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doc.: IEEE 802.15-<doc#>
<month year> doc.: IEEE <doc#> Nov 2004 Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [IEEE b High Rate Alt-PHY proposals - Further Performance Comparison] Date Submitted: [10 Nov, 2004] Source: [Francois Chin] Company: [Institute for Infocomm Research, Singapore] Address: [21 Heng Mui Keng Terrace, Singapore ] Voice: [ ] FAX: [ ] Re: [Response to the call for proposal of IEEE b, Doc Number: b] Abstract: [This presentation compares all proposals for the IEEE b PHY standard.] Purpose: [Proposal to IEEE b Task Group] Notice: This document has been prepared to assist the IEEE P 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 P Francois Chin, Institute for Infocomm Research (I2R) <author>, <company>

Nov 2004 Background Main contribution of current doc is to provide further simulation results based on 1000 channel realisation, for the PHY proposals using coherent detection Previous comparison used 100 channel realisation, as in IEEE Doc b Performance comparison herein done with {0,1,2} cyclic chip extension {1,2,3} RAKE fingers Francois Chin, Institute for Infocomm Research (I2R)

Nov 2004 Updates Corrected 3-RAKE multipath performance for all proposals (due to programme bug in previous version) Included PSSS performance with Precoding Determined RMS Delay Spread threshold below which cyclic chip extension is not necessary Include 868 MHz multipath performance with raised cosine filter (roll-off factor = 0.2) Include PER performance curves 915MHz Transmit PSD for COBI-16 & 868MHz Transmit PSD for COBI-8 & PSSS Stated Recommendation based on realistic channel RMS delay spread, achievable Transmit PSD and PER performance Francois Chin, Institute for Infocomm Research (I2R)

Nov 2004 Candidates for Multipath Performance Comparison (using Coherent Chip Despreading) Code Set E16 G16 C8 F31 Candidate for 915MHz 868MHz Description Orthogonal 16-DSSS 16-chip for Coh. Chip Despreading 8-chip for Coh. Chip Despreading PSSS Proposer Helicomm I2R Dr. Wolf & Assoc. Doc # 04-314 04-507 04-121 Sym-Chip mapping Orthogonal Cyclic & Odd Bit Inversion Multi-code Bit/sym 4 15 Chip/Sym 16 8 31+1 cyclic extension Bit/chip 0.25 0.50 ~0.47 Root Sequence N.A. 2F53 5C 08B3E375 Source: b Francois Chin, Institute for Infocomm Research (I2R)

System Parameters for low GHz Bands
Nov 2004 Ch #0 868MHz band Ch #1-10 906 – 924 MHz Band Bandwidth 600 kHz 2 MHz Code Set Candidate 8-chip COBI C8 PSSS F31 16-chip COBI G16 DSSS E16 Chip rate 400kcps 450kcps 1Mcps Pulse shape Raised cosine (roll off = 0.25) (roll off = 0.1) Half-sine Modulation OQPSK BPSK /ASK Offset QPSK OffsetQPSK Data rate 200 kbps 187.5 kbps 240 kbps 225 kbps 250 kbps Francois Chin, Institute for Infocomm Research (I2R)

Comparison Methodology
Nov 2004 Comparison Methodology Multipath robustness performance Investigation done with Zero, one and two Cyclic chip(s) extension One, two & three RAKE fingers Bandwidth efficiency (bps / Hz) RF requirement Memory requirement Francois Chin, Institute for Infocomm Research (I2R)

Multipath Realisations
Nov 2004 Multipath Realisations 1000 Channel Realisations at each RMS Delay Spread Francois Chin, Institute for Infocomm Research (I2R)

Proposed Symbol-to-Chip Mapping (8-chip Code Set C8)
Nov 2004 Proposed Symbol-to-Chip Mapping (8-chip Code Set C8) Decimal Value Binary Symbol Chip Value 0000 (Root – 5C) 1 1000 2 0100 3 1100 4 0010 5 1010 6 0110 7 1110 8 0001 9 1001 10 0101 11 1101 12 0011 13 1011 14 0111 15 1111 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)

Other Root Sequences (8-chip C8 for Coherent Despreading only)
Nov 2004 Other Root Sequences (8-chip C8 for Coherent Despreading only) The following Root Sequences are found through exhaustive search with identical low cross correlation and autocorrelation, in base 10: Francois Chin, Institute for Infocomm Research (I2R)

DSSS Sequence E16 Nov 2004 Source doc.: IEEE 802.15-04-0314-02-004b
Decimal Symbol Binary Symbol Chip Values 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 Source doc.: IEEE b Francois Chin, Institute for Infocomm Research (I2R)

PSSS Sequence F31 (15 bit/32 chip)
Nov 2004 PSSS Sequence F31 (15 bit/32 chip) Source doc.: IEEE b Francois Chin, Institute for Infocomm Research (I2R)

Proposed Symbol-to-Chip Mapping (16-chip Code Set G16)
Nov 2004 Proposed Symbol-to-Chip Mapping (16-chip Code Set G16) Decimal Value Binary Symbol Chip Value 0000 (Root - 2F53) 1 1000 2 0100 3 1100 4 0010 5 1010 6 0110 7 1110 8 0001 9 1001 10 0101 11 1101 12 0011 13 1011 14 0111 15 1111 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)

Other Root Sequences (8-chip G16 for Coherent Despreading only)
Nov 2004 Other Root Sequences (8-chip G16 for Coherent Despreading only) The following Root Sequences are found through exhaustive search with identical low cross correlation and autocorrelation, in base 10: Francois Chin, Institute for Infocomm Research (I2R)

Multipath Performance (COBI 16-chip)
Nov 2004 @ 1Mcps using O-QPSK For 16-chip COBI Sequence, No cyclic chip is needed when 3 RAKE is used. Francois Chin, Institute for Infocomm Research (I2R)

Multipath Performance (COBI 8-chip)
Nov 2004 For 8-chip COBI Sequence, 1 Chip Extension is needed even with 3-RAKE, due to weaker despreading strength (shorter code length). Francois Chin, Institute for Infocomm Research (I2R)

Multipath Performance (DSSS)
Nov 2004 For DSSS, No cyclic chip is needed when 3 RAKE is used. Francois Chin, Institute for Infocomm Research (I2R)

Multipath Performance (PSSS)
Nov 2004 For PSSS, best performance with 2 RAKE fingers + 1 chip extension. Precoding (according to b) & 3rd RAKE do not seem to help. Francois Chin, Institute for Infocomm Research (I2R)

What happened to PSSS? Nov 2004
Neighbouring parallel sequence is using M-Seq with 2 cyclic shifts in PSSS parallel sequence construction Source doc.: IEEE b While other schemes enjoy better multipath performance with more RAKE fingers, PSSS can only use up to 2 fingers as the 3rd RAKE is dominated by adjacent parallel bit sequence. PSSS is inter-parallel sequence interference limited Francois Chin, Institute for Infocomm Research (I2R)

915MHz Bands COBI-16 vs DSSS Nov 2004
Francois Chin, Institute for Infocomm Research (I2R)

915 MHz Coherent Receiver (BER Performance)
Nov 2004 915 MHz Coherent Receiver (BER Performance) Even upto 1.33us RMS Delay Spread 1 chip extension is NOT necessary for 16-chip sequence (COBI-16 & DSSS) if sufficient RAKE fingers (at least 3) are used, even in dense multipath environment General performance comparison: COBI sequence (16 chip) > DSSS Sequence (16 chip) Francois Chin, Institute for Infocomm Research (I2R)

915 MHz Coherent Receiver (PER Performance)
Nov 2004 915 MHz Coherent Receiver (PER Performance) Even upto 1.33us RMS Delay Spread 1 chip extension is NOT necessary for 16-chip sequence (COBI-16 & DSSS) if sufficient RAKE fingers (at least 3) are used, even in dense multipath environment General performance comparison: COBI sequence (16 chip) > DSSS Sequence (16 chip) Francois Chin, Institute for Infocomm Research (I2R)

Can Non-Coherent Detection be used for COBI-16?
Nov 2004 Can Non-Coherent Detection be used for COBI-16? The COBI are designed to give best performance with coherent detection receiver. Can receiver employs Differential Chip detection?: Yes, given 1% PER (20 octet packet) COBI sequence (16 chip) can handle multipath channels with RMS delay spread upto 0.3us for 915MHz bands using 1Mcps, which normally corresponds to short range indoor environment Francois Chin, Institute for Infocomm Research (I2R)

915 MHz Band Transmit PSD (COBI-16)
Nov 2004 915 MHz Band Transmit PSD (COBI-16) Beyond fc +/- 1.2 MHz, the highest sidelobe level is ~38 dB below the total transmit power and ~30 dB below the highest point in the PSD Therefore, ~10 dB of margin to the -20 dBr spec. For a device transmitting +10 dBm, there is ~8 dB of margin to the -20 dBm absolute spec. Propose to be same as existing 915MHz Mask Francois Chin, Institute for Infocomm Research (I2R)

868MHz Band COBI-8 vs PSSS Nov 2004

868 MHz Transmit PSD & Achievable Chip Rate
Nov 2004 868 MHz Transmit PSD & Achievable Chip Rate Transmit PSD is dependent on the truncation of the pulse shaping filter To support 450kcps, Raised cosine filter with roll-off 0.1 is suggested Let’s examine this effect on raised cosine filter with roll-off 0.1 using truncation of 20, 10 & 6 chip periods 6-chip period 12-chip period 20-chip period Francois Chin, Institute for Infocomm Research (I2R)

Nov 2004 COBI-8 Transmit PSD truncation of the raised cosine filter (Roll-off 0.1) at 20 chip periods Francois Chin, Institute for Infocomm Research (I2R)

Nov 2004 PSSS Transmit PSD truncation of the raised cosine filter (Roll-off 0.1) at 20 chip periods Francois Chin, Institute for Infocomm Research (I2R)

Nov 2004 868 MHz Transmit PSD & Achievable Chip Rate Transmit PSD is dependent on the truncation of the pulse shaping filter The longer the pulse shaping filter length, the higher the implementation complexity, the lower the PSD sidelobe level pulse shaping filter implementation complexity will have significant effect on meeting transmit PSD Mask and thus the achievable chip rate Transmit PSD mask: |f-fc|>0.3MHz, relative limit < -50dBr, abs limit <-36 dBm @ 450kcps, roll-off factor = 0.1, COBI-8 & PSSS does NOT satisfy Mask Francois Chin, Institute for Infocomm Research (I2R)

Nov 2004 868 MHz Transmit PSD & Achievable Chip Rate Lower chip rate has to be sought, such that transmit PSD requirement can be met with reasonable transmit implementation complexity 400kcps with raised cosine filter (roll-off 0.25) is proposed Francois Chin, Institute for Infocomm Research (I2R)

PSSS Transmit PSD @ 400kcps
Nov 2004 PSSS Transmit 400kcps Transmit PSD requirement can be met with reasonable transmit implementation complexity. Data rate = 400kcps * 15/32 = 187.5kbps Francois Chin, Institute for Infocomm Research (I2R)

COBI-8 Transmit PSD @ 400kcps
Nov 2004 COBI-8 Transmit 400kcps Transmit PSD requirement can be met with reasonable transmit implementation complexity. Data rate = 400kcps * 4/8 = 200kbps Francois Chin, Institute for Infocomm Research (I2R)

Should COBI-8 use O-QPSK or BPSK?
Nov 2004 Should COBI-8 use O-QPSK or BPSK? @ 400kcps, Raised Cosine roll-off factor = 0.25, O-QPSK does give less amplitude variation across symbol than BPSK. Thus, O-QPSK is preferred O-QPSK BPSK PAPR~4dB PAPR~6dB Francois Chin, Institute for Infocomm Research (I2R)

Amplitude variation for PSSS with Precoding
Nov 2004 Amplitude variation for PSSS with Precoding @ 400kcps, Raised Cosine roll-off factor = 0.25, PSSS with precoding does have larger amplitude variation PAPR > 10dB Francois Chin, Institute for Infocomm Research (I2R)

868 MHz COBI-8 vs PSSS (PER Performance Comparison)
Nov 2004 868 MHz COBI-8 vs PSSS (PER Performance Comparison) Raised cosine filter (roll-off factor = 0.25) @ 400 kcps Even upto 1.33us RMS Delay Spread Similar performance between COBI-8 and PSSS at 1% PER Francois Chin, Institute for Infocomm Research (I2R)

Can Non-Coherent Detection be used for COBI-8?
Nov 2004 Can Non-Coherent Detection be used for COBI-8? The COBI are designed to give best performance with coherent detection receiver. Can receiver employs Differential Chip detection?: Yes, given 1% PER (20 octet packet), COBI sequence (8 chip) can handle multipath channels with RMS delay spread upto 0.3us for 868MHz band using both 400kcps (roll-off factor = 0.25), at even shorter range Francois Chin, Institute for Infocomm Research (I2R)

868 MHz COBI-8 vs PSSS PSSS COBI-8 Transmit amplitude distribution
Nov 2004 868 MHz COBI-8 vs PSSS PSSS COBI-8 Transmit amplitude distribution Larger range Lower range Multipath performance Similar at low RMS delay spread Better in large RMS delay spread esp. at < 1% PER Bandwidth efficiency 15/32 ~ 0.47 0.50 Francois Chin, Institute for Infocomm Research (I2R)

Multipath Performance Summary (Coherent Chip Despreading)
Nov 2004 Multipath Performance Summary (Coherent Chip Despreading) To combat inter-chip interference due to channel delay spread with RMS delay spread upto 1.33us (e.g. industry application space): COBI 16-chip (O-QPSK with half-sine pulse shaping) is recommended for 915MHz bands; COBI 8-chip (O-QPSK with raised cosine pulse shaping roll-off 0.25) is recommended for 868MHz bands. RAKE combining (with at least 3 fingers) is necessary in receiver to combine path diversity; (this does not affect standard) Few RAKE fingers can be used in realistic channels with lower delay spread Differential chip despreading can also be used in shorter transmission range environment,e.g. residential space, where multipath channel RMS delay spread is upto 0.3us Francois Chin, Institute for Infocomm Research (I2R)

Summary of Comparsion Nov 2004 Note : Red - desirable Code Set E16 C8
G16 C8 F31 Candidate for 915MHz 868MHz Description Orthogonal 16-DSSS 16-chip for Coh. Chip Despreading 8-chip for Coh. Chip Despreading PSSS Proposer Helicomm I2R Dr. Wolf & Assoc. Doc # 04-314 04-507 04-121 Sym-Chip mapping Orthogonal Cyclic & Odd Bit Inversion Multi-code Bit/sym 4 15 Chip/Sym 16 8 31+1 cyclic extension Bit/chip 0.25 0.50 15/32 ~0.47 Multipath performance Best Better Good Memory requirement High 16 sequence Low Single sequence RF linearity requirement Moderate Note : Red - desirable Francois Chin, Institute for Infocomm Research (I2R)

System Parameters for low GHz Bands
Nov 2004 System Parameters for low GHz Bands Recommended Ch #0 868MHz band Ch #1-10 906 – 924 MHz Band Bandwidth 600 kHz 2 MHz Code Set Candidate 8-chip COBI C8 PSSS F31 16-chip COBI G16 DSSS E16 Chip rate 400kcps 450kcps 1Mcps Pulse shape Raised cosine (roll off = 0.25) (roll off = 0.1) Half-sine Modulation OQPSK BPSK /ASK Offset QPSK OffsetQPSK Data rate 200 kbps 187.5 kbps 240 kbps 225 kbps 250 kbps Does not meet Transmit PSD Mask Francois Chin, Institute for Infocomm Research (I2R)

Supporting Materials Nov 2004

Nov 2004 AWGN Performance Francois Chin, Institute for Infocomm Research (I2R)

Flat Fading Performance
Nov 2004 Flat Fading Performance Francois Chin, Institute for Infocomm Research (I2R)

Coherent Receiver Multipath Performance
Nov 2004 Coherent Receiver Multipath Performance What leads to Multipath robustness? Frequency selectivity leads to Inter-chip interference, and that is the killer…. To overcome, code must have good autocorrelation properties, i.e. low sidelodes Francois Chin, Institute for Infocomm Research (I2R)

How these codes achieve Multipath robustness?
Nov 2004 How these codes achieve Multipath robustness? COBI, maintain constant module, can at best achieve zero auto-correlation within 2 chips from cor. Peak; that is good enough to handle ICI of upto 2 chip periods DSSS, comprising Walsh sequences, is not designed with auto-correlation sidelodes in mind PSSS, uses flexibility in amplitude to achieve low (zero?) auto-correlation throughout for each parallel sequence. However, it is inter-parallel sequence interference limited COBI 8-chip autocorrelation matrix COBI 16-chip autocorrelation matrix Francois Chin, Institute for Infocomm Research (I2R)

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