IEEE 802.15 <PHY Proposal>

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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 9 Nov, 2004 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 [phone] 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 Code Sequences for IEEE 802.15.4a
Alt-PHY

• Francois Chin
• Institute for Infocomm Research
• Singapore

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Proposed System Parameters
Chip rate 16 Mcps
Pulse Rep. Freq. 16 MHz
Symbol Rate 0.5 MHz
Min. info. bit / sym. 4 bit / symbol
Max bit rate 4 x 0.5 2.0 Mbps
Chip / symbol (Code length) 32
Code Sequences/ piconet 16 (4 bit/symbol) Code position modulation (CPM)
Lower bit rate Pulse Repetition
Modulation On-Off Keying (OOK)
Total simultaneous piconets supported 6
Multple access for piconets Fixed band and sequence for each piconet
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UWB Pulse Spectrum

• 1.5 ns rectified rectified cosine shape
• 1400 MHz 10-dB bandwidth
• Centre frequency 4 GHz

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Code Sequence Set
Seq 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 1 1
Seq 2 1 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 3 1 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 4 0 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 5 1 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 6 0 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)

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Gray Coded Code Position Modulation (CPM)
Symbol Cyclic shift to right by n chips, n 32-Chip value
0000 0 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 1 1 1
0001 2 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 0 0
0011 4 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 1 1 0
0010 6 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 1 0 1
0110 8 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 0 1
0111 10 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 1 0
0101 12 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 0 0
0100 14 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 0
1100 16 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 1
1101 18 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 1
1111 20 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 1 1
1110 22 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 1
1010 24 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 1 1
1011 26 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 0
1001 28 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 1 0
1000 30 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 1 0
To obtain 32-chip per symbol, cyclic shift first,
then extend 1-chip
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Cyclic Extended Chip

• To avoid / reduce inter-symbol interference in
  channels with excess delay spread

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Properties of M-Sequences

• Cyclic auto-correlation of any antipodal sequence
  gives peak value of 31 and sidelobe value of -1
  throughout
• Cyclic correlation of any antipodal sequence with
  its corresponding uni-podal sequence give peak
  value of 16 and zero sidelobe throughout

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Synchronisation Preamble
Correlator output for synchronisation

• Code sequence has excellent autocorrelation
  properties
• Preamble is constructed by repeating base Code
  Sequence
• Unique no symbol spreading combination can
  construct this preamble
• Unlike 15.4, where preamble is constructed by 8x
  0000 symbols

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Comparison with other Sequences

• Say 31-chip Gold Sequences as follows

Seq 1 1 0 1 0 0 0 0 0 0 0 0 1 1 1 1 0 0 1 1 1 0 1 1 0 1 0 1 0 1 1 0
Seq 2 0 0 0 0 0 1 1 1 0 1 0 0 1 0 0 0 0 1 0 0 1 1 1 1 1 1 1 1 0 1 0
Seq 3 0 1 1 0 1 0 1 1 1 1 0 0 0 0 0 0 1 1 0 1 1 1 0 0 0 1 1 1 0 0 0
Seq 4 0 0 1 0 0 1 0 1 0 1 1 0 1 1 0 0 1 0 1 0 1 1 1 0 1 1 0 0 0 0 1
Seq 5 0 0 1 0 0 0 0 1 1 1 1 0 1 0 1 0 0 0 1 1 0 1 0 0 1 0 0 1 1 1 1
Seq 6 1 1 0 0 0 1 0 1 1 0 0 1 1 0 1 1 1 1 0 1 0 0 0 1 1 0 0 1 0 0 0
Grey coded CPM is also employed
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Comparison with other Sequences

• Using square envelop detector, integrate dump
  soft despreading, M-Sequence has better multipath
  performance in Residential LOS NLOS than Gold
  Sequences, by 1.5dB
• CM2 (NLOS) performance is slightly worst than CM1
  (LOS)

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Comparison with other Sequences
M-Sequence has better single isolated piconet
performance due to its excellent cross
correlation between mapping sequences
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Inter-Piconet Interference Suppression
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
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-Sequence 2.0x10-3 15.0 dB 11.8 dB
Gold sequence 1.2x10-2 14.5 dB 11.4 dB
M-Sequence Code Set gives lower false alarm
probability and better suppression
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Summary

• M-Sequence Codes is recommended for low rate
  low-power UWB
• Low cyclic auto-correlation
• One sequence for the entire piconet for
• Better synchronisation / acquisition performance
  due to low autocorrelation properties
• Simple and robust symbol-to-chip mapping using
  cyclic shifts
• One code set for simultaneous operating piconets
  with Good interference suppression capability
  among the piconets