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Nov 2004
Francois Chin, Institute for Infocomm Research (I2R)Slide 1
doc.: IEEE 802.15-04-0586-05-004b
Submission
Project: IEEE P802.15 Working Group for Wireless Personal Area Networks Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)(WPANs)
Submission Title: [IEEE 802.15.4b 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 119613]
Voice: [65-6874-5687] FAX: [65-6774-4990] E-Mail: [[email protected]]
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.
Nov 2004
Francois Chin, Institute for Infocomm Research (I2R)Slide 2
doc.: IEEE 802.15-04-0586-05-004b
Submission
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 15-04-0507-04-004b
– Performance comparison herein done with• {0,1,2} cyclic chip extension• {1,2,3} RAKE fingers
Nov 2004
Francois Chin, Institute for Infocomm Research (I2R)Slide 3
doc.: IEEE 802.15-04-0586-05-004b
Submission
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)
– Stated Recommendation based on realistic channel RMS delay spread
– 915MHz Transmit PSD for COBI-16
Nov 2004
Francois Chin, Institute for Infocomm Research (I2R)Slide 4
doc.: IEEE 802.15-04-0586-05-004b
Submission
Candidates for Multipath Performance Comparison (using Coherent Chip Despreading)
Code Set E16 G16 C8 F31
Candidate for 915MHz 915MHz 868MHz 868MHz
Description Orthogonal 16-DSSS
16-chip for Coh. Chip Despreading
8-chip for Coh. Chip Despreading
PSSS
Proposer Helicomm I2R I2R Dr. Wolf & Assoc.
Doc # 04-314 04-507 04-507 04-121
Sym-Chip mapping
Orthogonal Cyclic & Odd Bit Inversion
Cyclic & Odd Bit Inversion
Multi-code
Bit/sym 4 4 4 15
Chip/Sym 16 16 8 31+1 cyclic extension
Bit/chip 0.25 0.25 0.50 ~0.47
Root Sequence
N.A. 2F53 5C 08B3E375Source: 15-04-0507-04-004b
Nov 2004
Francois Chin, Institute for Infocomm Research (I2R)Slide 5
doc.: IEEE 802.15-04-0586-05-004b
Submission
System Parameters for low GHz Bands
Ch #0 868MHz band
Ch #1-10906 – 924 MHz
Band
Bandwidth 600 kHz 2 MHz
Code Set Candidate
8-chip COBIC8
PSSS F31
8-chip COBIC8
PSSS F31
8-chip COBIC8
PSSS F31
16-chip COBIG16
DSSS E16
Chip rate 300kcps 400kcps 500kcps 1Mcps 1Mcps
Pulse shape
Raised cosine (roll off = 1)
Raised cosine (roll off = 0.5)
Raised cosine (roll off = 0.2)
Half-sine
Half-sine
Modulation BPSK BPSK/ASK
BPSK BPSK/ASK
BPSK BPSK/ASK
OQPSK
OQPSK
Data rate 150 kbps
140.6 kbps
200 kbps
187.5 kbps
250 kbps
234.3 kbps
250 kbps
250 kbps
Nov 2004
Francois Chin, Institute for Infocomm Research (I2R)Slide 6
doc.: IEEE 802.15-04-0586-05-004b
Submission
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
Nov 2004
Francois Chin, Institute for Infocomm Research (I2R)Slide 7
doc.: IEEE 802.15-04-0586-05-004b
Submission
Multipath Realisations1000 Channel Realisations at each RMS Delay Spread
Nov 2004
Francois Chin, Institute for Infocomm Research (I2R)Slide 8
doc.: IEEE 802.15-04-0586-05-004b
Submission
Multipath Realisations1000 Channel Realisations at each RMS Delay Spread
Nov 2004
Francois Chin, Institute for Infocomm Research (I2R)Slide 9
doc.: IEEE 802.15-04-0586-05-004b
Submission
The sequences are related to each other through cyclic shifts and/or conjugation (i.e., inversion of odd-indexed chip values)
Proposed Symbol-to-Chip Mapping (8-chip Code Set C8)
Decimal Value Binary Symbol Chip Value
0 0000 0 1 0 1 1 1 0 0 (Root – 5C)
1 1000 0 0 1 0 1 1 1 0
2 0100 0 0 0 1 0 1 1 1
3 1100 1 0 0 0 1 0 1 1
4 0010 1 1 0 0 0 1 0 1
5 1010 1 1 1 0 0 0 1 0
6 0110 0 1 1 1 0 0 0 1
7 1110 1 0 1 1 1 0 0 0
8 0001 0 0 0 0 1 0 0 1
9 1001 1 0 0 0 0 1 0 0
10 0101 0 1 0 0 0 0 1 0
11 1101 0 0 1 0 0 0 0 1
12 0011 1 0 0 1 0 0 0 0
13 1011 0 1 0 0 1 0 0 0
14 0111 0 0 1 0 0 1 0 0
15 1111 0 0 0 1 0 0 1 0
Nov 2004
Francois Chin, Institute for Infocomm Research (I2R)Slide 10
doc.: IEEE 802.15-04-0586-05-004b
Submission
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:
9 18 23 29 33 36 46 58 66 71 72 92 111 113 116 123 132 139 142 144 163 183 184 189 197 209 219 222 226 232 237 246
Nov 2004
Francois Chin, Institute for Infocomm Research (I2R)Slide 11
doc.: IEEE 802.15-04-0586-05-004b
Submission
DSSS Sequence E16Decimal 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
Source doc.: IEEE 802.15-04-0314-02-004b
Nov 2004
Francois Chin, Institute for Infocomm Research (I2R)Slide 12
doc.: IEEE 802.15-04-0586-05-004b
Submission
PSSS Sequence F31 (15 bit/32 chip)
Source doc.: IEEE 802.15-04-0121-04-004b
Nov 2004
Francois Chin, Institute for Infocomm Research (I2R)Slide 13
doc.: IEEE 802.15-04-0586-05-004b
Submission
Proposed Symbol-to-Chip Mapping (16-chip Code Set G16)
The sequences are related to each other through cyclic shifts and/or conjugation (i.e., inversion of odd-indexed chip values)
Decimal Value Binary Symbol Chip Value
0 0000 0 0 1 0 1 1 1 1 0 1 0 1 0 0 1 1 (Root - 2F53)
1 1000 1 1 0 0 1 0 1 1 1 1 0 1 0 1 0 0
2 0100 0 0 1 1 0 0 1 0 1 1 1 1 0 1 0 1
3 1100 0 1 0 0 1 1 0 0 1 0 1 1 1 1 0 1
4 0010 0 1 0 1 0 0 1 1 0 0 1 0 1 1 1 1
5 1010 1 1 0 1 0 1 0 0 1 1 0 0 1 0 1 1
6 0110 1 1 1 1 0 1 0 1 0 0 1 1 0 0 1 0
7 1110 1 0 1 1 1 1 0 1 0 1 0 0 1 1 0 0
8 0001 0 1 1 1 1 0 1 0 0 0 0 0 0 1 1 0
9 1001 1 0 0 1 1 1 1 0 1 0 0 0 0 0 0 1
10 0101 0 1 1 0 0 1 1 1 1 0 1 0 0 0 0 0
11 1101 0 0 0 1 1 0 0 1 1 1 1 0 1 0 0 0
12 0011 0 0 0 0 0 1 1 0 0 1 1 1 1 0 1 0
13 1011 1 0 0 0 0 0 0 1 1 0 0 1 1 1 1 0
14 0111 1 0 1 0 0 0 0 0 0 1 1 0 0 1 1 1
15 1111 1 1 1 0 1 0 0 0 0 0 0 1 1 0 0 1
Nov 2004
Francois Chin, Institute for Infocomm Research (I2R)Slide 14
doc.: IEEE 802.15-04-0586-05-004b
Submission
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:
1915 3566 12115 21038 22715 31238 34297 42820 44497 53420 61969 63620
Nov 2004
Francois Chin, Institute for Infocomm Research (I2R)Slide 15
doc.: IEEE 802.15-04-0586-05-004b
Submission
Multipath Performance (COBI 16-chip)
@ 1Mcps using O-QPSKFor 16-chip COBI Sequence, No cyclic chip is needed when 3 RAKE is used.
Nov 2004
Francois Chin, Institute for Infocomm Research (I2R)Slide 16
doc.: IEEE 802.15-04-0586-05-004b
Submission
Multipath Performance (COBI 8-chip)
For 8-chip COBI Sequence, 1 Chip Extension is needed even with 3-RAKE, due to weaker despreading strength (shorter code length).
Nov 2004
Francois Chin, Institute for Infocomm Research (I2R)Slide 17
doc.: IEEE 802.15-04-0586-05-004b
Submission
Multipath Performance (DSSS)
For DSSS, No cyclic chip is needed when 3 RAKE is used.
Nov 2004
Francois Chin, Institute for Infocomm Research (I2R)Slide 18
doc.: IEEE 802.15-04-0586-05-004b
Submission
Multipath Performance (PSSS)
For PSSS, best performance with 2 RAKE fingers + 1 chip extension. Precoding (according to 15-04-0121-04-004b) & 3rd RAKE do not seem to help.
Nov 2004
Francois Chin, Institute for Infocomm Research (I2R)Slide 19
doc.: IEEE 802.15-04-0586-05-004b
Submission
What happened to PSSS?
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
Neighbouring parallel
sequence is using M-Seq with 2 cyclic shifts in
PSSS parallel sequence
construction
Source doc.: IEEE 802.15-04-0121-04-004b
Nov 2004
Francois Chin, Institute for Infocomm Research (I2R)Slide 20
doc.: IEEE 802.15-04-0586-05-004b
Submission
915 MHz Coherent Receiver Performance Under Various Channel Delay Spread
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)
Nov 2004
Francois Chin, Institute for Infocomm Research (I2R)Slide 21
doc.: IEEE 802.15-04-0586-05-004b
Submission
868 MHz Coherent Receiver Performance Under Various Channel Delay Spread
Raised cosine filter (roll-off factor = 1.0)Gives 300 kcps
Even upto 1.33us RMS Delay Spread
•1 chip extension is NOT necessary for COBI-8 if sufficient RAKE fingers (at least 3) are used, even in dense multipath environment
•General performance comparison:COBI sequence (8 chip) > PSSS Sequence
Nov 2004
Francois Chin, Institute for Infocomm Research (I2R)Slide 22
doc.: IEEE 802.15-04-0586-05-004b
Submission
868 MHz Coherent Receiver Performance Under Various Channel Delay Spread
Raised cosine filter (roll-off factor = 0.2)Gives 500 kcps
Even upto 1.33us RMS Delay Spread
•1 chip extension is NOT necessary for COBI-8 if sufficient RAKE fingers (at least 4) are used, even in dense multipath environment
•General performance comparison:COBI sequence (8 chip) > PSSS Sequence
Nov 2004
Francois Chin, Institute for Infocomm Research (I2R)Slide 23
doc.: IEEE 802.15-04-0586-05-004b
Submission
Summary of ComparsionCode Set E16
G16 C8 F31
Candidate for 915MHz 915MHz 868MHz 868MHz
Description Orthogonal 16-DSSS
16-chip for Coh. Chip Despreading
8-chip for Coh. Chip Despreading
PSSS
Proposer Helicomm I2R I2R Dr. Wolf & Assoc.
Doc # 04-314 04-507 04-507 04-121
Sym-Chip mapping
Orthogonal Cyclic & Odd Bit Inversion
Cyclic & Odd Bit Inversion
Multi-code
Bit/sym 4 4 4 15
Chip/Sym 16 16 8 31+1 cyclic extension
Bit/chip 0.25 0.25 0.50 15/32 ~0.47
Multipath performance
Good Best Better Good
Memory requirement
High16 sequence
LowSingle sequence
Low Single sequence
Low Single sequence
RF linearity requirement
Low Low Low Moderate ~ high
Note : Red - desirable
Nov 2004
Francois Chin, Institute for Infocomm Research (I2R)Slide 24
doc.: IEEE 802.15-04-0586-05-004b
Submission
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, COBI sequence (16 chip) can handle multipath channels with RMS delay spread upto 0.15us for 915MHz bands using 1Mcps, which normally corresponds to short range indoor environment
Nov 2004
Francois Chin, Institute for Infocomm Research (I2R)Slide 25
doc.: IEEE 802.15-04-0586-05-004b
Submission
The COBI are designed to give best performance with coherent detection receiver. Can receiver employs Differential Chip detection?:
•Yes, COBI sequence (8 chip) can handle multipath channels with RMS delay spread upto 0.1us for 868MHz band using both 300kcps (roll-off factor = 1,0) and 500kcps (roll-off factor = 0.2), at even shorter range
Can Non-Coherent Detection be used for COBI-8?
Nov 2004
Francois Chin, Institute for Infocomm Research (I2R)Slide 26
doc.: IEEE 802.15-04-0586-05-004b
Submission
•To combat inter-chip interference due to realistic channel delay spread with RMS delay spread upto 1.33us (e.g. industry application space):
•COBI 16-chip is recommended for 915MHz bands;•COBI 8-chip 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)•Chip extension is NOT necessary to avoid inter-symbol interference, if sufficient RAKE fingers are employed
•Differential chip despreading can also be used in shorter transmission range environment,e.g. residential space, where multipath channel RMS delay spread is upto 0.15us
Multipath Performance Summary (Coherent Chip Despreading)
Nov 2004
Francois Chin, Institute for Infocomm Research (I2R)Slide 27
doc.: IEEE 802.15-04-0586-05-004b
Submission
System Parameters for low GHz Bands
Ch #0 868MHz band
Ch #1-10906 – 924 MHz
Band
Bandwidth 600 kHz 2 MHz
Code Set Candidate
8-chip COBIC8
PSSS F31
8-chip COBIC8
PSSS F31
8-chip COBIC8
PSSS F31
16-chip COBIG16
DSSS E16
Chip rate 300kcps 400kcps 500kcps 1Mcps 1Mcps
Pulse shape
Raised cosine (roll off = 1)
Raised cosine (roll off = 0.5)
Raised cosine (roll off = 0.2)
Half-sine
Half-sine
Modulation BPSK BPSK/ASK
BPSK BPSK/ASK
BPSK BPSK/ASK
OQPSK
OQPSK
Data rate 150 kbps
140.6 kbps
200 kbps
187.5 kbps
250 kbps
234.3 kbps
250 kbps
250 kbps
Nov 2004
Francois Chin, Institute for Infocomm Research (I2R)Slide 28
doc.: IEEE 802.15-04-0586-05-004b
Submission
Beyond fc +/- 1.2 MHz, the highest sidelobe level is ~39 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 ~9 dB of margin to the -20 dBm absolute spec.•Propose to be same as existing 915MHz Mask
915 MHz Band Transmit PSD (COBI-16)
Nov 2004
Francois Chin, Institute for Infocomm Research (I2R)Slide 29
doc.: IEEE 802.15-04-0586-05-004b
Submission
Supporting Materials
Nov 2004
Francois Chin, Institute for Infocomm Research (I2R)Slide 30
doc.: IEEE 802.15-04-0586-05-004b
Submission
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
Coherent Receiver Multipath Performance
Nov 2004
Francois Chin, Institute for Infocomm Research (I2R)Slide 31
doc.: IEEE 802.15-04-0586-05-004b
Submission
•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
How these codes achieve Multipath robustness?
COBI 8-chip autocorrelation matrix
COBI 16-chip autocorrelation matrix