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Proposed Code Sequences for IEEE 802.15.4a Alt-PHY

This presentation compares all proposals for the IEEE802.15.4b PHY standard and proposes code sequences for the Alt-PHY.

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Proposed Code Sequences for IEEE 802.15.4a Alt-PHY

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  1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Proposed Code Sequences for IEEE 802.15.4a Alt-PHY] Date Submitted: [13 Sept, 2004] Source: [Francois Chin, Sam Kwok, Xiaoming Peng, Kannan, Yong- Huat Chew, Chin-Choy Chai, Hongyi Fu,Manjeet, Tung-Chong Wong, T.T. Tjhung, Zhongding Lei, Rahim] Company: [Institute for Infocomm Research, Singapore] Address: [21 Heng Mui Keng Terrace, Singapore 119613] Voice: [65-68745684] FAX: [65-67768109] E-Mail: [chinfrancois@i2r.a-star.edu.sg] Re: [Response to the call for proposal of IEEE 802.15.4b, Doc Number: 15-04-0239-00-004b] Abstract: [This presentation compares all proposals for the IEEE802.15.4b PHY standard.] Purpose: [Proposal to IEEE 802.15.4b Task Group] Notice: This document has been prepared to assist the IEEE P802.15. It is offered as a basis for discussion and is not binding on the contributing individual(s) or organization(s). The material in this document is subject to change in form and content after further study. The contributor(s) reserve(s) the right to add, amend or withdraw material contained herein. Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE and may be made publicly available by P802.15. Francois Chin, Institute for Infocomm Research (I2R)

  2. Proposed Code Sequences for IEEE 802.15.4a Alt-PHY • Francois Chin • Institute for Infocomm Research • Singapore Francois Chin, Institute for Infocomm Research (I2R)

  3. Proposed System Parameters Francois Chin, Institute for Infocomm Research (I2R)

  4. Code Sequence Set • 31-chip M-Sequence set • Only one sequence and one fixed band (no hopping) will be used by all devices in a piconet • Logical channels for support of multiple piconets • 6 sequences = 6 logical channels (e.g. overlapping piconets) Francois Chin, Institute for Infocomm Research (I2R)

  5. Gray Coded Code Position Modulation (CPM) To obtain 32-chip per symbol, cyclic shift first, then extend 1-chip Francois Chin, Institute for Infocomm Research (I2R)

  6. Cyclic Extended Chip • To avoid / reduce inter-symbol interference in channels with excess delay spread Francois Chin, Institute for Infocomm Research (I2R)

  7. Properties of M-Sequences • Cyclic auto-correlation of any antipodal sequence gives peak value of 31 and sidelobe value of -1 throughout • Cyclic correlation of any antipodal sequence with its corresponding uni-podal sequence give peak value of 16 and zero sidelobe throughout Francois Chin, Institute for Infocomm Research (I2R)

  8. Inter-Piconet Interference Suppression • With one overlapping piconet with asynchronous operation, the average interference suppression capability is 13.7dB Francois Chin, Institute for Infocomm Research (I2R)

  9. 31.25 kbps 0001 …. 1 1 1 1 1 0 0 0 1 1 0 1 1 1 0 1 0 1 0 0 0 0 1 0 0 1 0 1 1 0 0 0 …. 250 kcps 1 0 1 0 1 0 0 0 0 1 0 0 1 0 1 1 0 0 1 1 1 1 1 0 0 0 1 1 0 1 1 1 0 0 0 1 1 0 1 1 1 0 1 0 1 0 0 0 0 1 0 0 1 0 1 1 0 0 1 1 1 1 1 0 …. 2 Mcps 1 0 1 1 1 0 1 0 1 0 0 0 0 1 0 0 1 0 1 1 0 0 1 1 1 1 1 0 0 0 1 1 0 0 0 1 1 0 1 1 1 0 1 0 1 0 0 0 0 1 0 0 1 0 1 1 0 0 1 1 1 1 1 0 …. 16 Mcps N-layer CPM • To increase spreading gain to achieve reduce bit rate operation & coding gain • Operation - The output of the symbol-to-chip mapper is fed into the same symbol-to-chip mapper for N times • With N = 2, 4 bits is mapper to 32/4*32 = 256 chips • With N = 3, 4 bits is mapper to 32/4*32 /4 * 32 = 2048 chips Example of 3-layer CPM (for 31.25 kbps) Francois Chin, Institute for Infocomm Research (I2R)

  10. Coding Gain of multiple-layer CPM • AWGN performance @ BER=10-5 • 1-layer over PBSK: ~2.5 dB • 2-layer over 1-layer: ~ 5 dB • 3-layer over 2-layer: ~ 3.5 dB Francois Chin, Institute for Infocomm Research (I2R)

  11. Synchronisation Preamble Correlator output for synchronisation • Code sequence has excellent autocorrelation properties • Preamble is constructed by repeating base Code Sequence • Unique – no symbol & spreading combination can construct this preamble • Unlike 15.4, where preamble is constructed by 8x ‘0000’ symbols Francois Chin, Institute for Infocomm Research (I2R)

  12. Summary • Advantages of M-Sequence Codes • Low auto-correlation • One sequence for the entire piconet for • Better synchronisation / acquisition performance due to low autocorrelation properties; • Simple symbol-to-chip mapping; • Further symbol spreading through self-generation layered mechanism to achieve considerable coding gains, leading to better coverage at reduced bit rate operations • Reasonably good suppression capability for simultaneous operating piconets Francois Chin, Institute for Infocomm Research (I2R)

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