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Performance Investigation on Wake-Up Receiver

This investigation explores the performance of a low-power wake-up receiver using OOK modulation in various channel models.

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Performance Investigation on Wake-Up Receiver

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  1. Performance Investigationon Wake-Up Receiver Date: 2016-07-26 Authors: Eunsung Park, LG Electronics

  2. Introduction • In order to achieve a low power wake-up receiver, 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. Wake-Up Packet (1/2) • In [1], 802.11 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. 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 • In [1], OOK symbol is generated using 802.11 OFDM transmitter • Subcarrier width = 312.5kHz • OOK pulse BW = 13 subcarriers (4.06MHz) • 4us symbol period • In this contribution, the 802.11 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 • 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 • Wake-up packet structure • Preamble (11 bits) + data (100 bits) • Preamble sequence is simply set to {1 1 1 1 1 1 1 1 1 1 1} 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 • 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 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 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 in high SNR Eunsung Park, LG Electronics

  10. PER Performance (2/3) • TGn D channel For both cases, the frequency diversity has a significant effect on the performance in the high SNR region 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 For both cases, the frequency diversity has a significant effect on the performance in the high SNR region If we consider the target PER of 0.01, the cases with 13 and 64 subcarriers have good performance In both detections, cases except using 1 subcarrier are better than L-SIG The case using 1 subcarrier does not guarantee the PER of 0.01 Eunsung Park, LG Electronics

  12. 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. References [1] IEEE 802.11-16/0341r0 - LP-WUR (Low-Power Wake-Up Receiver) Follow-Up Eunsung Park, LG Electronics

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

  15. 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.) Eunsung Park, LG Electronics

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