Content for TR 45.912 Word version: 18.0.0
10 Latency enhancements
10.1 Introduction
10.2 Improved ACK/NACK reporting
10.3 Reduced transmission time interval
10.4 Variable-sized Radio Blocks
10.5 Combining Methods
10.6 Performance characterization of combined proposals
10.7 High Speed Hybrid ARQ
10.8 References
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10 Latency enhancements p. 301
10.1 Introduction p. 301
10.1.1 Performance gains p. 301
10.1.1.1 Web-browsing p. 301
10.1.1.2 Delay estimations p. 303
10.1.1.3 Email p. 305
10.1.1.4 Impact to TCP performance p. 307
10.2 Improved ACK/NACK reporting p. 315
10.2.1 Concept description p. 315
10.2.1.1 Event based RLC ACK/NACK reports p. 315
10.2.1.2 Event based RLC ACK/NACK reports p. 316
10.2.1.3 ACK/NACK in Uplink Data p. 317
10.2.1.3.1 ACK/NACK in RLC header p. 317
10.2.1.3.2 Fast Ack/Nack reporting sending Ack/Nack in payload of an RLC data block p. 317
10.2.1.4 Fast Ack/Nack reporting in UL and DL p. 322
10.2.1.4.1 BSN based short Ack/Nack report p. 322
10.2.1.4.2 Ack/Nack reporting sent in UL direction p. 324
10.2.1.4.3 Ack/Nack reporting sent in DL direction p. 325
10.2.1.5 Possible usage p. 326
10.2.2 Modelling assumptions and requirements p. 326
10.2.3 Performance characterization p. 327
10.2.3.1 Performance gain of "Event based RLC Ack/Nack reports" p. 327
10.2.3.2 Performance gain of the "Fast Ack/Nack reporting" mechanism p. 329
10.2.4 Impacts to the mobile station p. 330
10.2.5 Impacts to the BSS p. 330
10.2.6 Impacts to the Core Network p. 330
10.2.7 Impacts to the specifications p. 330
10.2.8 Open issues p. 330
10.3 Reduced transmission time interval p. 330
10.3.1 Concept description p. 330
10.3.1.1 Radio block mapping in time-slot domain p. 331
10.3.1.2 Radio block mapping in frequency domain (inter-carrier interleaving) p. 332
10.3.1.3 USF scheduling of shorter TTI and legacy mobile stations p. 332
10.3.1.3.1 Basic principle p. 332
10.3.1.3.2 Decoding USF in downlink when having both 10 ms and 20 ms TTIs p. 333
10.3.1.4 Introducing 2-burst radio block option p. 334
10.3.1.5 Detailed proposal for a 5 ms TTI solution p. 334
10.3.1.6 Coexistence of legacy and RTTI TBFs (including 4-burst and 2-burst options) p. 336
10.3.1.7 Coexistence of legacy and RTTI TBFs (simplified RTTI solution) p. 340
10.3.2 Link level performance p. 343
10.3.2.1 Modelling Assumptions and Requirements p. 343
10.3.2.2 Performance Characterization p. 343
10.3.2.3 Conversational services with reduced TTI p. 344
10.3.2.3.1 Introduction p. 344
10.3.2.3.2 Application Level Effects p. 344
10.3.2.3.3 Simulator settings p. 345
10.3.2.3.4 Simulation results p. 345
10.3.2.4 Reduced TTI and fast ACK/NACK p. 347
10.3.2.4.1 Definition of the new coding schemes p. 347
10.3.2.4.2 Header coding p. 348
10.3.2.4.3 Bitmap coding p. 349
10.3.2.4.4 Block code p. 349
10.3.2.4.5 Convolutional code p. 349
10.3.2.4.6 Puncturing p. 349
10.3.2.4.7 Interleaving and burst mapping p. 349
10.3.2.4.8 Data coding p. 349
10.3.2.4.9 Simulation results p. 349
10.3.3 Application performance p. 351
10.4 Variable-sized Radio Blocks p. 360
10.4.1 Introduction p. 360
10.4.2 Motivation p. 360
10.4.3 Concept Description p. 360
10.4.3.1 Overview p. 360
10.4.3.2 Example: TCP ACK (52 octets) p. 361
10.4.3.3 Signalling/Detection p. 362
10.4.3.4 Radio Block Capacity p. 362
10.4.3.5 Retransmissions p. 363
10.4.3.6 Benefits p. 363
10.4.4 Performance Characterization p. 363
10.4.4.1 Bandwidth Efficiency p. 363
10.4.4.2 Latency p. 363
10.4.4.3 Block Error Probability p. 364
10.4.4.4 Simulation results p. 364
10.4.5 Impacts on Network Entities and Standards p. 368
10.4.5.1 Impacts to the Mobile Station p. 368
10.4.5.2 Impacts to the BSS p. 369
10.4.5.3 Impacts to the Core Network p. 369
10.4.5.4 Impacts to the specifications p. 369
10.4.6 Comparison of VSRB and RTTI p. 369
10.5 Combining Methods p. 370
10.5.1 Preface p. 370
10.5.2 Early Decode with Multi-Frequency p. 371
10.5.3 Early Decode with VSRB p. 372
10.5.4 Early Decode with combined VSRB and Multi-Frequency p. 373
10.6 Performance characterization of combined proposals p. 374
10.7 High Speed Hybrid ARQ p. 379
10.7.1 Introduction p. 379
10.7.2 Comparison of EGPRS ARQ, Fast ARQ, Reduced TTI, and HS-HARQ p. 379
10.7.3 HS-HARQ Proposal p. 379
10.7.4 Channel Structures p. 380
10.7.5 Stop and Wait ARQ p. 381
10.8 References p. 381
