1. doc.: IEEE 802.15-05-0032-01-004a Submission Jan 2005 Francois Chin, Institute for Infocomm Research (I 2 R) Slide 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: [16 Jan 2005] 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: [65-68745687] FAX: [65-67744990] E-Mail: [chinfrancois@i2r.a-star.edu.sg] Re: [Response to the call for proposal of IEEE 802.15.4a, Doc Number: 15-04-0380-02-004a ] Abstract:[I2R’s Proposal to IEEE 802.15.4a Task Group] Purpose:[For presentation and consideration by the IEEE802.15.4a committee] 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.

2. doc.: IEEE 802.15-05-0032-01-004a Submission Jan 2005 Francois Chin, Institute for Infocomm Research (I 2 R) Slide 2 Proposed Code Sequences, Modulation & Coding for IEEE 802.15.4a Alt-PHY Francois Chin Institute for Infocomm Research Singapore

3. doc.: IEEE 802.15-05-0032-01-004a Submission Jan 2005 Francois Chin, Institute for Infocomm Research (I 2 R) Slide 3 Proposal Motivation –To satisfy IEEE 802.15.4a technical requirements, low power consumption is crucial –Conventional coherent UWB system based on correlator in the receiver can provide fairly good performance, but at the expense of implementation complexity, and consequently power consumption and system cost To meet low power and low cost requirement, UWB system with OOK (On- Off Keying) modulation and noncoherent detection is proposed In the proposed UWB OOK system, the signal demodulation is performed by simply integrating signal energy, thus omitting signal / pulse generator, significantly relieve the strict synchronization requirement and greatly simplify transceiver structure with the minimal power and cost demand However, some challenges of such OOK system are threshold setting, simultaneous operating piconets (SOP) & receiver timing sampling boundaries This proposal contains techniques that will overcome such limitation, and improve the overall system performance of the UWB OOK system

4. doc.: IEEE 802.15-05-0032-01-004a Submission Jan 2005 Francois Chin, Institute for Infocomm Research (I 2 R) Slide 4 Challenges for OOK systems Conventional OOK systems face challenges in Receiver On-Off threshold setting Chip period boundary determination Other piconet interference This proposal intend to overcome these issues with Despreading using soft decision chip values instead of hard thresholding to better suppress other piconet interference Oversampling, together with properly chosen orthogonal code sequences, to recover chip timing The success of this hinges on the choice of code sequence !!

5. doc.: IEEE 802.15-05-0032-01-004a Submission Jan 2005 Francois Chin, Institute for Infocomm Research (I 2 R) Slide 5 Features of Proposal Use soft chip values after energy integrator at receiver with oversampling will eliminate the need for On-Off threshold setting Chip period boundary determination Use orthogonal chip sequences for symbol mapping to carry more energy per chip (which is essential for OOK systems) and to suppress Other piconet interference Chip repetition to provide data rate / baseband operation frequency / power scalability

6. doc.: IEEE 802.15-05-0032-01-004a Submission Jan 2005 Francois Chin, Institute for Infocomm Research (I 2 R) Slide 6 Chip rate22 Mcps ** # Pulse / Chip Period1 Pulse Rep. Freq.22 MHz # Chip / symbol (Code length)32 Symbol Rate22/32 MHz = 687.5 kHz info. bit / sym (Mandatory Mode)4 bit / symbol Mandatory bit rate4 bit/sym x 687.5 kHz = 2.75 Mbps #Code Sequences/ piconet16 (4 bit/symbol) Code position modulation (CPM) Lower bit rate scalabilityChip Repetition Modulation{+1,-1} bipolar pulse train OR {1,0} bipolar pulse train + pulse jittering OR Periodic On-Off Chaotic signaling Total # simultaneous piconets supported 6 Multple access for piconetsFixed sequence for each piconet Proposed System Parameters

7. doc.: IEEE 802.15-05-0032-01-004a Submission Jan 2005 Francois Chin, Institute for Infocomm Research (I 2 R) Slide 7 Modulation & Coding Bit to symbol mapping: group every 4 bits into a symbol (for Mandatory bit rate of 2.75Mbps) Symbol-to-chip mapping: Each 4-bit symbol is mapped to one of 16 32-chip sequence, according to Gray Coded Code Position Modulation (CPM) Chip Repetition & On Off Control (Output @ 22Mcps / K): Depending on the type of devices… chip repetition for high rate FFD to transmit to RFD… During a wireless transmission from a FFD to RFD, FFD can run at 22 MHz with Chip repetition; RFD runs at 22MHz / K E.g. Factor of K=11 corresponds an On-off control output switching @ 2 MHz, giving 25 kbps Bit-to- Symbol On-Off control Symbol- to-Chip Binary data From PPDU {0,1} Sequence Pulse Generator Chip Repetition

8. doc.: IEEE 802.15-05-0032-01-004a Submission Jan 2005 Francois Chin, Institute for Infocomm Research (I 2 R) Slide 8 Modulation & Coding Pulse Generator can be one of the following: A. {+1,-1} bipolar RNS pulse generator @ 132 M pulse / sec (Mpps) B. {1,0} unipolar pulse sequence generator @ 132 M pulse / sec (Mpps) (with random pulse timing jittering to avoid spectrum spikes) C. {1,0} unipolar chaotic signal generator with periodic on-off frequency @ 22 MHz Bit-to- Symbol On-Off control Symbol- to-Chip Binary data From PPDU {0,1} Sequence Pulse Generator Chip Repetition

9. doc.: IEEE 802.15-05-0032-01-004a Submission Jan 2005 Francois Chin, Institute for Infocomm Research (I 2 R) Slide 9 Band Plan Proposed operating band : 3.1 ~ 5.1 GHz –To meet the FCC spectrum requirement for UWB systems –To avoid Interferences from 802.11a,n and other sources –Bands for the future : Approximately 6 ~ 10 GHz

10. doc.: IEEE 802.15-05-0032-01-004a Submission Jan 2005 Francois Chin, Institute for Infocomm Research (I 2 R) Slide 10 UWB Pulse & Spectrum 1.5 ns rectified cosine shape ~1400 MHz 10-dB bandwidth Centre frequency ~4 GHz

11. doc.: IEEE 802.15-05-0032-01-004a Submission Jan 2005 Francois Chin, Institute for Infocomm Research (I 2 R) Slide 11 Multiple access Multiple access within piconet: TDMA same as 15.4 Multiple access across piconets: CDM Different Piconet uses different Base Sequence

12. doc.: IEEE 802.15-05-0032-01-004a Submission Jan 2005 Francois Chin, Institute for Infocomm Research (I 2 R) Slide 12 The receiver Energy detection technique rather than coherent receiver, for low cost, low complexity Soft chip values gives best results Oversampling & sequence correlation is used to recovery chip timing recovery LPF / integrator and ADC sampling rate depends on types of devices –22MHz for high rate device –22MHz / K for low rate device (upto K = 55, for 5 kbps) –Low rate device can truly run only slower clock (e.g. with transmit pulsing jitterling) Synchronization fully re-acquired for each new packet received (=> no very accurate timebase needed) Scalability BPF( ) 2 LPF / integrator ADC Sample Rate 1/T c Soft Despread

13. doc.: IEEE 802.15-05-0032-01-004a Submission Jan 2005 Francois Chin, Institute for Infocomm Research (I 2 R) Slide 13 Criteria of Code Sequences 1.To minimise impact of DC noise effect on receiver For OOK signaling, the transmitter transmits {1,0} unipolar sequences Conventional receive code sequence – follows transmit sequence After the energy capture in the receiver, the noise has positive DC components in each chip; error occurs in thresholding, especially at lower SNR This will accumulate noise unevenly in symbol decision An ideal receive despreading chip sequence should then have bipolar chip values, preferrably with equal number of ‘+1 and ‘-1’ chips This, to certain extent, will nullify DC noise in symbol decision This, will also nullify unipolar signals from other interfering piconets Cyclic correlation of any antipodal sequence with its corresponding A good code set should, so that the DC noise effect in the receiver can be minimised This will also accumulate unipolar signals from other piconets

14. doc.: IEEE 802.15-05-0032-01-004a Submission Jan 2005 Francois Chin, Institute for Infocomm Research (I 2 R) Slide 14 Criteria of Code Sequences 2. The sequence should have orthogonal cross correlation properties to minimise symbol decision error

15. doc.: IEEE 802.15-05-0032-01-004a Submission Jan 2005 Francois Chin, Institute for Infocomm Research (I 2 R) Slide 15 Base Sequence Set Seq 11 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 Seq 21 0 1 1 1 0 0 0 1 0 1 0 1 1 0 1 0 0 0 0 1 1 0 0 1 0 0 1 1 1 1 Seq 31 1 0 1 1 1 1 1 0 1 0 0 0 1 0 0 1 0 1 0 1 1 0 0 0 0 1 1 1 0 0 Seq 40 1 0 1 1 1 0 1 1 0 0 0 1 1 1 1 1 0 0 1 1 0 1 0 0 1 0 0 0 0 1 Seq 51 1 1 1 0 0 1 0 0 1 1 0 0 0 0 1 0 1 1 0 1 0 1 0 0 0 1 1 1 0 1 Seq 60 0 1 1 1 0 0 0 0 1 1 0 1 0 1 0 0 1 0 0 0 1 0 1 1 1 1 1 0 1 1 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) The same base sequence will be used to construct the symbol-to- chip mapping table

16. doc.: IEEE 802.15-05-0032-01-004a Submission Jan 2005 Francois Chin, Institute for Infocomm Research (I 2 R) Slide 16 Symbol-to-Chip Mapping: Gray Coded Code Position Modulation (CPM) To obtain 32-chip per symbol, cyclic shift the Base Sequence first, then append a ‘0’-chip SymbolCyclic shift to right by n chips, n= 32-Chip value 000001 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 0 000121 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 001140 0 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 001061 1 0 0 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 0 011081 0 1 1 0 0 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 0 0111100 0 1 0 1 1 0 0 1 1 1 1 1 0 0 0 1 1 0 1 1 1 0 1 0 1 0 0 0 0 1 0 0101120 1 0 0 1 0 1 1 0 0 1 1 1 1 1 0 0 0 1 1 0 1 1 1 0 1 0 1 0 0 0 0 0100140 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 1 0 1 0 0 1100150 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 1 0 1 0 1101170 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 1 0 1111190 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 1110211 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 0 1010230 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 1011251 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 0 1001270 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 0 1000291 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 0

17. doc.: IEEE 802.15-05-0032-01-004a Submission Jan 2005 Francois Chin, Institute for Infocomm Research (I 2 R) Slide 17 Why M-Sequences? Cyclic auto-correlation of any bipolar sequence gives peak value of 31 and sidelobe value of -1 throughout Cyclic correlation of any bipolar sequence with its corresponding unipolar sequence give peak value of 16; and correlation with other 15 unipolar sequences with give zero sidelobe throughout i.e. Each transmit OOK sequence will give a peak correlator output at a correlator with its corresponding antipodal sequence & ZERO at other 15 correlators

18. doc.: IEEE 802.15-05-0032-01-004a Submission Jan 2005 Francois Chin, Institute for Infocomm Research (I 2 R) Slide 18 Zero Padding Chip To avoid / reduce inter-symbol interference in channels with excess delay spread To ensure same number of ‘+1’s and ‘-1’s in corresponding receive correlation sequences, and to remove uneven DC noise distribution across symbol decision matric in receiver

19. doc.: IEEE 802.15-05-0032-01-004a Submission Jan 2005 Francois Chin, Institute for Infocomm Research (I 2 R) Slide 19 Synchronisation Preamble Code sequences has excellent autocorrelation properties Preamble is constructed by repeating ‘0000’ symbols Correlator output for synchronisation

20. doc.: IEEE 802.15-05-0032-01-004a Submission Jan 2005 Francois Chin, Institute for Infocomm Research (I 2 R) Slide 20 Frame Format PPDU Octets: PHY Layer Preamble TDB 1 Frame Length SFD 1 SHRPHRPSDU MPDU Data: 32 (n=23) Frame Cont. Seq. #Address Data Payload CRC Octets: 210/4/82 MAC Sublayer n MHRMSDUMFR For ACK: 5 (n=0)

21. doc.: IEEE 802.15-05-0032-01-004a Submission Jan 2005 Francois Chin, Institute for Infocomm Research (I 2 R) Slide 21 AWGN Performance Given the same symbol mapping sequence, Soft value depreading gives 2 ~ 3 dB gain over conventional fixed & SNR-dynamic thresholding techniques

22. doc.: IEEE 802.15-05-0032-01-004a Submission Jan 2005 Francois Chin, Institute for Infocomm Research (I 2 R) Slide 22 M-Sequence has better single isolated piconet performance due to its excellent cross correlation between mapping sequences Comparison with other Sequences

23. doc.: IEEE 802.15-05-0032-01-004a Submission Jan 2005 Francois Chin, Institute for Infocomm Research (I 2 R) Slide 23 Let investigate the false alarm probability in the presence of one & two overlapping piconets with asynchronous operation, all piconets using sequences from either M-Sequence Code Set or Gold Sequence Code Set Inter-Piconet Interference Suppression Code Set for all piconets False Alarm Probability Interference suppression at corr output (1 interfering piconet) Interference suppression at corr. output (2 interfering piconets) M-Sequence2.0x10 -3 %15.0 dB11.8 dB Gold sequence 1.2x10 -2 %14.5 dB11.4 dB M-Sequence Code Set gives lower false alarm probability and better suppression

24. doc.: IEEE 802.15-05-0032-01-004a Submission Jan 2005 Francois Chin, Institute for Infocomm Research (I 2 R) Slide 24 Inter-Piconet Interference Suppression M-Sequence Code Set gives lower false alarm probability and better suppression false alarm Max Corr Value = 16 1 interfering piconet 2 interfering piconet

25. doc.: IEEE 802.15-05-0032-01-004a Submission Jan 2005 Francois Chin, Institute for Infocomm Research (I 2 R) Slide 25 Inter-Piconet Interference Suppression Code Set for all piconets False Alarm Probability Interference suppression at corr output (1 interfering piconet) Interference suppression at corr. output (2 interfering piconets) M-Sequence1.8x10 -3 %15.0 dB11.8 dB Gold sequence 1.2x10 -2 %14.5 dB11.4 dB M-Sequence Code Set gives lower false alarm probability and better suppression