1. Performance Investigation on Wake-Up Receiver
Month Year
doc.: IEEE yy/xxxxr0
July 2016
Performance Investigation on Wake-Up Receiver
Date:
Authors:
Name
Affiliation
Address
Phone
Eunsung Park
LG Electronics
19, Yangjae-daero 11gil, Seocho-gu, Seoul , Korea
Jinsoo Choi
Dongguk Lim
HanGyu Cho
Eunsung Park, LG Electronics
John Doe, Some Company

2. July 2016
Introduction
In order to achieve a low power wake-up receiver (LP WUR), a simple OOK modulation was introduced [1]
This contribution investigates PER performance for the wake-up receiver when the wake-up packet is computed by using the OOK modulation in various channel models
To this end, we apply several assumptions to the wake-up packet as proposed in [1]
Packet structure
OOK symbol
Decoding method
Eunsung Park, LG Electronics

3. July 2016
Wake-Up Packet (1/2)
In [1], compatible wake-up packet was proposed
In this contribution, we only focus on the payload of the wake-up packet and we further assume it consists of two parts, i.e., wake-up preamble and wake-up data
Eunsung Park, LG Electronics

4. July 2016
Wake-Up Packet (2/2)
The wake-up preamble part can be used for the wake-up packet detection, channel estimation, etc.
The wake-up data part can contain a receiver address and any other required information
By taking into account the possible purpose of each part like above, we need further discussion on the size of preamble and data later on
To show the performance, it is assumed that the number of bits (symbols) for wake-up preamble and wake-up data are just set to 11 and 100 bits, respectively, in the simulation
Eunsung Park, LG Electronics

5. OOK Symbol Generation July 2016
In [1], OOK symbol is generated using OFDM transmitter
Subcarrier width = 312.5kHz
OOK pulse BW = 13 subcarriers (4.06MHz)
4us symbol period
In this contribution, the OFDM transmitter is also adopted for the OOK symbol generation
In addition, our simulation includes various OOK pulse BWs (i.e., the number of subcarriers, k=1, 13, 64) and compares the performance among them
k subcarriers are used to indicate 1 bit, and thus 1 OOK symbol has only 1 bit information
It is assumed that to indicate information ‘0’ and ‘1’, the coefficients of all available subcarriers are set to zero and one, respectively
In the case of information ‘1’, sqrt(1/k) is multiplied for power normalization, and thus each subcarrier power increases as the number of available subcarriers decreases
Eunsung Park, LG Electronics

6. Wake-Up Packet Decoding
July 2016
Wake-Up Packet Decoding
In this contribution, we consider following two decoding methods
Coherent decoding
Receiver can separate in-phase and quadrature components
In the preamble part, channel estimation can be performed and the measured channel coefficients can be used to decode the wake-up data part
Non-coherent decoding
Receiver cannot separate in-phase and quadrature components
The preamble part can be used to measure the received signal power
Receiver just sees the envelope of the received wake-up data and decides whether the transmitted information is ‘0’ or ‘1’
Our simulation compares the performance between these two decoding methods
Eunsung Park, LG Electronics

7. Summary of Assumptions
July 2016
Summary of Assumptions
Wake-up packet structure
Preamble (11 bits) + data (100 bits)
Preamble sequence is simply set to { } in the simulation
The number of available subcarriers (k) for each OOK symbol
1 subcarrier
13 subcarriers
64 subcarriers
i.e. k subcarriers are used to indicate 1 bit (1 bit per 1 symbol(4us))
The coefficients of available subcarriers
Information bit ‘0’ is represented by setting all coefficients of available subcarriers to zero
Information bit ‘1’ is represented by setting all coefficients of available subcarriers to one (more accurately, sqrt(1/k) for power normalization)
Decoding methods
Coherent
Non-coherent
Eunsung Park, LG Electronics

8. Simulation Environment
July 2016
Simulation Environment
Channel models for the simulation
AWGN
TGn D channel
UMi NLOS
Channel estimation for the coherent receiver
Least square
No CFO, STO
Uncoded performance
For a reference, L-SIG performance for the conventional Wi-Fi (11n/ac) will be shown in TGn D and UMi channels
In 20MHz, L-SIG has 24 information bits per symbol(4us) by using 48 subcarriers
Eunsung Park, LG Electronics

9. PER Performance (1/3) AWGN
July 2016
PER Performance (1/3)
AWGN
K, the number of subcarriers, does not have an effect on the performance for the coherent detection
(please see the analysis in Appendix)
For the non-coherent detection, the less subcarriers (i.e., the more power of each subcarrier), the better performance in low SNR, while the more subcarriers, the steeper slope (frequency diversity) in high SNR
Eunsung Park, LG Electronics

10. PER Performance (2/3) TGn D channel
July 2016
PER Performance (2/3)
TGn D channel
The more subcarriers, the steeper slope in high SNR
If we consider the target PER of 0.01, the cases with 13 and 64 subcarriers have good performance
In the coherent detection, the cases with 13 and 64 subcarriers are better than L-SIG performance
In the non-coherent detection, the cases with 13 and 64 subcarriers have comparable performance
Eunsung Park, LG Electronics

11. PER Performance (3/3) UMi channel
July 2016
PER Performance (3/3)
UMi channel
The more subcarriers, the steeper slope in high SNR
If we consider the target PER of 0.01, the cases with 13 and 64 subcarriers have good performance
In both detections, cases except that with 1 subcarrier are better than L-SIG
The case with 1 subcarrier does not guarantee the PER of 0.01
Eunsung Park, LG Electronics

12. July 2016
Conclusion
We investigated the PER performance for the wake-up receiver when the wake-up packet is computed by the OOK modulation in various environments
We verified that the wake-up receiver has a comparable performance even for the non-coherent detection when using several subcarriers for the OOK modulation
We can further optimize the performance by applying channel coding
The wake-up packet using OOK modulation may be possible to guarantee the transmission range of the conventional Wi-Fi if the same transmit power is used
We confirmed that the number of available subcarriers for the OOK modulation has a significant effect on the performance
We should optimize the number of subcarriers by considering not only the performance but also the power consumption
Eunsung Park, LG Electronics

13. January 2016
References
[1] IEEE /0341r0 - LP-WUR (Low-Power Wake-Up Receiver) Follow-Up
Eunsung Park, LG Electronics

14. Appendix (1/3) Decision rule for the coherent detection July 2016
Eunsung Park, LG Electronics

15. Appendix (2/3) PER for coherent detection in AWGN If x0 is transmitted
July 2016
Appendix (2/3)
PER for coherent detection in AWGN
If x0 is transmitted
If x1 is transmitted
Eunsung Park, LG Electronics

16. Appendix (3/3) PER for the coherent detection in AWGN (contd.)
July 2016
Appendix (3/3)
PER for the coherent detection in AWGN (contd.)
Eunsung Park, LG Electronics