1. Various Symbol Types for WUR
Month Year
doc.: IEEE yy/xxxxr0
March 2017
Various Symbol Types for WUR
Date:
Authors:
Name
Affiliation
Address
Phone
Eunsung Park
LG Electronics
19, Yangjae-daero 11gil, Seocho-gu, Seoul , Korea
Dongguk Lim
Kiseon Ryu
Jinsoo Choi
HanGyu Cho
Eunsung Park, LG Electronics
John Doe, Some Company

2. March 2017
Introduction
Conventional Wi-Fi systems utilize various MCS levels which have different data rates and adapt the MCS level according to a channel condition
We can also think of this approach in WUR
As shown in the PAR document [1], one of the requirements of 11ba is the same range as the primary connectivity radio
“The WUR is a companion radio to the primary connectivity radio and meets the same range requirement as the primary connectivity radio”
To this end, 11ba should support a reliable and robust transmission such as a symbol repetition scheme as shown in [2]
However, a long symbol length may be too much burden on some of the WUR STAs which have a good channel state
For them, we can consider reducing the symbol time (denoted as a symbol time reduction type in this contribution) and support high data rate
In addition, we should consider a coexistence problem which may be caused by consecutive off-signals
Other devices which could not decode the L-SIG part on the WUR frame can determine the channel is idle if the off-duration of the WUR frame is long
In this contribution, we introduce several symbol types for various data rates such as
Normal OOK symbol
Manchester coding based OOK symbol
Symbol repetition
Symbol time reduction
Eunsung Park, LG Electronics

3. March 2017
Normal OOK Symbol
Each symbol consists of 4us off- or on-signals and indicates only one bit information (‘0’ or ‘1’) as follows
Data rate is 250Kbps
4us ON-Signal can be generated by using a conventional Wi-Fi transmitter as described in [3]
Symbol for information ‘0’
Symbol for information ‘1’
4us OFF-Signal
4us ON-Signal
Eunsung Park, LG Electronics

4. Manchester Coding Based OOK Symbol (1/2)
March 2017
Manchester Coding Based OOK Symbol (1/2)
Each symbol consists of 2us off- and on-signals and indicate only one bit information (‘0’ or ‘1’) as follows
Data rate is the same as that of normal OOK symbol type
2us ON-Signal can be generated by using the conventional Wi-Fi transmitter as described in [2]
Set the coefficients as follows
Every other available subcarrier : 1 or -1
Others : 0
E.g.) available subcarriers are -6 to 6
Conduct IFFT and generate a 3.2us signal that has a 1.6us periodicity
Choose either the first or second 1.6us part
Obtain 2us ON-Signal by inserting 0.4us cyclic prefix
Symbol for information ‘0’
Symbol for information ‘1’
2us ON-Signal + 2us OFF-Signal
2us OFF-Signal + 2us ON-Signal
… …
Eunsung Park, LG Electronics

5. Manchester Coding Based OOK Symbol (2/2)
March 2017
Manchester Coding Based OOK Symbol (2/2)
Then, each symbol can be constructed as below
As shown in Appendix, Manchester coding based OOK symbol type can provide a similar performance with the normal OOK symbol type in the indoor case, whereas, in the outdoor case, its performance is degraded due to a short CP length in each 2us ON- or OFF-Signal
However, it can avoid the coexistence problem with other and non devices by preventing consecutive off-signals
Information “0” CP
0us 0.4us us us
Information “1” CP
0us us 2.4us us
2us ON-Signal
2us OFF-Signal
2us OFF-Signal
2us ON-Symbol
Eunsung Park, LG Electronics

6. Symbol Repetition (1/2) March 2017
Assuming n normal OOK symbols or n Manchester coding based OOK symbols are repeated to compute one symbol for the symbol repetition type, the symbol time is n*4us
n normal OOK symbols or n Manchester coding based OOK symbols indicate only one bit information (‘0’ or ‘1’)
Data rate is 1/n*250Kbps
Assuming n=2 and normal OOK symbols are repeated, each symbol consists of two 4us normal OOK symbols as follows
Or, by applying Manchester code, each symbol which has a transition at its center can be composed as follows
This structure can reduce the max off duration by 8us
Symbol for information ‘0’
Symbol for information ‘1’
4us OFF-Signal + 4us OFF-Signal
4us ON-Signal + 4us ON-Signal
Symbol for information ‘0’
Symbol for information ‘1’
4us ON-Signal + 4us OFF-Signal
4us OFF-Signal + 4us ON-Signal
Eunsung Park, LG Electronics

7. Symbol Repetition (2/2) March 2017
Assuming n=2 and Manchester coding based OOK symbols are repeated, each symbol consists of two Manchester coding based OOK symbols as follows
We can further reduce the off duration (max duration: 4us)
As shown in Appendix, the symbol repetition type provide the best performance among four symbol types at the expense of the overhead
This symbol type can be used for STAs which have a poor channel condition or are located far from the transmitter
Symbol for information ‘0’
Symbol for information ‘1’
2us ON-Signal + 2us OFF-Signal
+ 2us ON-Signal + 2us OFF-Signal
2us OFF-Signal + 2us ON-Signal
+ 2us OFF-Signal + 2us ON-Signal
Eunsung Park, LG Electronics

8. Symbol Time Reduction March 2017
Assuming the symbol time is reduced by n times compared to the normal OOK symbol time, the symbol time is 1/n*4us
Each symbol indicates only one bit information (‘0’ or ‘1’)
Data rate is n*250Kbps
Assuming n=2, each symbol consists of 2us off- or on-signals as follows
2us ON-Signal can be obtained by applying the approach generating Manchester coding based OOK symbol
Although the symbol time reduction type has the worst performance as shown in Appendix, it can significantly reduce the overhead
This symbol type can be used for STAs which can receive a reliable signal (e.g. strong received signal strength) from the transmitter
Symbol for information ‘0’
Symbol for information ‘1’
2us OFF-Signal
2us ON-Signal
Eunsung Park, LG Electronics

9. Manchester coding based OOK symbol
March 2017
Summary
We introduced 4 symbol types as follows
By letting 11ba support various symbol types, the transmitter can choose a proper symbol type according to the environment such as channel quality, distance between TX and RX, etc.
We need to further consider a way to acquire the channel quality information at the transmitter efficiently and indicate the symbol type used for transmission to the WUR STAS
Symbol Types
Data Rate
[Kbps]
Pros
Cons
Normal OOK symbol
250
- Simple
- Long off duration
Manchester coding based OOK symbol
- Short off duration
- Additional procedure for 2us signal generation
Symbol repetition
(n=2)
125
Good performance
- Large overhead
Symbol time reduction
500
Small overhead
- Poor performance
Eunsung Park, LG Electronics

10. Straw Poll #1 Do you agree that 11ba support various symbol types?
March 2017
Straw Poll #1
Do you agree that 11ba support various symbol types?
Eunsung Park, LG Electronics

11. March 2017
Straw Poll #2
Do you agree to add the following symbol type to the 11ba SFD?
Each symbol consists of 4us off- or on-signals and indicates only one bit information (‘0’ or ‘1’) as follows
Data rate is 250Kbps
The method for computing 4us ON-Signal is TBD
Symbol for information ‘0’
Symbol for information ‘1’
4us OFF-Signal
4us ON-Signal
Eunsung Park, LG Electronics

12. March 2017
Straw Poll #3
Do you agree to add the following symbol type to the 11ba SFD?
Each symbol consists of 2us off- and on-signals and indicate only one bit information (‘0’ or ‘1’) as follows
Data rate is 250Kbps
The method for computing 2us ON-Signal is TBD
Symbol for information ‘0’
Symbol for information ‘1’
2us ON-Signal + 2us OFF-Signal
2us OFF-Signal + 2us ON-Signal
Eunsung Park, LG Electronics

13. Straw Poll #4 Do you agree that 11ba support a symbol longer than 4us?
March 2017
Straw Poll #4
Do you agree that 11ba support a symbol longer than 4us?
Eunsung Park, LG Electronics

14. March 2017
Straw Poll #5
Do you agree to add the following symbol type to the 11ba SFD?
Each symbol consists of two normal OOK symbols and indicate one bit information (‘0’ or ‘1’) as follows
Data rate is 125Kbps
The method for computing 4us ON-Signal is TBD
Symbol for information ‘0’
Symbol for information ‘1’
4us ON-Signal + 4us OFF-Signal
4us OFF-Signal + 4us ON-Signal
Eunsung Park, LG Electronics

15. March 2017
Straw Poll #6
Do you agree that 11ba support a symbol shorter than 4us?
Eunsung Park, LG Electronics

16. March 2017
Straw Poll #7
Do you agree to add the following symbol type to the 11ba SFD?
Each symbol consists of 2us off- or on-signals and indicate only one bit information (‘0’ or ‘1’) as follows
Data rate is 500Kbps
The method for computing 2us ON-Signal is TBD
Symbol for information ‘0’
Symbol for information ‘1’
2us OFF-Signal
2us ON-Signal
Eunsung Park, LG Electronics

17. March 2017
References
[1] IEEE /1045r9-0wur-a-par-proposal-wur-sg [2] IEEE wur-further-investigation-on-wur-performance [3] IEEE /0341r0 - LP-WUR (Low-Power Wake-Up Receiver) Follow-Up
Eunsung Park, LG Electronics

18. March 2017
Appendix
Eunsung Park, LG Electronics

19. Simulation Assumption (1/2)
March 2017
Simulation Assumption (1/2)
13 subcarriers are used for a symbol computation
A sequence mapped to 13 subcarriers in each symbol type is optimized in terms of the PAPR
WUR frame is composed of preamble and payload
Preamble has 6 normal OOK symbols (all ON-Signals) for measuring the received signal power to set the threshold for decoding
Payload consists of 48 symbols
Symbol structure is dependent on the symbol type
PER for payload will be shown
If 48 bits are set to the MAC address, PER is equivalent to the miss detection
No timing error, no phase noise
Raised cosine filter with 4MHz bandwidth and 0.2 roll off factor
4MHz sampling rate
TGnD and UMi NLoS channels
SNR is defined considering 20MHz
Eunsung Park, LG Electronics

20. Simulation Assumption (2/2)
March 2017
Simulation Assumption (2/2)
Normal OOK
Manchester coding based OOK
Symbol repetition
Symbol time reduction
Symbol for information ‘0’
Symbol for information ‘1’
4us OFF-Signal
4us ON-Signal
Symbol for information ‘0’
Symbol for information ‘1’
2us ON-Signal + 2us OFF-Signal
2us OFF-Signal + 2us ON-Signal
Symbol for information ‘0’
Symbol for information ‘1’
4us ON-Signal + 4us OFF-Signal
4us OFF-Signal + 4us ON-Signal
Symbol for information ‘0’
Symbol for information ‘1’
2us OFF-Signal
2us ON-Signal
Eunsung Park, LG Electronics

21. Simulation Results PER comparison among L-SIG and all symbol types
March 2017
Simulation Results
PER comparison among L-SIG and all symbol types
TGnD channel
UMi NLoS channel
Eunsung Park, LG Electronics