Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)

1. Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Quadrature COBI-16 with Offset QPSK for 802.15.4b High Rate Alt-PHY] Date Submitted: [30 Jan, 2004] Source: [Francois Chin, Lei Zhongding, Sam Kwok, Manjeet Singh] Company: [Institute for Infocomm Research, Singapore] Address: [21 Heng Mui Keng Terrace, Singapore 119613] Voice: [65-6874-5687] FAX: [65-6774-4990] 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. Motivation It is desirable choose a code sequences that will lead to efficient transmission and low implementation complexity. In particular, it should: • Avoid spikes in frequency spectrum • Simplify correlation operations • Enable simple frequency offset and DC compensation • Enable high data rate 200kbps Francois Chin, Institute for Infocomm Research (I2R)

3. Decimal Symbol Binary Symbol Chip Values 0 0 0 0 0 0 0 1 1 0 1 0 0 0 1 0 0 0 1 0 0 1 1 0 0 0 0 1 1 0 0 0 0 1 0 0 0 1 0 0 0 1 2 0 1 0 0 0 0 0 0 0 1 1 1 0 1 1 1 0 1 1 1 3 1 1 0 0 0 1 0 1 0 0 1 0 0 0 1 0 0 0 1 0 4 0 0 1 0 0 0 1 1 1 0 1 1 0 1 0 0 1 0 1 1 5 1 0 1 0 0 1 1 0 1 1 1 0 0 0 0 1 1 1 1 0 6 1 1 1 0 0 0 0 0 1 0 0 0 0 1 1 1 1 0 0 0 7 0 1 1 1 0 1 0 1 1 1 0 1 0 0 1 0 1 1 0 1 8 0 0 0 1 0 0 1 1 0 1 0 0 1 0 1 1 1 0 1 1 9 1 0 0 1 0 1 1 0 0 0 0 1 1 1 1 0 1 1 1 0 10 0 1 0 1 0 0 0 0 0 1 1 1 1 0 0 0 1 0 0 0 11 1 1 0 1 0 1 0 1 0 0 1 0 1 1 0 1 1 1 0 1 12 0 0 1 1 0 0 1 1 1 0 1 1 1 0 1 1 0 1 0 0 13 1 0 1 1 0 1 1 0 1 1 1 0 1 1 1 0 0 0 0 1 14 0 1 1 1 0 0 0 0 1 0 0 0 1 0 0 0 0 1 1 1 15 1 1 1 1 0 1 0 1 1 1 0 1 1 1 0 1 0 0 1 0 Current DSSS Sequence E16 has non-zero DC value …. DC values Total DC values = -16 • Source doc.: IEEE 802.15-04-0314-02-004b Francois Chin, Institute for Infocomm Research (I2R)

4. Motivation As such, it is desirable that the code sequences have the following properties: • All sequences contain an equal number of ones and zeros in total • All sequences contain an equal number of ones and zeros in the even numbered chips (I phase) • All sequences contain an equal number of ones and zeros in the odd numbered chips (Q phase) • Total phase rotation in I / Q plane accumulates to 0 degree over the complete symbol • The first 8 symbols are shifted versions of each other • The last 8 symbols have inverted odd numbered chips (Q phase); when compared to the 8 first symbols, have the exact inverted baseband phase Francois Chin, Institute for Infocomm Research (I2R)

5. Motivation The COBI-32 code sequences satisfy all the 6 requirements. Challenge: Can we find a shorter 16-chip code sequences that give better bandwidth efficiency and, at the same time, satisfy all the 6 requirements? And still give 200kbps?? Francois Chin, Institute for Infocomm Research (I2R)

6. YES!! Francois Chin, Institute for Infocomm Research (I2R)

7. Recap Proposed Symbol-to-Chip Mapping (Enhanced 16-chip COBI Code Set ω16) The sequences are related to each other through cyclic shifts and/or conjugation (i.e., inversion of odd-indexed chip values) Francois Chin, Institute for Infocomm Research (I2R)

8. Now, to achieve 200kbps,we need to carry 8 bits using 16 chip sequence • The 4 LSBs (b0, b1, b2, b3) of each octet shall map into one 16-chip O-QPSK data symbol, Sequence A, using Table A, and the 4 MSBs (b4, b5, b6, b7) of each octet shall map into another 16-chip O-QPSK data symbol , Sequence B, using Table B • Transmit Sequence A +j* Sequence B Francois Chin, Institute for Infocomm Research (I2R)

9. Proposed Symbol-to-Chip Mapping for {b0 b1 b2 b3} using ω16 Table A The sequences are related to each other through cyclic shifts and/or conjugation (i.e., inversion of odd-indexed chip values) Francois Chin, Institute for Infocomm Research (I2R)

10. Proposed Symbol-to-Chip Mapping for {b4 b5 b6 b7} using ω16 (flipped) Table B The sequences are related to each other through cyclic shifts and/or conjugation (i.e., inversion of odd-indexed chip values) Francois Chin, Institute for Infocomm Research (I2R)

11. Quadrature COBI-16 Sequences • The proposed code set STILL satisfy all 6 requirements!!! And carry 8 bits with 16 QPSK chip sequence…. Francois Chin, Institute for Infocomm Research (I2R)

12. Transmit PSD (16kHz RBW) 4x Oversampling Francois Chin, Institute for Infocomm Research (I2R)

13. Transmit PSD (100kHz RBW) 4x Oversampling Francois Chin, Institute for Infocomm Research (I2R)

14. Proposal for preamble Preamble as of 15.4 standard: The preamble comprises 8 ‘0000’ symbols from Table A Francois Chin, Institute for Infocomm Research (I2R)

15. Synchronisation - Auto-correlation of un-modulated COBI-16 Snapshot Of Normalized Correlation Values with 6 octet as example Francois Chin, Institute for Infocomm Research (I2R)

16. Cross-correlation of Enhanced COBI-16 from Table A There is a performance cost to pay for this quasi-orthogonality as compared to another orthogonal code, like DSSS Let’s quantify the loss… Francois Chin, Institute for Infocomm Research (I2R)

17. Simulation models Discrete exponential channel model –-Sampled version of diffuse channel model offer by Paul with 4x sampling rate; –PER calculated on 20 bytes PPDUs with preamble; Francois Chin, Institute for Infocomm Research (I2R)

18. System Performance Simulation parameters & assumptions: • Flat fading & 250ns rms delay spread Rayleigh Channel model • O-QPSK modulation + half sine pulse + Transmit filtering Raised cosine (r = 0.6) • 20 octets in each packet • 20,000 packets for Monte-Carlo simulation • No Sync error • Non-coherent demodulation • No SFD detection Francois Chin, Institute for Infocomm Research (I2R)

19. AWGN performance With coherent detection, Quad COBI-16 differs from DSSS by ~ 0.5dB due to quasi-orthogonal cross correlation among the sequences Francois Chin, Institute for Infocomm Research (I2R)

20. Source: 15-04-0628-03-004b-proposal-preamble-struture-ieee-802-15-4b-phy AWGN: Ideal Sync. vs. Correlation Sync. DSSS performance from previous page matches this Packet Number: 10000 PSDU Length: 20 Byte Tx/Rx Over Sample Rate: 2 Channel Over Sample Rate: 4 Frame Detection: No SFD: No Francois Chin, Institute for Infocomm Research (I2R)

21. Summary • Quad COBI-16 can satisfy the stated 6 criteria that will • Avoid spikes in frequency spectrum • Simplify correlation operations • Enable simple frequency offset and DC compensation; and • Provide 200kbps in 868kHz band • With coherent detection, it’s ~ 0.5dB worst than DSSS Francois Chin, Institute for Infocomm Research (I2R)