Non-Terrestrial Networks in 5G and 6G: Expanding the Frontiers of Wireless Communications

Self-contained resource on fundamental concepts and the planning, provisionining, design, and operations of 3GPP-based NTNs 3GPP-based Non-Terrestrial Networks in 5G and 6G: Expanding the Frontiers of Wireless Communications provides an overview of Non-Terrestrial Networks (NTNs) in the context of 3GPP systems such as 4G LTE and 5G NR. Unique challenges of NTNs such as long and variable propagation delays, large and time-varying Doppler shifts, different types of beams including Earth-fixed beams, quasi-Earth-fixed beams, and Earth-moving beams and transparent and regenerative payloads are discussed. The mechanisms that 3GPP foresees to tackle these NTN-specific challenges are described and, furthermore, the planning, provisioning, design, and operations of the radio and core networks for NTNs are illustrated. NTN considerations in the book range from physical-layer aspects (e.g., synchronization, random access, and uplink and downlink data transmission), to mobility management including handover and cell reselection, and to network architecture. Fundamentals of the associated concepts of NR, eMTC (i.e., LTE_M), and NB-IoT are described so that their customizations for NTNs become clear in NTN-specific discussions. NTN features in 3GPP Release 17, 18, and 19 are described andhe role of NTN in 6G is also summarized. A companion website provides exercises to help learners to reinforce concepts, along with software utilities (e.g., Excel spreadsheets) that provide templates to investigate the impact of various factors (e.g., carrier frequency and channel bandwidth) on the performance of NTNs (e.g., coverage and capacity/throughput). 3GPP-based Non-Terrestrial Networks in 5G and 6G includes information on: Earth-fixed beams, Earth-moving beams, and quasi-Earth-fixed beams, as well as characteristics of Geo Synchronous Orbit (GSO) and Non-GSO (NGSO) satellites such as Low Earth Orbit (LEO) satellites Challenges unique to NTNs including large coverage areas, mobility of cells, and different types of payloads (e.g., transparent and regenerative) Issues surrounding data transfer in NTNs such as time and frequency pre-compensation, timers for different radio protocol stack layers, and HARQ enabling/disabling Random access, RRC connection setup, registration/attach, and PDU session/EPS bearer setup for LTE-M, NB-IoT, and 5G NR 3GPP-based Non-Terrestrial Networks in 5G and 6G is an essential resource for wireless communications and satellite industry engineers and professionals seeking to facilitate the design, provisioning, deployment, operations, maintenance, and optimization of 5G-based NTNs and identify R&D areas for 5G-advanced-based and 6G-based NTNs.

Table of Contents:
About the Authors xvii Preface xix Acknowledgments xxiii Acronyms xxv About the Companion Website xxxv 1 Introduction to a Non-Terrestrial Network 1 1.1 Non-Terrestrial Networks The Definition 1 1.2 Simplified 3GPP NTN Architecture 2 1.3 Motivation for the NTN 3 1.4 An Overview of NTN Use Cases 4 1.5 3GPP NTN Roadmap 6 1.5.1 Release 15 (R15) 7 1.5.2 Release 16 (R16) 7 1.5.3 Release 17 (R17) 7 1.5.4 Release 18 (R18) 8 1.5.5 Release 19 (R19) and Beyond 8 1.6 Role of the NTN in 6G 8 1.7 Major Takeaways 9 References 10 2 Types of NTN Platforms 13 2.1 Types of NTN Platforms 13 2.2 Characteristics of Satellites 14 2.3 Characteristics of UASs of the NTN 16 2.4 Types of Beams 18 2.5 An Overview of Pre-5G Satellite Systems 20 2.6 Types of NTN Devices for the NTN 22 2.7 Trends in NTN Deployments 23 2.8 Major Takeaways 24 References 25 3 Radio Interfaces of LTE-M, NB-IoT, and NR A Concise Introduction 27 3.1 3GPP-Defined Wireless IoT Technologies and 5G New Radio A Concise Introduction 27 3.1.1 Wireless IoT Technologies and 4G Evolved Packet System 28 3.1.2 5G System 33 3.2 LTE-M A 3GPP-Defined Wireless IoT Technology 36 3.2.1 Key Features of LTE-M 36 3.2.1.1 Radio Interface 36 3.2.1.2 Deployment 37 3.2.1.3 Duplexing 37 3.2.1.4 Receiver Design 37 3.2.1.5 Device Characteristics 37 3.2.1.6 Coverage Enhancement 37 3.2.1.7 Long Battery Life 37 3.2.1.8 Reduced Signaling Load 38 3.2.1.9 LTE-MIoT Enhancements in the EPC 38 3.2.2 LTE-M Air Interface Protocol Stack and Physical Layer Frame Structure 38 3.2.2.1 LTE-M Radio Protocol Stack 38 3.2.2.2 LTE-M PHY Frame Structure 39 3.2.3 Summary of LTE-M Operations 40 3.2.3.1 Initial Attach and EPS Bearer Setup in LTE-M 41 3.2.3.2 Random Access in LTE-M 44 3.2.3.3 RRC Connection Setup in LTE-M 45 3.2.3.4 Example Downlink Data Transfer in LTE-M 46 3.2.3.5 Example Uplink Data Transfer in LTE-M 47 3.2.3.6 Handover in LTE-M 48 3.2.3.7 Activities of an LTE-M UE in the Idle Mode 51 3.3 NB-IoT A 3GPP-Defined Wireless IoT Technology 53 3.3.1 Key Features of NB-IoT 53 3.3.1.1 Radio Interface 54 3.3.1.2 Deployment 54 3.3.1.3 Duplexing 54 3.3.1.4 Receiver Design 54 3.3.1.5 Device Characteristics 54 3.3.1.6 Coverage Enhancement 54 3.3.1.7 Long Battery Life 55 3.3.1.8 Reduced Signaling Load 55 3.3.1.9 Mobility 55 3.3.1.10 NB-IoT Enhancements in the EPC 55 3.3.2 Summary of NB-IoT Operations 56 3.3.2.1 Initial Attach and EPS Bearer Setup in NB-IoT 56 3.3.2.2 Random-Access Procedure in NB-IoT 59 3.3.2.3 RRC Connection Setup in NB-IoT 60 3.3.2.4 Example DL Data Transfer in NB-IoT 61 3.3.2.5 Example UL Data Transfer in NB-IoT 62 3.3.2.6 Mobility Management of NB-IoT UEs 64 3.4 5G A 3GPP-Defined Transformational Technology 64 3.4.1 Key Features of 5G NR 64 3.4.1.1 Scalable and Flexible OFDM 64 3.4.1.2 Unified and Flexible Frame Structure 65 3.4.1.3 Variety of Spectrum 65 3.4.1.4 Massive MIMO and Advanced Beamforming 66 3.4.1.5 Advanced Channel Coding 66 3.4.1.6 Multi-radio Dual Connectivity (MR-DC) 66 3.4.2 5G NR Air Interface Protocol Stack and Physical Layer Frame Structure 67 3.4.2.1 5G-NR Radio Protocol Stack 67 3.4.2.2 5G-NR PHY Frame Structure 67 3.4.3 Summary of 5G NR Operations 68 3.4.3.1 Initial Registration in 5GS 68 3.4.3.2 Random Access in 5G NR 74 3.4.3.3 RRC Connection Setup in 5G NR 74 3.4.3.4 Example Downlink Data Transfer in 5G NR 75 3.4.3.5 Example Uplink Data Transfer in 5G NR 77 3.4.3.6 Handover in 5G NR 79 3.4.3.7 Activities of a 5G NR UE in the RRC_IDLE and RRC_INACTIVE States 81 3.5 LTE-M and NB-IoT Enhancements Beyond Release 13 83 3.5.1 Enhancements Common to LTE-M and NB-IoT 83 3.5.2 LTE-M Enhancements 84 3.6 Major Takeaways 85 References 86 4 Challenges of an NTN 87 4.1 An Overview of NTN-Specific Challenges 87 4.2 Long and Variable Propagation Delays 89 4.3 High and Variable Doppler Shifts 92 4.4 NTN Cell Size 94 4.5 NTN Cell Mobility 95 4.6 Type of Beams 95 4.7 Types of NTN Payloads 96 4.8 Propagation Path Loss 98 4.9 Long-Term Signal Strength Characteristics 98 4.10 Special Atmospheric Effects 99 4.10.1 Faraday Rotation 100 4.10.2 Scintillation 100 4.11 Feeder Link Switch 100 4.12 NoncontiguousNoncontinuous Coverage 101 4.13 3GPP Solutions to the NTN Challenges A High-Level Overview 102 4.14 Major Takeaways 102 References 103 5 NTN Architectures 105 5.1 NTN Network Architectures in a Nutshell 105 5.2 An NTN with a Transparent Payload 106 5.2.1 NR-NTN 107 5.2.2 IoT-NTN 108 5.3 An NTN Network Architecture with Regenerative Payloads 109 5.3.1 NR-NTN 109 5.3.2 IoT-NTN 110 5.4 Multi-connectivity NTNs 111 5.5 An NTN with a Transparent Payload A Closer Look 116 5.6 Enhanced Tracking Area Management for an NTN 117 5.7 Enhanced QoS for an NTN 119 5.8 Optical Communication for an NTN 119 5.9 Major Takeaways 120 References 121 6 RF Planning and Design Considerations for an NTN 123 6.1 RF Planning and Design for an NTN An Overview 123 6.1.1 RPD Inputs 124 6.1.1.1 Radio Access Technology 124 6.1.1.2 Target Service Requirements 124 6.1.1.3 NTN Configurations 124 6.1.1.4 NTN Spectrum 125 6.1.1.5 Device Types 125 6.1.1.6 RF Propagation Models 125 6.1.2 RPD Outputs 125 6.1.2.1 Link Budgets 125 6.1.2.2 Capacity and Throughput Analysis and Planning 126 6.1.2.3 NTN Configuration Guidelines 126 6.2 NTN Spectrum 126 6.3 NTN Devices 129 6.4 RF Propagation Models 130 6.4.1 RF Propagation in an NTN An Overview 130 6.4.2 RF Propagation Models for an NTN 131 6.4.2.1 Free-Space Path Loss 131 6.4.2.2 Shadow Fading 132 6.4.2.3 Building Penetration Loss 133 6.4.2.4 Atmospheric Absorption 134 6.4.2.5 Rain and Cloud Attenuation 134 6.4.2.6 Scintillation 135 6.4.2.7 Ionospheric Scintillation Attenuation 135 6.4.2.8 Tropospheric Scintillation Attenuation 135 6.4.2.9 Small-Scale Fading Models 136 6.5 Framework for NTN Link Budgets 136 6.5.1 A Note on NTN Link Budgets 145 6.6 NTN Capacity Planning 146 6.6.1 Capacity Planning in a Nutshell 146 6.6.1.1 Step 1 CapacityThroughput Estimation 146 6.6.1.2 Step 2 Traffic Analysis and Adjustment of Cells and Carriers 148 6.6.1.3 Step 3 Provisioning and Configuration of Network Equipment 148 6.6.2 Complexities of Capacity Planning for an NTN 148 6.6.2.1 Large Cells 148 6.6.2.2 Cell Mobility 149 6.6.2.3 Variable Cell Size 149 6.6.2.4 Variable Device-NTN Payload Distance 150 6.6.2.5 Unique Interfaces 151 6.6.3 Addressing the Complexities of NTN Capacity Planning 151 6.7 3GPP-Estimated Link Budgets and Throughput for an NTN 152 6.7.1 3GPP Link Budget Analysis 153 6.7.2 3GPP UE Throughput Analysis 154 6.8 Major Takeaways 155 References 156 7 Pre-Data Transfer Operations in an NTN 159 7.1 Overview of Pre-Data Transfer NTN Operations 159 7.1.1 Step 1 Network and System Information Acquisition 159 7.1.2 Step 2 Random-Access Procedure 160 7.1.3 Step 3 RRC Connection Setup 161 7.1.4 Step 4 Completion of the RRC Connection Setup and RegistrationAttach Request 161 7.1.5 Step 5 Mutual Authentication and NAS Security 161 7.1.6 Step 6 UE Capability Transfer 161 7.1.7 Step 7 Reconfiguration of the RRC Connection and RegistrationAttach Accept 161 7.1.8 Step 8 Completion of RegistrationAttach and Default EPS Bearer Setup 162 7.2 Pre-Data Transfer Operations in NR-NTN A Closer Look 162 7.2.1 Operational Enhancements in NR-NTN An Overview 162 7.2.2 Cell Selection and SI Acquisition in NR-NTN 163 7.2.2.1 NTN Cell Search and Cell Selection 163 7.2.2.2 Acquisition of MIB and SIB1 164 7.2.2.3 Acquisition of Additional SIBs 166 7.2.2.4 SIB2 166 7.2.2.5 SIB4 166 7.2.2.6 SIB9 167 7.2.2.7 SIB19 167 7.2.2.8 SIB25 170 7.2.2.9 Beyond the SI Acquisition 171 7.2.3 Random-Access Enhancements in NR-NTN 171 7.2.3.1 Step 0 Prior to RA Preamble Transmission 172 7.2.3.2 Step 1 RA Preamble Transmission 173 7.2.3.3 Step 2 Random-Access Response 173 7.2.3.4 Step 3 Msg3 Transmission 173 7.2.3.5 Step 4 Contention Resolution 174 7.2.3.6 Random Access in NR-NTN Additional Considerations 174 7.2.4 RRC Connection Setup in NR-NTN 174 7.2.5 Initial Registration via NR-NTN 175 7.2.5.1 Step 1 Network Acquisition 175 7.2.5.2 Step 2 Random-Access Procedure 176 7.2.5.3 Step 3 RRC Connection Setup 176 7.2.5.4 Step 4 Registration Request 176 7.2.5.5 Step 5 Authentication and Security Activation 177 7.2.5.6 Step 6 UE Capability Exchange 178 7.2.5.7 Step 7 Registration Accept 178 7.2.5.8 Step 8 Registration Complete 178 7.2.5.9 Coarse UE Location Reporting 178 7.2.5.10 Verification of the UE Location 178 7.2.6 UE Capability Exchange in NR-NTN 179 7.2.7 PDU Session Establishment in NR-NTN 180 7.2.7.1 Step 1 PDU Session Establishment Request 182 7.2.7.2 Step 2 SM Context Creation 182 7.2.7.3 Step 3 Subscription Data Retrieval 182 7.2.7.4 Step 4 SM Policy Association Establishment 182 7.2.7.5 Step 5 N4 Session Establishment 182 7.2.7.6 Step 6 N1N2 Message Transfer 183 7.2.7.7 Step 7 N2 PDU Session Request 183 7.2.7.8 Step 8 DRB Setup and PDU Session Establishment Accept 183 7.2.7.9 Step 9 N2 PDU Session Response 183 7.2.7.10 Step 10 SM Context Update 183 7.2.7.11 Step 11 N4 Session Modification 183 7.2.7.12 Step 12 IPv6 Router Advertisement 183 7.3 Selected Operations in IoT-NTN A Closer Look 184 7.3.1 Operational Enhancements in IoT-NTN An Overview 184 7.3.2 Cell Selection and SI Acquisition in IoT-NTN 185 7.3.2.1 Step 1 IoT-NTN Cell Search and Cell Selection 185 7.3.2.2 Step 2 in LTE-M NTN Acquisition of MIB and SIB1-BR 186 7.3.2.3 Step 2 in NB-IoT NTN Acquisition of MIB-NB and SIB1-NB 186 7.3.2.4 Cell Selection Criterion S in IoT-NTN 187 7.3.2.5 NTN Cell Indication and NTN Cell Barring in IoT-NTN 187 7.3.2.6 Step 3 in LTE-M NTN Acquisition of Additional SIBs 187 7.3.2.7 Step 3 in NB-IoT NTN Acquisition of Additional SIBs 192 7.3.3 Random-Access Enhancements in IoT-NTN 194 7.3.3.1 Step 0 Prior to RA Preamble Transmission 195 7.3.3.2 Step 1 RA Preamble Transmission 196 7.3.3.3 Step 2 Random-Access Response 196 7.3.3.4 Step 3 Msg3 Transmission 197 7.3.3.5 Step 4 Contention Resolution 197 7.3.3.6 Random Access in IoT-NTN Additional Considerations 197 7.3.4 RRC Connection Setup in IoT-NTN 198 7.3.5 Initial Attach via IoT-NTN 199 7.3.5.1 Step 1 Network Acquisition 199 7.3.5.2 Step 2 Random-Access Procedure 200 7.3.5.3 Step 3 RRC Connection Setup 200 7.3.5.4 Step 4 Attach Request 200 7.3.5.5 Step 5 Access Stratum Security Activation 200 7.3.5.6 Step 6 UE Capability Transfer 200 7.3.5.7 Step 7 Attach Accept 201 7.3.5.8 Step 8 Attach Complete 201 7.3.5.9 Coarse UE Location Reporting in IoT-NTN 201 7.3.6 UE Capability Transfer in IoT-NTN 202 7.3.6.1 LTE-M NTN UE Capabilities 202 7.3.6.2 NB-IoT NTN UE Capabilities 202 7.4 Major Takeaways 205 References 207 8 Downlink and Uplink Data Transfer in an NTN 209 8.1 Characteristics of Data Transfer in an NTN An Overview 209 8.1.1 Reuse of Data Transfer Frameworks 209 8.1.2 Timing Advance Reporting 210 8.1.3 Timing Offsets 210 8.1.4 HARQ Processes 210 8.1.5 HARQ Feedback Disabling 211 8.1.6 Uplink Control Information Reporting 211 8.1.7 DRX Enhancements 211 8.2 Data Transfer in the NR-NTN 211 8.2.1 Data Transfer Prerequisites in the NR-NTN 211 8.2.2 Timing Adjustments in the NR-NTN 212 8.2.2.1 NTN-Specific DL-UL Offset 213 8.2.2.2 Uplink Transmission Timing 214 8.2.2.3 Timing Advance Reporting 215 8.2.3 Downlink Data Transfer in the NR-NTN 215 8.2.4 Uplink Data Transfer in the NR-NTN 219 8.3 Data Transfer in the LTE-M NTN 222 8.3.1 Data Transfer Prerequisites in the LTE-M NTN 222 8.3.2 Timing Relationships in the LTE-M NTN 223 8.3.2.1 Uplink Transmission Timing 223 8.3.2.2 NTN-Specific DL-UL Offset 225 8.3.2.3 Timing Advanced Reporting by an LTE-M NTN UE 225 8.3.3 Downlink Data Transfer in the LTE-M NTN 225 8.3.4 Uplink Data Transfer in the LTE-M NTN 227 8.3.5 GNSS Measure Gap Procedure in the LTE-M NTN 229 8.4 Data Transfer in the NB-IoT NTN 230 8.4.1 Data Transfer Prerequisites in the NB-IoT NTN 230 8.4.2 Timing Relationships in the NB-IoT NTN 231 8.4.2.1 Uplink Transmission Timing in the NB-IoT NTN 231 8.4.2.2 NTN-Specific DL-UL Offset in the NB-IoT NTN 232 8.4.3 Downlink Data Transfer in the NB-IoT NTN 232 8.4.4 Uplink Data Transfer in the NB-IoT NTN 234 8.4.5 GNSS Measure Gap Procedure in the NB-IoT NTN 236 8.5 Major Takeaways 236 References 237 9 Mobility Management in an NTN 239 9.1 RRC States and Mobility Management in a TN and an NTN 239 9.2 Mobility Challenges in the NTN and Associated Solutions 241 9.3 Mobility Management in the NR-NTN 242 9.3.1 Handover in the NR-NTN 242 9.3.1.1 Measurements, Measurement Events, and Triggers for Handover 242 9.3.1.2 Types of Intra-NTN Handover in an NR-NTN 245 9.3.1.3 NTN-Specific Handover in the NR-NTN 246 9.3.1.4 NR-NTN Handover Signaling Flow 247 9.3.2 Mobility Management of the NR-NTN UE in the RRC_IDLE and RRC_INACTIVE States 249 9.3.2.1 NTN-Specific Mobility Management Enhancements of the NR-NTN UE in the RRC_IDLE and RRC_INACTIVE States 249 9.3.2.2 Activities of an NR-NTN UE in the RRC_IDLE and RRC_INACTIVE States 250 9.4 Mobility Management in the LTE-M NTN 253 9.4.1 Handover in the LTE-M NTN 253 9.4.1.1 Measurements and Events for Handover in the LTE-M NTN 253 9.4.1.2 Signaling Flow for Conditional Handover in the LTE-M NTN 255 9.4.2 Activities of an LTE-M NTN UE in the RRC_IDLE State 257 9.5 Mobility Management in the NB-IoT NTN 259 9.6 Feeder Link Switchover in the NTN 260 9.7 Discontinuous Coverage in the NR-NTN or IoT-NTN 261 9.8 Major Takeaways 261 References 263 10 Evolution of the NTN in 5G-Advanced and 6G 265 10.1 Evolution of the NTN 265 10.2 NTN Enhancements in Release 19 266 10.2.1 NR-NTN Enhancements in Release 19 266 10.2.1.1 Enhanced Downlink Coverage 266 10.2.1.2 Enhanced Uplink Capacity 267 10.2.1.3 Support for MBS 267 10.2.1.4 Support for 5G NFs on the NTN Platform 267 10.2.1.5 Support for RedCap UEs 267 10.2.2 IoT-NTN Enhancements in Release 19 267 10.2.2.1 Store & Forward (S&F) Using a Regenerative Payload 268 10.2.2.2 Uplink Capacity Enhancements 268 10.3 NTN and 6G 268 10.3.1 Key Organizations for 6G 268 10.3.2 6G Vision and Requirements 270 10.3.2.1 6G Usage Scenario Immersive Communication 271 10.3.2.2 6G Usage Scenario Massive Communication 271 10.3.2.3 6G Usage Scenario HRLLC 271 10.3.2.4 6G Usage Scenario Ubiquitous Connectivity 271 10.3.2.5 6G Usage Scenario Integrated AI and Communication 271 10.3.2.6 6G Usage Scenario Integrated Sensing and Communication 271 10.3.3 6G Performance Goals 271 10.3.4 6G Technology Enablers A Concise Overview 274 10.3.4.1 Component Technologies 275 10.3.4.2 Radio Technologies 280 10.3.4.3 System and Network Architectures 286 10.3.4.4 Network OA&M and Service Enablement 290 10.3.4.5 Trustworthiness 293 10.3.5 Role of the NTN in 6G 298 10.4 O-RAN-Based NTN Deployments 299 10.4.1 O-RAN A Concise Introduction 299 10.4.2 O-RAN-Based NTNs for 5G and 6G 301 10.4.2.1 ArchitecturalTopology Considerations 301 10.4.2.2 Use Cases 301 10.4.2.3 Security Considerations 301 10.5 NTN Research Directions 301 10.5.1 Regenerative Payload 302 10.5.2 Spectrum Sharing 302 10.5.3 Enhanced TN-NTN Interworking 302 10.5.4 Security 302 10.5.5 Multi-constellation Connectivity 302 10.5.6 6G Technologies with NTNs 303 10.6 Major Takeaways 303 References 304 Index 000

About the Author :
Dr. Nishith D. Tripathi is a Research Associate Professor at Virginia Tech, USA. Dr. Tripathi has 24 years of industry experience at Nortel Networks, Huawei Technologies, Award Solutions, and Samsung Research America. He is a co-author of five books related to cellular communications, AI, 5G, and O-RAN. Dr. Jeffrey H. Reed is the Willis G Worcester Professor of Electrical Engineering at Virginia Tech, USA. Dr. Reed is co-author or co-editor of five textbooks and is on the editorial board for IEEE/Wiley Press. He is a fellow of the IEEE for his contributions to software defined radio, communications signal processing, and engineering education.