1. doc.: IEEE 802.15-<doc#>
<month year>
doc.: IEEE <doc#>
March 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 Mar, 2004]
Source: [Francois Chin, Yuen-Sam Kwok, Lei Zhongding] 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. March 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. March 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)

4. Motivation The COBI-32 code sequences satisfy all the 6 requirements.
March 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)

5. March 2005
YES!!
Francois Chin, Institute for Infocomm Research (I2R)

6. Proposed Symbol-to-Chip Mapping (Enhanced 16-chip COBI Code Set ω16)
March 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)

7. March 2005
COBI-16 Sequences ω16
The proposed code set satisfy all 6 requirements!!!
Another Root Sequence, with identical performance, is also found through exhaustive search:
[ ] (Root – A47C)
Which is a direct left-right flip of previous root sequence
IN FACT, other base sequence can be established by
Any combination of cyclic shifts, bit inversion & sequence flips of the base sequence (3E25 hex)
Francois Chin, Institute for Infocomm Research (I2R)

8. TX PSD (915 MHz), RBW = 16 kHz March 2005 Meet Mask
Francois Chin, Institute for Infocomm Research (I2R)

9. TX PSD (915 MHz), RBW = 100 kHz March 2005 Meet Mask
Francois Chin, Institute for Infocomm Research (I2R)

10. TX PSD (868 MHz) Roll-off = 0.2, RBW = 16 kHz
March 2005
TX PSD (868 MHz) Roll-off = 0.2, RBW = 16 kHz
Meet ETSI Mask
Francois Chin, Institute for Infocomm Research (I2R)

11. TX PSD (868 MHz) Roll-off = 0.2, RBW = 100 kHz
March 2005
TX PSD (868 MHz) Roll-off = 0.2, RBW = 100 kHz
Meet ETSI Mask
Francois Chin, Institute for Infocomm Research (I2R)

12. TX PSD (868 MHz) Roll-off = 0.2, RBW = 16 kHz
March 2005
TX PSD (868 MHz) Roll-off = 0.2, RBW = 16 kHz
Not Meet ETSI Mask
Francois Chin, Institute for Infocomm Research (I2R)

13. TX PSD (868 MHz) Roll-off = 0.6, RBW = 16 kHz
March 2005
TX PSD (868 MHz) Roll-off = 0.6, RBW = 16 kHz
Not Meet ETSI Mask
Francois Chin, Institute for Infocomm Research (I2R)

14. TX PSD (868 MHz) Roll-off = 0.6, RBW = 16 kHz
March 2005
TX PSD (868 MHz) Roll-off = 0.6, RBW = 16 kHz
Not Meet ETSI Mask
Francois Chin, Institute for Infocomm Research (I2R)

15. TX PSD (868 MHz) Roll-off = 0.2, 16-Tap @ 4x sampling
March 2005
TX PSD (868 MHz) Roll-off = 0.2, 4x sampling
To meet ESTI mask with 40ppm crystal, small roll-off factor 0.2 has to be employed
The proposed tap weights are:
Francois Chin, Institute for Infocomm Research (I2R)

16. March 2005
EVM
Francois Chin, Institute for Infocomm Research (I2R)

17. Preamble structure is the same as of 15.4 standard:
March 2005
Preamble Structure
Preamble structure is the same as of 15.4 standard:
Francois Chin, Institute for Infocomm Research (I2R)

18. Auto-correlation of un-modulated COBI-16
March 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)

19. Cross-correlation of Enhanced COBI-16
March 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)

20. Simulation models –PER calculated on 20 bytes PPDUs with preamble;
March 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)

21. System Performance Simulation parameters & assumptions:
March 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 (roll-off = 0.2)
20 octets in each packet
20,000 packets for Monte-Carlo simulation
Sync + SFD error taken into account
2x oversampling
Non-coherent demodulation
Francois Chin, Institute for Infocomm Research (I2R)

22. 868 MHz AWGN (Non-coherent)
March 2005
868 MHz AWGN (Non-coherent)
Francois Chin, Institute for Infocomm Research (I2R)

23. 915 MHz AWGN (Non-coherent)
March 2005
915 MHz AWGN (Non-coherent)
Francois Chin, Institute for Infocomm Research (I2R)

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

25. Synchronisation False Alarm (915 MHz Band)
March 2005
Synchronisation False Alarm (915 MHz Band)
Francois Chin, Institute for Infocomm Research (I2R)

26. Synchronisation Miss Detection (915 MHz Band)
March 2005
Synchronisation Miss Detection (915 MHz Band)
Francois Chin, Institute for Infocomm Research (I2R)

27. Synchronisation False Alarm (868 MHz Band)
March 2005
Synchronisation False Alarm (868 MHz Band)
Francois Chin, Institute for Infocomm Research (I2R)

28. Synchronisation Miss Detection (868 MHz Band)
March 2005
Synchronisation Miss Detection (868 MHz Band)
Francois Chin, Institute for Infocomm Research (I2R)

29. Summary enhanced COBI-16 can satisfy the stated 6 criteria that will
March 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
Francois Chin, Institute for Infocomm Research (I2R)