Content for TR 38.874 Word version: 16.0.0
2 References
3 Definitions and abbreviations
4 Introduction
5 Requirements
6 Architectures
7 Physical layer aspects
8 Radio protocol aspects
9 Backhaul aspects
10 Comparison
11 Conclusion
A Evaluation methodology
$ Change History
2 References p. 7
3 Definitions and abbreviations p. 7
3.1 Definitions p. 7
3.2 Abbreviations p. 7
4 Introduction p. 8
5 Requirements p. 8
5.1 Use cases and deployment scenarios p. 8
5.1.1 Relay deployment scenarios p. 8
5.1.2 In-band vs. out-of-band backhaul p. 9
5.1.3 Access/backhaul RAT options p. 9
5.1.4 Standalone and non-standalone deployments p. 9
5.2 Architecture Requirements p. 10
6 Architectures p. 11
6.1 General p. 11
6.2 IAB Architectures proposed p. 13
6.3 Architecture group 1 p. 14
6.3.1 Architecture 1a p. 14
6.3.2 Architecture 1b p. 15
6.4 Architecture group 2 p. 15
7 Physical layer aspects p. 17
7.1 General p. 17
7.2 Backhaul link discovery and measurements p. 17
7.2.1 IAB-node initial access (Stage 1) p. 17
7.2.2 Inter-IAB-node discovery and measurement (Stage 2) p. 18
7.2.3 IAB-node RACH p. 18
7.2.4 Backhaul link management p. 18
7.3 Scheduling and resource allocation/coordination p. 19
7.3.1 Scheduling of backhaul and access links p. 19
7.3.2 Multiplexing of access and backhaul links p. 19
7.3.3 Resource coordination p. 21
7.4 IAB-node synchronization and timing alignment p. 23
7.5 Cross-link interference measurement and management p. 25
7.6 Spectral efficiency enhancements p. 25
7.7 Summary of Physical Layer Enhancements for IAB p. 25
8 Radio protocol aspects p. 26
8.1 Packet Processing p. 26
8.2 User-plane considerations for architecture group 1 p. 26
8.2.1 General p. 26
8.2.2 Adaptation Layer p. 28
8.2.3 Multi-hop RLC ARQ p. 30
8.2.4 Scheduler and QoS impacts p. 32
8.2.4.1 UE-bearer-to-BH-RLC-Channel mapping p. 32
8.2.4.2 Enforcement of Fairness Schemes p. 33
8.2.4.3 Radio aware scheduling p. 35
8.2.5 L2 structure p. 36
8.2.6 Flow control and congestion handling p. 39
8.2.7 UP support of IAB-node p. 41
8.2.8 Security protection of F1*-U p. 43
8.2.9 Unified design for architecture group 1 p. 44
8.2.10 Examples of unified design for architecture group 1 p. 44
8.2.10.1 Design Example 1 p. 45
8.2.10.2 Design Example 2 p. 47
8.3 Control-plane considerations for architecture group 1 p. 50
8.3.1 Routing and QoS enforcement for CP signaling p. 50
8.3.2 CP signaling protocols p. 51
8.3.3 Control plane transport requirements p. 51
8.3.4 CP signaling security protection p. 51
8.3.5 CP alternatives for architecture 1a p. 51
8.3.6 Control Signalling to BH-RLC-Channel mapping for architecture 1a p. 57
8.3.7 CP alternatives for architecture 1b p. 59
8.4 User-plane considerations for architecture group 2 p. 60
8.4.1 General p. 60
8.4.2 User-plane protocol stack p. 60
8.5 Control-plane considerations for architecture group 2 p. 61
8.6 Latency in UL scheduling p. 63
9 Backhaul aspects p. 64
9.1 Additional Interfaces p. 64
9.2 IAB Topologies p. 64
9.3 Integration of IAB-node p. 67
9.4 Modifications to CU/DU architecture p. 72
9.5 Backhaul bearer setup for architecture group 1 p. 72
9.5.1 Satisfying the QoS requirements p. 72
9.5.2 Signalling Procedures p. 72
9.5.3 QoS parameters p. 73
9.6 IAB Topology Discovery p. 74
9.6.1 Discovery procedure for architecture group 1 p. 74
9.6.2 Discovery procedure for architecture group 2 p. 75
9.7 Topology adaptation p. 76
9.7.1 Goals of IAB topology adaptation p. 76
9.7.2 Tasks pertaining to IAB topology adaptation p. 76
9.7.3 Topologies considered for architecture 1a p. 76
9.7.4 Topology adaptation scenarios in architecture 1a p. 77
9.7.5 Principal steps of intra-CU topology adaptation in architecture 1a p. 79
9.7.6 Principal steps of inter-CU topology adaptation in architecture 1a p. 82
9.7.7 Detailed steps of topology adaptation in architecture 1a p. 86
9.7.8 Goals of Topological Redundancy p. 86
9.7.9 Adding redundant routes in architecture 1a p. 87
9.7.10 Detailed steps of route addition in architecture 1a p. 89
9.7.11 Route Management p. 90
9.7.12 Backhaul-link-failure recovery scenarios p. 91
9.7.13 Principal steps of BH RLF recovery in architecture 1a p. 92
9.7.14 Downstream notification of BH RLF in architecture 1a p. 97
9.7.15 Efficient backhaul-link-failure recovery p. 98
9.8 LTE-access over NR backhaul p. 98
10 Comparison p. 99
10.1 Comparison of IAB architectures p. 99
10.2 Comparison of CP alternatives for IAB architectures 1a p. 101
11 Conclusion p. 103
A Evaluation methodology p. 104
A.1 Evaluation assumptions p. 104
A.2 Evaluation results p. 109
$ Change History p. 111
