Performance Evaluation of Channel Access Mechanisms in 6 GHz Spectrum 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)

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

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.

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); assuming –7 dB detection SINR of 11ax preamble without auto-detection.

Evaluation assumptions and methodology in TR38.889 Common configurations Carrier Frequency 6GHz Carrier Channel Bandwidth 20MHz baseline Number of carriers 1 Number of users per operator Exactly 5 per gNB per 20MHz Channel Model Indoor: NR InH Mixed Office model for all links Outdoor:NR UMi street canyon for all links BS/AP Tx Power 23dBm (total across all TX antennas) UE/STA Tx Power 18dBm (total across all TX antennas) BS/AP Antenna gain 0 dBi UE/STA Antenna gain BS/AP Noise Figure 5dB UE/STA Receiver Noise Figure 9dB UE receiver MMSE-IRC MIMO DL/UL MU MIMO + DL/UL OFDMA, ideal CSI/CQI feedback BS/AP antenna Array configuration (M, N, P, Mg, Ng) = (1, 2, 2, 1, 1), dH = dV = 0.5 λ UE/STA antenna Array configuration Tx/Rx: (M, N, P, Mg, Ng) = (1, 1, 2, 1, 1), dH = dV = 0.5 λ Traffic model Use 36.889 Table A.1.1. Note: Results based on the mixed traffic models can be used to determine the design. Indoor scenario outdoor scenario 1/2 system specific configurations NR-U 802.11ax Numerology 60kHz SCS + ~1.2us CP 78.125kHz SCS + 0.8us CP MCOT/TXOP 8ms 4ms Response timing K1 >= 0.75ms, K2 >= 0.75ms 16us SIFS Max MCS NR LDPC with 256QAM 802.11ac/ax LDPC with 256QAM Other CC-HARQ, 1 switching point within a COT. MPDU: 1500B MSDU + 14 B header RTS/CTS off; NAV on MAC header

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 Gain of Wi-Fi OP#1 when OP#2 replacing Wi-Fi AP with NR-U gNB Common ED=-82dBm (scheme2) Common ED=-72dBm (scheme3) Common ED=-62dBm (scheme4) Mean UPT (Wi-Fi in coex) 3.4% 21.4% 31.8% 5% UPT(Wi-Fi in coex) 3.1% 29.9% 73.4% Gain of NRU OP#2 in coex with Wi-Fi OP#1 (compared with scheme1) Common ED=-82dBm (scheme2) Common ED=-72dBm (scheme3) Common ED=-62dBm (scheme4) Mean UPT (NR-U in coex) -11.6% 0.9% 7.2% 5% UPT(NR-U in coex) -30.8% 2.1% 7.6% Note: DL performance with single stream, medium traffic load in indoor scenario

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. Gain of 11ax by introducing common preamble to NRU 11a preamble 11ax preamble Compared with scheme 1 Compared with scheme 4 Mean UPT (Wi-Fi in coex) -17.2% -18.4% -16.9% -18.2% 5% UPT(Wi-Fi in coex) -26.9% -40.9% -24.6% -39.1% Gain of NR-U by introducing common preamble to NRU 11a preamble 11ax preamble Compared with scheme 1 Compared with scheme 4 Mean UPT (Wi-Fi in coex) -13.0% -18.8% -12.7% -18.5% 5% UPT(Wi-Fi in coex) -34.8% -39.4% -30.9% -35.8% Note: DL performance with single stream, medium traffic load in indoor scenario

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

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

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

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

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

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

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

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