Content for TR 36.881 Word version: 14.0.0
2 References
3 Definitions, symbols and abbreviations
4 Study Objectives
5 Overview of LTE latency
6 Scenarios, Applications and Use Cases
7 Evaluation Structure and Assumptions
8 Solutions for latency reduction
9 Performance Evaluation
10 Conclusion
A Simulation assumptions
B System evaluation results
C Link-level evaluation results
$ Change History
2 References p. 6
3 Definitions, symbols and abbreviations p. 7
4 Study Objectives p. 8
5 Overview of LTE latency p. 8
5.1 Delay components p. 8
5.2 Current performance p. 12
5.2.1 UL and DL latency p. 12
5.2.2 Handover latency [11] p. 13
5.3 Existing means to limit latency p. 14
6 Scenarios, Applications and Use Cases p. 14
7 Evaluation Structure and Assumptions p. 15
8 Solutions for latency reduction p. 15
8.1 Semi-Persistent Scheduling p. 15
8.2 UL Grant reception p. 15
8.3 Handover Latency p. 16
8.3.1 Solution 1: RACH-less handover p. 16
8.3.2 Solution 2: Maintaining Source eNB Connection during Handover p. 17
8.4 Contention based PUSCH transmission p. 18
8.4.1 Solution 1 [16] p. 18
8.4.2 Solution 2 [17] p. 18
8.5 Reduced TTI and processing time p. 19
9 Performance Evaluation p. 20
9.1 Protocol evaluations on TTI reduction and Fast UL p. 20
9.1.1 Simulation 1: TCP slow-start behavior for FTP file download based on reduced TTI and reduced SR periodicity [4] p. 21
9.1.2 Simulation 2: Capacity and throughput gain with 0.5ms TTI [5] p. 24
9.1.3 Simulation 3: Throughput and packet download time with reduced latency in LTE [3] p. 26
9.1.4 Simulation 4: Latency evaluation results for TTI reduction and Fast UL [6] p. 27
9.1.4.1 Simulation assumptions p. 27
9.1.4.2 TTI shortening simulations p. 28
9.1.4.3 Fast UL system simulations p. 30
9.1.5 Simulation 5: System Performance with TTI shortening [6] p. 34
9.1.5.1 General information p. 34
9.1.5.2 Simulation assumptions and parameters p. 35
9.1.5.3 Performance results p. 35
9.1.6 Simulation 6: Evaluation results for TTI reduction [6] p. 44
9.1.7 Simulation 7: Performance evaluation of latency reduction enhancements [6] p. 46
9.1.7.1 Simulation setup p. 46
9.1.7.2 Simulated schemes p. 47
9.1.7.3 Simulation results for shorter TTI p. 48
9.1.7.4 Simulation results for Fast UL grant with shorter TTI p. 50
9.1.8 Simulation 8: TTI reduction gain with additional L1/L2 overhead [6] p. 52
9.1.9 Simulation 9: Effect of UE and eNB processing times on TCP performance [6] p. 54
9.1.10 Simulation 10: System Performance Gain with TTI reduction [6] p. 58
9.1.10.1 Faster UE Feedback and Rate Control p. 58
9.1.10.2 Simulation Assumptions: p. 59
9.1.10.3 Simulation Results p. 59
9.1.11 Simulation 11: TTI reduction gain with additional L2 overhead [9] p. 60
9.1.12 Simulation 12: TTI reduction gain with additional L2 overhead [10] p. 61
9.2 Protocol evaluations on Contention based PUSCH transmission p. 64
9.2.1 Evaluation 1 on solution 1 [16] p. 64
9.2.1.1 Resource efficiency p. 64
9.2.1.2 Uplink latency p. 65
9.2.2 Evaluation on solution 2 [17] p. 66
9.2.2.1 Resource efficiency analysis on current solutions p. 66
9.2.2.2 Uplink latency p. 67
9.2.2.3 Resource efficiency p. 69
9.2.3 Evaluation 2 on solution 1 [18] p. 70
9.3 Handover latency [11] p. 74
9.4 Findings from system evaluations on TTI reduction and reduced processing time p. 74
9.5 Findings from link evaluations on TTI reduction and reduced processing time p. 76
10 Conclusion p. 77
A Simulation assumptions p. 79
A.1 Protocol Simulations p. 79
A.1.1 Simulation 1 [4] p. 79
A.1.2 Simulation 2 [5] p. 81
A.1.3 Simulation 4 [6] p. 82
A.1.4 Simulation 9 [6] p. 83
A.1.5 Simulation 5 [6] p. 85
A.1.6 Simulation 11 [9] p. 87
A.1.7 Simulation on contention based PUSCH transmission p. 90
A.2 System simulation assumptions for reduced TTI and processing delay p. 92
A.3 Link level simulation assumptions p. 95
B System evaluation results p. 98
C Link-level evaluation results p. 98
$ Change History p. 98
