strong>of</strong> 1200 HBS in 1km 2 (which means<br />
that the distance between two interfering HBS<br />
is about 32 meters), if a user wants to have a<br />
guaranteed throughput <strong>of</strong> 10 Mbps (TVHD +<br />
other services):<br />
• he can be further than 16.2 meters from<br />
his serving HBS when the MS is in<br />
the same room,<br />
• he must not be further than 16.2 meters<br />
from his serving HBS when there is 1<br />
wall between the serving HBS and<br />
the MS,<br />
• he must not be further than 8.1 meters<br />
from his serving HBS when there are<br />
2 walls between the serving HBS and<br />
the MS,<br />
• he must not be further than 3.2 meters<br />
from his serving HBS when there are<br />
3 walls between the serving HBS and<br />
the MS.<br />
Figure 3-16 : Size <strong>of</strong> a femtocell depending on the<br />
spatial configuration.<br />
Considering only downlink transmission, we observed that interference mainly comes from the 1st<br />
ring <strong>of</strong> cells and we recommend to have no more than 2 walls between the serving HBS and the MS.<br />
To guarantee a 10 Mbps rate to deliver high QoS for multiplay <strong>of</strong>fer (TVHD plus other<br />
services) to one user using the whole bandwidth, the cell size radius is about (when there are 2 walls<br />
between the serving HBS and the MS) :<br />
• 14,3 meters (400 HBS in 1km 2 , distance between two interfering HBS is about 56.4 meters),<br />
• 8.1 meters (1200 HBS in 1km 2 , distance between two interfering HBS is about 32 meters).<br />
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3.1.2 Scenario 2: Interference between femto and macrocells<br />
The scenario 2 focuses on the assessment <strong>of</strong> the interference induced on a femtocell by both femtocell and<br />
macrocell networks, for particular location configurations and different pathloss. In this scenario, we use<br />
almost the same assumptions as in scenarios 1.<br />
The way we model interference from femto and macro is based on superposition <strong>of</strong> macrocells on<br />
femtocells as shown in Figure 3-17.<br />
Figure 3-17: scenario 2 modelling<br />
3.1.2.1 Assumptions<br />
In this scenario, we used the same pathloss formula as in the scenario 1 for all the HBSs:<br />
L log ( f ) + 28log ( r ) − 28 + N 12 .<br />
dB<br />
= 20<br />
10 MHz<br />
10 m<br />
walls<br />
×<br />
And the Cost231-Walfish-Ikegami Dense Urban pathloss formula for the macrocells at which we added a<br />
12dB loss for the penetration:<br />
L 38×<br />
log10 ( r ) + 150.9 .<br />
dB<br />
=<br />
Km<br />
This means for instance that a first ring macro cell interference on femtocell victim will be composed <strong>of</strong>:<br />
o dense urban path loss on a distance corresponding to the Macro radius<br />
o plus 12 dB due to outdoor to indoor penetration<br />
o plus femtocell radius with indoor path loss<br />
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In this study the HBS have all<br />
omnidirectional and macrocells are<br />
three-sectored. The antenna pattern is<br />
shown in Figure 18 and is calculated<br />
as follows:<br />
1<br />
0.9<br />
0.8<br />
0.7<br />
0.6<br />
Antenna pattern<br />
G 1<br />
(θ)<br />
G 2<br />
(θ)<br />
G 3<br />
(θ)<br />
2<br />
( θ ) = − min(12×<br />
( θ / 70) ,20)<br />
G ,<br />
( θ ) G( ),<br />
G =<br />
G<br />
1<br />
θ<br />
2<br />
( θ ) = G( θ + 2π<br />
),<br />
3<br />
( θ ) = G( θ + 4π<br />
)<br />
G<br />
3<br />
.<br />
3<br />
0.5<br />
0.4<br />
0.3<br />
0.2<br />
0.1<br />
-250 -200 -150 -100 -50 0 50 100 150 200 250<br />
Angle Theta<br />
Figure 3-18: Antenna Pattern.<br />
The SINR is calculated as shown hereafter. In this scenario we assess the interference induced on a<br />
femtocell by both femtocell and macrocell networks. The analytical model which takes the assumption is<br />
used to calculate the interference factor coming from macrocell network.<br />
F<br />
OMNI Macro<br />
2 × π × ρ<br />
=<br />
BS macro<br />
( η − 2)<br />
m<br />
× K<br />
× K<br />
Nown<br />
macro<br />
× P<br />
× P<br />
macro<br />
femto<br />
× r<br />
η<br />
f<br />
2−η<br />
m<br />
2−η<br />
m<br />
[( Rc + Rcm − r) − ( R − r)<br />
]<br />
Where r represents the varying distance between the HBS and MS, η f the exponential pathloss factor <strong>of</strong><br />
HBS, η m the exponential pathloss factor <strong>of</strong> macrocells, ρ BS macro the BS's density, Rc+Rcm the distance<br />
between two interfering cells, R the network's size in meters, P femto represents the HBS power in mW and<br />
P macro represents the macrocell power in mW. We define K Nown as a function <strong>of</strong> N walls for the serving HBS<br />
and MS:<br />
K<br />
Nown<br />
2 1.2 N walls −2.8<br />
= f × 10<br />
And K MACRO is calculated as follows:<br />
From the FLUID model:<br />
Where:<br />
a<br />
K macro<br />
= f<br />
× 10<br />
0 15.09−(38×<br />
log10<br />
( 1000 )/10)<br />
( θ ) × F b( θ )<br />
FSect Macro<br />
= a<br />
OMNI Macro<br />
+<br />
2π<br />
1 S<br />
omni<br />
G( )<br />
0<br />
( ) ∫ θ<br />
θ = ×<br />
And b ( θ ) = 0<br />
2π<br />
S<br />
sec t<br />
The Analytical model developed in Orange Labs is also used to calculate the interference factor coming<br />
from other HBS [Kel07].<br />
F<br />
OMNI Femto<br />
2×<br />
=<br />
× ρ<br />
( η − 2)<br />
× K<br />
× K<br />
× r<br />
f<br />
π 2−η<br />
f<br />
BS femto Nown<br />
f<br />
Nother<br />
η<br />
⎡<br />
⎢⎣<br />
2−η<br />
f<br />
( 2Rc<br />
− r) − ( R − r)<br />
⎤<br />
⎥⎦<br />
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Where r represents the varying distance between HBS and MS, η f the exponential pathloss factor, ρ BS femto<br />
the HBS's density, 2Rc the distance between two interfering HBS, R the network's size in meters and<br />
P femto represents the femtocell power in mW. We define K Nown and K Nother as a function <strong>of</strong> N walls for the<br />
serving femtocell and the others femtocells respectively:<br />
2 1.2 N walls −2.8<br />
K = f × 10<br />
N<br />
The total interference factor is obtained by summing the two interference factors above, as shown below:<br />
F = F + F<br />
TOTAL<br />
Sect Macro<br />
OMNI Femto<br />
The SINR is obtained as follows:<br />
SINR =<br />
F<br />
TOTAL +<br />
1<br />
Noise<br />
in which<br />
⎛<br />
⎜<br />
Thermal Noise × K<br />
Nown<br />
× r<br />
Noise =<br />
⎝<br />
Pfemto<br />
η f<br />
⎞<br />
⎟<br />
⎠<br />
The input parameters <strong>of</strong> the simulation studied in the next section are shown in Figure 3-19.<br />
Figure 3-19: Input parameters<br />
3.1.2.2 Interference between femto and macro cells: SINR results<br />
Let's start by the assessment <strong>of</strong> the SINR. Figure 26 shows the SINR considering the interference coming<br />
from the entire network (N other is the number <strong>of</strong> walls between the interfering cells and the MS and N own is<br />
the number <strong>of</strong> walls between the serving femtocell and the MS). In this scenario the HBS maximum<br />
transmitting power is set to 15 dBm, the macrocell maximum transmitting power is set to 47.8 dBm and<br />
cell load is uniformly set to 70%.<br />
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Plot <strong>of</strong> SINR<br />
From Figure 3-20 we can say that if there is one wall<br />
between the interfering cells and the MS and no wall<br />
between the serving HBS and the MS (which corresponds to<br />
N other =1 N own =0), the user experienced a SINR <strong>of</strong> about<br />
29.5 dB when he is at 6 meters from his serving HBS.<br />
As expected, it clearly appears that the best SINRs are<br />
obtained for the best location configurations. Indeed, when<br />
there is no wall between the serving HBS and the MS and 3<br />
walls between the interfering femtocells and the MS (which<br />
corresponds to N other =3 N own =0), the SINR reaches 55.2 dB<br />
when the MS is at 5 meters from its serving HBS (Figure<br />
19). Whereas, when there are 3 walls between the serving<br />
HBS and the MS and one wall between the interfering<br />
femtocells and the MS (which corresponds to N other =1 N own<br />
=3), the SINR reaches -4.1 dB when the MS is at 5 meters<br />
from its serving HBS.<br />
dB<br />
80<br />
60<br />
40<br />
20<br />
0<br />
-20<br />
-40<br />
0 5 10 15 20 25 30<br />
Distance between the serving femto cell and the MS in meters<br />
Figure 3-20: The entire network<br />
Another important result to notice is that some location configurations are almost equivalents. Indeed as<br />
in scenario 1, it is due to the analytical model and pathloss (underlined by the ratio calculation hereafter),<br />
which means that in this scenario the macrocells have a small impact on the femtocell network.<br />
Plot <strong>of</strong> SINR<br />
K<br />
K<br />
Nown<br />
Nother<br />
10<br />
=<br />
10<br />
1.2Nother<br />
−2.8<br />
1.2Nown<br />
−2.8<br />
= 10<br />
1.2<br />
( N −N<br />
)<br />
other<br />
own<br />
55<br />
50<br />
45<br />
Three equivalences (Figure 28):<br />
• N other =1 N own =0 ≡ N other =2 N own =1,<br />
• N other =1 N own =1 ≡ N other =2 N own =2,<br />
• N other =1 N own =2 ≡ N other =2 N own =3.<br />
It is also interesting to see that in this scenario the<br />
importance <strong>of</strong> N own grows as the number <strong>of</strong> walls<br />
between the interfering cells and the MS grows.<br />
dB<br />
40<br />
35<br />
30<br />
25<br />
20<br />
15<br />
2.1 2.2 2.3 2.4 2.5 2.6 2.7 2.8 2.9 3<br />
Distance between the serving femto cell and the MS in meters<br />
Figure 3-21: Equivalences<br />
In this report, we set an SINR threshold which depends on the number <strong>of</strong> users in the cell and on<br />
the requested service as can be seen in Table 3-6. As the targeted services in LTE need high throughput<br />
performances, this study focuses on a 5 Mbps service.<br />
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Table 3-6: SINR threshold for a requested service <strong>of</strong> 5 Mbps.<br />
SINR threshold<br />
1 user using the whole bandwidth (50RB/TTI) 1 dB<br />
5 users using 10RB/TTI 13.9 dB<br />
The SINR threshold values are obtained from the throughput performance curves generated by<br />
the simulator, called SOFFA, for an Indoor A 3km/h channel (6 paths) in a 2x2 MIMO with spatial<br />
multiplexing configuration which is a classical LTE configuration. Under the given thresholds the link<br />
quality is not good enough to satisfy the users.<br />
These thresholds are represented in Figure 3-22 by the red and black dashed lines. Considering the entire<br />
network, it is reasonable to think that the average number <strong>of</strong> walls between the interfering HBS and the<br />
MS is about 2. For this reason the following parts <strong>of</strong> the study will focus on this spatial configuration.<br />
N other =2<br />
N own =0<br />
N other =2<br />
N own =1<br />
N other =2<br />
N own =2<br />
N other =2<br />
N own =3<br />
Table 3-7: Configuration summary<br />
SINR Thresholds<br />
1 dB 13.9 dB<br />
Ok<br />
Ok<br />
Ok<br />
Ok If d
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In this section we focus on the throughput performances for a 2x2 MIMO configuration with spatial<br />
multiplexing. Indeed, with regard to the time required to assess radio link curves, we took what is seen as<br />
the most realistic deployment scenario for LTE. The simulation has been done with the following<br />
parameters:<br />
• Downlink OFDM LTE, Carrier frequency 2.6 GHz,<br />
• Indoor A 3km/h channel (6 paths),<br />
• Channel bandwidth 10Mhz<br />
• DTxAA MIMO scheme (spatial multiplexing the highest MCS used is 64 QAM, code rate 5/6),<br />
• Maximum power 15 dBm,<br />
• Without shadowing,<br />
• BER=0.01,<br />
• 1 user in the cell (using 10RB).<br />
The link curve has been generated by the simulator called SOFFA for an Indoor A 3km/h channel (6<br />
paths) and has been validated by comparing the obtained throughput performance curves to simulations<br />
done by a NEC 3GPP contribution. As the curve does not go under 0.5 dB, the values below have been<br />
extrapolated.<br />
Figure 3-23 shows the maximum throughput that<br />
can be achieved when the total system's<br />
bandwidth is used.<br />
As expected, the greatest total throughput is<br />
achieved by the best location configuration (N other<br />
=2 N own =0), as the throughput is calculated from<br />
the SINR.<br />
Another important result to notice is that the slope<br />
<strong>of</strong> the curve increases as the number <strong>of</strong> walls<br />
increases. Indeed when there is no wall between<br />
the user and his serving HBS, the throughput per<br />
TTI decreases from about 8,5 Mbps between 16<br />
meters and 26 meters.<br />
Whereas, when there are 3 walls between the user<br />
and his serving HBS, the throughput per TTI<br />
decreases from about 42.3 Mbps between 2 meters<br />
and 12 meters. Furthermore, in this configuration<br />
the user must not be further than 13 meters.<br />
The same observation is done for the number <strong>of</strong><br />
satisfied users shown in Figure 24. Indeed when<br />
there are 3 walls between the user and his serving<br />
HBS, the number <strong>of</strong> satisfied users decreases<br />
dramatically. When there are 3 walls between the<br />
user and his serving HBS, the number <strong>of</strong> satisfied<br />
users decreases from 10 users at 1 meter from the<br />
serving HBS to 2 users at 5 meters.<br />
From these results it can easily be seen that the<br />
performances are very similar to the ones obtained<br />
in scenario 1. This means that a femtocell network<br />
can be deployed on the same frequency band (here<br />
10MHz) as the outdoor macrocell network.<br />
Mbps<br />
Number <strong>of</strong> users satisfied<br />
60<br />
50<br />
40<br />
30<br />
20<br />
10<br />
Throughput per TTI<br />
N other<br />
=2 N ow n<br />
=0<br />
N other<br />
=2 N ow n<br />
=1<br />
N other<br />
=2 N ow n<br />
=2<br />
N other<br />
=2 N ow n<br />
=3<br />
0<br />
0 5 10 15 20 25 30<br />
Distance between the serving femto cell and the MS in meters<br />
Figure 3-23: Throughput performance for the whole<br />
bandwidth (50 RB/TTI)<br />
10<br />
9<br />
8<br />
7<br />
6<br />
5<br />
4<br />
3<br />
2<br />
1<br />
Number <strong>of</strong> satisfied users N other<br />
= 2 Service=5 Mbps<br />
N ow n<br />
=0<br />
N ow n<br />
=1<br />
N ow n<br />
=2<br />
N ow n<br />
=3<br />
0<br />
0 5 10 15 20 25 30<br />
Distance between the serving femto cell and the MS in meters<br />
Figure 3-24: Number <strong>of</strong> satisfied users<br />
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3.1.2.4 Scenario 2 conclusion<br />
In Table 3-9, we can see in which location configurations the system can achieve at least the SINR<br />
threshold corresponding to a 5 Mbps service (HBS density =0.0004m -2 , Node B density =2*10 -6 m -2 ). In<br />
Table 3-10, we can see in which location configurations the system can achieve at least the SINR<br />
threshold corresponding to a 5 Mbps service (HBS density =0.0004m -2 ).<br />
Table 3-9: Configuration summary (femto + macro)<br />
SINR Thresholds<br />
1 dB 13.9 dB<br />
N other =2 N own =0 Ok Ok<br />
N other =2 N own =1 Ok Ok If d
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femtocell network can be deployed on the carrier bandwidth frequency band (here 10MHz) as the<br />
outdoor macrocell network.<br />
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3.1.3 Scenario 3: Interference between femto and macrocells<br />
The scenario 3 focuses on the assessment <strong>of</strong> the interference induced on a macrocell by both femtocell<br />
and macrocell networks, for particular location configurations and different pathloss. In this scenario, we<br />
use almost the same assumptions as in scenario 2.<br />
3.1.3.1 Assumptions<br />
In this scenario, we use the same pathloss formula as in the scenario 1 for all the HBSs:<br />
L<br />
dB<br />
= 20<br />
10<br />
walls<br />
log10 ( f<br />
MHz<br />
) + 28log ( rm<br />
) − 28 + N × 12<br />
And the Cost231-Walfish-Ikegami Dense Urban pathloss formula for the macrocells:<br />
L<br />
dB<br />
=<br />
Km<br />
38×<br />
log10 ( r ) + 150.9<br />
In this study the HBS have all<br />
omnidirectional and macrocells are<br />
three-sectored. The antenna pattern<br />
is shown in Figure 26 and is<br />
calculated as follows:<br />
1<br />
0.9<br />
0.8<br />
0.7<br />
Antenna pattern<br />
G 1<br />
(θ)<br />
G 2<br />
(θ)<br />
G 3<br />
(θ)<br />
G<br />
2<br />
( θ ) = − min(12×<br />
( θ / 70) ,20)<br />
0.6<br />
0.5<br />
( θ ) G( ),<br />
G =<br />
1<br />
θ<br />
0.4<br />
G<br />
2<br />
( θ ) = G( θ + 2π<br />
),<br />
3<br />
( θ ) = G( θ + 4π<br />
)<br />
G<br />
3<br />
.<br />
3<br />
0.3<br />
0.2<br />
0.1<br />
-250 -200 -150 -100 -50 0 50 100 150 200 250<br />
Angle Theta<br />
Figure 3-26: Antenna Pattern<br />
The SINR is calculated as shown hereafter. In this scenario we assess the interference induced on a<br />
femtocell by both femtocell and macrocell networks. The analytical model is used to calculate the<br />
interference factor coming from macrocell network.<br />
F<br />
OMNI Macro<br />
2 × π × ρ<br />
=<br />
BS macro<br />
( η − 2)<br />
m<br />
× K<br />
× K<br />
macro<br />
macro<br />
× P<br />
× P<br />
macro<br />
macro<br />
× r<br />
η<br />
m<br />
2−η<br />
m<br />
2−η<br />
m<br />
[( 2Rcm<br />
− r) − ( R − r)<br />
]<br />
Where r represents the varying distance between the serving macrocell and MS, η m the exponential<br />
pathloss factor <strong>of</strong> macrocells, ρ BS macro the BS's density, 2Rcm the distance between two interfering cells,<br />
R the network's size in meters and P macro represents the macrocell power in mW. We define K MACRO as<br />
follows:<br />
K macro<br />
= f<br />
× 10<br />
0 15.09−(38×<br />
log10<br />
( 1000 )/10)<br />
From the analytical model:<br />
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( θ ) × F b( θ )<br />
FSect Macro<br />
= a<br />
OMNI Macro<br />
+<br />
Where:<br />
a<br />
2π<br />
1 S<br />
omni<br />
( θ )<br />
( θ ) ∫ G<br />
0<br />
= ×<br />
And b( θ )<br />
2π<br />
S × G ( θ )<br />
sec t<br />
1<br />
=<br />
3<br />
∑<br />
S = 2<br />
G<br />
1<br />
( θ )<br />
( θ )<br />
G<br />
The FLUID model is also used to calculate the interference factor coming from other HBS.<br />
F<br />
OMNI Femto<br />
2 ×<br />
=<br />
ηm<br />
π × ρ × K × P × r<br />
2−η<br />
f<br />
BS femto macro femto<br />
( η − 2) × K × P × G ( θ )<br />
f<br />
Nother<br />
macro<br />
1<br />
⎡<br />
⎢⎣<br />
2−η<br />
f<br />
( Rcm + Rc − r) − ( R − r)<br />
Where r represents the varying distance between the HBS and MS, η f the exponential pathloss factor <strong>of</strong><br />
HBS, η m the exponential pathloss factor <strong>of</strong> macrocells, ρ BS macro the BS's density, Rc+Rcm the distance<br />
between two interfering cells, R the network's size in meters, P femto represents the HBS power in mW and<br />
P macro represents the macrocell power in mW. We define K Nown and K Nother as a function <strong>of</strong> N walls :<br />
⎤<br />
⎥⎦<br />
K<br />
N<br />
2 1.2 N walls −2.8<br />
= f × 10<br />
And K MACRO is calculated as follows:<br />
K macro<br />
= f<br />
× 10<br />
2 15.09−(38×<br />
log10<br />
( 1000 )/10)<br />
The total interference factor is obtained by summing the two interference factors above, as shown below:<br />
F = F + F<br />
TOTAL<br />
Sect Macro<br />
OMNI Femto<br />
The SINR is obtained as follows:<br />
SINR =<br />
F<br />
TOTAL +<br />
1<br />
Noise<br />
in which<br />
⎛ Thermal Noise × K<br />
macro<br />
× r<br />
⎜<br />
Noise =<br />
⎝<br />
Pmacro<br />
η m<br />
⎞<br />
⎟<br />
⎠<br />
The input parameters <strong>of</strong> the simulation studied in the next section are shown in Figure 3-27.<br />
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Figure 3-27: Input parameters<br />
3.1.3.2 Interference between femto and macro cells: SINR results<br />
Let's start by the assessment <strong>of</strong> the SINR. Figure 3-28 shows the SINR considering the interference<br />
coming from the entire network (N other is the number <strong>of</strong> walls between the interfering cells and the MS<br />
and N own is the number <strong>of</strong> walls between the serving macrocell and the MS). In this scenario the HBS<br />
maximum transmitting power is set to 15 dBm, the macrocell maximum transmitting power is set to 47.8<br />
dBm and cell load is uniformly set to 70%.<br />
The most important phenomenon to notice is that the femtocells have an important impact on the<br />
macrocell SINR.<br />
20<br />
Plot <strong>of</strong> SINR<br />
15<br />
10<br />
5<br />
dB<br />
0<br />
-5<br />
-10<br />
-15<br />
0 50 100 150 200 250 300 350 400<br />
Distance between the serving femto cell and the MS in meters<br />
Indeed, from Figure 3-28 focusing on the results for two walls<br />
Figure 3-28: The entire network<br />
between the interfering cells and the MS and no wall between<br />
the serving macrocell and the MS (which corresponds to N other<br />
=2 N own =0), the user experiences an<br />
SINR <strong>of</strong> about:<br />
• 8.3 dB when he is at 300 meters from his serving e-Node B (considering 400 HBS in 1km 2 ),<br />
• 10.6 dB when he is at 300 meters from his serving e-Node B (considering 200 HBS in 1km 2 ),<br />
• 14.4 dB when he is at 300 meters from his serving e-Node B (considering no HBS).<br />
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As expected, it clearly appears that the best SINRs are obtained for the best location configurations.<br />
Indeed, when there is no wall between the serving macrocell and the MS and 4 walls between the<br />
interfering cells and the MS (which corresponds to N other =4 N own =0), the smallest achieved SINR is<br />
about 9.7 dB when the MS is at 400 meters from its serving e-Node B.<br />
Another important result to notice is that there is a maximum value <strong>of</strong> SINR (about 17 dB) which is<br />
underlined by the "No HBS" curve (which means that there is 0 femtocell). This limitation is explained<br />
by the fact that as the e-Node B are three-sectored, the studied sector suffers from interference coming<br />
from the two other sectors.<br />
3.1.3.3 Interference between femtocells: Throughput results<br />
As the extension to LTE and associated study were planed within 3 months long, simulation with impact<br />
from femto on macro cell throughput could not be performed. Hence, following scenario for a 2x2 MIMO<br />
configuration with spatial multiplexing for following parameters remains to be done:<br />
• Downlink OFDM LTE, Carrier frequency 2.6 GHz,<br />
• Outdoor pedestrian B 3km/h channel (6 paths),<br />
• Channel bandwidth 10MHz<br />
• DTxAA MIMO scheme (spatial multiplexing the highest MCS used is 64 QAM 5/6),<br />
• Maximum power 47.8 dBm (ENode B),<br />
• Without shadowing,<br />
• BER=0.01,<br />
• 1 user in the cell (using 10RB)<br />
A study on the throughput performance cannot be done.<br />
3.1.3.4 Scenario 3 conclusion<br />
The most important phenomenon to notice is that the femtocells have an important impact on the<br />
macrocell SINR. Another important result to notice is that there is a maximum value <strong>of</strong> SINR<br />
(about 17 dB) which is underlined by the "No HBS" curve (which means that there is 0 femtocell).<br />
This limitation is explained by the fact that as the e-Node B are three-sectored, the studied sector<br />
suffers from interference coming from the two other sectors.<br />
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3.2 Multi-Operator Resource Sharing Scenario in the Context <strong>of</strong> IMT-A Systems<br />
This subsection addresses spectrum and network sharing for IMT-A systems, and proposes an innovative<br />
way to coordinate and manage spectrum and network resources in the context <strong>of</strong> user centric mobile<br />
broadband services. The proposed concept is for the integration <strong>of</strong> the spectrum and resource coordination<br />
into a single framework with the objective to enable improved performance and capacity gains. It has not<br />
been researched before in the context <strong>of</strong> IMT-A systems.<br />
Decentralized spectrum and joint radio resource management are investigated in [SALL08], [PER04],<br />
[GRA05]. It is shown in [PER04] that competing UMTS operators can cooperate without operational<br />
information exchange and share a block <strong>of</strong> UMTS carriers simultaneously, to deploy multimedia services.<br />
An algorithm based on the total transmitted energy thresholds is proposed that limits the loading by<br />
individual operators in the shared band and allows for coexistence. It is shown that dynamic spectrum<br />
sharing <strong>of</strong>fers capacity gain due to the increase <strong>of</strong> the trunking efficiency in a spectrum-shared system.<br />
This improvement is achievable by the pooling <strong>of</strong> the radio channels belonging to different operators<br />
together. In [GRA05], it is shown that proper underlying spectrum sharing coordination processes are<br />
required to manage the interference and to further increase the achievable capacity gains. The<br />
investigations are performed for UMTS and with the use <strong>of</strong> joint radio resource management (JRRM).<br />
JRRM is a distributed approach to resource management [PER04]. Besides, it is shown that the different<br />
proposed schemes have to be dynamically managed as a function <strong>of</strong> the traffic loads through the<br />
activation <strong>of</strong> the right strategies. This appropriate capacity management facilitates to get the best<br />
spectrum reuse opportunities. Finally, [SALL08] extends the concept to a scenario <strong>of</strong> cognitive networks<br />
using a decentralized approach to both spectrum and radio resource management (RRM), i.e., JRRM. The<br />
proposed solution is based on a layered approach where spectrum sharing and JRRM are identified and<br />
integrated at both inter-and intra-operator levels.<br />
Work reported in [MIH09] goes beyond the above-mentioned concepts by exploring the possibilities <strong>of</strong><br />
spectrum sharing integration (e.g., spectrum aggregation) and RRM functionalities in the context <strong>of</strong> IMT-<br />
Advanced systems. The concept supports cooperation between operators also when different RATs must<br />
share resources. The required functionalities and interactions are defined and an integrated framework is<br />
proposed. A combined centralized and distributed approach to RRM (i.e, cooperative RRM) that is<br />
proposed for the WINNER system and analyzed in [MIH08] for inter and intra-system interworking is<br />
assumed. The spectrum management functionalities can be integrated with this framework to use further<br />
the advantages <strong>of</strong> higher performance and capacity gains.<br />
The WINNER project considers spectrum management and sharing but does not investigate it together<br />
with use over fragmented frequency bands and network resource coordination. <strong>Spectrum</strong> aggregation is<br />
proposed for LTE-A, an IMT-Advanced candidate concept evolving from LTE. Although LTE-A<br />
considers use <strong>of</strong> fragmented bands, it does not consider it together with network management strategies. It<br />
is proposed here to use the state <strong>of</strong> the art <strong>of</strong> the above system concepts and elevate them further by<br />
providing research results that are valuable to the definition <strong>of</strong> the deployment and user requirements <strong>of</strong><br />
IMT-A systems and mobile broadband services.<br />
The ITU-R M.1645 Recommendation provides the initial requirements for the IMT-Advanced system<br />
concept. Legacy systems, such as GSM, UMTS, and WLAN, would continue to provide services to users;<br />
therefore, a generic framework for the support <strong>of</strong> the interworking between these, essentially, different<br />
systems is required. Interworking implies coexistence and sharing <strong>of</strong> resources. Coexistence means the<br />
concurrent operation <strong>of</strong> different radio systems in the same or in adjacent frequency bands without<br />
causing degradation to any other system, with emphasis on the indicated limitations in terms <strong>of</strong>, e.g.,<br />
frequency separation, physical separation, and transmission resources. Sharing in the context <strong>of</strong> spectrum<br />
considers the use <strong>of</strong> the same frequency band by different radio systems, either with coordination or<br />
possibly without any coordination between the systems, with emphasis on the spectrum access schemes<br />
and methods. ‘Cooperation’ is the term used here to jointly refer to inter-working, coexistence and<br />
sharing.<br />
The system concept developed in [WINDIID6.13.4] proposed that cooperation (i.e., JRRM) mechanisms<br />
for intra-system interworking are developed at the radio segment level <strong>of</strong> new RANs, following a<br />
combined centralized and distributed approach, while inter-system interworking is handled by a central<br />
entity located outside <strong>of</strong> the RAN architecture following a centralized approach. A gateway (GW)<br />
functionality is an IP anchor to external data networks (e.g., Internet, corporate networks, operator<br />
controlled core networks) and operator services. It also terminates flows on the network side and serves as<br />
the anchor point for external routing. Thus, all functions that operate on user data traffic are located here.<br />
Figure 3-29 shows the interworking <strong>of</strong> cooperative RRM and spectrum management functions at different<br />
levels <strong>of</strong> the radio access network architecture.<br />
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Measurements<br />
(neighbouring cell lists;<br />
KPI calculation;<br />
Triggers)<br />
Multi‐RAN/multioperator<br />
Scenario?<br />
YES<br />
Cooperative<br />
RRM/<strong>Spectrum</strong><br />
Manager<br />
(centralized<br />
approach)<br />
Inter‐system<br />
interworking and<br />
spectrum<br />
management<br />
Handover<br />
Admission control,<br />
Congestion control<br />
Load control<br />
Coexistence and<br />
sharing<br />
NO<br />
Generic RRM/<br />
<strong>Spectrum</strong> Server<br />
(centralized and<br />
distributed<br />
approach)<br />
Intra‐system<br />
Interworking<br />
and<br />
spectrum<br />
control<br />
Intra‐system<br />
handover,<br />
load balancing,<br />
vertical<br />
specturm<br />
sharing<br />
Policy‐Based<br />
network and<br />
spectrum<br />
management<br />
Multi‐stage<br />
admission<br />
control<br />
Specific<br />
RRM/<br />
<strong>Spectrum</strong> assignment<br />
(distributed<br />
approach)<br />
Intra‐mode<br />
Interworking and<br />
spectrum control<br />
Intra‐mode<br />
handover,<br />
load balancing,<br />
horizontal<br />
specturm<br />
sharing<br />
Multi‐band<br />
Scheduling,<br />
admission<br />
Control,<br />
power control<br />
Figure 3-29: Cooperation framework for an IMT-Advanced candidate system<br />
The cooperative RRM and spectrum manager contain centralized RRM and spectrum sharing functions,<br />
and enable interworking, sharing and co-existence with other systems (RATs). These interface with the<br />
GW, which contains functionalities related to generic RRM and spectrum management on intra-system<br />
level in order to obtain information about the associated UEs and their characteristics. The generic RRM<br />
is in essence a centralized type <strong>of</strong> control but it allows a distributed approach, while the loads in the<br />
network are low-to-medium (i.e., specific RRM located at the level <strong>of</strong> BS or relay node (RN). The<br />
spectrum server communicates spectrum sharing and spectrum assignment decisions to the BS. The<br />
spectrum server is accessible via the GW for spectrum negotiations. The BS containing the specific RRM<br />
functions is a point <strong>of</strong> radio access. The BS performs all radio related functions for active UEs (i.e.,<br />
sending data) and is responsible for governing radio transmission to and reception from the UE in one<br />
cell. The interconnectivity <strong>of</strong> the functions in the support <strong>of</strong> the above framework is shown in the control<br />
and user plane from Figure 3-30. In practice, the amount <strong>of</strong> required spectrum bandwidth for a network<br />
operator will depend on the traffic / capacity requirements, the modulation scheme used, the cell sizes,<br />
and the frequency reuse factor. The optimum balance is a commercial decision, based on these technical<br />
considerations.<br />
3.2.1 <strong>Spectrum</strong> Aggregation Requirements<br />
The concept <strong>of</strong> spectrum aggregation consists <strong>of</strong> exploiting multiple, small spectrum fragments<br />
simultaneously to deliver a wider band service (i.e., not otherwise achievable when using a single<br />
spectrum fragment. The best choice <strong>of</strong> a frequency band for a mobile communications system depends on<br />
many different factors [DIX08]. In addition, once the spectrum has been obtained the problem <strong>of</strong><br />
managing the shared band implies proper user allocation mechanisms. <strong>Spectrum</strong> aggregation allows that<br />
new high data rate wireless communication systems can coexist while reusing the spectrum <strong>of</strong> legacy<br />
systems. In general, the lower frequency bands are better suited to longer range, higher mobility, lower<br />
capacity systems, while higher frequency bands are better suited to shorter range, lower mobility, and<br />
higher capacity systems. Therefore, for any given network the optimum frequency would vary depending<br />
on the required range, mobility and capacity [DIX08]. For a commercial mobile network, the required<br />
range and capacity varies by changing the number <strong>of</strong> BSs (i.e., changing the size <strong>of</strong> their coverage area)<br />
so that the level <strong>of</strong> investment in the network infrastructure can affect the optimum balance. The White<br />
Paper <strong>of</strong> WWRF WG 8 [DIX08] reports that spectrum for higher mobility applications (which are usually<br />
operating in interference limited scenarios) should be separated in the frequency domain from short-range<br />
applications (<strong>of</strong>ten noise limited scenarios) in order to avoid unnecessary complexity in sharing scenarios.<br />
This can be combined with a traffic split at higher RAN levels (i.e., GW level or generic RRM level) to<br />
explore the benefits <strong>of</strong> interworking at lower layers, while perceiving the network conditions and acting<br />
upon them.<br />
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Access to<br />
shared<br />
band<br />
IP Handover<br />
Admission<br />
Control and Flow<br />
Establishment<br />
Radio Handover<br />
Adaptive<br />
modulation and<br />
coding<br />
Resource<br />
access<br />
Flow Control<br />
Load Control<br />
Control Plane<br />
Congestion Control<br />
Scheduling<br />
Multi‐band<br />
Scheduling (MAC<br />
level)<br />
User Plane<br />
Figure 3-30: Interconnectivity <strong>of</strong> cooperative functions in the control and user planes<br />
Some factors, which should be taken into account to determine the best frequency band, depend on the<br />
individual service requirements and the network requirements. These are explained here together with<br />
some considerations on how radio frequency bands should be managed once access to frequency<br />
spectrum has been obtained [MIH09].<br />
3.2.2 Hypotheses for System and <strong>Spectrum</strong> Resource Usage<br />
The following research hypotheses for the system and the spectrum usage are made here:<br />
• It is possible to reuse the existing infrastructure in terms <strong>of</strong> signalling, measurement, and<br />
protocol procedures with novel interference and resource management schemes;<br />
• An integration <strong>of</strong> spectrum and network resource management functionalities can be exploited<br />
within an IMT-A scenario, while benefiting from higher performance and system capacity gains. The key<br />
to such integration is the pooling <strong>of</strong> the resources together; the integration allows for mapping <strong>of</strong> the<br />
service requirements onto an available spectrum amount and translates the latter into network loads;<br />
• It is possible to use the widely separated frequency bands for achieving lower delays and jitter<br />
and higher user throughput; this can be achieved by use <strong>of</strong> multi-band scheduling algorithms and<br />
exploiting the channel diversity;<br />
• User allocation on various frequency bands can be performed based on the UE capabilities and<br />
performance gains in terms <strong>of</strong> increased peak data rate that can be obtained by use <strong>of</strong> specially designed<br />
algorithms for the management <strong>of</strong> the shared band;<br />
• Information from the network about the system state (e.g., received signal strength, transmitted<br />
power, UE velocity, etc.) and used in RRM procedures based on cooperative RRM [MIH08], such as<br />
load, admission and congestion control can successfully be combined with dynamic spectrum use and<br />
reduce the need <strong>of</strong> spectrum aggregation in some cases; this will be achieved by the integration <strong>of</strong><br />
functionalities for spectrum and RRM use and further optimized by the implementation <strong>of</strong> joint policies;<br />
3.2.3 Intra-and Inter-Operator Sharing <strong>Aspects</strong><br />
3.2.3.1 Intra-Operator Sharing Considerations<br />
For simplicity, in the following discussions it is assumed that the UE is a single-band device. <strong>Spectrum</strong><br />
aggregation can appear when an operator’s dedicated band is not continuous but is split in two or more<br />
parts. In addition, spectrum aggregation can happen in scenarios, in which an operator accesses both a<br />
dedicated band, and a spectrum sharing band which is separated in frequencies from the dedicated<br />
operator’s band. This is also valid for the inter-operator scenario. Once a portion <strong>of</strong> the spectrum has been<br />
obtained, it is important to identify the load on the network that the subsequent allocation in the bands<br />
will create. This requires that service requirements are translated into load values and in addition mapped<br />
to the available spectrum amount. A possible traffic split at generic RRM level (i.e., centralized control)<br />
can act upon the current load network conditions and assist the distributed approach to allocating users in<br />
the frequency bands without disturbing the balance <strong>of</strong> the overall network. The envisioned relationships<br />
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between RRM and spectrum entities are shown in Figure 3-31. During spectrum aggregation, the amount<br />
<strong>of</strong> available spectrum resources in both shared band and dedicated bands will change.<br />
Cooperative<br />
RRM<br />
1. Estimation <strong>of</strong> available<br />
radio resources in controlling<br />
sub network (BS) and traffic split<br />
according to service<br />
requirements<br />
V1 V2 Vn<br />
A1 A2 An<br />
GW<br />
BS<br />
3. GW maps split traffic streams to allocation in bands<br />
inform Cooperative RRM server about timing requirements<br />
between sub-streams<br />
BS<br />
2. Users are allocated<br />
according to specific<br />
(CQIs) by multi-band<br />
scheduler and generic<br />
(network load) RRM<br />
requirements<br />
Multi‐band<br />
scheduler<br />
V D<br />
A C<br />
A D<br />
A D<br />
V C<br />
V C<br />
Band D<br />
Band C<br />
Figure 3-31: Translation <strong>of</strong> service requirements into network resources and mapping to spectrum<br />
availability<br />
A mechanism is required to match the available data in the queues to the available bandwidth. The<br />
scheduling <strong>of</strong> users over multiple frequency bands can be modelled in its most general form as a General<br />
Multi-Band Scheduling (GMBS) problem. A multi-band scheduler to manage the balance between the<br />
data pipe and the obtained extra source <strong>of</strong> spectrum is proposed in [WINIID5.9.1]. When the bandwidth<br />
from the shared band becomes available, the scheduler must be capable <strong>of</strong> realizing such a change in the<br />
spectrum pipe and shift some <strong>of</strong> the traffic load from the dedicated band to the shared band or vice versa.<br />
The scheduler must also be capable <strong>of</strong> further load balancing by actively monitoring the forthcoming<br />
changes in the spectrum and traffic data in order to shift the load from the shared band to dedicated one<br />
and vice- versa, if so required.<br />
Interworking between RRM and spectrum functions then can be translated into the objective <strong>of</strong><br />
maximizing the total throughput <strong>of</strong> the operator, while considering the QoS requirements <strong>of</strong> the service<br />
classes. The more resources are available for a system, the higher the multiuser diversity gain that can be<br />
obtained [LUO03], [E2RD5.3]. The performance is heavily dependent on the radio channel qualities for<br />
each user in the considered bands. The channel quality indicators (CQIs) depend on the path loss and on<br />
the distance from the BS. The operator will have good improvements when the UEs have heterogeneous<br />
spatial distribution in the cell (variable distances from the BS), i.e., different channel qualities in the<br />
considered bands. Here we can view the joint allocation on the dedicated and shared bands as cooperation<br />
at the scheduling level.<br />
Figure 3-30 shows that at intra-system cooperation level a multi-stage admission control mechanism is<br />
active that uses the benefits <strong>of</strong> a joint distributed and centralized control for the admission <strong>of</strong> users to the<br />
network, while balancing the load over a number <strong>of</strong> BSs and thus increasing the network throughput<br />
[MIH208]. It is shown that through load balancing both gains from interworking at MAC level (i.e.,<br />
multiplexing gain) as well as above the MAC (at generic RRM level) are realizable. It is proposed here to<br />
exploit this concept in relation to spectrum aggregation. The multi-band scheduling mechanism will be<br />
busy allocating users over the two frequency bands until the key performance indicators (KPIs) inform<br />
about a degradation <strong>of</strong> the QoS, which would mean that the allocation over the frequency bands does not<br />
match the current network (i.e., traffic) conditions. The operator then would rely on a generic or<br />
cooperative (i.e., centralized) RRM mechanism for restoring the network balance. Cooperative RRM<br />
would mean that the intra-system RRM has been exhausted and inter-system cooperation (still between<br />
systems belonging to the same operator) will be activated (i.e., cooperative RRM level). Such actions<br />
need to work concurrently with the scheduling over the available frequency bands. In this case, the<br />
achievable gain will be a combination <strong>of</strong> the gain from scheduling over separated frequency bands (i.e.,<br />
diversity gain) and the trunking gain from resource sharing (i.e., multiplexing gain achievable through<br />
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traffic splitting and BSs interworking [MIH208]). Future work will compare the achievable performance<br />
for each <strong>of</strong> the two gains.<br />
3.2.3.2 Inter-Operator Considerations<br />
The inter-operator sharing deployment is described in Section 3.2. In this scenario, each operator has<br />
access to a shared band, in addition to owning a dedicated band [WIN+D1.2]. Two general spectrumsharing<br />
deployments can be distinguished:<br />
• Common frequency pool, which is shared by all operators (considered here);<br />
• Separated frequency pools, which are shared by two neighbouring operators.<br />
In the inter-operator case, the interworking can be seen as interworking at cooperative RRM level and<br />
allocation in the shared band. The two mechanisms for coping with the traffic demands can be seen as<br />
exchange <strong>of</strong> resources between operators at a system (i.e., cooperative RRM) and at a user level (i.e.,<br />
sharing <strong>of</strong> the band). The multi-band scheduling mechanism can use the priority levels <strong>of</strong> the split traffic<br />
for assigning the traffic over the frequency bands and in case <strong>of</strong> changes in availability <strong>of</strong> the shared<br />
band, it can relocate traffic or decide to drop or reduce the bandwidth <strong>of</strong> less important flows. For this, an<br />
input from the sharing negotiation functionalities in the network is required. The exchange <strong>of</strong> resources at<br />
a system level is realized by using the logical functionality <strong>of</strong> the GW [WINIID6.13.4]. There are two<br />
types <strong>of</strong> GW logical nodes, the IP Anchor GW, and the control GW. The control GW provides control<br />
functions for UEs that are not active (i.e., not sending data) and functions that control and configure the<br />
IP Anchor GW. In practice, there would be several IP Anchor GWs as well as an independent number <strong>of</strong><br />
control GWs. One BS can be connected to multiple GW logical pairs and conversely, one GW logical pair<br />
can be connected to multiple BS. Thus, the logical pairs <strong>of</strong> the GW form a pool <strong>of</strong> equipment that may<br />
cover large areas, e.g., cities. In [TRA07] a hybrid handover is proposed based on the concept <strong>of</strong> using<br />
pools <strong>of</strong> GWs as a means to reduce the number <strong>of</strong> IP handovers (i.e., support <strong>of</strong> macro mobility). By<br />
using the logical association between the UE and GW independently <strong>of</strong> the BSs, the set <strong>of</strong> GWs can be<br />
seen as a pool <strong>of</strong> resources. This in essence is a trunking gain realized by the sharing <strong>of</strong> resources<br />
between GWs and can be extended to the concept <strong>of</strong> GWs belonging to different operators. When<br />
degradation in the QoS is observed based on monitoring information from the KPIs, adding or removing<br />
<strong>of</strong> GWs can help to bring the network in a balanced state (i.e., load balancing). This would reduce the<br />
observed delays due to signalling required for the user context transfer or the degradation <strong>of</strong> the QoS for<br />
some users, and even dropping <strong>of</strong> users due to the need to reallocate users in the shared band.<br />
Without the use <strong>of</strong> the pool <strong>of</strong> GWs, when the shared band is unavailable a fast transfer to the dedicated<br />
band might be required to maintain the connectivity, and provide basic and priority services. In addition,<br />
there can be various reasons to initiate a frequency band transfer, for example the load in the other system<br />
with whom the resources are shared may change, a user terminal might move into an area where it would<br />
interfere with the other system’s transmissions, and so forth. Realizing the pool <strong>of</strong> GWs reduces the need<br />
for such actions because it allows for a centralized balancing <strong>of</strong> the load and resources, while preserving<br />
the logical associations <strong>of</strong> the UEs. Anticipation <strong>of</strong> a band reallocation improves the system performance<br />
because the contexts can be exchanged before the connection on the band is actually lost [WINIID5.9.1].<br />
The information about this can be obtained by scanning other networks, or from the Cooperative RRM<br />
functionality that also implements a spectrum manager. The pooling concept is shown in Figure 3-32.<br />
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Figure 3-32: Pooling <strong>of</strong> resources <strong>of</strong> different operators<br />
<strong>Spectrum</strong> assignment is dictated on a short-term basis by the services used at the UE. As a result, it is a<br />
rather distributed method even though the information exchange between the different systems (belonging<br />
or not to different operators) can be distributed or centralized. The knowledge <strong>of</strong> the existing spectrum<br />
resources within a RAN may be centralized since this information belongs to each RAN, can be accessed<br />
through the spectrum server, and the available spectrum resources belong to a common pool between<br />
RANs. The spectrum information can be distributed to the BSs, which, in scenarios <strong>of</strong> low to medium<br />
loads, can take fast decisions and provide for multiplexing gain.<br />
The system performance is affected by the subsystem capacities, the selection <strong>of</strong> an RRM algorithm, and<br />
the use <strong>of</strong> available radio resources. Both, single operator scenarios as well as multi-operator scenarios<br />
can benefit from a framework that supports a joint centralized and distributed approach to resource<br />
sharing. If the decision comes from the spectrum manager or spectrum server entities located higher in the<br />
network, the delays associated with the signalling will interfere with the timely assignment <strong>of</strong> resources<br />
during radio access. Therefore, the spectrum assignment should be performed as a distributed approach.<br />
Interworking between entities for network resource management and entities for spectrum management<br />
can provide a two-fold gain (i.e., trunking and diversity gain). The performance gain in terms <strong>of</strong> diversity<br />
would depend on the maximum acceptable distance between fragmented bands that are aggregated; in this<br />
context, it would be useful to investigate the upper limits on the separation and the achievable gain.<br />
4. <strong>Spectrum</strong> Aggregation<br />
As illustrated in Figure 4-1 and Figure 4-2 spectrum aggregation can appear when operator’s dedicated<br />
DL or UL band is not continuous but is split in two or more parts. In addition, spectrum aggregation can<br />
happen in scenarios in which an operator accesses both dedicated band and a spectrum sharing band<br />
which is separated in frequencies from the dedicated operator’s band. The separated bands can be situated<br />
in the same frequency band (e.g., in C-band) or in separated bands (e.g., part in 2GHz band and part in C-<br />
band). Both options are illustrated in the case <strong>of</strong> DL in Figure 4-1 and Figure 4-2. More detailed options<br />
on spectrum sharing can be found in [R4051146].<br />
DL<br />
DL<br />
frequency<br />
Figure 4-1: <strong>Spectrum</strong> aggregation <strong>of</strong> operator’s dedicated bands in the same band, e.g., C-Band<br />
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DL<br />
DL<br />
frequency<br />
Figure 4-2: <strong>Spectrum</strong> aggregation <strong>of</strong> operator’s dedicated bands in two bands, e.g., 2 GHz band<br />
and C-band<br />
Note that the scenario depicted in Figure 4-2, i.e., spectrum aggregation from different frequency bands,<br />
represents a more complex solution and should be avoided if possible.<br />
The main open questions considering spectrum aggregation are:<br />
• What is the maximum acceptable distance between fragmented bands that are aggregated at the<br />
receiver? Does this constraint come due to hardware or some other restrictions?<br />
• How does the complexity grow with the number <strong>of</strong> fragmented bands aggregated at the receiver?<br />
What is the upper limit on the number <strong>of</strong> aggregated fragmented bands?<br />
4.1 <strong>Spectrum</strong> Aggregation with Multi-Band User Allocation over Two Frequency<br />
Bands<br />
Widely separated bands can <strong>of</strong>fer a significant level <strong>of</strong> diversity due to very different propagation<br />
characteristics <strong>of</strong> the radio waves [LEE93]. These show independent channel quality indicators (CQIs)<br />
over time and space. This is a source <strong>of</strong> diversity at the physical (PHY) layer, which <strong>of</strong>fers an important<br />
chance to achieve better quality <strong>of</strong> service (QoS) and spectrum efficiency [MEU09].<br />
The focus <strong>of</strong> the following investigation is on the aspects <strong>of</strong> how one operator can manage the user<br />
allocation over the dedicated and shared bands with the objective to achieve higher throughput. The<br />
evaluations are performed for a single RAT, which is assumed to be High Speed Downlink Packet Access<br />
(HSDPA), which was proposed as an enhancement to 3G by 3GPP. Because the goal is to prove that<br />
integration <strong>of</strong> dynamic spectrum use and RRM techniques leads to an overall increase in performance<br />
gains, the choice <strong>of</strong> RAT is not <strong>of</strong> consequence for the final results. <strong>Spectrum</strong> sharing mechanisms are<br />
beyond the scope <strong>of</strong> the investigation here, and therefore, it is assumed that the operator considered here<br />
has gained access to the frequency pool with a certain portion <strong>of</strong> the available spectrum. Once a part <strong>of</strong><br />
the spectrum has been obtained, the operator still faces the problem <strong>of</strong> allocating users on both bands.<br />
Depending on the capabilities at the UEs, each user could be allocated to a single frequency band or to<br />
both frequency bands. In the latter case, the UEs have multi-radio transceivers and can transmit and<br />
receive data on both bands. Here, focus is only on single-band UEs that need to be allocated over two<br />
possible bands.<br />
4.1.1 Problem Statement<br />
The objective is to determine the best user allocation for a single operator over two (or more) frequency<br />
bands in order to maximize the total network throughput. Two bands are analyzed. The operator has<br />
exclusive usage <strong>of</strong> the 2-GHz band and can access to the shared frequency pool at 5 GHz. The quantity <strong>of</strong><br />
radio resources available at 5 GHz is determined by spectrum trading (or bargaining) among all the<br />
operators that have been granted access to the frequency pool. The performance gains are analyzed in<br />
terms <strong>of</strong> data throughput.<br />
After the operator has gained access to a certain portion <strong>of</strong> the frequency pool there is still the problem <strong>of</strong><br />
allocating users in both bands. The performance is heavily dependent on the radio channel qualities for<br />
each user in the considered bands. The CQI depends on the path loss and on the distance from the BS.<br />
The operator will have good improvements when the UEs have heterogeneous spatial distribution in the<br />
cell (variable distances from the BS), i.e., different channel qualities in the considered spectrum bands.<br />
The problem <strong>of</strong> scheduling the users into two bands (2 GHz and part or all <strong>of</strong> the frequency pool at 5<br />
GHz) can be formulated as an Integer Programming (IP) optimization problem [KEL05], [KAR05]. The<br />
total throughput <strong>of</strong> the operator is the pr<strong>of</strong>it function to be maximized. QoS requirements are not<br />
considered at this stage. The pr<strong>of</strong>it function depends on the channel qualities and on the number <strong>of</strong> users<br />
in each band. Because the goal is to determine the user allocation, the optimization problem cannot be<br />
solved directly. Therefore, the problem is formulated in two steps: first, the number <strong>of</strong> users that can be<br />
allocated in the primary band (i.e., 2 GHz) are determined based on the load thresholds; then the multiband<br />
scheduling is determined as a General Assignment Problem (GAP) where the number <strong>of</strong> users in<br />
each band is upper bounded.<br />
The scheduling algorithm is implemented as a reduced-complexity sub-optimal allocation.<br />
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4.1.2 General Multi-band Scheduling <strong>Spectrum</strong> Sharing as a General Assignment<br />
Problem<br />
4.1.2.1 Pr<strong>of</strong>it Function<br />
The scheduling <strong>of</strong> users over multiple frequency bands can be modelled in its most general form as a<br />
General Multi-Band Scheduling (GMBS) problem, i.e., GAP problem.<br />
Optimization problems can have single or multiple objectives. Here, the objective is to maximize the total<br />
throughput <strong>of</strong> the operator without considering fairness and QoS requirements <strong>of</strong> the service classes.<br />
Other objectives can be easily implemented in the problem, such as the cost or pr<strong>of</strong>it functions, e.g.,<br />
maximizing the total rate while minimizing the QoS dissatisfaction indexes [MEU08]. Solving Multiple-<br />
Objectives GAP (MO-GAP) can be very difficult and usually the objectives are combined together via a<br />
linear combination, called “scalarization”.<br />
The pr<strong>of</strong>it function (PF) depends on the ratio between the service request and the goodput available for<br />
each user (on each band). Therefore, the problem is formulated with a load constraint for each<br />
band:<br />
The PF is thus defined considering the ratio between the requested rate by the service flow and the rate<br />
available on a single downlink channel. This weight accounts for a real usage <strong>of</strong> the capacity considering<br />
the source traffic generator. The PF to be maximized is the following:<br />
with<br />
(4-1)<br />
, (4-2)<br />
where is the service goodput request. is the throughput for user u on band b, and is an<br />
0-1 integer variable defining the user allocation over the bands that is mathematically<br />
represented by:<br />
For a single transceiver UEs, the GMBS has two constraints:<br />
1) Each user can be allocated only to a single frequency band with a single allocation channel. This<br />
results in an Allocation Constraint (AC);<br />
2) The total number <strong>of</strong> users on each band is upper bounded by the maximum load that can be handled<br />
in the band, i.e., the Bandwidth Constraint (BC)<br />
.<br />
, (4-3)<br />
. (4-4)<br />
In general, the throughput is a function <strong>of</strong> the channel quality <strong>of</strong> user u on band b: ,<br />
where is dependent on the Signal to Interference Ratio (SIR) that depends on the propagation<br />
conditions, on the interference from other cells and on power per code available:<br />
.<br />
The higher the number <strong>of</strong> users allocated in the band, the lower the CQI. This is mainly due to the power<br />
division by the used codes, which are using completely orthogonal codes. The decrease in the CQI that<br />
occurs when more users arrive to the system does not reflect the throughput decrease per user. Rbu can be<br />
changed ahead to depend on other variables, however, for simplicity, here it is dependent only on the<br />
CQI.<br />
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The GMBS problem is formulated into two steps. First, the maximum number <strong>of</strong> users that can be<br />
allocated on each frequency band is determined, then (i.e., throughput for user u on band b) is<br />
defined as the available throughput considering that users are allocated in the band. This is clearly a<br />
lower bound because<br />
and there is a lower level <strong>of</strong> interference. This allows for defining<br />
only as a function <strong>of</strong> the link budget,<br />
, and to proceed with the problem solving.<br />
The number <strong>of</strong> maximum users in each band is calculated depending on the load, as follows:<br />
,<br />
where L normalized is estimated based on the resources available for the cell. The normalized load is<br />
estimated as follows:<br />
L<br />
normalized<br />
( i)<br />
Nb<br />
∑<br />
u=<br />
= 1<br />
Load<br />
where N b is the number <strong>of</strong> HSDPA users in band b, R HSDPA is the number <strong>of</strong> High Speed Downlink Shared<br />
Channels (HS-DSCH) allocated in the cell, and Load(u) is the average number <strong>of</strong> HS-DSCH required by<br />
user u to support its service rate, R(u). This number is given by the following<br />
Load<br />
( u)<br />
=<br />
R(<br />
CQI<br />
bu<br />
R<br />
R<br />
) • N<br />
HSDPA<br />
( u)<br />
( u)<br />
HS−PDSCH<br />
( CQI )<br />
bu<br />
where, the average propagation condition determines the channel quality indicator ID <strong>of</strong> user u on band b,<br />
, R( ) is the achieved bit rate when one block is allocated in every frame and N HS-<br />
PDSCH( ) is the number <strong>of</strong> HS-DSCH associated to .<br />
Once has been determined, R bu , or the expected data rate for each user should be dependent on<br />
CQI bu , the effective packet error rate (PER) experienced (or predicted based on the position in case <strong>of</strong> a<br />
first transmission), and the number <strong>of</strong> users:<br />
The direct mapping between CQI bu and the throughput can be expressed as:<br />
4.1.2.2 Resource Allocation<br />
The resource allocation (RA) allocates the user packets to the available radio resources in order to satisfy<br />
the user requirements, and to ensure efficient packet transport to maximise spectral efficiency. The RA,<br />
an entity within the set <strong>of</strong> RRM algorithms, should have inherent tuning flexibility to maximise the<br />
spectral efficiency <strong>of</strong> the system for any type <strong>of</strong> traffic QoS requirements. The RA adopted here maps<br />
packets <strong>of</strong> variable size into variable length radio blocks for transmission over the PHY layer, and the<br />
length is dependent on the channel quality. The following events are performed:<br />
1. User packets awaiting transmission are prioritized according to the scheduling algorithm criteria.<br />
2. A CQI identifier is selected according to the link adaptation algorithm, using the available CQI<br />
options from the PHY layer.<br />
3. The scheduler calculates the number <strong>of</strong> MAC transport blocks required to transmit the scheduled<br />
packet. The number <strong>of</strong> HS-PDSCH channels is calculated according to<br />
where is the lowest integer higher or equal to x;<br />
4. An idle ARQ channel j is selected to hold and manage the ARQ transmission.<br />
5. The packet is transmitted and received at the UE. S<strong>of</strong>t retransmissions are combined with previous<br />
packet transmissions (chase combining) and the ARQ messages are generated accordingly. These<br />
are then signalled to the BS, and the ARQ processes are released if the messages are positive<br />
acknowledgments (ACKs).<br />
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4.1.2.3 Differences between the 2-GHz and 5-GHz frequency bands<br />
The 2-GHz and 5-GHz frequency bands are characterized over the same HSDPA architecture by<br />
assuming the models summarized in Table 4-1:<br />
Table 4-1: Models used for 2- and 5 GHz<br />
Carrier frequency 2 GHz 5GHz<br />
Bandwidth 5MHz 5MHz<br />
Path loss model: 128.1 + 37.6 Log 10 (R) 141.52+28log 10 (dkm)<br />
Shadowing decorrelation<br />
5 m 20 m<br />
length<br />
4.1.3 Suboptimal Multiband Allocation Algorithm<br />
UEs are able to use both <strong>of</strong> the frequencies. The CRRM entity keeps track <strong>of</strong> the CQI in both frequencies<br />
by making use <strong>of</strong> the pilot channel. By keeping the load at the same level in both frequencies the users<br />
may be scheduled on one frequency or another, depending also on the CQI available for the UE. When a<br />
user arrives to the system, the UE is allocated to the 2-GHz band. The load is checked in both bands. If<br />
the load is higher in the 2-GHz than in the 5-GHz one, the user with the highest CQI in the 2 GHz will be<br />
moved to the 5-GHz band. In a situation <strong>of</strong> higher network loads, the users with the lowest CQIs will be<br />
allocated to the non-shared 2-GHz band while the users with highest CQIs will be allocated on the shared<br />
band. The load is estimated based on the resources available for the cell, and actually consumed by user<br />
connections. The procedure is the same as the one described in [MON08].<br />
4.1.4 Results<br />
The performance <strong>of</strong> the algorithm is assessed by using the service throughput that is the total number <strong>of</strong><br />
bits that have been transmitted and correctly received by the all users in the cell:<br />
where b serv [p] is the number <strong>of</strong> bits received in given period p, T is the transmit time interval, k is the<br />
number <strong>of</strong> steps, and k⋅T is the simulation duration. Users are displaced in the cell within a distance from<br />
the BS from 300 to 3000 km with a uniform distribution. The NRTV calls are modelled by a Poisson<br />
distribution, the call duration is exponentially distributed with an average <strong>of</strong> 180s.<br />
4.2 Basic Transceiver Concepts for aggregated <strong>Spectrum</strong><br />
Future mobile and wireless communications will provide aggregated total throughput data rates up to 100<br />
Mbit/s for new mobile access and up to 1 Gbit/s for new nomadic local area access [M.1645]. The<br />
expected carrier bandwidth from technical reasons for these data rates is in the order <strong>of</strong> 100 MHz<br />
[Moh03]. However, the result WRC 2007 may not allow such wide carrier bandwidth with contiguous<br />
frequency bands for new radio systems. In this section a generic theoretical investigation is presented,<br />
which shows the basic impact <strong>of</strong> different parameters and topics affecting the system design and<br />
performance and the associated problems. The technical feasibility from the perspective <strong>of</strong> the<br />
infrastructure (base stations) and terminal devices is being assessed in the conclusions.<br />
4.2.1 Approach<br />
Today, several frequency bands are allocated to mobile and wireless communications. WRC 2007<br />
discussed the potential identification <strong>of</strong> new frequency bands to mobile and wireless communications. In<br />
the following the basic idea <strong>of</strong> use <strong>of</strong> fragmented spectrum bands is presented without detailed figures on<br />
the today’s allocated frequency bands.<br />
The approach is based on a joint simultaneous use <strong>of</strong> different frequency bands in the frequency range <strong>of</strong><br />
about 400 MHz up to about 6 GHz including the unlicensed frequency bands for WLAN applications.<br />
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Figure 4-3 shows the basic map <strong>of</strong> frequency bands for mobile and wireless applications excluding<br />
broadcast spectrum, because this is currently not available for such applications.<br />
Potentially<br />
available<br />
frequency<br />
bands<br />
1 2 3 4 5 6<br />
f [GHz]<br />
Figure 4-3: Basic allocated frequency band for mobile & wireless applications (qual. presentation)<br />
In the following it is assumed that the transceiver is processing the entire available frequency spectrum<br />
comprising the different part bands. There are now two basic concepts for a wideband communication<br />
system, which will be described hereafter in more detail:<br />
• Multi-band transmission system with several parallel transceivers for the different frequency<br />
bands, which are used simultaneously.<br />
• Wideband receiver, which is processing the entire frequency band from about 400 MHz to about<br />
6 GHz. The filtering should be done in the digital domain.<br />
The two basic transceiver concepts are shown in Figure 4-4 and Figure 4-5. The block diagrams are rather<br />
high-level in order to discuss the major impacts. Both concepts are explained only for the receiver<br />
section.<br />
RF<br />
bandpass<br />
per band<br />
RF<br />
frontend<br />
A<br />
D<br />
RF<br />
frontend<br />
A<br />
D<br />
Digital<br />
signal<br />
Detected signal<br />
processing<br />
RF<br />
frontend<br />
A<br />
D<br />
Figure 4-4: Multi-band received with parallel receivers for different bands<br />
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Broadband<br />
Antenna<br />
Broadband<br />
RF<br />
frontend<br />
A<br />
D<br />
Digital<br />
signal<br />
processing<br />
Detected signal<br />
RF<br />
bandpass<br />
0.4 to 6 GHz<br />
Figure 4-5: Wideband receiver for the entire band<br />
A first basic assessment <strong>of</strong> the different concept is as follows:<br />
Multi-band receiver:<br />
• The RF band pass filter per branch has a bandwidth corresponding to the allocated band. This<br />
filter is also needed as anti-aliasing filter.<br />
• The channel filtering per link will be done in the digital domain.<br />
• This concept will be feasible. It is similar to today’s multi-band terminals.<br />
• Several RF branches are needed, which need volume (RF filters).<br />
• The dynamic range should be feasible due to the limitation to useful bands and the avoidance <strong>of</strong><br />
adjacent disturbing signals as much as possible due to RF filtering.<br />
• However, this concept is rather complex. The different RF chains require filters, amplifiers,<br />
mixers and local oscillators.<br />
• Potentially, amplifiers, mixers and local oscillators can be re-used for different part-bands by<br />
changing RF-filters and local oscillator frequencies.<br />
• The number <strong>of</strong> parallel available RF chains corresponds to the number <strong>of</strong> part bands, which are<br />
simultaneously used.<br />
Wideband receiver:<br />
• The RF band pass is needed as anti-aliasing filter for wideband sampling. Its bandwidth covers<br />
the entire receiver bandwidth.<br />
• The channel filtering per link will be done in the digital domain.<br />
• This concept requires very wideband RF components.<br />
• A very high sampling rate is needed.<br />
• A much higher dynamic range is necessary in order to mitigate the impact <strong>of</strong> strong adjacent<br />
disturbing signals (e.g. broadcast and radar signals), which are within the wide input RF<br />
bandwidth but outside <strong>of</strong> one <strong>of</strong> the useful frequency bands.<br />
• This requires A/D-converters with very high resolution and linearity.<br />
• The RF components have to be very linear and to be able to handle high-amplitude signals.<br />
• With respect to the high required sampling rate and dynamic range (A/D-converter resolution)<br />
this concept will not be feasible with today's available technology.<br />
There are two basic concepts for the implementation <strong>of</strong> the wideband receiver according to Figure 3:<br />
• Either the A/D-conversion is performed directly in the RF domain with down-conversion (mixing)<br />
and channel filtering in the digital domain (version A) or<br />
• the wideband RF signal is down-converted in an IQ-mixer in the analogue domain to the base band<br />
and the I- and Q-channel are separately A/D-converted according to the band pass sampling theorem<br />
(version B) [Lue75].<br />
The two basic receiver implementations in the case <strong>of</strong> a general asymmetric input signal and band pass<br />
transfer function with respect to the center frequency show Figure 4-6 and Figure 4-7 [Lue75].<br />
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Broadband<br />
Antenna<br />
RF<br />
bandpass<br />
0.4 to 6 GHz<br />
Broadband<br />
RF<br />
frontend<br />
A<br />
D<br />
cos(2πf LO t)<br />
LO<br />
-sin(2πf LO t)<br />
h Tr (t)<br />
h Ti (t)<br />
-h Ti (t)<br />
h Tr (t)<br />
+<br />
+<br />
I<br />
Q<br />
Complex detected signal<br />
Digital signal processing<br />
Figure 4-6: Potential receiver implementation: Version A<br />
Broadband<br />
Antenna<br />
RF<br />
bandpass<br />
0.4 to 6 GHz<br />
Broadband<br />
RF<br />
frontend<br />
cos(2πf LO t)<br />
LO<br />
-sin(2πf LO t)<br />
A<br />
A<br />
D<br />
D<br />
h Tr (t)<br />
h Ti (t)<br />
-h Ti (t)<br />
h Tr (t)<br />
+<br />
+<br />
I<br />
Q<br />
Complex detected signal<br />
Figure 4-7: Potential receiver implementation: Version B<br />
Digital signal processing<br />
4.2.2 Brief Investigation <strong>of</strong> Several Topics Affecting the System Design<br />
The following investigation is mainly made for the wideband concept. The figures can easily be<br />
transformed to the multi-band concept. However, due to the different band pass filters the impact <strong>of</strong><br />
interference and other issues is basically smaller than in the wideband concept.<br />
4.2.2.1 Frequency Dependent Path Loss<br />
The frequency dependence <strong>of</strong> the path loss L(f c ) [dB] on the carrier frequency f c depends on the actual<br />
propagation conditions. For free-space propagation the frequency dependence corresponds to [MG86] pp.<br />
H12 and H30.<br />
⎛ fc,2<br />
L(<br />
fc, 2)<br />
L(<br />
fc,1)<br />
20 log [ dB]<br />
f ⎟ ⎞<br />
− = ⋅ ⎜<br />
(4-5)<br />
⎝ c,1<br />
⎠<br />
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With increasing carrier frequency the path loss is increasing quadratic. For shadowing propagation the<br />
increase <strong>of</strong> path loss is bigger with about 25 – 30 dB/decade for suburban areas and about 30 dB/decade<br />
for urban areas [Pa92][Ra96][Ha80][WB88].<br />
⎛ fc,2<br />
L(<br />
fc, 2)<br />
L(<br />
fc,1)<br />
30 log [ dB]<br />
f ⎟ ⎞<br />
= ⋅ ⎜<br />
⎝ c,1<br />
⎠<br />
− (4-6)<br />
For some propagation conditions this increase may be even bigger. Figure 4-8 shows this dependence in<br />
the frequency range 0.4 to 6 GHz. The relative path loss is normalized to 400 MHz.<br />
L(f c,2 ) – L(f c,1 ) [dB]<br />
40<br />
35<br />
30<br />
25<br />
20<br />
15<br />
10<br />
5<br />
0<br />
≈<br />
0.4 1 2 3 4 5 6<br />
Free space<br />
Shadowing<br />
f c [GHz]<br />
Figure 4-8: Relative path loss versus carrier frequency<br />
In the upper frequency bands the radio channel shows a significantly higher path loss. This results directly<br />
in a significant reduction <strong>of</strong> range for the upper bands. Within the bandwidth under discussion a huge<br />
difference in path loss has to be considered.<br />
4.2.2.2 Doppler Frequency and Doppler <strong>Spectrum</strong><br />
Due to moving receivers, transmitters and/or movements in the environment the radio channel is timevariant.<br />
This is described by the Doppler shift f d or in the case <strong>of</strong> multi-path propagation by a Doppler<br />
spectrum S E (f), which represents the different Doppler shifts from different received waves from different<br />
directions [MG86][Ja74]. Eq. (4-7) shows the Doppler shift versus mobile speed ν, the carrier wave<br />
length λ, the speed <strong>of</strong> light c 0 , the angle <strong>of</strong> arrival θ between the mobile direction and the incoming wave:<br />
v v<br />
f<br />
d<br />
= ⋅cos θ = ⋅ fc<br />
cosθ<br />
= f<br />
d , m<br />
⋅cosθ<br />
. (4-7)<br />
λ c<br />
The maximum Doppler shift is<br />
f<br />
v<br />
= ± ⋅ f<br />
0<br />
d , m<br />
c<br />
(4-8)<br />
c0<br />
with the Doppler spectrum under the assumption <strong>of</strong> a uniform distribution <strong>of</strong> incoming waves from all<br />
directions<br />
SE<br />
z<br />
( f ) =<br />
π ⋅ f<br />
d , m<br />
1<br />
1.5<br />
⎛<br />
− ⎜<br />
⎝<br />
f − f<br />
f<br />
d , m<br />
c<br />
⎞<br />
⎟<br />
⎠<br />
2<br />
for<br />
− . (4-9)<br />
f<br />
d , m<br />
≤ f − fc<br />
≤ f<br />
d , m<br />
Outside <strong>of</strong> this range the Doppler spectrum is zero. The maximum relative Doppler shift in the frequency<br />
range 0.4 to 6 GHz is directly proportional to the ratio <strong>of</strong> carrier frequencies (Figure 4-9):<br />
f<br />
f<br />
f<br />
d , m2<br />
c2<br />
= . (4-10)<br />
d , m1<br />
fc<br />
1<br />
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f d,m2 /f d,m1 14<br />
12<br />
10<br />
8<br />
6<br />
4<br />
2<br />
0<br />
0.4 1 2 3 4 5 6 f c [GHz]<br />
Figure 4-9: Relative maximum Doppler shift<br />
In the upper frequency bands the radio channel shows a significantly higher time variance than in the<br />
lower bands, which requires a higher update rate for adaptation algorithms such as equalization and<br />
power control. This may result in higher overhead in the upper bands for signalling.<br />
4.2.2.3 Effective Noise Power<br />
The thermal noise density power at an absolute temperature <strong>of</strong> 300 K corresponds to N 0 = -174 dBm/Hz<br />
[MG86]. Including the receiver noise figure F the effective noise power within the receive bandwidth B<br />
follows as:<br />
N eff<br />
= N 0<br />
⋅ B ⋅ F . (4-11)<br />
With a receiver noise figure F = 5 dB and the entire receive bandwidth B = 6 GHz – 0.4 GHz = 5.6 GHz<br />
the total noise power is given by<br />
N<br />
= N dBm/<br />
Hz]<br />
+ 10⋅<br />
Log(<br />
B )[ dBHz]<br />
+ F[<br />
dB]<br />
= 71. dBm . (4-12)<br />
[<br />
eff , total 0 total<br />
− 5<br />
From the perspective <strong>of</strong> terminal devices a noise figure <strong>of</strong> F = 5 dB is not feasible with reasonable cost.<br />
The receiver noise figure is frequency dependent due to the frequency dependent matching, which results<br />
in increasing effective noise figure with increasing relative receiver bandwidth. Base stations can provide<br />
lower noise figures than terminal devices. The noise power can directly be scaled by other noise figures.<br />
This noise power is significantly below the power levels <strong>of</strong> the receiver, where nonlinear effects might be<br />
expected. The noise power per band and the noise power density needs to be investigated.<br />
Under the assumption that the smallest signal bandwidth after base band filtering equals B min.ch = 1.25<br />
MHz the effective noise power follows as<br />
N N [<br />
eff , 1.25MHz<br />
0<br />
dBm/<br />
Hz]<br />
+ 10⋅<br />
Log(1.25MHz)[<br />
dBHz]<br />
+ F[<br />
dB]<br />
= −108.<br />
dBm<br />
= . (4-13)<br />
This might be the smallest noise power level, which has to be considered for the dynamic range <strong>of</strong> the<br />
receiver.<br />
4.2.2.4 Receiver Input Signal<br />
The receiver input signal is rather complex. After the RF band pass, which is also needed as anti-aliasing<br />
filter, useful signals in different part-bands and disturbing signals from other services between the<br />
different part-bands are present. Such disturbing signals may have very high transmit power such as<br />
broadcast and radar signals.<br />
The RF pre-selection band pass filter transfers all receive signals u r (t) according to (4-15) within the RF<br />
reception band according to its transfer function.<br />
All signals out <strong>of</strong> the RF reception band u r,out (t) are attenuated with respect to the band pass characteristic.<br />
– These signals are not considered in the following. –<br />
Useful receive signals within part-band j:<br />
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u<br />
( ω ⋅t<br />
+ ϕ ( t )<br />
I ( j)<br />
I ( j)<br />
r, band , j<br />
( t)<br />
= ∑ur,<br />
j,<br />
i<br />
( t)<br />
= ∑ar,<br />
j,<br />
i<br />
( t)<br />
⋅sin<br />
r,<br />
j,<br />
i r,<br />
j,<br />
i<br />
)<br />
i= 1<br />
i=<br />
1<br />
Useful receive signals in all part-bands:<br />
u<br />
( ⋅t<br />
+ ( t )<br />
J<br />
J I ( j)<br />
J I ( j)<br />
r, useful<br />
( t)<br />
= ∑ur,<br />
band , j<br />
( t)<br />
= ∑∑ur,<br />
j,<br />
i<br />
( t)<br />
= ∑∑ar,<br />
j,<br />
i<br />
( t)<br />
⋅sin<br />
r,<br />
j,<br />
i<br />
ϕr,<br />
j,<br />
i<br />
)<br />
j= 1 j= 1 i= 1 j= 1 i=<br />
1<br />
ω (4-14)<br />
Disturbing signals between part-bands:<br />
u<br />
( ω ⋅t<br />
+ ( t )<br />
K<br />
K<br />
r, disturbing<br />
( t)<br />
= ∑ur,<br />
k<br />
( t)<br />
= ∑ar,<br />
k<br />
( t)<br />
⋅sin<br />
r,<br />
k<br />
ϕr,<br />
k<br />
)<br />
k = 1 k = 1<br />
The total receive signal after the receive RF band pass including noise is as follows:<br />
u ( t)<br />
= u<br />
r<br />
=<br />
r,<br />
useful<br />
+<br />
J<br />
( t)<br />
+ u<br />
I ( j)<br />
∑∑<br />
( t)<br />
=<br />
r,<br />
disturbing<br />
( t)<br />
=<br />
r,<br />
j,<br />
i<br />
j= 1 i= 1 j= 1 i=<br />
1<br />
K<br />
∑<br />
u<br />
u<br />
K<br />
∑<br />
r,<br />
k<br />
k = 1 k = 1<br />
a<br />
J<br />
r,<br />
k<br />
( t)<br />
+ n(<br />
t)<br />
=<br />
I ( j)<br />
∑∑<br />
a<br />
r,<br />
j,<br />
i<br />
( t)<br />
⋅sin<br />
( t)<br />
⋅sin<br />
( ω ⋅t<br />
+ ϕ ( t)<br />
)<br />
( ω ⋅t<br />
+ ϕ ( t)<br />
)<br />
r,<br />
k<br />
r,<br />
j,<br />
i<br />
r,<br />
k<br />
+<br />
r,<br />
j,<br />
i<br />
+<br />
(4-15)<br />
+ n(<br />
t)<br />
Even if the sampling <strong>of</strong> the input signal is performed directly in the band pass domain without a mixing<br />
process to an intermediate frequency (IF), the signal to be detected has to be transformed to the base band<br />
domain in the digital signal processing. This does only correspond to one possibility <strong>of</strong> implementation.<br />
Therefore, issues like image rejection and reciprocal mixing etc. have to be considered in general.<br />
4.2.2.5 Nonlinearities in the Analogue Receiver Components<br />
In a simplified description the analogue active part <strong>of</strong> the receiver may be represented by a nonlinear<br />
characteristic (Taylor series):<br />
2<br />
3<br />
um ( t)<br />
= c0 + c1<br />
⋅ur<br />
( t)<br />
+ c2<br />
⋅ur<br />
( t)<br />
+ c3<br />
⋅ur<br />
( t)<br />
+ ...<br />
(4-16)<br />
Under overload conditions additional signals are generated due to distortion and intermodulation, which<br />
may disturb the demodulation process.<br />
• For one input signal a reduction <strong>of</strong> amplification due to nonlinear distortion for a cubic characteristic<br />
with increasing input signal amplitude (compression) occurs [Car90].<br />
• For – in minimum – two input signals (useful plus disturbing signal) intermodulation products result<br />
in reduction <strong>of</strong> the output signal amplitude <strong>of</strong> the useful signal for increasing disturbing signal input<br />
amplitude (desensitization or blocking) [Car90].<br />
• For multiple input signals intermodulation products are generated.<br />
The receiver nonlinearity can be characterized by the 2nd and 3rd order intercept points.<br />
4.2.2.6 Image Rejection<br />
The RF band pass is needed for some pre-selection with respect to the entire input signal and as image<br />
reject filter. However, due to the very complex input signal within the bandwidth <strong>of</strong> the RF band pass<br />
according to (4-15) disturbing signals with potentially high transmit power cannot be avoided directly by<br />
a band pass filter in front <strong>of</strong> the active receiver components (low noise RF amplifier, potential mixers).<br />
Such disturbing signals may be reduced by dedicated notch filters as part <strong>of</strong> the RF pre-selection filter.<br />
In the case <strong>of</strong> a mixing process with an IF f IF , different input signals at different receive carrier<br />
frequencies f r may lead to nonlinear distortion and harmonics <strong>of</strong> the local oscillator frequency f LO to this<br />
same IF-range.<br />
f<br />
IF<br />
= m⋅<br />
f ± n⋅<br />
f with m, n = 1, 2, 3 ... (4-17)<br />
r<br />
LO<br />
Therefore, the complex input signal may result in the active and usually nonlinear receiver components in<br />
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• linear spurious reception due to the mixing process (m = 1)<br />
• image reception<br />
• reciprocal mixing<br />
• nonlinear spurious reception due to receiver nonlinearities (m > 1)<br />
• overload, cross modulation, limiting and blocking<br />
• possible spurious reception frequencies (one signal at receiver input)<br />
In the case <strong>of</strong> f LO > f IF and no overloading <strong>of</strong> the RF pre-amplifier and mixer (m = 1) two possible receive<br />
frequencies per local oscillator harmonic (image reception) may be observed:<br />
f<br />
= n ⋅ f<br />
− f<br />
r, n /1 LO IF<br />
and<br />
r n / 2 LO IF<br />
f<br />
,<br />
= n ⋅ f + f . (4-18)<br />
Usually, contributions resulting from local oscillator harmonics (n > 1) are negligible. Therefore, the RF<br />
pre-selection band pass filter has to avoid signals at frequencies 2 f IF apart from useful signals with (c.f.<br />
Figure 4-10):<br />
2 ⋅ f ≥ . (4-19)<br />
IF<br />
B RF<br />
f r,n/1 f LO f r,n/2<br />
f IF<br />
f IF<br />
receive band<br />
B RF<br />
Figure 4-10: Relation between B RF and f IF<br />
In the case <strong>of</strong> a very big RF bandwidth in the order <strong>of</strong> B RF = 5.6 GHz the IF has to be f IF > 2.8. The<br />
requirements on the pre-selection filter slope are relaxed for increasing f IF . For very wideband RF band<br />
pass filter no high stop-band attenuation can be expected. Therefore, the main channel selection with high<br />
stop-band attenuation is performed in the IF- or base band stage to reduce the effective receiver noise<br />
bandwidth and to avoid overload in the main IF amplification due to high power out <strong>of</strong> IF band signals.<br />
However, this may not be possible in the concept according to Figure 3, where the main filtering is done<br />
in the digital domain. Therefore, the analogue receiver has to show a high resistance against overload<br />
conditions.<br />
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4.2.2.7 Receiver Performance (Desensitization, Blocking, Intermodulation)<br />
The basic performance <strong>of</strong> the receiver is summarized in Figure 4-11 [MG86].<br />
level <strong>of</strong> input signal P E [dBm]<br />
D<br />
F'<br />
IPIP3<br />
E'<br />
IPIP2<br />
C'<br />
C<br />
A<br />
F E B<br />
minimum required<br />
signal/noise-ratio<br />
level <strong>of</strong> input disturbing signals in [dBm]<br />
Figure 4-11: Receiver performance<br />
A: Receiver sensitivity due to noise, no interference.<br />
B – C: Impact <strong>of</strong> reciprocal mixing, required useful signal has to be increased proportionally to<br />
additional noise.<br />
C – C': Limit due to cross modulation for modulated interfering signal.<br />
D: Maximum level <strong>of</strong> useful input signal for one disturbing signal with same amplitude, in-band<br />
intermodulation products and/or harmonics determine output signal/intermodulation-ratio.<br />
E – E': For two input signals 3rd order intermodulation products proportional to third power <strong>of</strong><br />
disturbing signal level.<br />
F – F': For two input signals 2nd order intermodulation products proportional to second power <strong>of</strong><br />
disturbing signal level (less important due to RF pre-selection).<br />
IPIP3: Construction <strong>of</strong> 3rd order intercept point.<br />
IPIP2: Construction <strong>of</strong> 2nd order intercept point.<br />
4.2.2.8 Reciprocal Mixing and Receiver Noise Figure<br />
The receiver is not only affected by thermal noise and receiver internal additional noise sources. In a<br />
system with several carrier input signals in front <strong>of</strong> the mixer reciprocal mixing especially in the RF stage<br />
<strong>of</strong> the receiver may play a significant role. Figure 4-12 shows the effect <strong>of</strong> reciprocal mixing [Car90].<br />
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Amplitude<br />
Desired<br />
IF signal<br />
(noiseless)<br />
• Differencemixingwith high-side<br />
injection, down conversion<br />
Amplitude<br />
DesiredRF signal<br />
Local oscillator<br />
IF passband<br />
( unmodulated and<br />
(noiseless)<br />
f<br />
noiseless)<br />
Noise in IF<br />
Desired<br />
passband caused<br />
IF signal<br />
by oscillator noise<br />
Noise<br />
( noisy)<br />
sidebands<br />
• Extension <strong>of</strong> abovewhen oscillator<br />
noise is significant<br />
Amplitude<br />
Noise<br />
sidebands<br />
DesiredRF signal<br />
Local oscillator<br />
IF passband<br />
(unmodulated and<br />
(noisy)<br />
noiseless)<br />
Additional noisein<br />
Noise<br />
IF passband caused<br />
sidebands<br />
by oscillator noise<br />
f<br />
• Reciprocalmixing occurswhen an<br />
undesired signal mixes with<br />
oscillator noise to produceadditional<br />
noise in IF passband<br />
Undesired<br />
IF signal<br />
( noisy)<br />
UndesiredRF signal<br />
Local oscillator<br />
(unmodulated and<br />
(noisy)<br />
noiseless)<br />
f<br />
Figure 4-12: Reciprocal mixing<br />
The three figures are explained in the following:<br />
• Top: Difference mixing with high-side injection and down conversion based on the difference<br />
frequency between the local oscillator and the received signal.<br />
• Middle: Extension <strong>of</strong> the top figure when the oscillator noise is significant. The phase noise is down<br />
converted towards the IF.<br />
• Bottom: Reciprocal mixing occurs when an undesired signal (adjacent channel) mixes with the<br />
oscillator noise to produce additional noise in IF pass band.<br />
Reciprocal mixing results in an additional noise figure F RM proportional to the amplitude <strong>of</strong> the disturbing<br />
signal (adjacent channel) within the RF pass band and the single side band oscillator phase noise [MG86].<br />
However, F RM is independent <strong>of</strong> the receiver noise figure.<br />
F<br />
[ dB] P [ dBm] + ( f ) [ dBc / Hz] 174 [ dBm / Hz]<br />
= Φ (4-20)<br />
RM s<br />
e<br />
+<br />
The additional noise components due to the oscillator phase noise increase the effective receiver noise<br />
figure with increasing number <strong>of</strong> adjacent disturbing carriers. The resulting receiver noise figure for N<br />
input signals follows as:<br />
⎪⎧<br />
N<br />
F<br />
/ 10<br />
[ dB ] = 10log⎨10<br />
[ dB ] + ∑<br />
⎪⎩<br />
i=<br />
1<br />
F [ dB ] / 10<br />
F<br />
receiver RMi<br />
receiver,res<br />
10<br />
. (4-21)<br />
In the case <strong>of</strong> the wideband received according to Figure 4-5 there is a high likelihood for many high<br />
power disturbing signals. These relations have to be considered in the design <strong>of</strong> the RF filters and the<br />
local oscillator phase noise requirements. The relation in (4-20) is shown in Figure 4-13 [MG86].<br />
⎪⎫<br />
⎬<br />
⎪⎭<br />
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adjacent carrier P s<br />
[dBm]<br />
40<br />
20<br />
0<br />
-20<br />
-40<br />
-60<br />
-80<br />
F RM<br />
= 140 dB<br />
120<br />
100<br />
80<br />
60<br />
40<br />
20<br />
0<br />
example point<br />
-40 -60 -80 -100 -120 -140 -160 ⎝ e<br />
(f) [dBc/Hz]<br />
Figure 4-13: Additional noise figure F RM due to reciprocal mixing<br />
When the receive level <strong>of</strong> an adjacent carrier is below -44 dBm and the oscillator phase noise reaches -<br />
130 dBc/Hz, the additional noise figure due to reciprocal mixing would be F RM = 0 dB. The effect <strong>of</strong><br />
reciprocal mixing can be reduced further by oscillators with low phase noise and for low effective<br />
adjacent channel amplitude.<br />
The receiver chain noise figure (Friis formula) according to [MG86] follows as<br />
F<br />
receiver<br />
N<br />
Fadd<br />
,2<br />
Fadd<br />
,3<br />
, res<br />
= F1<br />
+ + + ∑10<br />
L L ⋅ L<br />
v1<br />
v1<br />
v2<br />
FRMi<br />
[ dB]<br />
/10<br />
... +<br />
(4-22)<br />
i=<br />
1<br />
with, e.g.,<br />
• index 1 – antenna cable plus image reject filter,<br />
• index 2 – pre-amplifier and<br />
• index 3 – mixer (without reciprocal mixing).<br />
A high receiver sensitive requires<br />
• low noise first receiver stages (F 1 and F add,2 ) plus high amplification (L v1 ⋅ L v2 ) to reduce the impact<br />
<strong>of</strong> mixer conversion loss and<br />
• oscillators with low phase noise to reduce the impact <strong>of</strong> reciprocal mixing.<br />
The additional noise figure F RM due to reciprocal mixing increases with an increasing number N and<br />
amplitude <strong>of</strong> input signals independent <strong>of</strong> the receiver noise figure F receiver without reciprocal mixing. On<br />
the other hand a reduced impact <strong>of</strong> intermodulation is achieved through a low gain RF amplifier.<br />
Therefore, a trade-<strong>of</strong>f between the receiver sensitivity and the impact <strong>of</strong> intermodulation has to be<br />
implemented for overall optimal performance.<br />
4.2.2.9 Band Pass Filters and Filter Slope for Stop-band Attenuation<br />
The following general description <strong>of</strong> the RF band pass filter is done for lossless filters. The feasibility<br />
concerning<br />
• insertion loss,<br />
• achievable stop band attenuation,<br />
• group delay distortion,<br />
• possible filter order,<br />
• filter size and<br />
• cost<br />
is not considered.<br />
The overall filtering is usually distributed between the base band, the IF and the RF domain. In the RF<br />
band the maximum receive power at the input <strong>of</strong> the RF low noise amplifier has to be sufficiently low to<br />
avoid blocking <strong>of</strong> the receiver. As shown in Section 4.2.2.10 very high input signal amplitudes from<br />
disturbing signals within the wideband band pass bandwidth have to be expected.<br />
The low pass (LP) and the band pass (BP) domain are related by the LP-BP-transformation with the band<br />
pass cut-<strong>of</strong>f frequencies f c1 and f c2 [Zv67][Sa79], the normalizing frequency<br />
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f<br />
n = fc1<br />
⋅ fc2<br />
, (4-23)<br />
the normalized band pass frequency<br />
f<br />
F BP = , (4-24)<br />
f<br />
n<br />
and the normalized low pass frequency for filter design<br />
F<br />
LP<br />
=<br />
F<br />
BP,<br />
c2<br />
1<br />
− F<br />
BP,<br />
c1<br />
⎛<br />
⋅<br />
⎜ F<br />
⎝<br />
BP<br />
1<br />
−<br />
F<br />
BP<br />
⎞<br />
⎟<br />
⎠<br />
. (4-25)<br />
The RF frequency range is allocated between f c1 = 0.4 to f c2 = 6 GHz. With an assumed reference RF<br />
bandwidth <strong>of</strong><br />
f<br />
− f 5. GHz<br />
(4-26)<br />
c2 c1<br />
= 6<br />
the relative RF bandwidth with an average carrier frequency <strong>of</strong><br />
fc 1<br />
+ fc2<br />
= 3. 2GHz<br />
(4-27)<br />
2<br />
is in the order <strong>of</strong> 175 %, which results in a very low Q-factor. The RF filter should be designed according<br />
to Figure 4-5 as band pass filter for the entire receive and transmit band. The channel filtering should be<br />
performed in the digital base band or possibly IF domain. Due to the very high relative bandwidth the RF<br />
band pass shows a very asymmetric attenuation slope for the upper and the lower bound with a different<br />
but low increase in stop band attenuation.<br />
Under the assumption that the maximum attenuation in the pass band at the band edge corresponds to<br />
3 dB, the RF band edge frequencies 0.4 and 6 GHz correspond in the equivalent LP domain to the band<br />
edge frequency f LP,c = 2.8 GHz corresponding to the normalized frequency F LP,c = 1. The following<br />
figures apply:<br />
f n = 1.549 GHz<br />
f c1 = 400 MHz F BP,c1 = 0.258 (4-28)<br />
f c2 = 6 GHz F BP,c2 = 3.873 .<br />
In Figure 4-14 the equivalent normalized LP frequency in the stop band is presented for the lower and the<br />
upper slope <strong>of</strong> the wideband RF band pass.<br />
F LP<br />
0<br />
F LP<br />
45<br />
40<br />
35<br />
30<br />
25<br />
20<br />
15<br />
Lower bound slope<br />
Upper bound slope<br />
10<br />
5<br />
0<br />
0 100 200 300 390<br />
Offset frequency [MHz]<br />
Figure 4-14: Normalized LP frequency for the lower and upper bound slope <strong>of</strong> the RF band pass<br />
At the upper bound a reasonable attenuation can only be achieved for very high frequency separation.<br />
Therefore, disturbing signals beyond 6 GHz have to be taken into account. In addition, the band pass does<br />
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not serve as anti-aliasing filter. At the lower bound, a reasonable stop band attenuation can be achieved<br />
for a separation <strong>of</strong> several 100 MHz. However, also here disturbing signals below 400 MHz have to be<br />
considered.<br />
In the case <strong>of</strong> a Butterworth filter <strong>of</strong> the order n the attenuation follows the function:<br />
2⋅n<br />
( + )<br />
a( F )[ dB]<br />
= 10 ⋅ log 1 . (4-29)<br />
LP<br />
F LP<br />
Figure 4-15 shows the achievable attenuation versus <strong>of</strong>fset frequency from the band edge for a<br />
Butterworth filter <strong>of</strong> the order <strong>of</strong> n. Here a filter order n = 6 is assumed.<br />
Attenuation [dB]<br />
250<br />
200<br />
150<br />
100<br />
Lower bound<br />
Upper bound<br />
50<br />
0<br />
0 100 200 300 390<br />
Offset frequency [MHz]<br />
Figure 4-15: Attenuation at the lower and upper bound slope <strong>of</strong> the RF band pass<br />
The low attenuation at the upper bound will result is serious problem with disturbing signal above 6 GHz.<br />
4.2.2.10 Maximum Input Signal<br />
Within the RF bandwidth very strong disturbing signals such as broadcast <strong>of</strong> radar signals may occur,<br />
which potentially impact the receiver performance. Therefore, the receiver has to have a sufficient<br />
dynamic range in order to avoid overload conditions.<br />
In a simplified worst-case estimation a broadcast transmitter with the following parameters is assumed:<br />
• Transmit power: 20 kW<br />
• Broadcast transmitter antenna gain: 20 dBi<br />
• Terminal antenna gain: 0 dBi<br />
• Distance between transmitter and receiver: 300 m<br />
• Transmitter carrier frequency: 800 MHz<br />
In the case <strong>of</strong> broadcast transmitters the main lobe <strong>of</strong> the transmitter antenna is horizontally oriented.<br />
Therefore, close to the broadcast transmitter location a terminal device does see the broadcast antenna for<br />
negative elevation angles θ. This results in a lower effective antenna gain than in the main lobe. The<br />
effective transmitter antenna gain G t,eff (θ)
<strong>WINNER+</strong> D3.2<br />
Elevation diagram<br />
θ<br />
Broadcast<br />
transmitter<br />
Distance d<br />
Transmitter antenna<br />
Terminal<br />
Figure 4-16: Interference scenario between a broadcast transmitter and a mobile terminal<br />
This scenario with the assumptions above results in a maximum receive power in the order <strong>of</strong><br />
G t,i (θ=0) = 20 dBi<br />
G t,eff (θ) = 0 dBi<br />
P r<br />
2. 8mW<br />
P r<br />
, max<br />
= corresponding to 4.5 dBm<br />
, max<br />
= 28μW<br />
corresponding to -15.5 dBm<br />
(4-31)<br />
at the terminal. However, blocking levels <strong>of</strong> terminal device receivers are usually in the order <strong>of</strong> -40 to -<br />
20 dBm. Under these conditions the receiver should not show desensitization or blocking as well as<br />
nonlinear distortion. However, without RF-filtering to reduce such high power interfering signals the<br />
blocking levels would significantly be exceeded even with lower effective transmitter antenna gain<br />
G t,eff (θ).<br />
4.2.2.11 Sampling Theorem for Both Receiver Versions<br />
Figure 4 presents the two versions <strong>of</strong> the receiver implementation:<br />
• Version A with direct sampling in the RF domain,<br />
• Version B based on the band pass sampling theorem.<br />
Both versions have a different impact on the sampling rate.<br />
Under the assumption <strong>of</strong> an ideal rectangular RF band pass as anti-aliasing filter the following sampling<br />
rates are necessary [Lue75]. – However, such filters are not feasible and with respect to Section 4.8 the<br />
attenuation at the upper bound is very small. –<br />
• Version A: Maximum signal frequency, which needs to be sampled in the RF domain<br />
corresponds to f max = 6 GHz. This results in a minimum sampling rate <strong>of</strong> 12 G-samples/s for real<br />
signal. In this case a A/D-converter with a sampling rate <strong>of</strong> 12 G-samples/s is required.<br />
• Version B: According to the band pass sampling theorem for a band pass bandwidth B = 5.6<br />
GHz the sampling rate per I- and Q-channel corresponds to two times the RF bandwidth B.<br />
Therefore, the sampling rate for the complex base band signals corresponds to 5.6 G-samples/s<br />
or to 5.6 + 5.6 G-samples/s for the I- and Q-channel. In this case two A/D-converters with a<br />
sampling rate <strong>of</strong> 5.6 G-samples/s each are needed.<br />
These high necessary sampling frequencies are theoretical values under the assumptions above for very<br />
wideband transceivers. It is shown in the following that such requirements are technically not feasible.<br />
4.2.2.12 A/D-Converter Dynamic Range and Output Data Rate<br />
The A/D-converter has a limited resolution. It generates quantization noise. According to [TS80] the<br />
signal/noise-ratio between the effective values <strong>of</strong> a sinusoidal input signal U s,eff and the triangular<br />
quantization error U q,eff for a resolution <strong>of</strong> N bits is given by:<br />
S<br />
N<br />
quantization<br />
U<br />
s,<br />
eff<br />
= 20⋅log<br />
[ dB]<br />
= N ⋅6dB<br />
+ 1.8dB<br />
. (4-32)<br />
U<br />
q,<br />
eff<br />
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The quantization noise should be below the effective receiver noise level in order not to increase the<br />
effective noise figure. With respect to [MG86] the A/D-converter dynamic range D ADC follows under this<br />
condition as<br />
D ADC<br />
= N ⋅6dB<br />
− (5 to 10)<br />
dB . (4-33)<br />
With respect to the maximum input power according to (4-31) and the minimum noise power for narrow<br />
band signals in (4-13) a minimum dynamic range <strong>of</strong> 112.5 dB is needed. Under the assumption that for<br />
the narrow band signal with 1.25 MHz carrier bandwidth (like TD-SCDMA, cdma2000) spread spectrum<br />
modulation may be applied, receive signals below the noise level may be detected using processing gain.<br />
Then the required dynamic range is in the order <strong>of</strong><br />
D ADC<br />
= 120 to 130dB<br />
. (4-34)<br />
This corresponds to a required A/D-converter resolution <strong>of</strong> 21 to 24 bit.<br />
This results with Section 4.10 in the following data rates for the output signal <strong>of</strong> the A/D-conversion<br />
before digital signal processing:<br />
• Version A: Minimum sampling rate <strong>of</strong> 12 G-samples/s for real signal with an A/D-converter<br />
resolution <strong>of</strong> 21 to 24 bit provides a data rate for digital signal processing <strong>of</strong><br />
252 to 288 Gbit/s (31.5 to 36 Gbyte/s) . (4-35)<br />
• Version B: Minimum sampling rate for the complex base band signals corresponding to 5.6 + 5.6 G-<br />
samples/s for the I- and Q-channel provides a data rate for digital signal processing <strong>of</strong><br />
117 + 117 to 134 + 134 Gbit/s (2 ⋅ 14.6 to 2 ⋅ 16.75 Gbyte/s) (4-36)<br />
Such high data rate signals would need to be processed in the receiver. Such processing rates are not<br />
feasible with today's technology. In addition, the A/D-converter power consumption would be huge and<br />
not be available in terminal devices.<br />
4.2.2.13 A/D-Converter Performance Development<br />
There is a relation between the sampling rate and the resolution <strong>of</strong> the A/D-converters. Figure 4-17 shows<br />
the currently (status 2006) valid limiting curve between the numbers <strong>of</strong> bits versus sampling rate. With<br />
respect to the requirements in Sections 4.10 and 4.11 there will be no A/D-converters in the foreseeable<br />
future available, which will support<br />
• a sampling rate in the order <strong>of</strong> several GHz and<br />
• a dynamic range in the order <strong>of</strong> 120 to 130 dB.<br />
Basic limitations for the progress <strong>of</strong> the development <strong>of</strong> A/D-converters are also confirmed by Analog<br />
Devices, Inc. in [BH06]. According to [BH06] no significant progress is expected in the near future. New<br />
processes for semiconductor technology will be needed.<br />
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Figure 4-17: Resolution-bandwidth trade-<strong>of</strong>f<br />
For a potentially expected channel bandwidth <strong>of</strong> about 100 MHz with an ideal rectangular channel filter<br />
for anti-aliasing purposes in minimum 100 M-samples for the complex base band signal or 100 + 100 M-<br />
samples for the real and imaginary component are required. Such sampling rates correspond with Figure<br />
4-17 to in maximum 11 bits and thereby in a A/D-converter dynamic range in the order <strong>of</strong> 71 to 76 dB.<br />
Therefore, adjacent carrier interference has to be avoided in front <strong>of</strong> the A/D-converter by using a channel<br />
bandpass filter in the IF-domain in order to reduce the necessary dynamic range. In addition, an AGC<br />
(Automatic Gain Control) in the RF receiver in the IF-domain after channel filtering is required.<br />
In conclusion, if fragmented frequency spectrum should be applied in order to support wideband systems<br />
with a total channel bandwidth in the order <strong>of</strong> 100 MHz, a receiver concept according to Figure 4-4 is a<br />
feasible solution. A wideband receiver according to Figure 4-5 will not be feasible due to the huge<br />
necessary dynamic range. In the ideal case the necessary channel bandwidth should be available in a<br />
single consecutive frequency block.<br />
4.2.3 Conclusions<br />
In this document the basic concept <strong>of</strong> a very wideband receiver for the use <strong>of</strong> fragmented frequency<br />
spectrum for broadband application for IMT-Advanced systems has been theoretically investigated under<br />
the assumption <strong>of</strong> a very wideband and flexible receiver to the entire frequency band from about 400<br />
MHz to about 6 GHz. It is not the intention <strong>of</strong> this Chapter to provide any final decisions. This Chapter is<br />
mainly summarising such major issues, which need further evaluation such as:<br />
• Frequency Dependent Path Loss<br />
• Doppler Frequency and Doppler <strong>Spectrum</strong><br />
• Effective Noise Power<br />
• Impact <strong>of</strong> receiver nonlinearities due to very high disturbing input signals within the receive<br />
band<br />
• RF band pass filtering for image rejection, anti-aliasing and rejection <strong>of</strong> strong disturbing signal<br />
within the RF receiver bandwidth<br />
• Estimation <strong>of</strong> required receiver dynamic range<br />
• Necessary dynamic range <strong>of</strong> the A/D-converter<br />
• Data rate for digital signal processing.<br />
These issues have to be evaluated for potential future implementation with respect to technology<br />
roadmaps for<br />
• RF receiver components,<br />
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• A/D-converters and<br />
• available signal processing power<br />
with respect to implementation cost, form factor and power consumption.<br />
First investigations have already been made in the WINNER project [WIND22] under less challenging<br />
requirements. A more in-depth investigation will require significant effort to look at the different aspects.<br />
However, the available information on the expected performance <strong>of</strong> A/D-converters in terms <strong>of</strong> number<br />
<strong>of</strong> bits versus sampling rate provide a clear indication that due to the strict limitations for the achievable<br />
dynamic range and sampling rate only a receiver concept according to Figure 4-4 will be feasible. The<br />
impact <strong>of</strong> adjacent channels has to be avoided by channel filtering to reduce the necessary dynamic range.<br />
In the ideal case the number <strong>of</strong> receiver chains per transmission channel should be as small as possible;<br />
therefore, a single block <strong>of</strong> spectrum is desired.<br />
The concept <strong>of</strong> a very wideband receiver according to Figure 4-5 with very high sampling rates <strong>of</strong> several<br />
GHz and huge dynamic range or A/D-converter resolution, which may be affected by strong adjacent<br />
carrier signals, is not feasible with today's technology.<br />
Therefore, only a transceiver concept with several parallel RF chains for the different part bands<br />
according to Figure 4–4 is a feasible technical solution, if aggregated or fragmented spectrum use is<br />
required.<br />
4.3 Actual discussions in 3GPP and ITU-R on the implementation <strong>of</strong> identified<br />
frequency spectrum in WRC 2007<br />
WRC 2007 identified additional frequency spectrum for mobile and wireless applications. However, these<br />
identifications are not accepted on global level. There are regional differences. Regional regulators bodies<br />
such as CEPT ECC PT1 in Europe and system specification bodies like 3GPP are currently investigating<br />
options how to use these bands. WRC 2007 identified the following frequency bands for further<br />
consideration:<br />
• 450 – 470 MHz<br />
• 698 – 806 MHz<br />
1)<br />
• 2300 – 2400 MHz<br />
2)<br />
• 3400 – 3600 MHz<br />
3)<br />
The following remarks have to be taken into account for these bands:<br />
1)<br />
The whole band 698 – 960 MHz is not identified on a global basis for IMT due to variation in the<br />
primary mobile service allocations and uses across the three ITU Regions. In particular 698 – 806<br />
MHz in Region 2 and nine countries in Region 3, 790 – 862 MHz in Region 1 and other countries in<br />
Region 3<br />
2)<br />
3)<br />
This band is not available in Europe.<br />
In some countries identified via footnotes in the ITU-R Radio Regulations. CEPT ECC PT1 will also<br />
address the band 3600-3800 MHz for IMT.<br />
In the following the status <strong>of</strong> the discussion in ITU-R and 3GPP are summarised as basis for an<br />
evaluation <strong>of</strong> potential receiver implementations according to Section 4.2.2.<br />
4.3.1 Frequency arrangements in the ITU-R WP5D meeting in Geneva, Switzerland, from<br />
February 10 – 17, 2009<br />
The different identified frequency bands have been discussed:<br />
Figure 4-18 shows the progress <strong>of</strong> discussion on the frequency band 450 – 470 MHz.<br />
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Figure 4-18: Figure Potential frequency arrangements in the band 450 – 470 MHz<br />
The arrangements D1 – D6 have been implemented by some countries taking into account their national<br />
conditions. The arrangement D7 can be implemented by countries that have the whole 450 – 470 MHz<br />
band available for IMT. This band is requiring flexibility in the implementation <strong>of</strong> frequency allocation <strong>of</strong><br />
transmitters and receivers.<br />
In the frequency band 698 – 806 MHz different options are being discussed. There are two new<br />
frequency plans added to the discussion:<br />
• A3 is a placeholder for the band 790 – 862 MHz for IMT systems operating in FDD mode, which are<br />
using a reversed duplex direction in order to avoid interference at the upper band edge, e.g. with<br />
GSM. This frequency arrangement will be developed in ECC PT1 and it is a harmonized solution for<br />
European countries.<br />
• In the A4 band plan administrations can use the band for TDD, FDD or some combination <strong>of</strong> TDD<br />
and FDD. In this case administrations can use any FDD duplex direction (Figure 4-19).<br />
M Hz 690 700 710 720 730 740 750 760 770 780 790 800 810<br />
A4<br />
MS Tx<br />
or TDD<br />
Un-paired<br />
BS Tx<br />
or TDD<br />
BS Tx<br />
or TDD<br />
MS Tx<br />
or TDD<br />
698 716 728 746<br />
763 776 793<br />
Figure 4-19: Potential frequency arrangement A4 in the band 698 – 806 MHz<br />
The frequency band 2300 – 2400 MHz is getting particular interest in China. A TDD and a flexible<br />
FDD/TDD option are under discussion (Figure 4-20). It has been decided that the APT Wireless Forum<br />
(AWF) will study and develop frequency arrangements for the 2 300-2 400 MHz band in the Asia-Pacific<br />
Region. This arrangement will be available for the 6 th meeting <strong>of</strong> ITU-R WP5D in October 2009.<br />
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Figure 4-20: Potential frequency arrangements in the band 2300 – 2400 MHz<br />
Similar to the discussion on the band 2300 – 2400 MHz in the frequency band 3400 – 3600 MHz an FDD<br />
and a TDD solution are under discussion (Figure 4-21). Details are not yet fixed such as<br />
• the size <strong>of</strong> the segments for the FDD uplink (MS Tx) and downlink (BS Tx). Basically, also one <strong>of</strong><br />
the links (uplink or downlink allocation could disappear (i.e., zero width);<br />
• the size <strong>of</strong> the centre gap for duplex separation;<br />
• the arrangement <strong>of</strong> the segments (i.e., FDD UL and DL direction);<br />
• the use <strong>of</strong> the external bands (i.e., combination <strong>of</strong> any FDD pairing with the bands other than 3400 –<br />
3600 MHz);<br />
• the possible frequency arrangement for the simultaneous accommodation <strong>of</strong> both FDD and TDD<br />
arrangements.<br />
MHz<br />
3400 3600<br />
F1<br />
(1 ), ( 2)<br />
MS Tx<br />
BS Tx<br />
3400 3600<br />
F2<br />
TDD<br />
3400 3600<br />
Figure 4-21: Potential frequency arrangements in the band 3400 – 3600 MHz<br />
The following notes have to be considered for the time being before final decisions are made:<br />
• NOTE 1 – MS Tx and/or BS Tx segments could be paired with the external bands.<br />
• NOTE 2 – The horizontal arrow pointing both directions between the “MS Tx” and “BS Tx”<br />
segments indicates that the size <strong>of</strong> segments for DL and UL and subsequently that <strong>of</strong> the centre gap<br />
and duplex separation, would be determined in the later stage.<br />
4.3.2 Status <strong>of</strong> discussion on the implementation <strong>of</strong> identified additional IMT frequency<br />
bands in the 3GPP TSG-RAN meting in Athens, Greece, in February 3 – 13, 2009<br />
According to TS 36.104 in chapter 5.3, E-UTRA is designed to operate in the following bands as shown<br />
in Table 4-2. These bands are partly the basis for considerations in 3GPP on the implementation <strong>of</strong><br />
identified frequency bands. In particular 3GPP is investigating already allocated frequency bands for<br />
mobile and wireless communications and newly identified frequency bands.<br />
Table 4-2: E-UTRA frequency bands<br />
E_UTRA<br />
Band<br />
Uplink (UL)<br />
BS receive<br />
Downlink (DL)<br />
BS transmit<br />
Duplex<br />
Mode<br />
UE transmit<br />
UE receive<br />
F UL_Low – F UL_high<br />
F DL_Low – F DL_high<br />
1 1920 MHz – 1980 MHz 2110 MHz – 2170 MHz FDD<br />
2 1850 MHz – 1910 MHz 1930 MHz – 1990 MHz FDD<br />
3 1710 MHz – 1785 MHz 1805 MHz – 1880 MHz FDD<br />
4 1710 MHz – 1755 MHz 2110 MHz – 2155 MHz FDD<br />
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5 824 MHz – 849 MHz 869 MHz – 894 MHz FDD<br />
6 830 MHz – 840 MHz 875 MHz – 885 MHz FDD<br />
7 2500 MHz – 2570 MHz 2620 MHz – 2690 MHz FDD<br />
8 880 MHz – 915 MHz 925 MHz – 960 MHz FDD<br />
9 1749.9 MHz – 1784.9 MHz 1844.9 MHz – 1879.9 MHz FDD<br />
10 1710 MHz – 1770 MHz 2110 MHz – 2170 MHz FDD<br />
11 1427.9 MHz – 1452.9 MHz 1475.9 MHz – 1500.9 MHz FDD<br />
12 698 MHz – 716 MHz 728 MHz – 746 MHz FDD<br />
13 777 MHz – 787 MHz 746 MHz – 756 MHz FDD<br />
14 788 MHz – 798 MHz 758 MHz – 768 MHz FDD<br />
…<br />
17 704 MHz – 716 MHz 734 MHz – 746 MHz FDD<br />
…<br />
33 1900 MHz – 1920 MHz 1900 MHz – 1920 MHz TDD<br />
34 2010 MHz – 2025 MHz 2010 MHz – 2025 MHz TDD<br />
35 1850 MHz – 1910 MHz 1850 MHz – 1910 MHz TDD<br />
36 1930 MHz – 1990 MHz 1930 MHz – 1990 MHz TDD<br />
37 1910 MHz – 1930 MHz 1910 MHz – 1930 MHz TDD<br />
38 2570 MHz – 2620 MHz 2570 MHz – 2620 MHz TDD<br />
39 1880 MHz – 1920 MHz 1880 MHz – 1920 MHz TDD<br />
40 2300 MHz – 2400 MHz 2300 MHz – 2400 MHz TDD<br />
3GPP RAN WG4 is currently discussing several implementation concepts for IMT-Advanced according<br />
to Table 4-3. These scenarios are partly using already allocated frequency bands to mobile wireless<br />
services and newly identified frequency bands in WRC 2007. Some <strong>of</strong> the scenarios are not using all the<br />
identified and/or allocated frequency bands based on the available information from 3GPP. 3GPP is<br />
proposing to limit pairing to a maximum <strong>of</strong> three bands per active connection/terminal in order to limit<br />
the overall implementation complexity (e.g., scenario 10).<br />
In the following sections the different scenarios are briefly analysed to understand their feasibility and<br />
potential constraints.<br />
Scenario<br />
No.<br />
Deployment<br />
Scenario<br />
1 Single-band<br />
contiguous spectrum<br />
allocation @ 3.5GHz<br />
band for FDD<br />
Scenario 1<br />
Table 4-3: 3GPP spectrum implementation scenarios<br />
Transmission<br />
BWs <strong>of</strong> LTE-<br />
A carriers<br />
UL: 40 MHz<br />
DL: 80 MHz<br />
No <strong>of</strong> LTE-A component<br />
carriers<br />
UL: Contiguous 2x20 MHz CCs<br />
DL: Contiguous 4x20 MHz CCs<br />
Bands for LTE-A<br />
carriers<br />
Duplex<br />
modes<br />
3.5 GHz band FDD<br />
Figure 4-22 illustrates this scenario. The following conditions and comments are relevant:<br />
• There is some relation to the F1 scenario in ITU-R (Figure 4-21).<br />
• FDD duplex scheme.<br />
• In the given frequency band only one UL and one DL carrier is possible. 80 MHz are not used.<br />
• Basically, there is flexibility, where to allocate the UL band within 3400 – 3500 MHz and the DL band<br />
within 3500 – 3600 MHz.<br />
• In order to support competition infrastructure sharing will be needed.<br />
• The implementation is feasible with a single transceiver, because a contiguous frequency band is used.<br />
• The maximum sampling bandwidth is 80 MHz. Technically, this will be feasible to implement.<br />
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UL<br />
DL<br />
3300 3400 3500 3600 3700<br />
MHz<br />
Figure 4-22: Potential band and carrier allocation in scenario 1<br />
CEPT is considering to extend the frequency band up to 3800 MHz in CEPT countries. Under these<br />
conditions additional uplink and downlink FDD carriers could be added as long as the bandwidth <strong>of</strong> the<br />
uplink and downlink carrier bandwidth remains 40 MHz and 80 MHz. The carriers in this case could be<br />
allocated as follows:<br />
• Uplink:<br />
o Carrier 1: 3400 – 3440 MHz<br />
o Carrier 2: 3440 – 3480 MHz<br />
o Carrier 3: 3480 – 3520 MHz<br />
• Downlink:<br />
o Carrier 1: 3560 – 3640 MHz<br />
o Carrier 2: 3640 – 3720 MHz<br />
o Carrier 3: 3720 – 3800 MHz<br />
This would result in a much better spectrum usage than only providing the frequency band from 3400 –<br />
3600 MHz.<br />
2 Single-band<br />
contiguous spectrum<br />
allocation @ Band 40<br />
for TDD<br />
Scenario 2<br />
100 MHz Contiguous 5x20 MHz CCs Band 40 (2.3<br />
GHz)<br />
The frequency allocation in this scenario (Figure 4-23) corresponds to Band 40.<br />
• This corresponds to the E1 scenario in ITU-R (Figure 4-20).<br />
• TDD duplex scheme.<br />
• In the given frequency band only one UL and one DL connection is possible. The entire band is used.<br />
• In order to support competition infrastructure sharing will be needed.<br />
• The implementation is feasible with a single transceiver, because a contiguous frequency band is used.<br />
• The maximum sampling bandwidth is 100 MHz. Technically, this will be feasible to implement.<br />
TDD<br />
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UL/DL<br />
Band 40<br />
2200 2300 2400 2500<br />
MHz<br />
Figure 4-23: Potential band and carrier allocation in scenario 2<br />
3 Single-band 100 MHz Contiguous 5x20 MHz CCs 3.5 GHz band TDD<br />
contiguous spectrum<br />
allocation @ 3.5GHz<br />
band for TDD<br />
Scenario 3<br />
Figure 4-24 shows scenario 3.<br />
• This corresponds to the F2 scenario in ITU-R (Figure 4-21).<br />
• TDD duplex scheme.<br />
• In the given frequency band two UL and one DL carriers/connections are possible. The entire band is<br />
used.<br />
• In order to support competition some lighter approach for infrastructure sharing may be needed.<br />
• The implementation is feasible with a single transceiver, because a contiguous frequency band is used.<br />
• The maximum sampling bandwidth is 100 MHz. Technically, this will be feasible to implement.<br />
UL/DL<br />
UL/DL<br />
3300 3400 3500 3600 3700<br />
MHz<br />
Figure 4-24: Potential band and carrier allocation in scenario 3<br />
CEPT is considering extending the frequency band up to 3800 MHz in CEPT countries. Under these<br />
conditions two additional uplink and downlink TDD carriers could be added as long as the bandwidth <strong>of</strong> the<br />
TDD carrier bandwidth remains 100 MHz. The TDD carriers in this case could be allocated as follows:<br />
• TDD carriers up- and downlink:<br />
o Carrier 1: 3400 – 3500 MHz<br />
o Carrier 2: 3500 – 3600 MHz<br />
o Carrier 3: 3600 – 3700 MHz<br />
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o Carrier 4: 3700 – 3800 MHz.<br />
This would result in a complete usage <strong>of</strong> the available frequency spectrum.<br />
4 Single-band, noncontiguous<br />
spectrum<br />
allocation @ 3.5GHz<br />
band for FDD<br />
Scenario 4<br />
UL: 40 MHz<br />
DL: 80 MHz<br />
UL: Non-contiguous 20 + 20<br />
MHz CCs<br />
DL: Non-contiguous 2x20 +<br />
2x20 MHz CCs<br />
3.5 GHz band FDD<br />
This scenario is shown in Figure 4-25.<br />
• There is some relation to the F1 scenario in ITU-R (Figure 4-21).<br />
• FDD duplex scheme.<br />
• In the given frequency band only one UL (theoretically two) and one DL carrier is possible. 80 MHz<br />
are not used.<br />
• Basically, there is flexibility, where to allocate the UL band within 3400 – 3500 MHz and the DL band<br />
within 3500 – 3600 MHz.<br />
• In order to support competition infrastructure sharing will be needed.<br />
• The implementation is feasible either with a single transceiver or two parallel transceivers, because a<br />
nearly contiguous frequency band is used, where some gaps may not be used.<br />
• The maximum sampling bandwidth is 100 MHz. Technically, this will be feasible to implement.<br />
UL<br />
DL<br />
3300 3400 3500 3600 3700<br />
MHz<br />
Figure 4-25: Potential band and carrier allocation in scenario 4<br />
CEPT is considering extending the frequency band up to 3800 MHz in CEPT countries. Under these<br />
conditions additional uplink and downlink FDD carriers could be added as long as the bandwidth <strong>of</strong> the<br />
uplink and downlink carrier bandwidth remains 40 MHz and 80 MHz. If a non-contiguous spectrum<br />
allocation is assumed, then only one additional uplink and downlink carrier could be added with the<br />
following carrier allocation:<br />
• Uplink:<br />
o Carrier 1: 3420 – 3440 MHz plus 3460 – 3480 MHz<br />
o Carrier 2: 3520 – 3540 MHz plus 3560 – 3580 MHz<br />
• Downlink:<br />
o Carrier 1: 3600 – 3640 MHz plus 3660 – 3700 MHz<br />
o Carrier 1: 3700 – 3740 MHz plus 3760 – 3800 MHz.<br />
If the condition <strong>of</strong> non-contiguous spectrum allocation is not considered anymore, this would result in the<br />
same case as in scenario 1 with the following carrier allocation:<br />
• Uplink:<br />
o Carrier 1: 3400 – 3440 MHz<br />
o Carrier 2: 3440 – 3480 MHz<br />
o Carrier 3: 3480 – 3520 MHz<br />
• Downlink:<br />
o Carrier 1: 3560 – 3640 MHz<br />
o Carrier 2: 3640 – 3720 MHz<br />
o Carrier 3: 3720 – 3800 MHz<br />
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The first version would result in the same non-ideal spectrum usage as the original 3GPP scenario 4. The<br />
second version would result in a much better spectrum usage.<br />
5 Single-band noncontiguous<br />
spectrum<br />
allocation @ Band 8<br />
for FDD<br />
Scenario 5<br />
UL: 10 MHz<br />
DL: 10 MHz<br />
UL/DL: Non-contiguous 5 MHz<br />
+ 5 MHz CCs<br />
Band 8 (900<br />
MHz)<br />
This scenario is using today's 2G frequency bands (Figure 4-26). Reforming <strong>of</strong> such bands would be<br />
needed.<br />
• FDD duplex scheme.<br />
• In the given frequency band three UL and three DL carrier are possible. 2 times 5 MHz are not used.<br />
• Basically, there is flexibility, where to allocate the UL band within 880 – 915 MHz and the DL band<br />
within 925 – 960 MHz.<br />
• In order to support more competition infrastructure sharing may be needed. However, three<br />
independent operators may be active.<br />
• The implementation is feasible with a single transceiver, because a contiguous frequency band is used.<br />
• The maximum sampling bandwidth is 10 MHz. Technically, this will be feasible to implement.<br />
FDD<br />
UL UL UL DL DL DL<br />
Band 8<br />
950 880 915 925 960 1000<br />
MHz<br />
6 Single-band noncontiguous<br />
spectrum<br />
allocation @ Band 38<br />
for TDD<br />
Scenario 6<br />
Figure 4-26: Potential band and carrier allocation in scenario 5<br />
80 MHz Non-contiguous 2x20 + 2x20<br />
MHz CCs<br />
Band 38 (2.6<br />
GHz)<br />
Figure 4-27 shows the understanding <strong>of</strong> this scenario. Band 38 has a bandwidth <strong>of</strong> 50 MHz. On the other<br />
hand the scenario description is requesting a non-contiguous TDD carrier <strong>of</strong> effective bandwidth <strong>of</strong> 80<br />
MHz. This is not consistent (see also Table 4-2) and will be resolved be 3GPP in upcoming meetings.<br />
• TDD duplex scheme.<br />
• In the given frequency band in maximum only one UL and one DL carrier/connection is possible.<br />
• In order to support competition infrastructure sharing will be needed.<br />
• The implementation may be feasible with a single transceiver, is the entire 80 MHz effective carrier<br />
bandwidth may be allocated within band 7.<br />
• Possible, band 7 is meant.<br />
• The maximum sampling bandwidth is not yet known.<br />
TDD<br />
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UL/DL<br />
Band 38<br />
2500 2570 2620 2670<br />
MHz<br />
7 Multi-band noncontiguous<br />
spectrum<br />
allocation @ Band 1,<br />
3 and 7 for FDD<br />
Scenario 7<br />
Figure 4-27: Potential band and carrier allocation in scenario 6<br />
UL: 40 MHz<br />
DL: 40 MHz<br />
UL/DL: Non-contiguous 10<br />
MHz CC@Band 1 + 10 MHz<br />
CC@Band 3 + 20 MHz<br />
CC@Band 7<br />
Band 3 (1.8 GHz)<br />
Band 1 (2.1 GHz)<br />
Band 7 (2.6 GHz)<br />
Scenario 7 is the most difficult one by combining several bands (Figure 4-28).<br />
• FDD duplex scheme.<br />
• In the given frequency band four UL and four DL carrier are possible. 80 MHz are not used in total.<br />
This could be used for guard bands.<br />
• Basically, there is not much flexibility, where to allocate the different UL and DL carriers.<br />
• In order to support competition different operators may receive different carrier frequencies. However,<br />
in some cases more complex base stations for aggregated frequency bands would be needed, which is<br />
not very attractive.<br />
• The implementation is feasible in general with two parallel transceivers, because in some cases a<br />
contiguous frequency band is used and in some cases two bands are combined to achieve 40 MHz<br />
carrier bandwidth.<br />
• However, a single more wideband transceiver would also be feasible, because the maximum sampling<br />
bandwidth would be 100 MHz and it can be expected that no major interferers are active in the band<br />
gaps.<br />
• Therefore, both concepts seem to be technically feasible to implement.<br />
FDD<br />
UL UL<br />
UL UL<br />
DL<br />
DL<br />
DL<br />
DL<br />
Band 3 Band 1<br />
Band 7<br />
1710 1785<br />
19201980 2110<br />
1805 1880<br />
2170<br />
2500 2570<br />
2620 2690<br />
MHz<br />
Figure 4-28: Potential band and carrier allocation in scenario 7<br />
8 Multi-band non- 30 MHz Non-contiguous 1x15 + 1x15 Band 1 (2.1 GHz) FDD><br />
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contiguous spectrum<br />
MHz CCs<br />
Band 3 (1.8GHz)<br />
allocation @ Band 1<br />
and Band 3 for FDD<br />
Scenario 8<br />
This scenario shows a symmetric spectrum allocation for uplink and downlink (Figure 4-29).<br />
• FDD duplex scheme.<br />
• In the given frequency nine UL and nine DL carriers are possible. The entire bands are used.<br />
• This spectrum allocation allows for high competition.<br />
• The implementation is feasible with a single transceiver, because a contiguous frequency band is used<br />
per carrier.<br />
• The maximum sampling bandwidth is 15 MHz. Technically, this is feasible to implement.<br />
UL<br />
DL<br />
UL<br />
DL<br />
Band 3 Band 1<br />
1710 1785<br />
1920 1980 2110 2170<br />
1805 1880<br />
Figure 4-29: Potential band and carrier allocation in scenario 8<br />
MHz<br />
9 Multi-band noncontiguous<br />
spectrum<br />
allocation @ 800<br />
MHz band and Band<br />
8 for FDD<br />
Scenario 9<br />
UL: 20 MHz<br />
DL: 20 MHz<br />
UL/DL: Non-contiguous 10<br />
MHz CC@UHF + 10 MHz<br />
CC@Band 8<br />
800 MHz band<br />
Band 8 (900<br />
MHz)<br />
Figure 4-30 illustrates this scenario.<br />
• FDD duplex scheme.<br />
• In the given frequency band three UL and three DL carriers are possible. 22 MHz are not used.<br />
• Basically, there is some flexibility, where to allocate the UL band within the UHF band and the DL<br />
band within band 8.<br />
• This approach does allow for some competition.<br />
• The implementation is feasible with a single transceiver, because mostly a contiguous frequency band<br />
is used. or two aggregated bands within 35 MHz bandwidth.<br />
• The maximum sampling bandwidth is 35 MHz. Technically, this will be feasible to implement.<br />
FDD<br />
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UL DL DL<br />
UHF Band 8<br />
10 Multi-band noncontiguous<br />
spectrum<br />
allocation @ Band<br />
39, 34, and 40 for<br />
TDD<br />
Scenario 10<br />
790 862<br />
925 960 MHz<br />
880 915<br />
Figure 4-30: Potential band and carrier allocation in scenario 9<br />
90 MHz Non-contiguous 2x20 + 10 +<br />
2x20 MHz CCs<br />
Band 39 (1.8GHz)<br />
Band 34 (2.1GHz)<br />
Band 40 (2.3GHz)<br />
This scenario is using three different bands (Figure 4-31).<br />
• There is some relation to the E1/E2 scenario in ITU-R (Figure 4-20).<br />
• Possibly, not the entire band 40 is used, because this is not available in several regions.<br />
• TDD duplex scheme.<br />
• In the given frequency bands only one UL/DL carrier/connection is possible. 75 MHz are not used.<br />
• Basically, there is flexibility, where to allocate the UL/DL part bands within band 34 from 2010 – 2025<br />
and band 40 from 2300 – 2400 MHz.<br />
• In order to support competition infrastructure sharing will be needed.<br />
• The implementation is feasible with three parallel transceivers. The total bandwidth from 1880 – 2400<br />
MHz will be too big for a wideband transceiver with respect to the sampling bandwidth and potentially<br />
other interfering signals in the band gaps. In this case the maximum sampling bandwidth would be 520<br />
MHz which can not be supported with sufficient dynamic range with today's technology and<br />
reasonable power consumption in particular in the terminal.<br />
• The maximum sampling bandwidth per part band would be 20 MHz. Technically, this is feasible to<br />
implement.<br />
TDD<br />
UL/DL UL/DL UL/DL<br />
Band 39 Band 34<br />
Band 40<br />
1880<br />
1920<br />
2010<br />
2025<br />
2300 2400<br />
MHz<br />
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11 Single-band<br />
Contiguous spectrum<br />
allocation @ Band 7<br />
for FDD<br />
Scenario 11<br />
Figure 4-31: Potential band and carrier allocation in scenario 10<br />
UL: 20 MHz<br />
DL: 40 MHz<br />
UL: 1x20 MHz CCs<br />
DL: 2x20 MHz CCs<br />
Band 7 (2.6 GHz)<br />
Figure 4-32 is an implementation in an already allocated frequency band.<br />
• FDD duplex scheme.<br />
• In the given frequency band only one UL and one DL carrier is possible. 80 MHz are not used in this<br />
asymmetrical frequency allocation.<br />
• Basically, there is flexibility, where to allocate the UL band within 2500 – 2570 MHz and the DL band<br />
within 2620 – 2690 MHz.<br />
• In order to support competition infrastructure sharing will be needed.<br />
• The implementation is feasible with a single transceiver, because a contiguous frequency band is used.<br />
• The maximum sampling bandwidth is 20 MHz. Technically, this is feasible to implement.<br />
FDD<br />
UL<br />
DL<br />
Band 7<br />
2500 2570 2620 2690<br />
MHz<br />
Figure 4-32: Potential band and carrier allocation in scenario 11<br />
All scenarios, which are currently being discussed in 3GPP, can be implemented either with a single band<br />
transceiver or in maximum with up to three parallel transceivers in order to avoid too high requirement on<br />
sampling bandwidth and dynamic range <strong>of</strong> the receivers and A/D-converters. Therefore, such concepts<br />
are feasible to implement.<br />
However, the identified frequency bands are not fully used. In some cases significant parts <strong>of</strong> potentially<br />
available bands remain unused in the proposed scenarios.<br />
4.3.3 Conclusions<br />
Section 4.3 is looking at the currently being discussed spectrum implementation issues in ITU-R and<br />
3GPP. The 3GPP scenarios can be implemented mostly with single band transceivers. In some cases two<br />
or in maximum three parallel transceivers are needed in order to implement the system with sufficient<br />
dynamic range and low sampling bandwidth and to avoid the impact <strong>of</strong> interfering signals in band gaps<br />
between part bands. Three parallel transceivers seem to be feasible with respect to today's terminal<br />
implementation, which is supporting up to four frequency bands for 2G systems and in parallel 3G,<br />
WLAN GPS and DVB in a single high-end device. From a complexity perspective such implementations<br />
are feasible.<br />
However, the use <strong>of</strong> single band transceivers provides lower complexity and cost and will most probably<br />
be preferred. Therefore, the implementation <strong>of</strong> wideband carriers in contiguous bands would be a solution<br />
with lower complexity. With respect to the available and identified frequency bands this may require<br />
infrastructure sharing in order to support competition between operators. Such concepts may change the<br />
role models <strong>of</strong> operators.<br />
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Several <strong>of</strong> the 3GPP scenarios do not fully exploit potentially available frequency bands.<br />
International specification, standardisation and regulatory bodies will discuss spectrum scenarios further<br />
by taking into account national, regional and international constraints on the availability and different<br />
frequency bands.<br />
5. References<br />
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