IEEE 802.15 <PHY Proposal>

1
Project IEEE P802.15 Working Group for Wireless
Personal Area Networks (WPANs) Submission Title
COBI-8 with Offset QPSK for 802.15.4b High Rate
Alt-PHY for 868MHz band Date Submitted 13
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_at_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.
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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
The sequences are related to each other through
cyclic shifts and/or conjugation (i.e., inversion
of odd-indexed chip values)
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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

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Frequency Responseraised cosine filter r0.2
SUPPOSE 1, 1.6MHz (4x)sampling rate 2, 250kHz
pass band
3, Tx digital FIR filter 4, 8 taps
Source - 15-04-0628-03-004b-proposal-preamble-stru
ture-ieee-802-15-4b-phy
5
Impulse response of Tx filter raised cosine
filter r0.2
SUPPOSE 1, 1.6MHz (4x)sampling rate 2, 250kHz
pass band
3, Tx digital FIR filter 4, 8 taps
Source - 15-04-0628-03-004b-proposal-preamble-stru
ture-ieee-802-15-4b-phy
6
PSD for Half-sine with Tx filter

• 100kbps
• 400k chip rate
• 600k bandwidth
• half sine pulse shape
• 8 taps FIR Tx filter
• Raised cosine filter
• with r0.2
• 4x over sampling rate
• (1.6M sampling rate)

Source - 15-04-0628-03-004b-proposal-preamble-stru
ture-ieee-802-15-4b-phy
7
Nonlinear PA Characteristics
Source - 15-04-0628-03-004b-proposal-preamble-stru
ture-ieee-802-15-4b-phy
8
Impact of PA Nonlinearity 4x sampling rate
(2)
(1)
(1) Tx PSD without Tx filter or PA (2) Tx PSD
with Tx filter, no PA (3) Tx PSD with Tx filter
and PA At 4x sampling rate, the impact of
PA nonlinearity is neglectable.
(3)
Source - 15-04-0628-03-004b-proposal-preamble-stru
ture-ieee-802-15-4b-phy
9
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
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Proposal for preamble
Preamble of 15.4 standard
Preamble here proposed for 15.4b 868MHz consists
of 8 octets (each octet comprises the least
significant symbol 0000 and the most
significant symbol 0111) and the chip sequence
will be -1 1 -1 1 1 1 -1
-1 -1 -1 1 -1 -1 1 -1
-1
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Auto-correlation of un-modulated COBI-8
Snapshot Of Normalized Correlation Values with 6
octet as example
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Synchronisation Performance

• Simulation parameters assumptions
• AWGN
• O-QPSK half-sine pulse shaping Transmit
  filtering Raised cosine (r0.2)
• 4x oversampling _at_ 1.6MHz (chip rate 400kcps)
• Frequency offset 30ppm

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Synchronisation Performance
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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 0.2)
• 20 octets in each packet
• 50,000 packets for Monte-Carlo simulation
• No Sync error
• Non-coherent demodulation
• No SFD detection

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AWGN
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Non-Coherent Receiver
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Coherent Receiver