1. Submission Title: [Pulse code proposal] Date Submitted: [June 2005]
Project: IEEE P Working Group for Wireless Personal Area Networks
Submission Title: [Pulse code proposal]
Date Submitted: [June 2005]
Source: [Dan Raphaeli, Gidi Kaplan] Company [SandLinks Ltd.]
Address [Hanehoshet 6 Tel Aviv Israel]
Voice:[],
Re: []
Abstract: []
Purpose: [Contribution to TG4a]
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
Dani Raphaeli, SandLinks

2. A Burst Sequence Proposal for Coherent Pulse Compression
June 2005
A Burst Sequence Proposal for Coherent Pulse Compression
Dani Raphaeli & Gidi Kaplan
Sandlinks
June 3rd, 05
Dani Raphaeli, SandLinks

3. Terminology [Terminology - as agreed lately over the reflector]
June 2005
Terminology
[Terminology - as agreed lately over the reflector]
Pulse – a single UWB pulse (on the order of 1-2 nsec)
Burst – a sequence of ‘L’ UWB pulses (each pulse possibly modulated, the whole sequence has some ‘code’). Possibly, L may be between 11 to 33.
Symbol - for data or ranging – comprises of M bursts.
Each pulse has energy of
Ep= Es/(L*M)
where Es is the symbol energy.
Dani Raphaeli, SandLinks

4. Burst Code Selection Criteria
June 2005
Burst Code Selection Criteria
Signal Spectrum Flatness.
Autocorrelation Goodness.
Length.
Complexity of generation and correlation.
Ability to provide SOP separation
Dani Raphaeli, SandLinks

5. Optimization of Sequence
June 2005
Optimization of Sequence
The sequences which give almost ideal autocorrelation, and therefore a flat spectrum are called “barker sequence”.
The largest known binary barker sequence is of length 11 [in binary form: ]
Larger sequences, even of length much larger, e.g. 32, cannot yield as good autocorrelation as the above.
Dani Raphaeli, SandLinks

6. Consequences of not good autocorrelation
June 2005
Consequences of not good autocorrelation
As a first result of ‘moderate’ autocorrelation, the spectrum will have peaks.
Since FCC limits measure the peak in the spectrum - the effect is a decrease in the allowed power level (at the transmitter).
Barker sequence have only 1dB peaks. Other sequences have larger peaks – up to 5dB (see a)
Note – to assure this good spectrum, care must be taken to modulate the bursts with good sequence and random like data
Dani Raphaeli, SandLinks

7. June 2005
Spectrum of Barker-11
Dani Raphaeli, SandLinks

8. Consequences of not good autocorrelation
June 2005
Consequences of not good autocorrelation
Another consequence of ‘moderate’ autocorrelation - the autocorrelation sidelobes will be high
The effect is a ghost multipath, leading to reduced performance or failures in ranging
Barker sequence have only -20dB sidelobes.
Dani Raphaeli, SandLinks

9. Using sequences with perfect periodic autocorrelation
June 2005
Using sequences with perfect periodic autocorrelation
There exist some sequences with good periodic autocorrelation: PN codes, Ipatov sequences
The problems is that in order to take advantage of this property, the sequence should be sent repetitively without a gap or without modulation, limiting their usefullness
Although such periodic sequence can be used in the preamble, it will make an adverse effect on the spectrum – resulting in peaks in the repetition frequency.
Dani Raphaeli, SandLinks

10. Supporting multiple Piconets
June 2005
Supporting multiple Piconets
Can one practically achieve physical piconet seperation using a short code?
Codes with no crosscorrelation cannot exist if codes are non synchronized
Due to Near-far effect one cannot use CDMA type separation in 4a application unless the code is very large (e.g. l000 pulses) or alternatively, there is effective time hopping code with very large discrete resolution. Both approaches lead to complicated receiver
Conclusion – SOP should be differentiated logically if more than 3 needed. Not a big issue in 4a, where traffic is low.
Dani Raphaeli, SandLinks