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: [Enhanced COBI-16 with Offset QPSK for b High Rate Alt-PHY]
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 ]
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>

2. Jan 2005
Motivation
It is desirable choose a code sequences that will lead to efficient transmission and low implementation complexity. In particular, it should:
Avoid spikes in frequency spectrum
Simplify correlation operations
Enable simple frequency offset and DC compensation
Francois Chin, Institute for Infocomm Research (I2R)

3. Current DSSS Sequence E16 has non-zero DC value ….
Jan 2005
Current DSSS Sequence E16 has non-zero DC value ….
DC values
Decimal Symbol
Binary Symbol
Chip Values 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Total DC values = -16
Source doc.: IEEE b
Francois Chin, Institute for Infocomm Research (I2R)

4. Jan 2005
Motivation
As such, it is desirable that the code sequences have the following properties:
All sequences contain an equal number of ones and zeros in total
All sequences contain an equal number of ones and zeros in the even numbered chips (I phase)
All sequences contain an equal number of ones and zeros in the odd numbered chips (Q phase)
Total phase rotation in I / Q plane accumulates to 0 degree over the complete symbol
The first 8 symbols are shifted versions of each other
The last 8 symbols have inverted odd numbered chips (Q phase); when compared to the 8 first symbols, have the exact inverted baseband phase
Francois Chin, Institute for Infocomm Research (I2R)

5. Motivation The COBI-32 code sequences satisfy all the 6 requirements.
Jan 2005
Motivation
The COBI-32 code sequences satisfy all the 6 requirements.
Challenge:
Can we find a shorter 16-chip code sequences that give better bandwidth and, at the same time, satisfy all the 6 requirements?
Francois Chin, Institute for Infocomm Research (I2R)

6. Jan 2005
YES!!
Francois Chin, Institute for Infocomm Research (I2R)

7. Proposed Symbol-to-Chip Mapping (Enhanced 16-chip COBI Code Set ω16)
Jan 2005
Proposed Symbol-to-Chip Mapping (Enhanced 16-chip COBI Code Set ω16)
Decimal Value
Binary Symbol
Chip Value
0000
(Root – 3E25) 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)

8. Other COBI-16 Sequences ω16 (that meets the 6 requirements)
Jan 2005
Other COBI-16 Sequences ω16 (that meets the 6 requirements)
The proposed code set satisfy all 6 requirements!!!
The following 2 Root Sequences, with identical performance, are also found through exhaustive search:
[ ] (Root – 48F9)
[ ] (Root – 6B70)
Francois Chin, Institute for Infocomm Research (I2R)

9. Preamble here proposed for 15.4b:
Jan 2005
Proposal for preamble
Preamble of 15.4 standard:
Preamble here proposed for 15.4b:
The preamble field proposed here consists of 6 octets.
Francois Chin, Institute for Infocomm Research (I2R)

10. Auto-correlation of un-modulated COBI-16
Jan 2005
Auto-correlation of un-modulated COBI-16
Snapshot Of Normalized Correlation Values with 6 octet as example
Francois Chin, Institute for Infocomm Research (I2R)

11. Cross-correlation of Enhanced COBI-16
Jan 2005
Cross-correlation of Enhanced COBI-16
There is a performance cost to pay for this quasi-orthogonality
as compared to another orthogonal code, like DSSS
Let’s quantify the loss…
Francois Chin, Institute for Infocomm Research (I2R)

12. Simulation models –PER calculated on 20 bytes PPDUs with preamble;
Jan 2005
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;
Francois Chin, Institute for Infocomm Research (I2R)

13. System Performance Simulation parameters & assumptions:
Jan 2005
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 & 0.6)
20 octets in each packet
20,000 packets for Monte-Carlo simulation
No Sync error
Non-coherent demodulation
No SFD detection
Francois Chin, Institute for Infocomm Research (I2R)

14. AWGN (Non-coherent) Jan 2005
Enhanced COBI-16 differs from DSSS by ~ 0.5dB due to
quasi-orthogonal cross correlation among the sequences
Francois Chin, Institute for Infocomm Research (I2R)

15. AWGN: Ideal Sync. vs. Correlation Sync.
Jan 2005
Source: b-proposal-preamble-struture-ieee b-phy
AWGN: Ideal Sync. vs. Correlation Sync.
DSSS performance
from previous page
matches this
Packet Number: 10000
PSDU Length: 20 Byte
Tx/Rx Over Sample Rate: 2
Channel Over Sample Rate: 4
Frame Detection: No
SFD: No
Francois Chin, Institute for Infocomm Research (I2R)

16. Non-Coherent Receiver (with Tx Filter r=0.2)
Jan 2005
Non-Coherent Receiver (with Tx Filter r=0.2)
Francois Chin, Institute for Infocomm Research (I2R)

17. Non-Coherent Receiver (with Tx Filter r=0.6)
Jan 2005
Non-Coherent Receiver (with Tx Filter r=0.6)
Francois Chin, Institute for Infocomm Research (I2R)

18. Summary enhanced COBI-16 can satisfy the stated 6 criteria that will
Jan 2005
Summary
enhanced COBI-16 can satisfy the stated 6 criteria that will
Avoid spikes in frequency spectrum
Simplify correlation operations
Enable simple frequency offset and DC compensation
At the performance cost of ~ 0.5dB worst than DSSS
Francois Chin, Institute for Infocomm Research (I2R)