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

2. July 2017
Introduction
Similar to a/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

3. 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 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

4. 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 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

5. 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

6. 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 packets
Rui Cao, Marvell

7. 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

8. 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

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

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

11. 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

12. July 2017
Summary
To meet the requirement of achieving same coverage as of 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

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

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

15. July 2017
Appendix
Rui Cao, Marvell

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

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

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