1. doc.: IEEE 802.15-05-0222-00-004a Submission April, 2005 Brethour, Time DomainSlide 1 Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Objectives of Signaling for Ranging] Date Submitted: [24 April, 2005] Source: [Vern Brethour] Company [Time Domain Corp.] Address [7057 Old Madison Pike; Suite 250; Huntsville, Alabama 35806; USA] Voice:[(256) 428-6331], FAX: [(256) 922-0387], E-Mail: [vern.brethour@timedomain.com] Re: [802.15 4a.] Abstract:[A discussion of the purpose of a ranging header in a proposed 802.15.4a message. ] Purpose:[To establish a common notion of ranging signal processing for 802.15.4a.] 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.

2. doc.: IEEE 802.15-05-0222-00-004a Submission April, 2005 Brethour, Time DomainSlide 2 Signaling for ranging for 802.15.4a Emphasis on the “why” of the a ranging header.

3. doc.: IEEE 802.15-05-0222-00-004a Submission April, 2005 Brethour, Time DomainSlide 3 UWB Ranging is all about determining time of flight of our UWB signal. The “start time” is a time stamp embedded in the message. The “stop time” is when the message arrives at the receiver. Sounds simple enough, but let’s look closer.

4. doc.: IEEE 802.15-05-0222-00-004a Submission April, 2005 Brethour, Time DomainSlide 4 The question today is: WHEN exactly do we click these stopwatches? Device ADevice B Two equations in two unknowns yield: * US Naval Observatory, Telstar Satellite, circa 1962 http://www.boulder.nist.gov/timefreq/time/twoway.htm Unmatched detect-delays in the two devices may require one-time offset calibration. Unknown propagation delay Unknown clock offset Message 1 Message 2 Multiple measurements of t p and t o yield finer precision & accuracy, and allow frequency offset correction. This picture is from 04-0581r5

5. doc.: IEEE 802.15-05-0222-00-004a Submission April, 2005 Brethour, Time DomainSlide 5 Artists’ concept of a UWB message: Acquisition Channel sounding Data (to include the time stamp of when the delimiter was at the antenna of the transmitter. The “Delimiter” is a unique signal event that defines the end of the acquisition header.

6. doc.: IEEE 802.15-05-0222-00-004a Submission April, 2005 Brethour, Time DomainSlide 6 So we have the answer to the first question: When did the clock start (the first time stamp)? Acquisition Channel sounding Data (to include the time stamp of when the delimiter was at the antenna of the transmitter. It was when this event was at the transmit antenna

7. doc.: IEEE 802.15-05-0222-00-004a Submission April, 2005 Brethour, Time DomainSlide 7 It might seem like there is a simple answer to the second question: When did the clock stop (the second time stamp)? Acquisition Channel sounding Data (to include the time stamp of when the delimiter was at the antenna of the transmitter. It was when this event was at the receive antenna, but let’s look closer: When, really, was that?

8. doc.: IEEE 802.15-05-0222-00-004a Submission April, 2005 Brethour, Time DomainSlide 8 Artists’ concept of a single pulse at the receive antenna after it has gone through (a really benign) channel: Leading edge of the pulse energy: corresponding to the line of sight path Other reflections of the pulse in the environment corresponding to other paths.

9. doc.: IEEE 802.15-05-0222-00-004a Submission April, 2005 Brethour, Time DomainSlide 9 A hallway in the Time Domain office UWB Radio on a cart This ceiling is fake

10. doc.: IEEE 802.15-05-0222-00-004a Submission April, 2005 Brethour, Time DomainSlide 10 What is above the fake ceiling? This is Time Domain Shipping/Receiving area where we don’t have the fake ceiling. Very reflective steel underlayment of the real roof

11. doc.: IEEE 802.15-05-0222-00-004a Submission April, 2005 Brethour, Time DomainSlide 11 In Time Domain’s office, (typical commercial construction) there will often be a return off of the roof underlayment that is bigger that the line of sight path. Leading edge of the pulse energy: corresponding to the line of sight path Signal off the roof (for example).

12. doc.: IEEE 802.15-05-0222-00-004a Submission April, 2005 Brethour, Time DomainSlide 12 If acquisition picks up the receive waveform here Do we call that the receive time? We better not: The receive time is here.

13. doc.: IEEE 802.15-05-0222-00-004a Submission April, 2005 Brethour, Time DomainSlide 13 Actual channel sounding in Time Domain’s office hallway. Our UWB radio acquisition algorithm picked up the waveform here. (That’s why it says zero on the display!) The actual line of sight energy is arriving here

14. doc.: IEEE 802.15-05-0222-00-004a Submission April, 2005 Brethour, Time DomainSlide 14 So that’s what “channel sounding” is about! Acquisition: At the end of this time we only know we have a signal, but we are here: Channel sounding: During this time we are building the rest of the picture, so we can find the leading edge of our arriving pulse energy. Data

15. doc.: IEEE 802.15-05-0222-00-004a Submission April, 2005 Brethour, Time DomainSlide 15 Let’s go back to our artists’ concept signal. It’s not even enough to find which of the arriving pulses was the first one. In addition, the start of that pulse must be resolved to under a nanosecond. (Our target error budget of 15 cm is half a nano-second.) Other reflections of the pulse in the environment corresponding to other paths.

16. doc.: IEEE 802.15-05-0222-00-004a Submission April, 2005 Brethour, Time DomainSlide 16 So that’s why the “channel sounding” part is relatively long. Acquisition Channel sounding: During this time we are suppressing the noise so that we can resolve this event to half a nano-second. Data (to include the time stamp of when the delimiter was at the antenna of the transmitter.

17. doc.: IEEE 802.15-05-0222-00-004a Submission April, 2005 Brethour, Time DomainSlide 17 Summary When Ranging, it is not enough to acquire a UWB signal. Following acquisition, we must do a channel sounding to find the offset from our acquisition point to the first arriving energy of our acquisition pattern. During channel sounding, we must do significant signal integration to suppress the noise in the earliest pulse such that the pulse’s leading edge can be resolved to half a nano-second.