1. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
Jan 2005
Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: [Proposed Code Sequences for IEEE a 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 ]
Voice: [ ] FAX: [ ]
Re: [Response to the call for proposal of IEEE a, Doc Number: a ]
Abstract: [I2R’s Proposal to IEEE a Task Group]
Purpose: [For presentation and consideration by the IEEE a committee]
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>

2. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
Jan 2005
Proposed Code Sequences,
Modulation & Coding
for IEEE a Alt-PHY
Francois Chin
Institute for Infocomm Research
Singapore
Francois Chin, Institute for Infocomm Research (I2R)
<author>, <company>

3. Jan 2005
Proposal Motivation
To satisfy IEEE a 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
Francois Chin, Institute for Infocomm Research (I2R)

4. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
Jan 2005
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 !!
Francois Chin, Institute for Infocomm Research (I2R)
<author>, <company>

5. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
Jan 2005
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 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
Francois Chin, Institute for Infocomm Research (I2R)
<author>, <company>

6. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
Jan 2005
Proposed System Parameters
Chip rate
22 Mcps **
# Pulse / Chip Period 1
Pulse Rep. Freq.
22 MHz
# Chip / symbol (Code length) 32
Symbol Rate
22/32 MHz = kHz
info. bit / sym (Mandatory Mode)
4 bit / symbol
Mandatory bit rate
4 bit/sym x kHz = 2.75 Mbps
#Code Sequences/ piconet
16 (4 bit/symbol)
Code position modulation (CPM)
Lower bit rate scalability
Chip 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 piconets
Fixed sequence for each piconet
Francois Chin, Institute for Infocomm Research (I2R)
<author>, <company>

7. Modulation & Coding Bit to symbol mapping:
Jan 2005
Modulation & Coding
Binary
data
From
PPDU
Bit-to-
Symbol
Symbol-
to-Chip
Chip
Repetition
On-Off
control
{0,1} Sequence
Pulse
Generator
Bit to symbol mapping:
group every 4 bits into a symbol (for Mandatory bit rate of 2.75MHz)
Symbol-to-chip mapping:
Each symbol is mapped to a 32-chip {0,1} sequence, according to Gray Coded Code Position Modulation (CPM)
Chip Repetition & On Off Control 22Mcps / K):
Depending on the type of devices…
E.g. Factor of K=11 corresponds an On-off control output 2 MHz, giving 25 kbps
During a wireless transmission from a FFD to RFD, FFD can run at 22 MHz with Chip repetition; RFD runs at 22MHz / K
Francois Chin, Institute for Infocomm Research (I2R)

8. Modulation & Coding Pulse Generator can be one of the following:
Jan 2005
Modulation & Coding
Binary
data
From
PPDU
Bit-to-
Symbol
Symbol-
to-Chip
Chip
Repetition
On-Off
control
{0,1} Sequence
Pulse
Generator
Pulse Generator
can be one of the following:
A. {+1,-1} bipolar RNS pulse 132 M pulse / sec (Mpps)
B. {1,0} unipolar pulse sequence 132 M pulse / sec (Mpps) (with random pulse timing jittering)
C. {1,0} unipolar chaotic signal generator with periodic on-off 22 MHz
Francois Chin, Institute for Infocomm Research (I2R)

9. Band Plan Proposed operating band : 3.1 ~ 5.1 GHz
Jan 2005
Band Plan
Proposed operating band : 3.1 ~ 5.1 GHz
To meet the FCC spectrum requirement for UWB systems
To avoid Interferences from a,n and other sources
Bands for the future : Approximately 6 ~ 10 GHz
Francois Chin, Institute for Infocomm Research (I2R)

10. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
Jan 2005
UWB Pulse & Spectrum
1.5 ns rectified cosine shape
~1400 MHz 10-dB bandwidth
Centre frequency ~4 GHz
Francois Chin, Institute for Infocomm Research (I2R)
<author>, <company>

11. Multiple access Multiple access within piconet: TDMA, same as 15.4.
Jan 2005
Multiple access
Multiple access within piconet:
TDMA, same as 15.4.
Multiple access across piconets:
CDM
Different Piconet uses different Base Sequence
Francois Chin, Institute for Infocomm Research (I2R)

12. Jan 2005
The receiver
LPF /
integrator
BPF
( )2
ADC
Soft
Despread
Sample Rate 1/Tc
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
Francois Chin, Institute for Infocomm Research (I2R)

13. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
Jan 2005
Criteria of Code Sequences
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
Francois Chin, Institute for Infocomm Research (I2R)
<author>, <company>

14. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
Jan 2005
Criteria of Code Sequences
2. The sequence should have orthogonal cross correlation properties to minimise symbol decision error
Francois Chin, Institute for Infocomm Research (I2R)
<author>, <company>

15. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
Jan 2005
Base Sequence Set
Seq 1
Seq 2
Seq 3
Seq 4
Seq 5
Seq 6
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
Francois Chin, Institute for Infocomm Research (I2R)
<author>, <company>

16. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
Jan 2005
Symbol-to-Chip Mapping:
Gray Coded Code Position Modulation (CPM)
Symbol
Cyclic shift to right by n chips, n=
32-Chip value
0000
0001 2
0011 4
0010 6
0110 8
0111 10
0101 12
0100 14
1100 15
1101 17
1111 19
1110 21
1010 23
1011 25
1001 27
1000 29
To obtain 32-chip per symbol, cyclic shift the Base Sequence first, then append a ‘0’-chip
Base Sequence #1
Francois Chin, Institute for Infocomm Research (I2R)
<author>, <company>

17. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
Jan 2005
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
Francois Chin, Institute for Infocomm Research (I2R)
<author>, <company>

18. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
Jan 2005
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
Francois Chin, Institute for Infocomm Research (I2R)
<author>, <company>

19. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
Jan 2005
Synchronisation Preamble
Correlator output for synchronisation
Code sequences has excellent autocorrelation properties
Preamble is constructed by repeating ‘0000’ symbols
Francois Chin, Institute for Infocomm Research (I2R)
<author>, <company>

20. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
Jan 2005
Frame Format
Octets: 2 1
0/4/8 n 2
MAC
Sublayer
Frame
Cont.
Data Payload
Seq. #
Address
CRC
MHR
MSDU
MFR
Octets:
TDB 1 1
Data: 32 (n=23)
For ACK: 5 (n=0)
PHY
Layer
Frame
Length
Preamble
SFD
MPDU
SHR
PHR
PSDU
PPDU
Francois Chin, Institute for Infocomm Research (I2R)
<author>, <company>

21. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
Jan 2005
AWGN Performance
Soft value depreading gives 2 ~ 3 dB gain over thresholding techniques
Francois Chin, Institute for Infocomm Research (I2R)
<author>, <company>

22. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
Jan 2005
Comparison with other Sequences
M-Sequence has better single isolated piconet performance due to its excellent cross correlation between mapping sequences
Francois Chin, Institute for Infocomm Research (I2R)
<author>, <company>

23. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
Jan 2005
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
Francois Chin, Institute for Infocomm Research (I2R)
<author>, <company>

24. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
Jan 2005
Inter-Piconet Interference Suppression
Max Corr Value
2 interfering piconet
1 interfering piconet
false alarm
M-Sequence Code Set gives lower false alarm probability and better suppression
Francois Chin, Institute for Infocomm Research (I2R)
<author>, <company>

25. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
Jan 2005
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-Sequence
1.8x10-3%
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
Francois Chin, Institute for Infocomm Research (I2R)
<author>, <company>