1. November, 2003
doc.: IEEE
November 2003
Project: IEEE P Working Group for Wireless Personal Area Networks (WPANs)
Submission Title: [Sparse Preambles for Enhanced SOP Separation]
Date Submitted: [November 10, 2003]
Source: [Yossi Erlich] Company [Infineon Technologies]
Address [P.O.Box 8631, Poleg Industrial Area, Netanya 42504, Israel]
Voice:[ ], FAX: [ ],
Re: []
Abstract: [A new set of preambles are suggested for the MB-OFDM. The set enhances the preamble detection performance under SOP, and reduces its complexity.]
Purpose: [Technical contribution to the MB-OFDM proposal]
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
Erlich, Infineon Technologies
Erlich, Infineon

2. Sparse Preambles for Enhanced SOP Separation
November 2003
Sparse Preambles for Enhanced SOP Separation
Erlich, Infineon Technologies

3. Drawbacks of Currently Proposed Sequences
November, 2003
doc.: IEEE
November 2003
Drawbacks of Currently Proposed Sequences
The cross-correlation functions have high peaks
Increased false alarm, i.e., detecting preamble of other channels (piconets) when the channel of interest does not exists
Prevent the detection of the channel of interest when two or more SOP exists
The preamble auto-correlation has a wide main lobe
Results in increased decision threshold, which in turn reduces probability of detection.
Erlich, Infineon Technologies
Erlich, Infineon

4. Solution: Use Ternary Sequences
November 2003
Solution
It is widely accepted that there are no binary sequences that have:
Good cross-correlation properties
Good auto-correlation properties
Low complexity
Solution: Use Ternary Sequences
Erlich, Infineon Technologies

5. Binary and Ternary Sequences
November 2003
Binary and Ternary Sequences
Binary sequences use {+1,-1} as their elements
For example the sequence 1,1,-1,1,-1,1,1,1,-1,-1,…
The complexity of correlating the received signal with an hierarchy binary sequence is proportional to the summation of their respective hierarchy lengths. Currently 24 (16+8).
Ternary sequences use {+1,0,-1} as their elements
For example the sequence 1,1,-1,0,0,1,-1,-1,0,0,0,1,0,…
The complexity of correlating the received signal with a ternary sequence is proportional to the number of non-zero elements in the sequences
Erlich, Infineon Technologies

6. Sequences Construction
November 2003
Sequences Construction
Design sequences with non-equal number zeros between any two non-zero elements results in sequences with
Excellent cross-correlation function between sequences
Narrow main lobe in the auto-correlation function
Flattening the spectrum can be achieved by virtue of Sony’s contribution (IEEE /r1)
Erlich, Infineon Technologies

7. The Proposed Sequences
November 2003
The Proposed Sequences
The proposed sequences have the following canonical structure
Where 0n represents a sequence of n zeros.
The 14 non-zero elements corresponding to the four preambles are: s0 s1 s2 s3 s4 s5 s6 s7 s8 s9
S10
s11
s12
s13 #1 1 -1 #2 #3 #4
Complexity: The correlator requires 13 additions (14 non-zero elements) instead of the 23 additions (hierarchy 16+8) required by the current sequences. Low Complexity!
Erlich, Infineon Technologies

8. The Proposed Vs. Current Preambles: Example
November 2003
The Proposed Vs. Current Preambles: Example
The original sequence
The sequence after applying spectrum flattening
Erlich, Infineon Technologies

9. The Auto-Correlation Function
November 2003
The Auto-Correlation Function
The proposed sequence after applying spectrum flattening
The current sequence after applying spectrum flattening
The side peaks of the auto correlation functions are practically the same
However the main lobe is narrower in the proposed sequences
Erlich, Infineon Technologies

10. The Cross-Correlation Functions
November 2003
The Cross-Correlation Functions
proposed
current
Unwanted peaks for the current sequences
Erlich, Infineon Technologies

11. Simulations: Signal Only
November 2003
Simulations: Signal Only
Consider a sequence detector that searches sequence A within 1mSec of a single band, tuned for 10-3 false-alarm, designed for worst channel model
Assume that only sequence A was transmitted (no other preambles from other channels)
Erlich, Infineon Technologies

12. Simulations: Interference Only
November 2003
Simulations: Interference Only
Assume that the receiver tries to detect channel A, and channel B or C preamble is transmitted
The following figure shows the squared correlator output when Channel C preamble is transmitted, CM=3
Peak due to the high cross-correlation in the current preambles
Proposed preamble
Current Preamble
Erlich, Infineon Technologies

13. Simulations: Interference Only
November 2003
Simulations: Interference Only
The following figure depicts the probability of detecting wrong channel as channel A using a correlation based detector
Erlich, Infineon Technologies

14. Simulations: Signal + Interference
November 2003
Simulations: Signal + Interference
Assume that the receiver tries to detect Channel A and both Channel A and C preambles are transmitted. The following figure shows the squared correlation signal, CM=2, SIR=-5dB
Current preambles
Interference
Required Signal
Proposed preambles
Erlich, Infineon Technologies

15. Simulations: Signal + Interference
November 2003
Simulations: Signal + Interference
The following figure shows the probability to detect Channel A in the presence of Channel B or C as an Interference
Wrong decision is made when the maximum of windowed squared correlator output corresponds to an interfering signal
Erlich, Infineon Technologies

16. Summary and Conclusions
November 2003
Summary and Conclusions
We propose a family of new preambles based on ternary sequences
The proposed preambles offer additional 6dB resistance against interference
The detection complexity of the proposed preambles is lower than the complexity of detecting the current ones
The proposed preambles improve the SOP performance by enabling acquisition even in the presence of strong interferences
Erlich, Infineon Technologies