WUR Preamble SYNC Field Design Month Year doc.: IEEE 802.11-yy/xxxxr0 July 2017 WUR Preamble SYNC Field Design Date: 2017-07-09 Authors: Rui Cao, Marvell John Doe, Some Company

July 2017 Introduction Similar to 802.11a/g/n/ac/ax LSTF portion, the Wake- up Radio (WUR) preamble needs a SYNC field to serve the purpose of carrier sensing, time synchronization, gain adjustment and etc. In previous contributions, the design of the SYNC field mostly focus on same on-off keying (OOK) design as data field [1, 2] We propose the design of SYNC field with some sequence(s) and no “OFF” period to achieve better performance Rui Cao, Marvell

July 2017 WUR Frame Format LSTF LLTF LSIG WUR Preamble WUR Data BPSK Symbol WUR SYNC WUR Header 20MHz Legacy preambles: LSTF+LLTF+LSIG+BPSK symbol, which is utilized to spoof 802.11 devices [3] The WUR preamble May be designed based on narrow band (e.g. 4MHz) signaling May consist of SYNC field and/or PHY header field SYNC field can be used for carrier sensing, synchronization, gain control, etc. PHY header may be needed for PHY parameter signaling, such as data rate, packet length, and etc. Rui Cao, Marvell

SYNC Field Design Criteria July 2017 SYNC Field Design Criteria To serve the desired goals, the SYNC field needs to be designed such that: The miss detection rate (Pmiss) of carrier sensing needs to match the packet error rate of lowest WUR data rate and legacy WiFi data rate The false detection rate (Pfalse) of carrier sensing needs to be low, triggered by L-STF field, and other 802.11 packets For symbol timing: needs to find accurate symbol timing and frame delimiter Zero DC in digital domain to enable the receiver to remove LO leakage Good signal power profile that facilitates simpler AGC Rui Cao, Marvell

July 2017 SYNC Sequence Design Option 1: Construct SYNC based on on-off keying (OOK) Reuse similar OFDM waveform generation architecture of data portion Each sequence is of 4us, and can be either “ON” or “OFF” Option 2: Design SYNC with no OFF symbol Design: SYNC field consist of N SYNC sequences No “OFF” symbol, which sends zero energy Each sequence can be “ON”, “-ON”, BPSK, QPSK, or any other design Each sequence will be DC free Choose SYNC sequences with good auto/cross-correlation properties, and can ease AGC adjustment ON OFF … WUR SYNC1 WUR SYNC2 … … WUR SYNCN Rui Cao, Marvell

Advantages of SYNC with no OFF Period July 2017 Advantages of SYNC with no OFF Period “OOK” based SYNC design, solely energy detection will NOT have sufficient performance for carrier sensing, symbol timing and etc. Some correlation will be necessary The “OFF” period design will waste the air time no-OFF SYNC design, The continuous sequence design facilitates both cross-correlation and auto-correlation for carrier sensing and time synchronization Good for AGC without OFF symbol Flexibility of sequence design Choose length and pattern depending on the performance requirement, not restricted to 4us duration Helps reducing false trigger in data portion which is 4us period Helps reducing false trigger from other 802.11 packets Rui Cao, Marvell

SYNC Field Design with no-OFF Period July 2017 SYNC Field Design with no-OFF Period SYNC sequence design One sequence design: S0 Design one SYNC sequence with good correlation property and zero DC One example of SYNC field design with S0 Dual sequence design Design a SYNC sequence pair with good cross-correlation and autocorrelation properties and zero DC: Sa and Sb For example, Golay complementary sequence (GCS) pair Sa and Sb can be of different length One example of SYNC field design with Sa and Sb S0 … … -S0 Sa … … Sb Rui Cao, Marvell

Simulation Settings 20MHz bandwidth, 4MHz signal July 2017 Simulation Settings 20MHz bandwidth, 4MHz signal SNR defined on 20MHz noise Sampling rate is 20MHz 4MHz LPF is added at receiver CFO = 200kHz No phase noise Legends: O means ON symbol F means OFF symbol with no energy M means “–ON” (minus of ON symbol) CS Pfalse is simulated with 11ax packet transmission Rui Cao, Marvell

Carrier Sensing Performance: AWGN July 2017 Carrier Sensing Performance: AWGN OFOFOF with energy detection show worse Pmiss and Pfalse error floor @ 0.1% Pfalse is zero for other cases Rui Cao, Marvell

Synchronization Performance July 2017 Synchronization Performance Pmiss = (timing is not found) || (timing is found, but T < Tgenie-CP || T > Tgenie+10) Rui Cao, Marvell

Discussion on Time Synchronization July 2017 Discussion on Time Synchronization Minus symbol vs OFF symbol OOOOOM rolls off two times faster than OOOOOF The sign flip property can be utilized for better timing Rui Cao, Marvell

July 2017 Summary To meet the requirement of achieving same coverage as of 802.11 main radio, WUR data needs to have one low data rate, for example 62.5kbps or 31.25kbps [4]. WUR preamble needs to be more reliable than the lowest rate data transmission SYNC sequence based on “ON” and “OFF” and energy detection cannot meet the requirement on both miss detection and false detection We propose no “OFF” SYNC sequence design, which achieves required performance with the same SYNC duration facilitates simple AGC design enables flexible SYNC sequence design Rui Cao, Marvell

July 2017 Straw Poll 1 Do you agree to design the WUR SYNC field with no- OFF period? Yes No Abstain Rui Cao, Marvell

July 2017 Reference [1] 11-16-0950-00-0wur-considerations-on-wur-design [2] 11-17-0679-02-00ba-1-wur-packet-format-and- preamble-design [3] Wake-up radio (WUR) Preamble Design, Rui Cao and Hongyuan Zhang [4] 11-17-0656-00-00ba-wur-phy-performance-study-with- phase-noise-and-aci.ppdx Rui Cao, Marvell

July 2017 Appendix Rui Cao, Marvell

Synchronization Performance: Mean Timing July 2017 Stable mean timing across SNR facilitates better timing offset setting Rui Cao, Marvell

Synchronization Performance: Variance July 2017 Synchronization Performance: Variance Small timing variance shows better timing accuracy Rui Cao, Marvell

PER with CS/ST: 250kbps July 2017 Small timing variance shows better timing accuracy Rui Cao, Marvell