TR 38.869
Study on low-power Wake-up Signal and Receiver for NR

3GPP‑Page

V18.0.0 (Wzip) 2023/12 261 p.

Rapporteur:: Mr. Pan, Xueming
vivo Mobile Communication Co.,

full Table of Contents for TR 38.869 Word version: 18.0.0

1 Scope p. 10

The present document is intended to capture the output of study item for " Study on low-power wake up signal and receiver for NR" [2].

The study includes investigations to

the impact of low-power wake-up signal and receiver , including power saving benefit, coverage, system overhead impact, network energy impact and other related aspects.
the receiver architecture for low-power wake-up receiver and provide analysis for power consumption, noise figure and etc.
L1 designs and procedures changes needed to support the wake-up signal and evaluations for the link performances.
higher layer protocol changes needed to support the wake-up signals
related RAN4 impacts

2 References p. 10

3 Definitions of terms, symbols and abbreviations p. 12

4 Introduction p. 14

5G systems are designed and developed targeting for both mobile telephony and vertical use cases. Besides latency, reliability, and availability, UE energy efficiency is also critical to 5G. Currently, 5G devices may have to be recharged per week or day, depending on individual's usage time. In general, 5G devices consume tens of milliwatts in RRC idle/inactive state and hundreds of milliwatts in RRC connected state. Designs to prolong battery life is a necessity for improving energy efficiency as well as for better user experience.

Energy efficiency is even more critical for UEs without a continuous energy source, e.g., UEs using small rechargeable and single coin cell batteries. Among vertical use cases, sensors and actuators are deployed extensively for monitoring, measuring, charging, etc. Generally, their batteries are not rechargeable and expected to last at least few years as described in TR 38.875. Wearables include smart watches, rings, eHealth related devices, and medical monitoring devices. With typical battery capacity, it is challenging to sustain up to 1-2 weeks as required.

The power consumption depends on the configured length of wake-up periods, e.g., paging cycle. To meet the battery life requirements above, eDRX cycle with large value is expected to be used, resulting in high latency, which is not suitable for such services with requirements of both long battery life and low latency. For example, in fire detection and extinguishment use case, fire shutters shall be closed and fire sprinklers shall be turned on by the actuators within 1 to 2 seconds from the time the fire is detected by sensors, long eDRX cycle cannot meet the delay requirements. eDRX is apparently not suitable for latency-critical use cases. Thus, the intention is to study ultra-low power mechanism that can support low latency in Rel-18, e.g. lower than eDRX latency.

Currently, UEs need to periodically wake up once per DRX cycle, which dominates the power consumption in periods with no signalling or data traffic. If UEs are able to wake up only when they are triggered, e.g., paging, power consumption could be dramatically reduced. This can be achieved by using a wake-up signal to trigger the main radio and a separate receiver which has the ability to monitor wake-up signal with ultra-low power consumption. Main radio works for data transmission and reception, which can be turned off or set to deep sleep unless it is turned on.

The power consumption for monitoring wake-up signal depends on the wake-up signal design and the hardware module of the wake-up receiver used for signal detecting and processing.

The study should primarily target low-power WUS/WUR for power-sensitive, small form-factor devices including IoT use cases (such as industrial sensors, controllers) and wearables. Other use cases are not precluded, e.g.XR/smart glasses, smart phones.

As opposed to the work on UE power savings in previous releases, this study will not require existing signals to be used as WUS. All WUS solutions identified shall be able to operate in a cell supporting legacy UEs. Solutions should target substantial gains compared to the existing Rel-15/16/17 UE power saving mechanisms. Other aspects such as detection performance, coverage, UE complexity, should be covered by the evaluation.

TR 38.869 Study on low-power Wake-up Signal and Receiver for NR

full Table of Contents for TR 38.869 Word version: 18.0.0

1 Scope p. 10

2 References p. 10

3 Definitions of terms, symbols and abbreviations p. 12

3.1 Terms p. 12

3.2 Symbols p. 13

3.3 Abbreviations p. 13

4 Introduction p. 14

5 Use cases & KPI p. 15

6 Evaluation methodology p. 16

6.1 General performance metrics p. 16

6.2 Evaluation assumptions p. 17

6.2.1 General evaluation assumptions p. 17

6.2.2 Coverage evaluation assumptions p. 18

6.2.3 Link performance evaluation assumptions p. 20

6.3 Power consumption model p. 23

6.3.1 Power model for Main Radio (MR) p. 23

6.3.2 Power model for LP-WUR (LR) p. 24

7 LP-WUR and LP-WUS design p. 25

7.1 LP-WUS receiver architectures p. 25

7.1.1 General description of receiver types p. 25

7.1.1a Analysis of LP-WUR architectures p. 32

7.1.1a.1 OOK-1/2/4 p. 33

7.1.1a.1.1 RF envelope detection p. 33

7.1.1a.1.2 Heterodyne architecture with IF envelope detection p. 33

7.1.1a.1.3 Homodyne/zero-IF architecture with baseband envelope detection p. 33

7.1.1a.2 FSK p. 34

7.1.1a.2.1 Parallel RF envelope detection p. 34

7.1.1a.2.2 Parallel heterodyne architecture p. 34

7.1.1a.2.3 Parallel homodyne architecture p. 34

7.1.1a.2.4 Heterodyne architecture with frequency to amplitude conversion p. 35

7.1.1a.2.5 Homodyne architecture with frequency to amplitude conversion p. 35

7.1.1a.3 OFDMA-based signal p. 35

7.1.1a.3.1 Time-domain correlation (without FFT) p. 35

7.1.1a.3.2 Frequency-domain correlation (with FFT) p. 35

7.1.2 RAN4 studies of the receiver p. 36

7.1.2.1 General p. 36

7.1.2.2 ACS evaluation p. 37

7.1.2.3 ASCS evaluation p. 56

7.1.2.4 Phase noise p. 66

7.1.2.5 gNodeB RF impacts p. 66

7.1.2.6 Multi-band capability p. 67

7.1.2.7 Noise Figure p. 67

7.1.2.8 Band operation for LP-WUS p. 67

7.2 LP-WUS design and L1 procedure p. 67

7.2.1 Signal design p. 68

7.2.1.1 Waveform p. 68

7.2.1.1.1 MC-ASK waveform p. 69

7.2.1.1.2 FSK waveform p. 71

7.2.1.1.3 OFDM waveform p. 71

7.2.1.2 Bandwidth and location p. 71

7.2.1.3 LP-WUS content p. 72

7.2.2 L1 procedures p. 73

7.2.2.1 RRM measurements p. 73

7.2.2.2 Synchronization of LP-WUR p. 74

7.2.2.3 LP-WUS monitoring p. 75

7.2.2.4 Activation/Deactivation procedures of LP-WUS p. 75

7.2.2.5 Coverage p. 75

7.2.2.6 Additional L1 procedures for RRC CONNECTED mode p. 76

7.2.2.7 Additional L1 procedures for RRC IDLE/INACTIVE modes p. 77

7.2.2.8 Others p. 77

7.3 Higher-layer aspects p. 77

7.3.1 RRC_IDLE/INACTIVE mode p. 77

7.3.1.1 RRC_IDLE/INACTIVE mode procedures p. 77

7.3.1.2 LP-WUS monitoring and wake up procedure p. 77

7.3.1.3 LP-WUS coverage and trigger condition p. 79

7.3.1.4 Configuration p. 80

7.3.1.5 System information update and PWS p. 80

7.3.1.6 Mobility and RRM p. 80

7.3.2 RRC_CONNECTED mode p. 81

7.3.2.1 RRC_CONNECTED mode procedures p. 81

7.3.2.2 LP-WUS monitoring p. 81

7.3.2.3 LP-WUS use options p. 82

7.3.2.4 Configuration p. 85

7.3.2.5 LP-WUS coexistence with DCP p. 86

7.4 RAN4 RRM study p. 86

8 Evaluation results p. 87

8.1 Power and latency evaluation p. 87

8.1.1 RRC IDLE/INACTIVE mode p. 87

TR 38.869
Study on low-power Wake-up Signal and Receiver for NR