Performance Evaluation of C hannel Access Mechanisms in 6 GHz Spectrum

1. IEEE Vienna, 17 July 2019 802.11 Coexistence Workshop Performance Evaluation of Channel Access Mechanisms in 6 GHz Spectrum • Jiayin Zhang (zhangjiayin@huawei.com) • Weiwei Fan (fanweiwei3@huawei.com) • David Mazzarese (david.mazzarese@huawei.com) • Mohamed Salem (Mohamed.Salem@huawei.com)

2. Background • Potential Access Mechanisms in 20MHz operation bandwidth • Evaluation assumptions, methodologies and results • Narrow band vs. Wideband LBT in 6 GHz • Conclusions

3. Background • There are discussions to open 6 GHz for unlicensed usage in both USA and EU • In FCC, the potential spectrum is from 5.925GHz to 7.125GHz, further divided into 4 bands of UN-II-5/6/7/8. • In ETSI, new WI on 5.925GHz to 6.425GHz was approved in June 2019 by TC BRAN (BRAN(19)102016r2). • The 6 GHz unlicensed spectrum attracted interests from both IEEE802.11 and 3GPP NR-U • 3GPP NR-U in Release 16 will support operations in 6 GHz (RAN1 freeze at the end of 2019) . • IEEE802.11ax extended design of 5 GHz into 6 GHz. The testing in WFA (WiFi6) for 6GHz is expected in Jan 2021. • IEEE802.11be will also support 6 GHz spectrum in the future. • In 3GPP NR-U Rel-16 Study item and Work Item • The coexistence between NR-U and 802.11ax in 6 GHz spectrum were evaluated by several companies. The schemes defined in 5 GHz were the starting points. • The support of wideband LBT (>20MHz) as well as narrow band LBT (per 20MHz) was also discussed to simplify the implementation.

4. Potential Access Mechanisms in 6GHz • Baseline: (existing scheme for 5GHz LAA) • Scheme 1: 11ax PD=-82dBm, ED=-62dBm; NR-U ED only=-72dBm • Common ED threshold between 802.11ax and NR-U • Scheme 2: 11ax PD=-82dBm, ED=-82dBm; NRU ED only=-82dBm • Scheme 3: 11ax PD=-82dBm, ED=-72dBm; NRU ED only=-72dBm • Scheme 4: 11ax PD=-82dBm, ED=-62dBm; NRU ED only=-62dBm • Common preamble : • Scheme 5: • Common 11a preamble (L-STF+L-LTF+L-SIG); • 11ax/NRU PD=-82dBm, ED=-62dBm; • assuming –4 dB detection SINR of 11a preamble • Scheme 6: • Common 11ax preamble (L-STF+L-LTF+L-SIG+RL-SIG); • 11ax/NRU PD=-82dBm, ED=-62dBm; • assuming –7 dB detection SINR of 11ax preamble without auto-detection.

5. Evaluation assumptions and methodology in TR38.889 Indoor scenario outdoor scenario 1/2

6. Performance comparison with common ED • When one of operator #2 replace Wi-Fi AP with NR-U gNB, the UPT of remaining Wi-Fi operator (#1) increased when common ED threshold is adopted by both Wi-Fi and NR-U. • In most cases, adopting common ED threshold of -62dBm between Wi-Fi and NR-U could achieve best performance of mean and 5th percentile UPT. • The NR-U performance could also benefit from the increased common ED threshold in most cases Note: DL performance with single stream, medium traffic load in indoor scenario

7. Performance comparison with common preamble • 11ax performance is degraded due to less spatial reuse opportunities when all NR-U bursts are treated same as Wi-Fi using -82dBm PD level. • NR-U performance is also degraded because of less spatial reuse (PD=-82dBm for all burst) and limited detection sensitivity of 11a and 11ax preamble. Note: DL performance with single stream, medium traffic load in indoor scenario

8. Narrow band vs. Wideband LBT in 6 GHz • NR-U Rel-16 supports component carrier of at most 100MHz, as NR in Rel-15. Multiple such carriers (inter/intra band) can be aggregated. • The use of 320MHz channel bandwidth is also under discussion in 802.11be for higher peak throughput. • Transmitter should perform LBT at each Observation Slot of 9 μs on each of 20MHz operation channel, assuming similar multi-carrier channel access defined in 5GHz (option1 in ETSI 301 893, or type A in 3GPP TS37.213). The complexity is quite high when the operation bandwidth is wide. • Simplification can be achieved, if option 2 in ETSI 301 893 or type B in 3GPP TS37.213 is adopted, at the cost of limitation on the channel bonding patterns. • Wi-Fi performs ED on P20/S20/S40/S80 hierarchically when 160MHz operating bandwidth is configured. • Wideband LBT could simplify the implementation of wideband operation when it can be guaranteed that the channel is free of narrow band interference. • limiting usage of narrow band signal (20MHz) on certain sub-band • By long/short term measurement and LBT bandwidth adaption. • FFS: ED threshold

9. Conclusions • Common ED threshold (e.g. -62dBm) can benefit both 802.11ax and NR-U due to additional spatial reuse gain. • A common preamble and PD/ED threshold, such 11a preamble with PD=-82dBm and ED=-62dBm, degrades performance of both NR-U and Wi-Fi as it prohibits spatial reuse • Wideband LBT is beneficial for system operating with wide bandwidth to simplify LBT implementation. • IEEE and 3GPP should explore the possibility to mandate a minimum bandwidth larger than 20 MHz in greenfield 6 GHz spectrum

11. Evaluation results – indoor scenario [TR38.889] (1 spatial stream)

12. Evaluation results – outdoor scenario 1 [TR38.889](1 spatial stream)

13. Evaluation results – outdoor scenario 2 [TR38.889] (1 spatial stream)

14. Evaluation results – indoor scenario [TR38.889] (<=4 spatial streams)

15. Evaluation results – outdoor scenario 1 [TR38.889] (<=4 spatial streams)

16. Evaluation results – outdoor scenario 2 [TR38.889] (<=4 spatial streams)