Content for TR 23.700-33 Word version: 18.0.0
5 Key Issues
6 Solutions
7 Overall Evaluation
8 Conclusions
A Layer-2 Architecture Reference Model
$ Change history
5 Key Issues p. 13
5.1 Key Issue #1: Support of UE-to-UE Relay p. 13
5.2 Key Issue #2: Support of path switching between two indirect network communication paths for UE-to-Network Relaying with service continuity consideration p. 14
5.3 Key Issue #3: Support direct communication path switching between PC5 and Uu (i.e. non-relay case) p. 15
5.4 Key Issue #4: Support of path switching between direct network communication path and indirect network communication path for Layer-2 UE-to-Network Relay with session continuity consideration p. 16
5.5 Key Issue #5: Support of multi-path transmission for UE-to-Network Relay p. 16
5.6 Key Issue #6: Support of PC5 Service Authorization and Policy/Parameter Provisioning p. 17
5.7 Key Issue #7: Support of Emergency for UE-to-Network Relaying p. 17
6 Solutions p. 19
6.0 Mapping of Solutions to Key Issues p. 19
6.1 Solution #1: UE-to-UE Relay Selection Without Relay Discovery p. 20
6.1.1 Description p. 20
6.1.2 Procedures p. 21
6.1.2.1 UE-to-UE relay discovery and selection is integrated into the unicast link establishment procedure (Alternative 1) p. 21
6.1.2.2 UE-to-UE relay discovery and selection is integrated into Model B direct discovery procedure (Alternative 2) p. 22
6.1.3 Impacts on services, entities and interfaces p. 24
6.2 Solution #2: ProSe 5G Layer-3 UE-to-UE Relay based on IP routing p. 24
6.2.1 Description p. 24
6.2.2 Procedures p. 26
6.2.3 Impacts on services, entities and interfaces p. 26
6.3 Solution #3: Stateful UE-to-UE Layer-2 or Layer-3 Relay for Public Safety p. 26
6.3.1 Introduction p. 26
6.3.2 Functional Description p. 27
6.3.3 Procedures p. 27
6.3.3.1 UE-to-UE Relay discovery p. 27
6.3.3.1.1 Model A p. 27
6.3.3.1.2 Model B p. 28
6.3.3.2 Communication via the stateful UE-to-UE Relay p. 30
6.3.4 Impacts on services, entities and interfaces p. 31
6.4 Solution #4: QoS control for UE-to-UE Relay p. 31
6.4.1 Description p. 31
6.4.2 Procedures for Layer 3 UE-to-UE Relay p. 32
6.4.3 Procedures for Layer 2 UE-to-UE Relay p. 33
6.4.4 Impacts on services, entities and interfaces p. 34
6.5 Solution #5: Support Layer-3 UE-to-UE Relay Based on IPv6 link-local addresses p. 34
6.5.1 Description p. 34
6.5.2 Procedures p. 34
6.5.2.1 Relay path establishment procedure p. 34
6.5.2.2 Path switch from one UE-to-UE relay to another UE-to-UE relay p. 35
6.5.3 Impacts on services, entities and interfaces p. 36
6.6 Solution #6: Support Layer-3 UE-to-UE Relay to Handle Non-IP Traffic p. 37
6.6.1 Description p. 37
6.6.2 Procedures p. 38
6.6.3 Impacts on Existing Nodes and Functionality p. 41
6.7 Solution #7: Negotiated UE-to-UE Relay Reselection p. 41
6.7.1 Description p. 41
6.7.2 Procedures p. 41
6.7.2.1 Layer-2 based UE-to-UE Relay Re-selection p. 42
6.7.2.2 Layer-3 based UE-to-UE Relay Re-selection p. 44
6.7.3 Impacts on services, entities and interfaces p. 46
6.8 Solution #8: Authorization for 5G ProSe UE-to-UE Relay Service p. 46
6.8.1 Description p. 46
6.8.2 Procedures p. 47
6.8.2.1 Procedure Enhancement for Information Provisioning to a 5G ProSe Remote UE/UE-to-UE Relay p. 47
6.8.2.2 The Policy/parameter to a 5G ProSe UE-to-UE Relay p. 47
6.8.2.3 The Policy/parameter to a 5G ProSe Remote UE p. 48
6.8.2.4 5G ProSe UE-to-UE Relay Discovery parameters p. 49
6.8.2.5 Procedures for Service Authorization related to UE-to-UE Relay operation to NG-RAN p. 49
6.8.3 Impacts on services, entities and interfaces p. 49
6.9 Solution #9: Model A discovery for 5G ProSe Layer-3 UE-to-UE Relay scenario p. 50
6.9.1 Description p. 50
6.9.2 Procedures p. 51
6.9.3 Impacts on services, entities and interfaces p. 52
6.10 Solution #10: Consolidated Solution for UE-to-UE Relay discovery and selection based on Model A and Model B discovery p. 52
6.10.1 Description p. 52
6.10.2 Procedures p. 52
6.10.2.1 Model A discovery p. 52
6.10.2.2 Model B discovery p. 53
6.10.3 Impacts on services, entities and interfaces p. 55
6.11 Solution #11: Consolidated Solution for Layer-3 UE-to-UE Relay communication setup after Model A and Model B discovery p. 55
6.11.1 Description p. 55
6.11.2 Procedures p. 55
6.11.3 Impacts on services, entities and interfaces p. 57
6.12 Solution #12: Layer-3 UE-to-UE Relay discovery and communication p. 58
6.12.1 Description p. 58
6.12.2 Procedures p. 59
6.12.2.1 Procedures for UE-to-UE Relay discovery p. 59
6.12.2.1.1 Procedure for UE-to-UE Relay discovery with Model A p. 59
6.12.2.1.2 Procedure for UE-to-UE Relay discovery with Model B p. 60
6.12.2.2 Procedures for UE-to-UE Relay communication p. 61
6.12.3 Impacts on services, entities and interfaces p. 63
6.13 Solution #13: Layer-2 UE-to-UE Relay p. 63
6.13.1 Description p. 63
6.13.2 Procedures p. 64
6.13.3 Impacts on services, entities and interfaces p. 66
6.14 Solution #14: Criteria for two indirect network path switches p. 66
6.14.1 Description p. 66
6.14.2 Criteria for path switching for 5G ProSe Layer-3 relay without N3IWF p. 67
6.14.3 Criteria for path switching for 5G ProSe Layer-3 relay with N3IWF p. 67
6.14.4 Criteria for path switching for 5G ProSe Layer-2 relay p. 68
6.14.5 Impacts on Existing Nodes and Functionality p. 68
6.15 Solution #15: Service continuity support for path switch between two indirect network communication paths p. 68
6.15.1 General Description p. 68
6.15.2 Procedures p. 69
6.15.3 Impacts on Existing Nodes and Functionality p. 70
6.16 Solution #16: Provisioning policy based direct communication path switching between PC5 and Uu reference points p. 70
6.16.1 Description p. 70
6.16.2 Procedures p. 71
6.16.3 Impacts on Existing Nodes and Functionality p. 72
6.17 Solution #17: Path switching between PC5 path and Uu path p. 72
6.17.1 Description p. 72
6.17.2 Procedures p. 73
6.17.3 Impacts on services, entities and interfaces p. 75
6.18 Solution #18: UE Negotiation-based path switching from PC5 to Uu p. 75
6.18.1 Description p. 75
6.18.2 Procedures for path switching from PC5 to Uu with negotiation p. 76
6.18.3 Procedures of deactivating path switching p. 77
6.18.4 Procedures for path switching from Uu to PC5 with negotiation p. 77
6.18.5 Impacts on Existing Nodes and Functionality p. 78
6.19 Solution #19: Path switching between PC5 and Uu reference points based on path permission policy p. 78
6.19.1 Description p. 78
6.19.2 Procedures p. 79
6.19.2.1 Path permission policy description p. 79
6.19.2.2 Path permission policy provision procedure p. 79
6.19.2.3 Path switching based on path permission policy procedure p. 79
6.19.3 Impacts on Existing Nodes and Functionality p. 81
6.20 Solution #20: Switching back from Uu path to PC5 path p. 81
6.20.1 Description p. 81
6.20.2 Procedures p. 82
6.20.3 Impacts on services, entities and interfaces p. 83
6.21 Solution #21: Support direct communication path switching between PC5 and Uu p. 84
6.21.1 Description p. 84
6.21.2 Procedures p. 84
6.21.3 Impacts on services, entities and interfaces p. 85
6.22 Solution #22: Direct Communication Path switching between PC5 and Uu p. 86
6.22.1 Description p. 86
6.22.2 Procedures p. 86
6.22.2.1 Direct Communication Path switching from PC5 to Uu p. 86
6.22.2.2 Direct Communication Path switching from Uu to PC5 p. 88
6.22.3 Impacts on services, entities and interfaces p. 89
6.23 Solution #23: Session Continuity for path switching for L2 U2N Relay p. 89
6.23.1 Description p. 89
6.23.2 Procedures p. 89
6.23.2.1 Xn based inter-gNB indirect-to-direct path switching p. 89
6.23.2.2 Xn based inter-gNB direct-to-indirect path switching p. 90
6.23.2.3 N2 based inter-gNB indirect-to-direct path switching p. 91
6.23.2.4 N2 based inter-gNB direct-to-indirect path switching p. 92
6.23.3 Impacts on services, entities and interfaces p. 94
6.24 Solution #24: Service continuity support for path switch between direct network communication path and indirect network communication path for Layer-2 UE-to-Network Relay p. 94
6.24.1 General Description p. 94
6.24.2 Procedures p. 95
6.24.3 Impacts on Existing Nodes and Functionality p. 96
6.25 Solution #25: Authorization for Multi-path Transmission via UE-to-Network Relay and direct Uu using URSP p. 96
6.25.1 Description p. 96
6.25.2 Procedures p. 96
6.25.2.1 Procedure Enhancement for Multi-path Policy Provisioning to a 5G ProSe Remote UE p. 96
6.25.2.2 The Multi-path Policy to a 5G ProSe Remote UE using URSP p. 98
6.25.2.3 Using Multi-Path preference at UE p. 100
6.25.3 Impacts on services, entities and interfaces p. 100
6.26 Solution #26: Multi-path transmission via Layer-2 UE-to-Network Relay p. 100
6.26.1 Description p. 100
6.26.2 Procedures p. 101
6.26.3 Impacts on services, entities and interfaces p. 101
6.27 Solution #27: Remote UE traffic handling for Multi-Path with Layer-3 relay without N3IWF p. 102
6.27.1 Description p. 102
6.27.2 Procedure for Remote UE traffic handling for Multi-Path with Layer-3 relay without N3IWF p. 103
6.27.2.1 Establishment of multipath transmission using Layer-3 UE-to-Network Relay p. 103
6.27.2.2 Procedure p. 104
6.27.3 Impacts on Existing Nodes and Functionality p. 107
6.28 Solution #28: Multi-path transmission support for one direct path and one indirect network communication path p. 108
6.28.1 General Description p. 108
6.28.2 Procedures p. 109
6.28.3 Impacts on Existing Nodes and Functionality p. 110
6.29 Solution #29: multi-path transmission for Layer-3 UE-to-Network Relay without N3IWF p. 110
6.29.1 Description p. 110
6.29.1.1 Overview p. 110
6.29.1.2 Policy for Multi-path Transmission via Layer-3 UE-to-Network Relay without N3IWF p. 110
6.29.2 Procedures p. 111
6.29.3 Impacts on services, entities and interfaces p. 114
6.30 Solution #30: Layer-2 UE-to-UE Relaying p. 114
6.30.1 Description p. 114
6.30.2 Procedures p. 114
6.30.2.1 Procedures for UE-to-UE Relay discovery p. 114
6.30.2.1.1 Procedure for UE-to-UE Relay discovery with Model A p. 114
6.30.2.1.2 Procedure for UE-to-UE Relay discovery with Model B p. 114
6.30.2.2 Procedures for Layer-2 UE-to-UE Relay connection establishment p. 115
6.30.3 Impacts on services, entities and interfaces p. 116
6.31 Solution #31: ProSe 5G Layer-3 UE-to-UE Relay Authorization for IP address sharing p. 116
6.31.1 Introduction p. 116
6.31.2 Authorization for IP address sharing support p. 117
6.31.2.1 Function Description p. 117
6.31.2.2 Procedures p. 117
6.31.3 Impacts on services, entities and interfaces p. 118
6.32 Solution #32: Link Identifier Update procedure when using UE-to-UE Relay p. 118
6.32.1 Description p. 118
6.32.2 Layer-2 UE-to-UE Relay p. 118
6.32.2.1 Description p. 118
6.32.2.2 Procedures p. 119
6.32.3 Layer-3 UE-to-UE Relay p. 121
6.32.3.1 Description p. 121
6.32.3.2 Procedures p. 121
6.32.4 Impacts on services, entities and interfaces p. 122
6.33 Solution #33: Layer-2 UE-to-UE Relay discovery and communication p. 123
6.33.1 Description p. 123
6.33.2 Procedures p. 124
6.33.2.1 Procedures for UE-to-UE Relay discovery p. 124
6.33.2.1.1 Procedure for UE-to-UE Relay discovery with Model A p. 124
6.33.2.1.2 Procedure for UE-to-UE Relay discovery with Model B p. 125
6.33.2.2 Procedures for UE-to-UE Relay communication p. 126
6.33.3 Impacts on services, entities and interfaces p. 128
6.34 Solution #34: ProSe UE-to-UE relay support p. 128
6.34.1 General Description p. 128
6.34.2 Procedures p. 129
6.34.3 Impacts on Existing Nodes and Functionality p. 134
6.35 Solution #35: Solution for path switching between two indirect network communication paths p. 134
6.35.1 Description p. 134
6.35.2 Procedures p. 135
6.35.3 Impacts on Existing Nodes and Functionality p. 136
6.36 Solution #36: Path switching between two indirect Layer-3 UE-to-Network Relay paths using N3IWF p. 136
6.36.1 Description p. 136
6.36.2 Protocol stacks p. 136
6.36.3 Path switching procedure p. 137
6.36.4 Impacts on services, entities and interfaces p. 138
6.37 Solution #37: Path switching of remote UE(s) having an indirect connection via a L2 UE-NW Relay p. 138
6.37.1 Description p. 138
6.37.2 Procedures p. 139
6.37.3 Impacts on services, entities and interfaces p. 140
6.38 Solution #38: Switching from direct network communication to indirect network communication p. 140
6.38.1 Description p. 140
6.38.2 Procedures p. 141
6.38.3 Impacts on services, entities and interfaces p. 142
6.39 Solution #39: Multi-path transmission for Layer-2 UE-to-Network Relay Using Redundant PDU Sessions p. 142
6.39.1 Description p. 142
6.39.2 Procedures p. 143
6.39.3 Impacts on Existing Nodes and Functionality p. 143
6.40 Solution #40: 5GC influenced multi-path transmission via Layer-2 UE-to-Network Relay p. 144
6.40.1 Description p. 144
6.40.2 5GC influenced multi-path transmission procedure including L2 relay p. 144
6.40.3 Impacts on Existing Nodes and Functionality p. 145
6.41 Solution #41: Improve communication reliability with two-path transmission p. 145
6.41.1 Description p. 145
6.41.2 Procedures p. 146
6.41.3 Impacts on services, entities and interfaces p. 148
6.42 Solution #42: Emergency Services for UE to Network Relaying p. 149
6.42.1 Description p. 149
6.42.2 Procedures p. 150
6.42.3 Impacts on services, entities and interfaces p. 152
6.43 Solution #43: Emergency Services over UE-to-Network Relay p. 152
6.43.1 Description p. 152
6.43.2 Procedures p. 152
6.43.3 Impacts on services, entities and interfaces p. 154
6.44 Solution #44: Emergency services for 5G ProSe Layer-3 UE-to-Network Relay without N3IWF p. 154
6.44.1 Introduction p. 154
6.44.2 Functional description p. 154
6.44.3 Procedures p. 154
6.44.4 Impacts on services, entities and interfaces p. 155
6.45 Solution #45: Solution for support of emergency service for U2N relay p. 156
6.45.1 Description p. 156
6.45.2 Principles for support of emergency service for U2N relay p. 156
6.45.3 Procedure to ensure emergency service via Layer-2 U2N relay p. 157
6.45.4 Procedure for Layer-3 U2N relay to avoid emergency service conflict p. 158
6.45.5 Impacts on Existing Nodes and Functionality p. 158
6.46 Solution #46: Emergency service via 5G ProSe Layer-3 UE-to-Network Relay with and without N3IWF p. 158
6.46.1 Description p. 158
6.46.2 Procedures p. 159
6.46.2.1 Procedures via 5G ProSe Layer-3 U2N relay without N3IWF p. 159
6.46.2.2 Procedures via 5G ProSe Layer-3 U2N relay with N3IWF p. 160
6.46.3 Impacts on services, entities and interfaces p. 161
6.47 Solution #47: Emergency call via 5G ProSe UE-to-Network Relay p. 161
6.47.1 Description p. 161
6.47.2 Procedures p. 162
6.47.3 Impacts on services, entities and interfaces p. 163
6.48 Solution #48: Emergency support via 5G ProSe Layer-3 UE-to-Network Relay p. 163
6.48.1 Description p. 163
6.48.2 Procedures p. 164
6.48.3 Impacts on services, entities and interfaces p. 164
7 Overall Evaluation p. 165
7.1 Key Issue #1: Support of UE-to-UE Relay p. 165
7.2 Key Issue #2: Support of path switching between two indirect network communication paths for UE-to-Network Relaying with service continuity consideration p. 167
7.3 Key Issue #3: Support direct communication path switching between PC5 and Uu (i.e. non-relay case) p. 168
7.4 Key Issue #4: Support of path switching between direct network communication path and indirect network communication path for Layer-2 UE-to-Network Relay with session continuity consideration p. 168
7.5 Key Issue #5: Support of multi-path transmission for UE-to-Network Relay p. 169
7.6 Key Issue #6: Support of PC5 Service Authorization and Policy/Parameter Provisioning p. 170
7.7 Key Issue #7: Support of Emergency for UE-to-Network Relaying p. 170
8 Conclusions p. 174
8.1 Key Issue #1: Support of UE-to-UE Relay p. 174
8.2 Key Issue #2: Support of path switching between two indirect network communication paths for UE-to-Network Relaying with service continuity consideration p. 177
8.3 Key Issue #3: Support direct communication path switching between PC5 and Uu (i.e. non-relay case) p. 177
8.4 Key Issue #4: Support of path switching between direct network communication path and indirect network communication path for Layer-2 UE-to-Network Relay with session continuity consideration p. 178
8.5 Key Issue #5: Support of multi-path transmission for UE-to-Network Relay p. 178
8.6 Key Issue #6: Support of PC5 Service Authorization and Policy/Parameter Provisioning p. 179
8.7 Key Issue #7: Support of Emergency for UE-to-Network Relaying p. 179
A Layer-2 Architecture Reference Model p. 182
$ Change history p. 184
