LTE Advanced E-Book

• Herausgeber: John Wiley & Sons
• Kategorie: Wissenschaft und neue Technologien
• Sprache: Englisch

Seitenzahl: 357

Veröffentlichungsjahr: 2012

Beschreibung

From the editors of the highly successful LTE for UMTS: Evolution to LTE-Advanced, this new book examines the main technical enhancements brought by LTE-Advanced, thoroughly covering 3GPP Release 10 specifications and the main items in Release 11. Using illustrations, graphs and real-life scenarios, the authors systematically lead readers through this cutting-edge topic to provide an outlook on existing technologies as well as possible future developments.

The book is structured to follow the main technical areas that will be enhanced by the LTE-Advanced specifications. The main topics covered include: Carrier Aggregation; Multiantenna MIMO Transmission, Heterogeneous Networks; Coordinated Multipoint Transmission (CoMP); Relay nodes; 3GPP milestones and IMT-Advanced process in ITU-R;  and LTE-Advanced Performance Evaluation.

Key features:

• Leading author and editor team bring their expertise to the next generation of LTE technology
• Includes tables, figures and plots illustrating the concepts or simulation results, to aid understanding of the topic, and enabling readers to be ahead of the technological advances

Leseprobe

Cover

Title Page

Copyright

Dedication

List of Contributors

Preface

Acknowledgements

List of Abbreviations

Chapter 1: Introduction

1.1 Introduction

1.2 Radio Technology Convergence Towards LTE

1.3 LTE Capabilities

1.4 Underlying Technology Evolution

1.5 Traffic Growth

1.6 LTE-Advanced Schedule

1.7 LTE-Advanced Overview

1.8 Summary

Chapter 2: LTE-Advanced Standardization

2.1 Introduction

2.2 LTE-Advanced and IMT-Advanced

2.3 LTE-Advanced Requirements

2.4 LTE-Advanced Study and Specification Phases

2.5 Further LTE-Advanced 3GPP Releases

2.6 LTE-Advanced Specifications

2.7 Conclusions

References

Chapter 3: LTE Release 8 and 9 Overview

3.1 Introduction

3.2 Physical Layer

3.3 Architecture

3.4 Protocols

3.5 EPC and IMS

3.6 UE Capability and Differences in Release 8 and 9

3.7 Conclusions

References

Chapter 4: Downlink Carrier Aggregation

4.1 Introduction

4.2 Carrier Aggregation Principle

4.3 Protocol Impact from Carrier Aggregation

4.4 Physical Layer Impact from Carrier Aggregation

4.5 Performance

4.6 Band Combinations for Carrier Aggregation

4.7 Conclusions

Reference

Chapter 5: Uplink Carrier Aggregation

5.1 Introduction

5.2 Uplink Carrier Aggregation Principle

5.3 Protocol Impacts from Uplink Carrier Aggregation

5.4 Physical Layer Impact from Uplink Carrier Aggregation

5.5 Performance

5.6 Band Combinations for Carrier Aggregation

5.7 Conclusions

References

Chapter 6: Downlink MIMO

6.1 Introduction

6.2 Downlink MIMO Enhancements Overview

6.3 Protocol Impact from Downlink MIMO Enhancements

6.4 Physical Layer Impact from Downlink MIMO

6.5 Performance

6.6 Conclusions

References

Chapter 7: Uplink MIMO

7.1 Introduction

7.2 Uplink MIMO Enhancements Overview

7.3 Protocol Impacts from Uplink MIMO

7.4 Physical Layer Impacts from Uplink MIMO

7.5 Performance

7.6 Conclusions

References

Chapter 8: Heterogeneous Networks

8.1 Introduction

8.2 Base Station Classes

8.3 Traffic Steering and Mobility Management

8.4 Interference Management

8.5 Performance Results

8.6 Local IP Access (LIPA)

8.7 Summary

References

Chapter 9: Relays

9.1 Introduction

9.2 General Overview

9.3 Physical Layer

9.4 Architecture and Protocols

9.5 Radio Resource Management

9.6 Coverage and Capacity

9.7 Relay Enhancements

9.8 Summary

References

Chapter 10: Self-Organizing Networks (SON)

10.1 Introduction

10.2 SON Roadmap in 3GPP Releases

10.3 Self-Optimization

10.4 Self-Healing

10.5 SON Features in 3GPP Release 11

10.6 Summary

References

Chapter 11: Performance Evaluation

11.1 Introduction

11.2 LTE-Advanced Targets

11.3 LTE-Advanced Performance Evaluation

11.4 Network Capacity and Coverage

11.5 Summary

References

Chapter 12: Release 11 and Outlook Towards Release 12

12.1 Introduction

12.2 Release 11 LTE-Advanced Content

12.3 Advanced LTE UE Receiver

12.4 Machine Type Communications

12.5 Carrier Aggregation Enhancements

12.6 Enhanced Downlink Control Channel

12.7 Release 12 LTE-Advanced Outlook

12.8 Conclusions

References

Chapter 13: Coordinated Multipoint Transmission and Reception

13.1 Introduction

13.2 CoMP Concept

13.3 Radio Network Architecture Options

13.4 Downlink CoMP Transmission

13.5 Uplink CoMP Reception

13.6 Downlink CoMP Gains

13.7 Uplink CoMP Gains

13.8 CoMP Field Trials

13.9 Summary

References

Chapter 14: HSPA Evolution

14.1 Introduction

14.2 Multicarrier Evolution

14.3 Multiantenna Evolution

14.4 Multiflow Transmission

14.5 Small Packet Efficiency

14.6 Voice Evolution

14.7 Advanced Receivers

14.8 Flat Architecture

14.9 LTE Interworking

14.10 Summary

References

Index

This edition first published 2012

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Library of Congress Cataloguing-in-Publication Data

LTE-advanced : 3GPP solution for IMT-advanced / edited by Harri Holma, Antti Toskala.

p. cm.

Includes bibliographical references and index.

ISBN 978-1-119-97405-5 (cloth)

1. Long-Term Evolution (Telecommunications) I. Holma, Harri, 1970–II. Toskala, Antti.

TK5103.48325.L73 2012

621.3845′6–dc23

2012012173

A catalogue record for this book is available from the British Library.

ISBN: 9781119974055

To Kiira and Eevi

—Harri Holma

To Lotta-Maria, Maija-Kerttu and Olli-Ville

—Antti Toskala

List of Contributors

All contributors from Nokia Siemens Networks unless otherwise indicated.

Mieszko Chmiel

Amitava Ghosh

Kari Hooli

Pasi Kinnunen

Troels Kolding

Jari Lindholm

Timo Lunttila

Patrick Marsch

Klaus Pedersen

Bernhard Raaf

Karri Ranta-aho

Rapeepat Ratasuk

Simone Redana

Claudio Rosa

Cinzia Sartori

Peter Skov

Jun Tan

Hua Wang∗

Xiaoyi Wang

YuYu Yan

∗ This contributor is from Aalborg University, Denmark.

Preface

The data usage growth in the mobile networks has been very fast during the last few years: the networks have turned rapidly from voice-dominated into data-dominated. The data growth has been fuelled by the availability of mobile broadband coverage and by the higher data rate capabilities. LTE networks were launched early 2009 pushing the data rates up to 100 Mbps. The LTE-capable devices including smartphones and tablet computers became widely available during 2012 boosting the demand for LTE networks and data rates. The further evolution continues on top of LTE, called LTE-Advanced, pushing the data rates beyond 1 Gbps and increasing the system capacity. This book presents 3GPP LTE-Advanced technology in Release 10 and evolution to Release 11 and beyond. The expected practical performance is also illustrated in this book.

The book is structured as follows. Chapter 1 presents an introduction. The standardization schedule and process is described in Chapter 2. An overview of LTE in Release 8 and 9 is given in Chapter 3. Chapters 4 and 5 present the carrier aggregation solution in downlink and in uplink. Chapters 6 and 7 illustrate the multiantenna Multiple Input Multiple Output (MIMO) techniques in downlink and in uplink. The multilayer and multitechnology heterogeneous networks are covered in Chapter 8. Chapter 9 introduces relays and their benefits, and Chapter 10 describes Self-Organizing Network (SON) algorithms. The radio performance evaluation is discussed in Chapter 11. The outlook towards future standardization is presented in Chapter 12. The coordinated multipoint concept is illustrated in Chapter 13. Chapter 14 summarizes the latest enhancements in High Speed Packet Access (HSPA) evolution.

Figure P.1 Contents of the book.

Acknowledgements

The editors would like to acknowledge the hard work of the contributors from Nokia Siemens Networks: Mieszko Chmiel, Amitava Ghosh, Kari Hooli, Pasi Kinnunen, Troels Kolding, Jari Lindholm, Timo Lunttila, Patrick Marsch, Klaus Pedersen, Bernhard Raaf, Rapeepat Ratasuk, Karri Ranta-aho, Simone Redana, Claudio Rosa, Cinzia Sartori, Peter Skov, Jun Tan, Hua Wang, Xiaoyi Wang and Yuyu Yan.

We also would like to thank the following colleagues for their valuable comments: Ömer Bulakci, Lars Dalsgaard, Matthias Hesse, Krzysztof Kordybach, Peter Merz, Sari Nielsen, Sabine Rössel and Hanns Jürgen Schwarzbauer.

The editors appreciate the fast and smooth editing process provided by the publisher, John Wiley & Sons, Ltd and especially Mariam Cheok, Richard Davies, Sandra Grayson and Mark Hammond.

We are grateful to our families, as well as the families of all the authors, for their patience during the late night and weekend editing sessions.

The editors and authors welcome any comments and suggestions for improvements or changes that could be implemented in forthcoming editions of this book. The feedback is welcome to editors' e-mail addresses [email protected] and [email protected].

List of Abbreviations

3GPPThird Generation Partnership ProjectAAAAuthentication, Authorization and AccountingABSAlmost Blank SubframeACKAcknowledgementACLRAdjacent Channel Leakage RatioADCAnalogue-to-Digital ConversionADSLAsymmetric Subscriber LineA-GWAccess GatewayAMAcknowledged ModeAMCAdaptive Modulation and CodingAMRAdaptive MultiRateAMR-NBAMR NarrowBandAMR-WBAMR WideBandANDSFAccess Network Discovery and Selection FunctionAPApplication ProtocolASN.1Abstract Syntax Notation OneCACarrier AggregationCAPEXCapital ExpendituresCBCoordinated BeamformingCCComponent CarrierCCOCoverage and Capacity OptimizationCCSComponent Carrier SelectionCDDCyclic Delay DiversityCDMCode Division MultiplexCDMACode Division Multiple AccessCGICell Global IdentityCIFCarrier Indicator FieldCMCubic MetricCO2Carbon DioxideCOCCell Outage CompensationCoMPCoordinated MultiPointCPCContinuous Packet ConnectivityCQIChannel Quality IndicatorCRSCommon Reference SignalsCSCoordinated SchedulingCSCircuit SwitchedCSGClosed Subscriber GroupCSIChannel State InformationCSoHSPACircuit Switched Voice over HSPADACDigital-to-Analogue ConversionDASDistributed Antenna SystemDCCDownlink Component CarrierDCCHDedicated Control ChannelDCHDedicated ChannelDC-HSDPADual Cell HSDPADCIDownlink Control InformationDCSDynamic Cell SelectionDIPDominant Interferer ProportionDM-RSDemodulation Reference SignalDPCCHDedicated Physical Control ChannelDRXDiscontinuous ReceptionDTXDiscontinuous TransmissionDwPTSDownlink Pilot Time SloteICICEnhanced Inter-Cell Interference CoordinationEIRPEquivalent Isotropic Radiated PowereNBeNodeBEPCEvolved Packet CoreePDCCHenhanced Physical Downlink Control ChannelESEnergy SavingFACHForward Access ChannelFDDFrequency Division DuplexFGIFeature Group IndicatorsGGSNGateway GPRS Support NodeGNSSGlobal Navigation Satellite SystemGPGuard PeriodGPRSGeneral Packet Radio ServiceGSMGlobal System for Mobile CommunicationGTPGPRS Tunnelling ProtocolGWGatewayHARQHybrid Automatic Repeat-reQuestHetNetHeterogeneous NetworksHLRHome Location RegisterHOHandoverHSDPAHigh Speed Downlink Packet AccessHS-FACHHigh Speed FACHHSPAHigh Speed Packet AccessHSSHome Subscriber ServerHSUPAHigh Speed Uplink Packet AccessICInterference CancellationICICInter-Cell Interference CoordinationIDIdentityIMSIP Multimedia Sub-systemIMTInternational Mobile TelecommunicationsIPInternet ProtocolIPSecIP SecurityIQImaginary QuadraticIRCInterference Rejection CombiningISDInter-Site DistanceITUInternational Telecommunication UnionJTJoint TransmissionKPIKey Performance IndicatorLGWLocal GatewayLIPALocal IP AccessLLRLog-likelihood RatioLTELong Term EvolutionMACMedium Access ControlMBMSMultimedia Broadcast Multicast ServiceMBSFNMulticast Broadcast Single Frequency NetworkMCLMinimum Coupling LossMDTMinimization of Drive TestingMIBMaster Information BlockMIMOMultiple Input Multiple OutputMLBMobility Load BalancingMMEMobility Management EntityMRCMaximal Ratio CombiningMROMobility RobustnessMMSEMinimum Mean Square ErrorMPRMaximum Power ReductionMTCMachine Type CommunicationMU-MIMOMulti-User MIMOOAMOperation Administration MaintenanceOCCOrthogonal Cover CodesOFDMOrthogonal Frequency Division MultiplexingO&MOperation and MaintenanceOPEXOperating ExpendituresOTDOAObserved Time Difference Of ArrivalPAPower AmplifierPBCHPhysical Broadcast ChannelPCCPrimary Component CarrierPCCPolicy and Charging ControlPCellPrimary CellPCFICHPhysical Control Format Indicator ChannelPCHPaging ChannelPCIPhysical Cell IdentityPCRFPolicy and Charging Resource FunctionPDCCHPhysical Downlink Control ChannelPDCPPacket Data Convergence ProtocolPDNPacket Data NetworkPDPPacket Data ProtocolPDUPayload Data UnitP-GWPDN GatewayPHICHPhysical HARQ Indicator ChannelPHRPower Headroom ReportingPICParallel Interference CancellationPMIPrecoding Matrix IndicatorPRBPhysical Resource BlockPRGPrecoding Resource block GroupPSSPrimary Syncronization SignalPUCCHPhysical Uplink Control ChannelPUSCHPhysical Uplink Shared ChannelQAMQuadrature Amplitude ModulationQCIQoS Class IdentifierQoSQuality of ServiceQPSKQuadrature Phase Shift KeyingRACHRandom Access ChannelRANRadio Access NetworkRATRadio Access TechnologyRERange ExtensionRERRe-Establishment RequestRETRemote Electrical TiltRFRadio FrequencyRIRank IndicatorRIMRAN Information ManagementRLCRadio Link ControlRLFRadio Link FailureRNRelay NodeRNCRadio Network ControllerRNTPRadio Network Temporary IdentifierR-PDCCHRelay PDCCHRRCRadio Resource ControlRSRPReference Signal Received PowerRSRQReference Signal Received QualityRTPReal Time ProtocolRRHRemote Radio HeadRRMRadio Resource ManagementSASystem AspectsSAESystem Architecture EvolutionSAPSingle Antenna PortSCellSecondary CellSFNSingle Frequency NetworkSGSNServing GPRS Support NodeS-GWServing GatewaySIBSystem Information BlockSINRSignal to Interference and Noise RatioSONSelf-Organizing NetworksSORTDSpace-Orthogonal Resource Transmit DiversitySPSSemi-Persistent SchedulingSRSSounding Reference SignalSR-VCCSingle Radio Voice Call ContinuitySSSSecondary Synchronization SignalTCOTotal Cost of OwnershipTDDTime Division DuplexTMTransmission ModeTTGTunnel Termination GatewayTTITransmission Time IntervalUCIUplink Control InformationUDPUser Datagram ProtocolUEUser EquipmentULAUniform Linear ArraysUMUnacknowledged ModeURSUE specific Reference SignalUpPTSUplink Pilot Time SlotUSBUniversal Serial BusVoIPVoice over IPVoLTEVoice over LTEWCDMAWideband Code Division Multiple AccessWiFiWireless FidelityWiMAXWorldwide Interoperability for Microwave AccessWLANWireless Local Area Network

Chapter 1

Introduction

Harri Holma and Antti Toskala

1.1 Introduction

The huge popularity of smartphones and tablet computers has pushed the need for mobile broadband networks. Users find increasing value in mobile devices combined with a wireless broadband connection. Users and new applications need faster access speeds and lower latency while operators need more capacity and higher efficiency. LTE is all about fulfilling these requirements. GSM made voice go wireless, HSPA made initial set of data connections go wireless and now LTE offers massive capabilities for the mobile broadband applications.

The first set of LTE specifications were completed in 3GPP in March 2009. The first commercial LTE network opened in December 2009. There were approximately 50 commercial LTE networks by the end of 2011 and over 100 networks are expected by the end of 2012. The first LTE smartphones were introduced in 2011 and a wide selection of devices hit the market during 2012. An example LTE smartphone is shown in Figure 1.1: the Nokia 900 with 100 Mbps LTE data rate and advanced multimedia capabilities. Overall, LTE technology deployment has been a success story. LTE shows attractive performance in the field in terms of data rates and latency and the technology acceptance has been very fast. The underlying technology capabilities evolve further which allows pushing also LTE technology to even higher data rates, higher base station densities and higher efficiencies. This book describes the next step in LTE evolution, called LTE-Advanced, which is set to increase the data rate even beyond 1 Gbps.

Figure 1.1 An example of an LTE smartphone – Nokia Lumia 900.

1.2 Radio Technology Convergence Towards LTE

The history of mobile communications has seen many competing radio standards for voice and for data. LTE changes the landscape because all the existing radios converge towards LTE. LTE is the evolution of not only GSM/HSPA operators but also CDMA and WiMAX operators. Therefore, LTE can achieve the largest possible ecosystem. LTE co-exists smoothly with the current radio networks. Most GSM/HSPA operators keep their existing GSM and HSPA radio networks running for long time together with LTE, and they also keep enhancing the existing networks with GSM and HSPA evolutions. The LTE terminals are multimode capable supporting also GSM and HSPA. The radio network solution is based on multi-radio base station which is able to run simultaneously all three radios. Many operators introduce multi-radio products to their networks together with LTE rollouts to simplify the network management and to modernize the existing networks.

The starting point for CDMA and WiMAX operators is different since there is no real evolution for those radio technologies happening. Therefore, CDMA and WiMAX operators tend to have the most aggressive plans for LTE rollouts to get quickly to the main stream 3GPP radio technology to enjoy the LTE radio performance and to get access to the world market terminals.

The high level technology evolution is illustrated in Figure 1.2.

Figure 1.2 Radio technology convergence towards LTE.

1.3 LTE Capabilities

LTE Release 8 offers peak data rate of 150 Mbps in downlink by using 20 MHz of bandwidth and 2 × 2 MIMO. The first LTE devices support up to 100 Mbps while the network capability is up to 150 Mbps. The average data rates in the commercial networks range between 20 and 40 Mbps in downlink and 10–20 Mbps in uplink with 20 MHz bandwidth. Example drive test results are shown in Figure 1.3. Practical LTE data rates in many cases are higher than the available data rates in fixed Asymmetric Digital Subscriber Lines (ADSL). LTE has been deployed using number of different bandwidths: most networks use bandwidth from 5 to 20 MHz. If the LTE bandwidth is smaller than 20 MHz, the data rates scale down correspondingly. LTE has been rolled out both with Frequency Division Duplex (FDD) and Time Division Duplex) TDD variants. LTE has the benefit that both the FDD and TDD modes are highly harmonized in standardization.

Figure 1.3 Example drive test data rates in LTE network with 20 MHz bandwidth.

The end user performance is also enhanced by low latency: the LTE networks can offer round trip times of 10–20 ms. The LTE connections support full mobility including seamless intra-frequency LTE handovers and inter-RAT (Radio Access Technology) mobility between LTE and legacy radio networks. The terminal power consumption is optimized by using discontinuous reception and transmission (DRX/DTX).

LTE also offers benefits for the operators in terms of simple network deployment. The flat architecture reduces the number of network elements and the interfaces. Self-Organizing Network (SON) has made the network configuration and optimization simpler enabling faster and more efficient network rollout.

LTE supports large number of different frequency bands to cater the needs of all global operators. The large number of RF bands makes it challenging to make universal LTE devices. The practical solution is to have several different device variants for the different markets. The roaming cases are handled mainly by legacy radios.

Initial LTE smartphones have a few different solutions for voice: Circuit Switched Fallback (CSFB) handover from LTE to legacy radio (GSM, HSPA, CDMA) or dual radio CDMA + LTE radio. Both options use the legacy circuit switched network for voice and LTE network for data. The Voice over LTE (VoLTE) solution with Voice over IP (VoIP) also started during 2012.

1.4 Underlying Technology Evolution

The radio technology improvements need to be supported by the evolution of the underlying technologies. The technology components – including mass storage, baseband, RF and batteries – keep evolving and help the radio improvements to materialize. The size of the mass storage is expected to have fastest growth during the next ten years which allows for storing more data on the device and which may fuel data download over the radio. The memory size can increase from tens of Gigabytes to several Terabytes. Also the digital processing has its strong evolution. The digital processing power has improved according to Moore's law for several decades. The evolution of the integration level will not be as easy as in earlier times, especially when we need to minimize the device power consumption. Still, the digital processing capabilities will improve during the 2010s, which allows for processing of higher data rates and more powerful interference cancellation techniques. Another area of improvement is the RF bandwidth which increases mainly because of innovations in digital front end processing. The terminal power consumption remains one of the challenges because the battery capacity is expected to have relatively slow evolution. Therefore, power saving features in the devices will still be needed. The technology evolution is illustrated in Figure 1.4.

Figure 1.4 Evolution of underlying technology components.

LTE-Advanced devices and base stations will take benefit of the technology evolution. Higher data rates and wider bandwidth require baseband and RF evolution. The attractive LTE-Advanced devices also benefit from larger memory sizes and from improved battery capacity.

1.5 Traffic Growth

The data volumes in mobile networks have increased considerably during the last few years and the growth is expected to continue. The traffic growth since 2007 and the expected growth until 2015 are illustrated in Figure 1.5. The graph shows the total global mobile network data volume in Exabytes; that is, millions of Terabytes. The traffic is split into voice traffic and data traffic from laptops, tablets and smartphones. The data traffic exceeded the voice traffic during 2009 in terms of carried bytes. The initial data growth was driven by the laptop modems; see an example in Figure 1.6. It is also expected that the LTE-Advanced capabilities, like higher data rates, are first introduced for the laptop modems. The relatively fastest growth from 2012 to 2015 is expected to come from smartphones. The smartphones make nearly half of the traffic by 2015. The total traffic by 2015 will be approximately 40 times more than the traffic 2007. The share of voice traffic is expected to shrink to less than 5% by 2015. Some of the advanced markets already have the total traffic 50 times more than the voice traffic; that means voice is less than 2% of total traffic.

Figure 1.5 Expected traffic growth (Nokia Siemens Network estimate 2011).

Figure 1.6 Example of a 100 Mbps USB modem – Nokia Siemens Networks 7210.

It is not only the data volume that is growing in the networks but also the amount of signalling grows and the number of connected devices grows. The radio evolution work needs to address all these growth factors.

1.6 LTE-Advanced Schedule

The first set of LTE-Advanced is specified in 3GPP Release 10. That release was completed in June 2011. The target date for Release 11 is December 2012. The typical release cycle in 3GPP has been 1.5 years – except for some smaller releases like Release 9 that was completed in a year. It tends to take another 1.5 years from the specification's completion until the first commercial networks and devices are available. Some small features can be implemented faster while some major features requiring heavy redesign may take more time. We could then expect that the first LTE-Advanced features are commercially available during 2013, and Release 11 features towards end of 2014. The LTE-Advanced schedule is shown in Figure 1.7.

Figure 1.7 3GPP timing of LTE-Advanced.

1.7 LTE-Advanced Overview

The main features of LTE-Advanced are summarized in Figure 1.8.

Figure 1.8 Overview of LTE-Advanced main features.

Downlink carrier aggregation to push the data rate initially to 300 Mbps with 20 + 20 MHz spectrum and 2 × 2 MIMO, and later to even 3 Gbps by using 100 MHz bandwidth and 8 × 8 MIMO. More bandwidth is the handy solution to increase the data rates.Multiantenna MIMO evolution to 8 × 8 in downlink and 4 × 4 in uplink. The multiantenna MIMO can also be used at the base station while keeping the number of terminal antennas low. This approach offers the beamforming benefits increasing the network capacity while keeping the terminal complexity low. Multiantennas increase the data rates and the network capacity.Heterogeneous network (HetNet) for the co-channel deployment of macrocells and small cells. HetNet features enable interference coordination between the cell layers. Those features enhance the network capacity and coverage with high density of small cells while sharing the frequency with large macrocells.Relay nodes for backhauling the base stations via LTE radio interface. The transmission link can use inband or outband transmission. Relays are practical for increasing network coverage if the backhaul connections are not available.Coordinated multipoint transmission and reception allows using several cells for the data connection towards one terminal. Coordinated multipoint improves especially the cell edge data rates that are limited by inter-cell interference.Self-organizing network features make the network rollout faster and simpler, and improves the end user performance by providing correct configurations and optimized parameter setting.

LTE-Advanced features in Release 10 can be upgraded flexibly on top of Release 8 network on the same frequencies while still supporting all legacy Release 8 terminals. Therefore, the evolution from LTE to LTE-Advanced will be a smooth one. All these features will be described in detail in this book.

1.8 Summary

LTE Release 8 has turned out to be a successful technology in terms of practical performance and in terms of commercial network and terminal launches. At the same time the high popularity of smartphones pushes the need for further mobile broadband evolution. LTE-Advanced is designed to enhance LTE capabilities in terms of data rates, capacity, coverage and operational simplicity. The first set of LTE-Advanced specifications was completed in 3GPP during 2011 and the features are expected to be commercially available 2013. LTE-Advanced is backwards compatible with LTE and can co-exist with LTE Release 8 terminals on the same frequency.

Chapter 2

LTE-Advanced Standardization

Antti Toskala

2.1 Introduction

This chapter presents the Long Term Evolution (LTE)-Advanced standardization aspects. The standardization of LTE-Advanced is handled by the 3rd Generation Partnership Project (3GPP). 3GPP produced also the earlier LTE versions, Release 8 and 9, as well as the Wideband CDMA (WCDMA) and High Speed Packet Access (HSPA) Releases (and later GSM evolution Releases also). 3GPP has become the leading standards forum for the 4th generation mobile communication systems, following the wide adoption of LTE and LTE-Advanced technology path as the future choice by all the major operators from WCDMA/HSPA, CDMA and WiMAX technology camps. The 3GPP consists of all the major vendors and equipment manufacturers, including all the global players providing infrastructure, terminals, chipsets or wireless test equipment. The 3GPP is consisting of 384 member organizations and approximately 4000 delegate days every month invested in progressing the technology with around 9000 change requests approval to the specifications annually. Tens of thousands of input documents are submitted from different companies to different 3GPP working groups each year. The 3GPP structure and process is covered more detail in [1]. This chapter introduces the relevant 3GPP Release schedule for LTE-Advanced and then presents an overview of the LTE-Advanced study phase done before the actual specification work started in 3GPP. The requirements set for LTE-Advanced by the 3GPP community, as well as ITU-R for the IMT-Advanced submission process, are reviewed and then foreseen steps for later LTE Releases are covered. This chapter concludes with the introduction of relevant 3GPP specifications for LTE-Advanced.

2.2 LTE-Advanced and IMT-Advanced

The International Telecommunication Union Radiocommunication Sector (ITU-R) [2] started process for the new system, International Mobile Telecommunications Advanced (IMT-Advanced), with the circular letter distributed in 2008 to call for radio technology proposals, following the earlier process for IMT-2000 as covered in [1]. ITU-R called for proposals for radio technologies that could meet the requirements set for a versatile radio technology to qualify as an IMT-Advanced technology, often also denoted as the 4th generation (4G) mobile communication system. 3GPP responded to the circular letter with the submission of the Release 10 LTE-Advanced and evaluation results of the achievable performance with LTE-Advanced. The process was completed with the full set of specifications submitted at the end of 2010, with some updates during 2011. The ITU-R IMT-Advanced and 3GPP LTE-Advanced process schedules are shown in Figure 2.1.

Figure 2.1 LTE-Advanced standardization and IMT-Advanced process schedule.

2.3 LTE-Advanced Requirements

The ITU-R defined the requirements for the IMT-Advanced such that the system should be able to [3]:

Enable 100 Mbps peak data rate support for high mobility and up to 1 Gbps peak data rate for low mobility case;Allow inter-working with other radio access systems;Enabling high quality mobile services;Worldwide roaming capability;Flexibility to allows cost efficient support of wide range of service and applications.

Further there were requirements in the following areas:

Cell spectral efficiency, ranging from the 3 bits/Hz/cell in the indoor downlink scenario, to the 0.7 bits/Hz/cell in the high speed uplink scenario;Peak spectral efficiency, ranging up to 15 bits/s/Hz;Bandwidth scalability up to and including 40 MHz, up to 100 MHz should also be considered;Cell edge user spectral efficiency, ranging from 0.015 bits/s/Hz up to 0.1 bits/s/Hz;Latency requirements for control plane to achieve 100 ms transition time between idle and active state, and respectively to enable 10 ms user plane latency (in unloaded conditions);Mobility support with up to 350 kmph (smaller data rate allowed compared to the stationary use case);Handover interruption of 27.5 ms for intra frequency case and 40 and 60 ms for the inter-frequency within the band and between the bands respectively;VoIP capacity, with the numbers of users ranging from 30 to 50 users per sector/MHz.

3GPP also defined its own requirements for LTE-Advanced, which are in many cases tighter than the requirements for IMT-Advanced. This was due to the Release 8 LTE being quite an advanced system already, so that it could meet the IMT-Advanced requirements in many areas already (especially in the high mobility cases). Thus there was desire to ensure in 3GPP that there would be sufficient incremental steps between Release 8/9 LTE capabilities and Release 10 LTE-Advanced capabilities and performance.

Table 2.1 summarizes the key performance requirements from ITU-R and 3GPP [4], indicating the difference especially on the peak spectrum efficiency and on the cell edge spectral efficiency requirements. The latency requirement was identical in both cases. A more detailed treatment on the requirements and achievable performance can be found from Chapter 11.

Table 2.1 Comparison of the ITU-R and 3GPP requirements.

System Performance Requirements3GPP RequirementITU-R RequirementDownlink peak spectrum efficiency30 bits/s/Hz (max 8 antennas)15 bits/s/Hz (max 4 antennas)Uplink peak spectrum efficiency15 bits/s/Hz (max 4 TX antennas)6.75 bits/s/Hz (max 2 TX antennas)Uplink cell edge user spectral efficiency0.04–0.07 bits/s/Hz0.03 bits/s/HzDownlink cell edge user spectral efficiency0.07–0.12 bits/s/Hz0.06 bits/s/HzUser plane latency10 ms10 ms

2.4 LTE-Advanced Study and Specification Phases

The first part of the work in 3GPP was the study phase, which started in early 2008 with the findings on physical layer covered in [5] and overall conclusions presented in [6]. There were several areas studied as part of the study phase, including:

Achievable capacity and cell edge performance, both for data and VoIP;Latency, both for control plane and user plane;Handover performance;Achievable peak spectral efficiency (and peak data rates);Radio Frequency (RF) aspects of supporting the considered technologies.

The results from 3GPP showed that the technology components under consideration can meet or exceed the requirements, as shown with the study phase reports in Chapter 11.

Following the study phase, the work item phase (when actual specifications are produced) was started which produced the first full set of specifications at the end of 2010. This is part of the 3GPP Release 10 specifications, which were finalized in June 2011.

2.5 Further LTE-Advanced 3GPP Releases

3GPP continues the work full speed ahead after the first LTE-Advanced Release. Release 11 work followed immediately Release 10 activity with plenty of proposed work items to further enhance the LTE-Advanced capabilities from Release 10. In order to maintain the schedule 3GPP had to take special actions to prioritize the Release 11 content in September 2011. The selected content is expected to be finalized during second half of 2012 with the specification freeze scheduled to take place at the end of 2012, as shown in Figure 2.2. The key areas where further work was identified included carrier aggregation enhancements and enhanced downlink control channel, as explained with the Release 11 content in more detail in Chapter 12.

Figure 2.2 LTE-Advanced upcoming release schedule and expected market deployment.

3GPP is preparing also the Release 12 and beyond LTE-Advanced content. The 3GPP TSG RAN Release 12/13 workshop in June 2012 collected the vision of the content of the Releases ahead from 3GPP operators and manufacturers. The official Release 12 timing has not yet been decided though with the typical 18-month Release duration and Release 12 could be expected to finalize during the second half of 2014. Figure 2.2 shows also the estimated milestones for the Release 10, 11 and 12 terminals to enter the market based on the assumption of the availability of the first implementations 18 months after the freeze of the protocol specifications (ASN.1 protocol language start of backwards compatibility, as explained in details in [2]) of the corresponding Release.

2.6 LTE-Advanced Specifications

Following the 3GPP Release principle, the LTE-Advanced technology components were added in Release 10 version of the existing LTE specifications, which already contained the Release 8 and 9 LTE features. In some areas new specifications were created, such as for the physical layer of the relay backhaul operation [7] as shown in Figure 2.3, while for example the physical layer impacts of carrier aggregation or multiple antenna enhancements were captured in the existing 36.2xx specification series. The carrier aggregation band combinations are Release independent, with each band combination done as a separate work item, as shown in [8] as an example. The carrier aggregation band combinations can be implemented on top of Release 10 if there is no need for any of the Release 11 specific features. If some of the Release 11 features would be needed by the deployment scenario, such as multiple uplink timing advance values, then the band combination should be based on Release 11 version of the LTE-Advanced specification. With the same principle a new frequency band can be added in 3GPP specifications in a Release independent way so that if a new band is finalized during Release 11 or 12 timeframe one does not need to wait for the ongoing Release to be completed and terminals to be available, but one can implement still for example Release 8 based terminal to the new frequency band (or Release 10 based if LTE-Advanced features are desired) as long as fulfilling the band specific RF and performance requirements.

Figure 2.3 LTE-Advanced in 3GPP specifications.

2.7 Conclusions

In the previous sections, we have covered the LTE-Advanced standardization aspects. The 3GPP has really become the spearhead of development in mobile radio technology with a large attendance from all over the world. The 3GPP is continuing toward further development steps of LTE-Advanced with the ongoing Release 11 work and with the preparation of the plans for Release 12 and 13 as summarized in [9]. Continuous evolution work ensure the LTE-Advanced will stay the most advanced solution for the mobile operators worldwide which is demonstrated by the large participation of the operators in the LTE standardization work from all major markets and with varying technology backgrounds in terms of legacy systems deployed.

References

1. Holma, H. and Toskala, A. (2010) WCDMA for UMTS, 5th edn, John Wiley & Sons, Ltd, Chichester.

2. ITU-R Home Page. Available at: http://www.itu.int/ITU-R (accessed May 2, 2012).

3. ITU-R report, M.2134 (November 2008), Requirements related to technical performance for IMT-Advanced radio interface(s).

4. 3GPP technical report TR 36.913 (March 2009) Requirements for further advancements for Evolved Universal Terrestrial Radio Access (E-UTRA) (LTE-Advanced), V8.0.1.

5. 3GPP technical report TR 36.814 (March 2010), Feasibility study for Further Advancements for E-UTRA (LTE-Advanced).

6. 3GPP technical report TR 36.912 (March 2010) Feasibility study for Further Advancements for E-UTRA (LTE-Advanced), v 9.2.0.

7. 3GPP technical specification TS 36.216 (September 2010) Physical layer for relaying operation, V10.0,0.

8. 3GPP Tdoc RP-100668 (June 2010) Work Item Description: LTE-Advanced Carrier Aggregation of Band 3 and Band 7, TeliasSonera.

9. 3GPP Tdoc RWS-120045 (June 2012) Summary of TSG-RAN workshop on Release 12 and onward, TSG-RAN Chairman.

Chapter 3

LTE Release 8 and 9 Overview

Antti Toskala

3.1 Introduction

This chapter presents the overview of Long Term Evolution (LTE) Release 8 and 9. The principles of the first two LTE Releases produced by 3GPP before LTE-Advanced in Release 10 are presented. In many areas of the LTE-Advanced Release 10, the design is based on the Release 8 and 9 principles with only slight modifications or enhancements to improve the performance. Especially the architecture and protocol solutions in many cases are actually unchanged with LTE-Advanced, perhaps only adding necessary elements to activate the introduced LTE-Advanced physical layer features. This chapter first introduces the LTE physical layer principles and then continues to cover the architecture and protocols solutions in Release 8 and 9. This chapter continues further to cover the overview of the Evolved Packet Core (EPC) and IP Multimedia System (IMS). This chapter is concluded with the UE capability and introduction of the differences between Release 8 and Release 9.

3.2 Physical Layer

The LTE multiple access is based on Orthogonal Frequency Division Multiple Access (OFDMA) in the downlink direction and on the Single Carrier Frequency Division Multiple Access (SC-FDMA) in the uplink direction.

The OFDMA parameterization is based on the 15 kHz sub-carrier spacing to ensure sufficient robustness to large velocity and frequency error, while at the same time the resulting sampling rates allow to have compatibility with the WCDMA sampling rates to facilitate easier multimode implementation both in the UE and the network side. The ODFMA transmitter and receiver chain example is shown in Figure 3.1.

Figure 3.1 LTE downlink OFDMA principle.

In the uplink direction the SC-FDMA facilitates power efficient terminal transmitter implementation since there are no parallel waveforms transmitted but the transmission principle is based on the use of a digital QAM modulation coupled with the cyclic prefix use after a block of symbols. The Peak to Average Ratio (PAR) or more specifically Cubic Metric (CM) is lower with SC-FDMA than with OFDMA, thus allowing avoiding the use of efficient power amplifier without excessive power back-off to maximize the uplink range, as presented in more details in [1].

Adding a cyclic prefix after every QAM symbol is not feasible due to the short symbol duration in time, which would result in massive overheads. Now the addition of the cyclic prefix is done after the block of symbols which was equal duration to a single OFDMA symbol in the downlink. Thus the uplink and downlink overheads from the use of cyclic prefix are identical. An example of the LTE uplink SC-FDMA transmitter and receiver chain is shown in Figure 3.2. The transmitter uses FFF and IFFT pair to enable the frequency division by allowing placing the transmitted signal easily and efficiently in the instructed part of the uplink bandwidth.

Figure 3.2 LTE uplink SC-FDMA principle.

The LTE bandwidths supported in Release 8 and 9 are 1.4, 3, 5, 10, 15 and 20 MHz. In the downlink direction the bandwidth is filled with 15 kHz sub-carriers still leaving room for the necessary reduction of the waveform from the neighbouring carrier. For example with 10 MHz bandwidth there are 600 sub-carriers, thus corresponding to 9 MHz of fully used spectrum. The actual resolution of the resource allocation in frequency domain, both for the uplink and downlink, is 180 kHz. The resource allocation over 180 kHz and for the 1 ms sub-frame corresponds to a single LTE Physical Resource Block (PRB). This is equal to 12 sub-carriers. The parameterization for different bandwidths is shown in Table 3.1. The smallest allocation is thus 6 PRBs, equal to 1.08 MHz and the largest 100 PRBs, equal to 18 MHz. The corresponding bandwidths for normal deployment are then 1.4 and 20 MHz respectively to allow reaching the required values for example for the interference to the adjacent channel, Adjacent Channel Leakage Ratio (ACLR).

Table 3.1 LTE physical layer bandwidth options and bandwidth specific parameters.

The multiple access principle with the use of 180 kHz physical resource block is shown in Figure 3.3 for the downlink direction. An eNodeB is allocating resources every 1 ms for those UEs that have downlink data to be transmitted. The eNodeB scheduler will determine when to transmit data to each UE based on different criteria, including amount of data in the buffer, user priority, service type and momentary channel conditions.

Figure 3.3 Downlink multiple access principle.

In the uplink direction the operation is similar; the eNodeB will inform each UE whether it can transmit in the uplink direction with the allocation received on the Physical Downlink Control Channel (PDCCH). If UE receives the allocation, it contains information on where in frequency domain the UE is able to transmit the data. In uplink the allocation is always continuous n times 180 kHz, while in the downlink direction and allocation could be with one or two gaps (latter with larger bandwidths only). The uplink operation is shown in Figure 3.4, with the UEs receiving every ms allocation whether they are allowed to transmit or not (and in which part of the frequency) in the following uplink sub-frame.

Figure 3.4 Uplink multiple access principle.

The frame structure is based on the 10 ms frame which then contains 1 ms sub-frames (that are the equal to the resource allocation period). As shown in Figure 3.5, the sub-frame is divided between control and data parts. The control part can be 1–3 symbols, and corresponded to the Physical Downlink Control Channel (PDCCH). With the smallest bandwidth of 1.4 MHz the allocation range is from 2–4 symbols to ensure enough transmission capability for the PDCCH link adaptation in case cell edge users. The rest of the sub-frame is filled with data, which corresponds to the Physical Downlink Shared channel (PDSCH). The allocation space for the PDCCH is dynamically signalled every sub-frame on the Physical Control Format Indicator Channel (PCFICH) which informs whether a single OFDMA symbol is needed for the PDCCH capacity needs or if two or three symbols are used.

Figure 3.5 LTE FDD downlink frame structure.

Besides the earlier mentioned downlink physical channels, there is the physical HARQ Indicator Channel (PHICH) which informs the UE whether a packet in the uplink has been correctly received or not. Further there is the Physical Broadcast Channel (PBCH) carrying system information, or rather the Master Information Block (MIB) to indicate when the actual System Information Blocks (SIBs) are transmitted on PDSCH.