Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [DecaWave UWB SFD Proposal] Date Submitted: [11 February, 2010] Source: [Michael McLaughlin] Company [DecaWave] Address [Digital Depot, Thomas Street, Dublin 8, Ireland] Voice:[+353 688 2514], FAX: [none], E-Mail:[michael.mclaughlin@decawave.com] Re: [Recommendation for SFD for UWB RFID PHY] Abstract: [Proposal describing a length 16 SFD which is very robust against bit errors in the preamble and SFD] Purpose: [To resolve one of the TBDs in the merged IEEE 802.15.4f merged 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.

Introduction This submission discusses the criteria for a good SFD and recommends a particular sequence

Look in these positions Looking for SFD Cross correlate with SFD Only look in pulse positions different to preamble E.g. if SFD = 10010011 Cross correlate with 01101100 The more zeros in the SFD, the more positions you need to look at and the more chance that there will be errors. Equivalently, the greater the number of noise sources. Look in these positions

Maximise minimum distance Need to maximise the distance between cross correlation with SFD and cross correlation with preamble. Also must maximise the distance between and cross correlation with SFD and with transition sequence between the preamble and the SFD

Example Bad SFD Small distance Large distance

Minimise # occurrences of Min Distance If minimum distance occurs only once, this is better than occurring many times Rule of thumb: 0.2dBs worse for each doubling of # of symbols in Preamble to SFD transition sequence where min distance occurs Translates to -0.2×Log2(# mds) # times min distance occurs

SFD Scoring Formula for how good SFD is: 20Log10(Min Dist/sqrt(# zeros))-0.2Log2(#mds) Gives performance in dBs

5 places where error most likely Time Domain proposal Score = 3.94 dB Equal best min dist. of 5 Ends in ‘1’ Nine ‘0’s Noise/Error sources Five symbols at min distance 5 error opportunities 5 places where error most likely

Same, but fewer error opportunities Score = 4.22 dB Equal best min dist. of 5 Ends in ‘1’ Two symbols at min distance 2 error opportunities Nine ‘0’s Noise/Error sources 2 places where error most likely

Best Score ending in ‘1’ Score = 4.93 dB Equal best min dist. of 5 Seven ‘0’s Noise/Error sources Ends in ‘1’ Seven symbols at min distance 7 error opportunities One of eight equivalent SFDs

Best Score Score = 4.97 dB Equal best min dist. of 5 Seven ‘0’s Noise/Error sources Six symbols at min distance 6 error opportunities Ends in ‘0’ One of twelve equivalent SFDs

0101110110110001 Recommendation Best Score is 4.97dB Implementations may not see last pulse in time to switch Best score where last pulse is “one” i.e. does not need to be looked at is only 0.04dBs worse at 4.93dBs DecaWave Recommended SFD is: 0101110110110001