5G Techniques for Ultra Reliable Low Latency Communication Dr. Janne Peisa Principal Researcher, Ericsson Research
5G is use case driven Massive MTC Critical MTC LOGISTICS TRAFFIC SAFETY & CONTROL SMART AGRICULTURE FLEET MANAGEMENT INDUSTRIAL APPLICATION & CONTROL REMOTE TRAINING SMART METER TRACKING REMOTE MANUFACTURING REMOTE SURGERY LOW COST, LOW ENERGY SMALL DATA VOLUMES MASSIVE NUMBERS Enhanced mobile broadband ULTRA RELIABLE VERY LOW LATENCY VERY HIGH AVAILABILITY ENTERPRISE VR/AR HOME MOBILE/ WIRELESS/ FIXED SMARTPHONES BROADCASTING VENUES NON-SIM DEVICES 4K/8K UHD
Use case evolution with supporting technology Current On the road to 5G 5G experience Enhanced Mobile Broadband Screens everywhere VR New tools AR 4K 8K VR Immersive experience Automotive On demand information Real-time information vehicle to vehicle Autonomous control Manufacturing Process automation Flow management and remote supervision Cloud robotics and remote control Energy & Utilities Metering and smart grid Resource management and automation AI Machine intelligence and real-time control Healthcare Connected doctors and patients Monitoring and medication e-care Remote operations Technologies Multi-standard network Cat-M1/NB-IoT Cloud optimized network functions VNF orchestration Gigabit LTE (TDD, FDD, LAA) Massive MIMO Network Slicing Dynamic service orchestration Predictive analytics 5G NR Virtualized RAN Federated network slicing Distributed Cloud Real time machine learning/ai
5G is use case driven Massive MTC Critical MTC LOGISTICS TRAFFIC SAFETY & CONTROL SMART AGRICULTURE FLEET MANAGEMENT INDUSTRIAL APPLICATION & CONTROL REMOTE TRAINING SMART METER TRACKING REMOTE MANUFACTURING REMOTE SURGERY LOW COST, LOW ENERGY SMALL DATA VOLUMES MASSIVE NUMBERS Enhanced mobile broadband ULTRA RELIABLE VERY LOW LATENCY VERY HIGH AVAILABILITY ENTERPRISE VR/AR HOME MOBILE/ WIRELESS/ FIXED SMARTPHONES BROADCASTING VENUES NON-SIM DEVICES 4K/8K UHD
C-MTC Use cases Latency & Reliability 100ms Remote Control Automated Guided Vehicle Process Automation High reliability CDF [%] 100-50 Guaranteed latency bound E2E Latency 10ms ITS Smart Grid latency [ms] The reliability is specified by the failure probability ε of packets which are not successfully delivered to the receiver within the latency bound, as they are either erroneous, lost or arrive too late. 1ms Tactile Internet Factory Automation 10-0 10-1 10-2 10-3 10-4 10-5 10-6 10-7 10-8 10-9 Failure rate ( )
C-MTC Use cases Latency & Reliability E2E Latency 100ms 10ms Remote Control Automated Guided Vehicle ITS Process Automation Smart Grid RAN latency & reliability e.g. smart grid End-to-end latency 3GPP/ITU target on RAN latency and reliability. 1ms 3GPP Tactile Internet 3GPP/ITU Factory Automation 10-0 10-1 10-2 10-3 10-4 10-5 10-6 10-7 10-8 10-9 Failure rate ( )
Automotive use case Evolution WiFi Hotspot On demand GPS map data Over-the-air software updates Current Predictive maintenance of vehicle Capturing sensor data for realtime traffic, weather, parking, and mapping services On the road to 5G Autonomous vehicle control Cooperative collision avoidance Vulnerable road user discovery 5G Experience (2021+)
Automotive use case Requirements Current On the road to 5G 5G Experience (2021+) TECHNICAL REQUIREMENTS Coverage Robust performance Reduced latency High throughput Latency: 5ms Availability: 99.999% Reliability: 99.999% Mobility: High TECHNOLOGIES Multi-standard networks Cloud optimized network functions VNF orchestration Gigabit LTE (TDD, FDD, LAA) Massive MIMO Network Slicing Dynamic service orchestration Predictive analytics 5G NR RAN virtualization Federated network slicing Distributed Cloud Real time Machine learning/ai
Manufacturing use case evolution Intra-/inter enterprise communication Connected goods Collaborative robots Distributed control system Remote quality inspection Remote control of robots Augmented reality support in training, maintenance, construction and repair Current On the road to 5G 5G Experience (2022+)
Manufacturing requirements Current On the road to 5G 5G Experience (2022+) TECHNICAL REQUIREMENTS Coverage Robust performance Reduced latency High throughput Latency: Down to below 1ms Reliability: Down to packet loss of less than 10-9 TECHNOLOGIES Multi-standard networks Cat-M1/NB-IoT Cloud optimized network functions VNF orchestration Gigabit LTE (TDD, FDD, LAA) Massive MIMO Network Slicing Dynamic service orchestration Predictive analytics 5G NR RAN virtualization Federated network slicing Distributed Cloud Real time Machine learning/ai
5G: A network for the Networked Society 10-100x 1000x 5x 100x Cost 10+ +20dB END-USER DATA RATES MOBILE DATA VOLUMES LOWER LATENCY MORE DEVICES DEVICE COST REDUCTION YEARS BATTERY LIFE BETTER COVERAGE Management Access Applications Cloud Infrastructure Transport One architecture supporting multiple industries
3GPP 5g timeplan ITU IMT-2020 Requirements Proposals Specifications SI: Channel mod. SI: Requirements 3GPP NR Study Item NR SIs Phase 2 SI Self-evaluation NR WI Phase 1 NR WIs Phase 2 NR evolution LTE evo LTE evo LTE evo Rel-14 Rel-15 Rel-16 2015 2016 2017 2018 2019 2020 NR non-standalone NR standalone Full IMT-2020
5G Radio Access Evolution of existing technology + New radio-access technology Evolution of LTE Backwards compatible Tight interworking NR No compatibility constraints 1 GHz 3 GHz 10 GHz 30 GHz 100 GHz 1 GHz 3 GHz 10 GHz 30 GHz 100 GHz Spectrum flexibility: licensed, licensed shared, unlicensed FDD, TDD
NR selected design targets Ultra-lean Forward compatibility Minimize network transmissions? not directly related to user-data delivery Multiconnectivity Multi-service Network Slices Beam centric Low latency Mini-slot One slot
NR Waveform Based on OFDM Flexible/scalable numerology (sub-carrier spacing, CP, TTI) Windowing / filtering for enhanced spectral confinement Enables mixing of numerologies on the same carrier Compatibility with LTE-M / NB-IoT, sync signals Complementary DFT-precoding option for low PAPR in uplink Numerology Symbol Cyclic Prefix Slot duration / TTI DFT NX downlink and uplink IFFT CP insertion Scalable numerology Windowing 15 khz 66.67 µs 4.76 µs 500 µs (7s) or 1000 µs (14s) 30 khz 33.33 µs 2.38 µs 250 µs (7s) or 500 µs (14s) 60 khz 16.67 µs 1.19 µs 125 µs (7s) or 250 µs (14s) 120 khz 8.33 µs 0.59 µs 125 µs (14s) 240 khz 4.17 µs 0.30 µs 63 µs (14s) Shorter slots / lower latency at higher numerologies
Numerology & Deployments cell size Decreasing numerology due to time dispersion vs. cyclic prefix large medium (or extended cyclic prefix) small low medium high frequency Increasing numerology due to phase noise
Numerology & Deployments cell size Decreasing numerology due to time dispersion vs. cyclic prefix large medium 15 khz 15 khz 30 khz 30 khz (or extended cyclic prefix) small 15 khz 30 khz 60 khz 30 khz 60 khz 60 khz 120 khz low medium high frequency Increasing numerology due to phase noise
Slot Structures Typical slots of 7 or 14 symbols 14 symbols 14 symbols 14 symbols var. start var. length Possibility of mini-slots Suitable for low latency transmission (URLLC) Can be punctured into other transmissions Efficient multiplexing of URLLC services with e.g. embb traffic 14 symbols mini-slot 14 symbols Symbol CP Slot 15 khz 66.67 µs 4.76 µs 1000 µs (14s) 30 khz 33.33 µs 2.38 µs 500 µs (14s) 60 khz 16.67 µs 1.19 µs 250 µs (14s) 120 khz 8.33 µs 0.59 µs 125 µs (14s)
Fast Uplink Access Scheduling-request based uplink access Improved latencies and turn-around times due to very fast processing in NR New data UE TA SR SG BS Data Grant-free uplink access Direct access to channel Provide configured transmission opportunities in uplink Avoids need for scheduling request and scheduling grant UE Grant-free data configuration BS data delivered Preferably avoiding explicit time alignment (TA), i.e. asynchronous access Provides similar latencies in uplink as in downlink New data Grant-free data data delivered
NR Techniques for Low Latency General High numerologies for shorter slot lengths Mini-slots for e.g. low latency transmissions Fast processing Fast decoding for quick turn-around Enables fast HARQ and fast dynamic scheduling slot x1 RX TX turn-around slot x4 mini-slot Fast HARQ Fast dynamic scheduling FDD TDD Can be specifically for URLLC Frequent change of UL-DL allocations needed Trade-off of slot length vs. switching overhead Fast processing / turn-around FDD Downlink mini-slots fast processing / turn-around FDD Uplink mini-slots instant uplink access fast processing / turn-around DL UL TDD
Example NR RAN Latencies Latencies depend on NR configurations numerology slot structure uplink access scheme TDD DL & grantfree UL SR-based UL Retx delay 30kHz, 7s 1071 µs 2321 µs +n * 1250 µs 60kHz, 7s 554 µs 1179 µs +n * 625 µs 120kHz, 14s 536 µs 1161 µs +n * 625 µs FDD DL & grantfree UL SR-based UL Retx delay 15kHz, 7s 1643 µs 3143 µs +n * 1500 µs Latencies assumed with worst-case timing ( what can be guaranteed ) but assuming fast NR processing 15kHz, 2s (mini-slot) 571 µs 1000 µs +n * 429 µs 30kHz, 7s 821 µs 1571 µs +n * 750 µs 30kHz, 2s (mini-slot) 286 µs 500 µs +n * 214 µs 60kHz, 2s (mini-slot) 161 µs 268 µs +n * 107 µs 120kHz, 2s (mini-slot) 89 µs 143 µs +n * 54 µs
Techniques for High reliability at low Latency Exploit all diversity levels Multi-antenna: diversity coding over all antenna elements / sites Frequency: send over wide bandwidth Robust coding and modulation (MCS selection) ( ) Select a very low code rate and low modulation constellation order For a given SINR, the MCS should provide very low BLER Robust channel (state) estimation ( ) Extra robust channel estimation, in particular for low SINR Margin for channel estimation error Multi-connectivity on different frequencies (RATs) Intra-site or inter-site Constant connectivity during mobility Spectral efficiency MBB URLLC SINR
Bandwidth How to reach reliability One-shot transmission Use low code rate to obtain low error low efficiency, and requires robust control Many-shot transmissions Repeat transmission of standard reliability in time or frequency less efficient, but less demanding Retransmission (HARQ-based) Repeat only when needed The more retransmissions possible the higher code rate can be used higher efficiency Processing, alignment Short latency req. Low code rate Frequency duplication Repetitions Retransmissions (Rare) Processing (Very rare) Retransmission, fast HARQ Retransmission over longer period Allowing more retransmissions: - Shorter TTI (mini-slots, numerology) - Shorter processing & turnaround - Relaxed latency requirement Relaxed latency req. Processing
Cost of reliability?
5G will enable ultra-reliable and low latency communication 5g Low latency via flexible numerology, mini-slots, grant-free instant uplink, fast processing High reliability via multi-connectivity, diversity and robust PHY design