LTE SMALL CELLOPTIMIZATION

LTE SMALL CELLOPTIMIZATION3GPP EVOLUTION TO RELEASE 13

Edited by

Harri HolmaAntti ToskalaJussi Reunanen

This edition first published 2016© 2016 John Wiley & Sons Ltd

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1 2016

Contents

Preface xiii

Acknowledgements xv

List of Abbreviations xvii

1 Introduction 1Harri Holma

1.1 Introduction 11.2 LTE Global Deployments and Devices 21.3 Mobile Data Traffic Growth 31.4 LTE Technology Evolution 41.5 LTE Spectrum 51.6 Small Cell Deployments 61.7 Network Optimization 71.8 LTE Evolution Beyond Release 13 81.9 Summary 9

References 9

2 LTE and LTE Advanced in Releases 8–11 11Antti Toskala

2.1 Introduction 112.2 Releases 8 and 9 LTE 11

2.2.1 Releases 8 and 9 Physical Layer 122.2.2 LTE Architecture 172.2.3 LTE Radio Protocols 17

2.3 LTE Advanced in Releases 10 and 11 192.3.1 Carrier Aggregation 192.3.2 Multiple Input Multiple Output Enhancements 232.3.3 HetNet Enhanced Inter-cell Interference Coordination 232.3.4 Coordinated Multipoint Transmission 25

2.4 UE Capability in Releases 8–11 262.5 Conclusions 28

References 28

vi Contents

3 LTE-Advanced Evolution in Releases 12–13 29Antti Toskala

3.1 Introduction 293.2 Machine-Type Communications 293.3 Enhanced CoMP 343.4 FDD–TDD Carrier Aggregation 353.5 WLAN-Radio Interworking 373.6 Device-to-Device Communication with LTE 393.7 Single Cell Point to Multipoint Transmission 413.8 Release 12 UE Capabilities 423.9 Conclusions 42

References 43

4 Small Cell Enhancements in Release 12/13 45Antti Toskala, Timo Lunttila, Tero Henttonen and Jari Lindholm

4.1 Introduction 454.2 Small Cell and Dual Connectivity Principles 454.3 Dual Connectivity Architecture Principle 464.4 Dual Connectivity Protocol Impacts 474.5 Dual Connectivity Physical Layer Impacts and Radio Link Monitoring 494.6 Other Small Cell Physical Layer Enhancement 53

4.6.1 256QAM for LTE Downlink 534.6.2 Small Cell ON/OFF Switching and Enhanced Discovery 534.6.3 Power Saving with Small Cell ON/OFF 564.6.4 Over the Air Synchronization Between eNodeBs 56

4.7 Release 13 Enhancements 564.8 Conclusions 57

References 57

5 Small Cell Deployment Options 59Harri Holma and Benny Vejlgaard

5.1 Introduction 595.2 Small Cell Motivation 605.3 Network Architecture Options 605.4 Frequency Usage 645.5 Selection of Small Cell Location 655.6 Indoor Small Cells 67

5.6.1 Distributed Antenna Systems 675.6.2 Wi-Fi and Femto Cells 685.6.3 Femto Cell Architecture 705.6.4 Recommendations 72

5.7 Cost Aspects 725.7.1 Macro Network Extension 735.7.2 Outdoor Small Cells 73

Contents vii

5.7.3 Outdoor Pico Cluster 735.7.4 Indoor Offloading 74

5.8 Summary 74References 75

6 Small Cell Products 77Harri Holma and Mikko Simanainen

6.1 Introduction 776.2 3GPP Base Station Categories 786.3 Micro Base Stations 786.4 Pico Base Stations 806.5 Femtocells 836.6 Low-Power Remote Radio Heads 84

6.6.1 Alternative Remote Radio Head Designs for Indoor Use 866.7 Distributed Antenna Systems 876.8 Wi-Fi Integration 876.9 Wireless Backhaul Products 896.10 Summary 90

Reference 90

7 Small Cell Interference Management 91Rajeev Agrawal, Anand Bedekar, Harri Holma, Suresh Kalyanasundaram,Klaus Pedersen and Beatriz Soret

7.1 Introduction 917.2 Packet Scheduling Solutions 937.3 Enhanced Inter-cell Interference Coordination 97

7.3.1 Concept Description 977.3.2 Performance and Algorithms 101

7.4 Enhanced Coordinated Multipoint (eCoMP) 1107.5 Coordinated Multipoint (CoMP) 1147.6 Summary 119

References 120

8 Small Cell Optimization 121Harri Holma, Klaus Pedersen, Claudio Rosa, Anand Bedekar and Hua Wang

8.1 Introduction 1218.2 HetNet Mobility Optimization 1228.3 Inter-site Carrier Aggregation with Dual Connectivity 126

8.3.1 User Data Rates with Inter-site Carrier Aggregation 1268.3.2 Mobility with Dual Connectivity 131

8.4 Ultra Dense Network Interference Management 1358.4.1 Ultra Dense Network Characteristics 1358.4.2 Proactive Time-Domain Inter-cell Interference Coordination 1368.4.3 Reactive Carrier-Based Inter-cell Interference Coordination 138

viii Contents

8.5 Power Saving with Small Cell On/Off 1398.6 Multivendor Macro Cell and Small Cells 1418.7 Summary 143

References 143

9 Learnings from Small Cell Deployments 145Brian Olsen and Harri Holma

9.1 Introduction 1459.2 Small Cell Motivations by Mobile Operators 1459.3 Small Cell Challenges and Solutions 1469.4 Summary of Learnings from Small Cell Deployments 1479.5 Installation Considerations 1519.6 Example Small Cell Case Study 152

9.6.1 Site Solution and Backhaul 1529.6.2 Coverage and User Data Rates 1539.6.3 Macro Cell Offloading and Capacity 1549.6.4 KPIs in Network Statistics 1559.6.5 Mobility Performance 1569.6.6 Parameter and RF Optimization 157

9.7 Summary 158

10 LTE Unlicensed 159Antti Toskala and Harri Holma

10.1 Introduction 15910.2 Unlicensed Spectrum 16010.3 Operation Environment 16110.4 Motivation for the Use of Unlicensed Spectrum with LTE 16210.5 Key Requirements for 5 GHz Band Coexistence 16210.6 LTE Principle on Unlicensed Band 16410.7 LTE Performance on the Unlicensed Band 16510.8 Coexistence Performance 16610.9 Coverage with LTE in 5 GHz Band 17010.10 Standardization 17210.11 Conclusions 172

References 173

11 LTE Macro Cell Evolution 175Mihai Enescu, Amitava Ghosh, Bishwarup Mondal and Antti Toskala

11.1 Introduction 17511.2 Network-Assisted Interference Cancellation 17611.3 Evolution of Antenna Array Technology 18111.4 Deployment Scenarios for Antenna Arrays 182

Contents ix

11.5 Massive-MIMO Supported by LTE 18711.5.1 Sectorization (Vertical)-Based Approaches 18711.5.2 Reciprocity-Based Approaches 188

11.6 Further LTE Multi-antenna Standardization 18911.7 Release 13 Advanced Receiver Enhancements 19211.8 Conclusions 192

References 193

12 LTE Key Performance Indicator Optimization 195Jussi Reunanen, Jari Salo and Riku Luostari

12.1 Introduction 19512.2 Key Performance Indicators 19612.3 Physical Layer Optimization 19712.4 Call Setup 200

12.4.1 Random Access Setup 20212.4.2 RRC Connection Setup 20812.4.3 E-RAB Setup 215

12.5 E-RAB Drop 21812.5.1 Handover Performance 21812.5.2 UE-Triggered RRC Connection Re-establishments 22212.5.3 eNodeB-triggered RRC Connection Re-establishments 226

12.6 Handover and Mobility Optimization 22812.7 Throughput Optimization 232

12.7.1 MIMO Multi-stream Usage Optimization 23412.8 High-Speed Train Optimization 24312.9 Network Density Benchmarking 24612.10 Summary 247

References 248

13 Capacity Optimization 249Jussi Reunanen, Riku Luostari and Harri Holma

13.1 Introduction 24913.2 Traffic Profiles in Mass Events 25113.3 Uplink Interference Management 255

13.3.1 PUSCH 25713.3.2 PUCCH 26513.3.3 RACH and RRC Setup Success Rate 26513.3.4 Centralized RAN 269

13.4 Downlink Interference Management 27013.4.1 PDSCH 27113.4.2 Physical Downlink Control Channel 276

13.5 Signalling Load and Number of Connected Users Dimensioning 27913.5.1 Signalling Load 28013.5.2 RRC-Connected Users 280

x Contents

13.6 Load Balancing 28413.7 Capacity Bottleneck Analysis 28613.8 Summary 291

References 292

14 VoLTE Optimization 293Riku Luostari, Jari Salo, Jussi Reunanen and Harri Holma

14.1 Introduction 29314.2 Voice Options for LTE Smartphones 29314.3 Circuit Switched Fallback 294

14.3.1 Basic Concepts 29414.3.2 CSFB Call Setup Time, Transition to Target RAT 29614.3.3 CSFB Call Setup Success Rate 30214.3.4 Return to LTE after CSFB Call 302

14.4 Voice over LTE 30714.4.1 Setup Success Rate and Drop Rate 30714.4.2 TTI Bundling and RLC Segmentation 31014.4.3 Semi-persistent Scheduling 31214.4.4 Packet Bundling 31414.4.5 Re-establishment with Radio Preparations 31514.4.6 Voice Quality on VoLTE 315

14.5 Single Radio Voice Call Continuity 32214.5.1 Signalling Flows 32214.5.2 Performance 326

14.6 Summary 331References 331

15 Inter-layer Mobility Optimization 333Jari Salo and Jussi Reunanen

15.1 Introduction 33315.2 Inter-layer Idle Mode Mobility and Measurements 334

15.2.1 Initial Cell Selection and Minimum Criteria for UE toCamp on a Cell 334

15.2.2 Summary of Cell Reselection Rules 33615.2.3 Idle Mode Measurements 338

15.3 Inter-layer Connected Mode Measurements 34415.4 Inter-layer Mobility for Coverage-Limited Network 350

15.4.1 Basic Concepts 35015.4.2 Mapping Throughput Target to SINR, RSRQ and RSRP 35315.4.3 Inter-layer Mobility Example #1 (Non-equal Priority Non-equal

Bandwidth LTE Layers) 36115.4.4 Inter-layer Mobility Example #2 (Equal Priority Equal Bandwidth

LTE Layers) 368

Contents xi

15.5 Inter-layer Mobility for Capacity-Limited Networks 37015.5.1 Static Load Balancing via Mobility Thresholds 37115.5.2 Dynamic Load Balancing via eNodeB Algorithms 375

15.6 Summary 377References 377

16 Smartphone Optimization 379Rafael Sanchez-Mejias, Laurent Noel and Harri Holma

16.1 Introduction 37916.2 Smartphone Traffic Analysis in LTE Networks 380

16.2.1 Data Volumes and Asymmetry 38016.2.2 Traffic-Related Signalling 38116.2.3 Mobility-Related Signalling 38216.2.4 User Connectivity 382

16.3 Smartphone Power Consumption Optimization 38416.3.1 Impact of Downlink Carrier Aggregation 38416.3.2 Impact of Discontinuous Reception 385

16.4 Smartphone Operating Systems 39116.5 Messaging Applications 39116.6 Streaming Applications 39316.7 Voice over LTE 394

16.7.1 VoLTE System Architecture 39516.7.2 VoLTE Performance Analysis 39616.7.3 Standby Performance 40416.7.4 Impact of Network Loading and Radio Quality 405

16.8 Smartphone Battery, Baseband and RF Design Aspects 40616.8.1 Trends in Battery Capacity 40616.8.2 Trends in Cellular Chipset Power Consumption 40916.8.3 Impact of Small Cells on Smartphone Power Consumption 412

16.9 Summary 421References 421

17 Further Outlook for LTE Evolution and 5G 423Antti Toskala and Karri Ranta-aho

17.1 Introduction 42317.2 Further LTE-Advanced Beyond Release 13 42317.3 Towards 5G 42617.4 5G Spectrum 42717.5 Key 5G Radio Technologies 42817.6 Expected 5G Schedule 43017.7 Conclusions 432

References 432

Index 433

Preface

We have witnessed a fast growth in mobile broadband capabilities during the last 10 years interms of data rates, service availability, number of customers and data volumes. The launch ofthe first LTE network in December 2009 further boosted the growth of data rates and capacities.LTE turned out to be a success because of efficient performance and global economics of scale.The first LTE-Advanced network started in 2013, increasing the data rate to 300 Mbps by 2014,450 Mbps in 2015 and soon to 1 Gbps. The number of LTE networks had grown globally tomore than 460 by end 2015.

This book focuses on those solutions improving the practical LTE performance: small cellsand network optimization. The small cells are driven by the need to increase network capacityand practical user data rates. The small cell deployment creates a number of new challengesfor practical deployment ranging from interference management to low-cost products, sitesolutions and optimization. The network optimization targets to squeeze everything out of theLTE radio in terms of coverage, capacity and end-user performance.

3. LTE-Advanced in

Releases 12–13

1. Introduction

2. LTE and LTE-Advanced

in Releases 8–11

5. Small Cell Deployment Options

6. Small Cell Products

7. Small Cell Interference Managements

8. Small Cell Optimization

9. Learnings from Small Cell Deployments

4. Small Cell

Enhancements in 3GPP

10. LTE on Unlicensed Spectrum

11. LTE Macro Cell

Evolution

12. LTE Key Performance Optimization

13. LTE Capacity Optimization

14. LTE Voice Optimization

16. Smartphone

Optimization

ResidentialEnterprisePublic indoorPublic outdoor

FemtoPico or enterprise femto

PicoMicro

Pico

5 GHz

15. LTE Inter-Layer Mobility

Optimization

17. Future Outlook for LTE Evolution

Figure P.1 Contents of the book

xiv Preface

Smartphones, tablets and laptops are the main use cases for LTE networks currently, but LTEradio will be the foundation for many new applications in the future. Internet of things, publicsafety, device-to-device communication, broadcast services and vehicle communication are afew examples that can take benefit of future LTE radio.

The contents of the book are summarized in Figure P.1. Chapters 1–3 provide an introduc-tion to LTE in 3GPP Releases 8–13. The small cell-specific topics are discussed in Chapters4–10 including 3GPP features, network architecture, products, interference management, opti-mization, practical learnings and unlicensed spectrum. The LTE optimization is presented inChapters 11–16 including 3GPP evolution, performance, voice, inter-layer and smartphoneoptimization. Chapter 17 illustrates the outlook for further LTE evolution.

Acknowledgements

The editors would like to acknowledge the hard work of the contributors from Nokia Net-works, T-Mobile USA and Videotron Canada: Rajeev Agrawal, Anand Bedekar, Mihai Enescu,Amitava Ghosh, Tero Henttonen, Wang Hua, Suresh Kalyanasundaram, Jari Lindholm, TimoLunttila, Riku Luostari, Bishwarup Mondal, Laurent Noel, Brian Olsen, Klaus Pedersen, KarriRanta-aho, Claudio Rosa, Jari Salo, Rafael Sanchez-Mejias, Mikko Simanainen, Beatriz Soretand Benny Vejlgaard.

The editors also would like to thank the following colleagues for their valuable comments andcontributions: Petri Aalto, Yin-tat Peter Chiu, Bong Youl (Brian) Cho, Jeongho (Jackson) Cho,Jinho (Jared) Cho, Anthony Ho, Richa Gupta, Kari Hooli, Kyeongtaek Kim, Kimmo Kivilahti,Ekawit Komolpun, Wai Wah (Endy) Kong, Dinesh Kumar, Karri Kuoppamaki, Andrew Lai,Franck Laigle, Mads Lauridsen, Hyungyoup (Henry) Lee, Jasin (Jason) Lee, Sami Lehesaari,Jun Liu, Jarkko Lohtaja, Yi-Nan (Evan) Lu, Mark McDiarmid, Luis Maestro, Deshan Miao,Marko Monkkonen, Balamurali Natarajan, Nuttavut Sae-Jong, Shuji Sato, Changsong Sun,Wangkeun (David) Sun, Kirsi Teravainen, Jukka Virtanen, Eugene Visotsky and Veli Voipio.

The editors appreciate the fast and smooth editing process provided by Wiley publisher andespecially Tiina Wigley and Mark Hammond.

The editors are grateful to their families, as well as the families of all the authors, for theirpatience during the late night writing and weekend editing sessions.

The editors and authors welcome any comments and suggestions for improvements orchanges that could be implemented in forthcoming editions of this book. The feedback may beaddressed to: harri.holma@nokia.com, antti.toskala@nokia.com and jussi.reunanen@nokia.com

List of Abbreviations

3D Three Dimensional3GPP Third Generation Partnership ProjectAAS Active Antenna SystemABS Almost Blank SubframeAC Alternating CurrentACK AcknowledgementAIR Antenna Integrated RadioAM Acknowledge ModeAMR Adaptive MultirateANDSF Access Network Discovery and Selection FunctionANR Automatic Neighbour RelationsAPP ApplicationsAPT Average Power TrackingARFCN Absolute Radio Frequency Channel NumberARQ Automatic Repeat RequestAS Application ServerASA Authorized Shared AccessAWS Advanced Wireless SpectrumBBU Baseband UnitBCCH Broadcast ChannelBLER Block Error RateBSIC Base Station Identity CodeBSR Buffer Status ReportBTS Base StationC-RNTI Cell Radio Network Temporary IdentifierCA Carrier AggregationCAPEX Capital ExpenditureCAT CategoryCC Component CarrierCCA Clear Channel AssessmentCCE Control Channel ElementCDF Cumulative Density FunctionCDMA Code Division Multiple AccesscDRX Connected Discontinuous Reception

xviii List of Abbrivitions

CoMP Coordinated MultipointCPRI Common Public Radio InterfaceCN Core NetworkCPICH Common Pilot ChannelCPU Central Processing UnitCQI Channel Quality IndicatorCRC Cyclic Redundancy CheckCRAN Centralized Radio Access NetworkCRS Common Reference SignalsCRS-IC Common Reference Signal interference cancellationCS Circuit SwitchedCS Cell SelectionCSCF Call Session Control FunctionCSFB Circuit Switched FallbackCSG Closed Subscriber GroupCSI Channel State InformationCSI-RS Channel State Information Reference SignalsCSMO Circuit Switched Mobile OriginatedCSMT Circuit Switched Mobile TerminatedCSSR Call Setup Success RateCWIC Code Word Interference CancellationCWDM Coarse Wavelength Division MultiplexingD2D Device-to-DeviceDAS Distributed Antenna SystemDC Direct CurrentDC Dual ConnectivityDCCH Dedicated Control ChannelDCH Dedicated ChannelDCI Downlink Control InformationDCR Drop Call RateDFS Dynamic Frequency SelectionDMCR Deferred Measurement Control ReadingDMRS Demodulation Reference SignalsDMTC Discovery Measurement Timing ConfigurationDPS Dynamic Point SelectionDRB Data Radio BearerDRS Discovery Reference SignalsDRX Discontinuous ReceptionDSL Digital Subscriber LineDTX Discontinuous TransmissionDU Digital UnitECGI E-UTRAN Cell Global IdentifiereCoMP Enhanced Coordinated MultipointEDPCCH Enhanced Downlink Physical Control ChannelEFR Enhanced Full RateeICIC Enhanced Inter-Cell Interference Coordination

List of Abbrivitions xix

eMBMS Enhanced Multimedia Broadcast Multicast SolutionEPA Enhanced Pedestrian AEPC Evolved Packet CoreEPRE Energy Per Resource ElementeRAB Enhanced Radio Access BearerESR Extended Service RequestET Envelope TrackingEVM Error Vector MagnitudeEVS Enhanced Voice ServicesFACH Forward Access ChannelFD-LTE Frequency Division Long Term EvolutionFDD Frequency Division DuplexfeICIC Further Enhanced Inter-Cell Interference CoordinationFFT Fast Fourier TransformationFSS Frequency Selective SchedulingFTP File Transfer ProtocolGBR Guaranteed Bit RateGCID Global Cell IdentityGERAN GSM EDGE Radio Access NetworkGPON Gigabit Passive Optical NetworkGPS Global Positioning SystemGS Gain SwitchingGSM Global System for Mobile CommunicationsHARQ Hybrid Automatic Repeat RequestHD High DefinitionHetNet Heterogeneous NetworkHFC Hybrid Fibre CoaxialHO HandoverHOF Handover FailureHPM High-Performance MobileHSPA High-Speed Packet AccessHSDPA High-Speed Downlink Packet AccessHSUPA High-Speed Uplink Packet AccessHTTP Hypertext Transfer ProtocolIAS Integrated Antenna SystemIC Interference CancellationICIC Inter-Cell Interference CoordinationIRC Interference Rejection CombiningIEEE Institute of Electrical and Electronics EngineersIM Instant MessagingIMEI International Mobile Station Equipment IdentityIMPEX Implementation ExpenditureIMS Internet Protocol Multimedia SubsystemIMT International Mobile TelecommunicationIoT Internet-of-ThingsIQ In-phase and Quadrature

xx List of Abbrivitions

IRC Interference Rejection CombiningIRU Indoor Radio UnitISD Inter Site DistanceIT Information TechnologyITU-R International Telecommunications Union – Radiocommunications SectorJP Joint ProcessingJT Joint TransmissionKPI Key Performance IndicatorLAA Licensed Assisted AccessLAN Local Area NetworkLAU Location Area UpdateLBT Listen-Before-TalkLMMSE-IRC Linear Minimum Mean Squared Error Interference Rejection CombiningLOS Line of SightLP Low PowerLTE Long-Term EvolutionLTE-A LTE-AdvancedLU Location UpdateMAC Medium Access ControlMBSFN Multicast Broadcast Single Frequency NetworkMDT Minimization of Drive TestingMeNB Macro eNodeBMeNodeB Master eNodeBM2M Machine-to-MachineMCL Minimum Coupling LossMCS Modulation and Coding SchemeML Maximum LikelihoodMLB Mobility Load BalancingMIMO Multiple Input Multiple OutputMME Mobility Management EntityMMSE Minimum Mean Square ErrorMOS Mean Opinion ScoreMRC Maximal Ratio CombiningMRO Mobility Robustness OptimizationMSS Mobile Switching centre ServerMTC Machine Type CommunicationsMTC Mobile Terminating CallMTRF Mobile Terminating Roaming ForwardingMTRR Mobile Terminating Roaming RetryM2M Machine-to-MachineNAICS Network Assisted Interference Cancellation and SuppressionNAS Non-access StratumNB NarrowbandNLOS Non-line of SightNOMA Non-orthogonal Multiple AccessOBSAI Open Base Station Architecture Initiative

List of Abbrivitions xxi

O&M Operations and MaintenanceOFDM Orthogonal Frequency Division MultiplexingOFDMA Orthogonal Frequency Division Multiple AccessOPEX Operating ExpenditureOS Operating SystemOSG Open Subscriber GroupOTT Over the TopPA Power AmplifierPBCH Physical Broadcast ChannelPCell Primary CellPCFICH Physical Control Format Indicator ChannelPCH Paging ChannelPCI Physical Cell IdentityPDCCH Physical Downlink Control ChannelPDCP Packet Data Convergence ProtocolPDF Power Density FunctionPDSCH Physical Downlink Shared ChannelPDU Protocol Data UnitPESQ Perceptual Evaluation of SpeechPHR Power Headroom ReportPWG Packet Data Network GatewayPLMN Public Land Mobile NetworkPMI Precoding Matrix IndicatorPoE Power over EthernetPOLQA Perceptual Objective Listening QualityPON Passive Optical NetworkPRB Physical Resource BlockPSCCH Physical Sidelink Control ChannelPSBCH Physical Sidelink Broadcast ChannelPSCCH Physical Sidelink Control ChannelPSD Power Spectral DensityPSDCH Physical Sidelink Discovery ChannelPSM Power-Saving ModePSSCH Physical Sidelink-Shared ChannelPUCCH Physical Uplink-Control ChannelPUSCH Physical Uplink-Shared ChannelpRRU Pico Remote Radio UnitQAM Quadrature Amplitude ModulationQCI Quality of Service Class IdentifierQoS Quality of ServiceRA-RNTI Random Access Radio Network Temporary IdentifierRACH Random Access ChannelRAN Radio Access NetworkRAO Random Access OpportunityRAT Radio Access TechnologyRB Radio Bearer

xxii List of Abbrivitions

RCS Rich Call ServicesRE Range ExtensionRET Remote Electrical TiltingRF Radio FrequencyRHUB Remote Radio Unit HubRI Rank IndicatorRIM Radio Information ManagementRLC Radio Link ControlRNC Radio Network ControllerRRH Remote Radio HeadRAT Radio Access TechnologyRLF Radio Link FailureRLM Radio Link MonitoringRNC Radio Network ControllerRNTP Relative Narrow-Band Transmit PowerROHC Robust Header CompressionRoT Rise over ThermalRRC Radio Resource ControlRRM Radio Resource ManagementRS Reference SignalRSCP Received Signal Code PowerRSRP Reference Signal Received PowerRSRQ Reference Signal Received QualityRSSI Received Signal Strength IndicationRX ReceptionSC-FDMA Single Carrier Frequency Division Multiple AccessSDU Service Data UnitS-GW Serving GatewayS-TMSI SAE Temporary Mobile Subscriber IdentityS1AP S1 Application ProtocolSeNB Small eNodeBSeNodeB Secondary eNodeBSCell Secondary CellSCS Short Control SignallingSFN Single Frequency NetworkSGW Serving GatewaySI-RNTI System Information Radio Network Temporary IdentifierSIB System Information BlockSINR Signal to Interference and Noise RatioSIP Session Initiation ProtocolSISO Single Input Single OutputSLIC Symbol Level Interference CancellationSMS Short Message ServiceSNR Signal-to-Noise RatioSON Self-Organizing NetworkSPS Semi Persistent Scheduling

List of Abbrivitions xxiii

SR Scheduling RequestSRB Signalling Radio BearerSRS Sounding Reference SignalsSRVCC Single Radio Voice Call ContinuitySU Single UserSWB Super WidebandTA Timing AdvanceTAU Tracking Area UpdateTBS Transport Block SizeTC Test CaseTCO Total Cost of OwnershipTCP Transmission Control ProtocolTDD Time Division DuplexTD-LTE Time Division Long-Term EvolutionTETRA Terrestrial Trunked RadioTM Transmission ModeTPC Transmission Power ControlTTI Transmission Time IntervalTTT Time to TriggerTX TransmissionUCI Uplink Control InformationUDN Ultra Dense NetworkUDP User Datagram ProtocolUE User EquipmentUPS Uninterruptible Power SupplyUSB Universal Serial BusUSIM Universal Subscriber Identity ModuleUTRA Universal Terrestrial Radio AccessUTRAN Universal Terrestrial Radio Access NetworkVAD Voice Activity DetectionVDSL Very High Bit Rate Digital Subscriber LineVoLTE Voice over LTEV2X Vehicle to InfrastructureV2V Vehicle to VehicleWB WidebandWCDMA Wideband Code Division Multiple AccessWDM Wavelength Division MultiplexingWi-Fi Wireless FidelityWLAN Wireless Local Area NetworkX2AP X2 Application Protocol

1Introduction

Harri Holma

1.1 Introduction 11.2 LTE Global Deployments and Devices 21.3 Mobile Data Traffic Growth 31.4 LTE Technology Evolution 41.5 LTE Spectrum 51.6 Small Cell Deployments 61.7 Network Optimization 71.8 LTE Evolution Beyond Release 13 81.9 Summary 9

References 9

1.1 Introduction

Mobile broadband technology has experienced an incredibly fast evolution during the last10 years. The first High-Speed Downlink Packet Access (HSDPA) network was launched 2005enabling the high-speed mobile broadband and the first iPhone was launched 2007 creating themassive need for the mobile broadband. The data rates have increased more than 100-fold andthe data volumes by more than 1000-fold during the last 10 years. The HSDPA started with3.6 Mbps while the latest Long-Term Evolution (LTE)-Advanced networks deliver user datarates of 300 Mbps during 2014 and 450 Mbps during 2015. But still, we have just seen the firstpart of the mobile broadband era – the fast evolution continues forward. Also, the number ofmobile broadband subscribers is increasing rapidly with affordable new smartphones providingthe internet access for the next billions of users.

This chapter shortly introduces the status of LTE networks globally, the traffic growth, LTEin Third Generation Partnership Project (3GPP) and the spectrum aspects. The chapter alsodiscusses the importance of the small cell deployments, the network optimization and the LTE.

LTE Small Cell Optimization: 3GPP Evolution to Release 13, First Edition.Edited by Harri Holma, Antti Toskala and Jussi Reunanen.© 2016 John Wiley & Sons, Ltd. Published 2016 by John Wiley & Sons, Ltd.

2 LTE Small Cell Optimization

Commercially launched LTE networks

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Figure 1.1 Commercially launched LTE networks [1]

1.2 LTE Global Deployments and Devices

The first commercial LTE network was opened by Teliasonera in Sweden in December2009 marking the new era of high-speed mobile communications. The number of commercialLTE networks has already increased to 460 in more than 140 countries by end 2015. Thefast growth of launches has happened during 2012–2015. It is expected that more than 500operators in more than 150 countries will soon have commercial LTE network running. Thenumber of launched networks is shown in Figure 1.1.

The very first LTE devices supported 100 Mbps in the form factor of Universal Serial Bus(USB) modem. Soon LTE capability was introduced into high end and mid-priced smartphoneswith the bit rate up to 150 Mbps. By 2015, LTE radio is found in most smartphones excludingthe very low end segment at 50-USD. The data rate capability is increased to 300 Mbps, and450 Mbps, in the latest devices. An example drive test throughput is shown in Figure 1.2illustrating that it is possible to get very close to 300 Mbps in the good channel conditions in

20 + 20 MHz in the field

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Figure 1.2 Drive test data rate with Category 6 LTE device

Introduction 3

Figure 1.3 Example Category 6 LTE device supporting 300 Mbps

the field with Category 6 devices. An example of such a device is shown in Figure 1.3. Also,the support for Voice over LTE (VoLTE) is included, which allows to use LTE network notonly for data connections but also for voice connections.

1.3 Mobile Data Traffic Growth

The mobile data traffic has grown rapidly during the last few years driven by the new smart-phones, large displays, higher data rates and higher number of mobile broadband subscribers.The mobile data growth for 2-year period is illustrated in Figure 1.4. These data are collectedfrom more than 100 major operators globally. The absolute data volume in this graph is morethan million terabytes, that is, exabytes, per year. The data traffic has grown by a factor of3.6× during the 2-year period, which corresponds to 90% annual growth. The fast growth ofmobile data is expected to continue. The data growth is one of the reasons why more LTEnetworks are required, more spectra are needed, radio optimization is necessary and whysmall cells will be deployed. All this data growth must happen without increase in the operatorrevenues. Therefore, the cost per bit must decrease and the network efficiency must increasecorrespondingly.

4 LTE Small Cell Optimization

0.0

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Mobile data growth during 2-year period from2012 to 2014

Figure 1.4 Mobile data growth during 2-year period

1.4 LTE Technology Evolution

The LTE technology has been standardized by Third Generation Partnership Project (3GPP).The LTE was introduced in 3GPP Release 8. The specifications were completed and thebackwards compatibility started in March 2009. Release 8 enabled peak rate of 150 Mbpswith 2×2 MIMO, low latency, flat network architecture and the support for 4-antenna basestation transmission and reception. Release 8 enabled in theory also 300 Mbps with 4×4MIMO but the practical devices so far have two antennas limiting the data rate to 150 Mbps.Release 9 was a relatively small update on top of Release 8. Release 9 was completed 1 yearafter Release 8 and the first deployments started during 2011. Release 9 brought enhancedMultimedia Broadcast Multicast Solution (eMBMS) also known as LTE-Broadcast, emer-gency call support for VoLTE, femto base station handovers and first set of Self-OrganizingNetwork (SON) functionalities. Release 10 provided a major step in terms of data ratesand capacity with Carrier Aggregation (CA), higher order MIMO up to eight antennas indownlink and four antennas in uplink. The support for Heterogeneous Network (HetNet)was included in Release 10 with the feature enhanced Inter-Cell Interference Coordination(eICIC). Release 10 was completed in June 2011 and the first commercial carrier aggrega-tion network started in June 2013. Release 10 is also known as LTE-Advanced. Release11 enhanced LTE-Advanced with Coordinated Multipoint (CoMP) transmission and recep-tion, with further enhanced ICIC (feICIC), advanced UE interference cancellation and carrieraggregation improvements. First Release 11 commercial implementation was available during2015. Release 12 was completed in 3GPP in March 2015 and the deployments are expected by2017. Release 12 includes dual connectivity between macro and small cells, enhanced CoMP(eCoMP), machine-to-machine (M2M) optimization and device-to-device (D2D) communica-tion. Release 13 work started during second half of 2014 and is expected to be completed during2016. Release 13 brings Licensed Assisted Access (LAA) also known as LTE for Unlicensedbands (LTE-U), Authorized Shared Access (ASA), 3-dimensional (3D) beamforming and D2Denhancements.