November, 2003 doc.: IEEE 802.15-03-0454 November 2003 Project: IEEE P802.15 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:[+972-9-8924100], FAX: [972-9-8658756], E-Mail:[Yossi.Erlich@infineon.com] 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 P802.15. 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 P802.15. Erlich, Infineon Technologies Erlich, Infineon

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

Drawbacks of Currently Proposed Sequences November, 2003 doc.: IEEE 802.15-03-0454 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

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

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

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 802.15-03-0337/r1) Erlich, Infineon Technologies

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

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

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

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

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

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

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

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

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

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