1. doc.: IEEE 802.15-05-0514-00-004a Submission September, 2005 Brethour, Time DomainSlide 1 Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [Ranging Values for a Positioning Solver] Date Submitted: [11 September, 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:[Making the case for augmenting timestamp information with figures of merit. ] Purpose:[To start a discussion of range figures of merit 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 802.15-05-0514-00-004a Submission September, 2005 Brethour, Time DomainSlide 2 Ranging values in Position Applications The case for including “Figure of Merit” values with timestamps in the 802.15.4a specification.

3. doc.: IEEE 802.15-05-0514-00-004a Submission September, 2005 Brethour, Time DomainSlide 3 Review of ranging vs. positioning Remember that for a position solution, we are looking for the intersection of spheres. For this presentation, let’s do it in 2-D and think about the intersection of circles.

4. doc.: IEEE 802.15-05-0514-00-004a Submission September, 2005 Brethour, Time DomainSlide 4 The solver problem The solver is not part of our standard. We will probably discuss the solver in an informative annex, but we certainly will not specify how an application does that job.

5. doc.: IEEE 802.15-05-0514-00-004a Submission September, 2005 Brethour, Time DomainSlide 5 The solver will often have more ranges than the minimum needed for a relative position solution. We are supposed to decide where all these circles intersect.

6. doc.: IEEE 802.15-05-0514-00-004a Submission September, 2005 Brethour, Time DomainSlide 6 Let’s look at our example: If trustworthy ranges are blue and untrustworthy ranges are red….. We will call the positioning solution here

7. doc.: IEEE 802.15-05-0514-00-004a Submission September, 2005 Brethour, Time DomainSlide 7 Let’s look again: If trustworthy ranges are blue and untrustworthy ranges are red….. We will call the positioning solution here

8. doc.: IEEE 802.15-05-0514-00-004a Submission September, 2005 Brethour, Time DomainSlide 8 Our Experience: Experience says that the solver is aided greatly by figures of merit being attached to individual range computations. The important information is to have a hint about which ranges to believe.

9. doc.: IEEE 802.15-05-0514-00-004a Submission September, 2005 Brethour, Time DomainSlide 9 Maybe the solver does some fancy weighting thing, maybe it just throws out the turkeys. What the solver then does with the information is beyond our standard. Each range gets a figure of merit which is the composite of two channel soundings.

10. doc.: IEEE 802.15-05-0514-00-004a Submission September, 2005 Brethour, Time DomainSlide 10 Where does the figure of merit come from? The actual line of sight energy is arriving here We must make a determination about how much we trust our judgment, given the specific trace.

11. doc.: IEEE 802.15-05-0514-00-004a Submission September, 2005 Brethour, Time DomainSlide 11 The solver needs to know which situation it’s dealing with: Case 1 Case 2

12. doc.: IEEE 802.15-05-0514-00-004a Submission September, 2005 Brethour, Time DomainSlide 12 Issues with computing the Figures of merit. If we are going to run solvers and do positioning only in networks where all units are from the same vendor, then it’s easy. We just set some bits aside for a figure of merit associated with each report of a ranging timestamp and we’re done.

13. doc.: IEEE 802.15-05-0514-00-004a Submission September, 2005 Brethour, Time DomainSlide 13 Figure of merit on heterogeneous networks doing positioning. This is harder, because now the figure of merit will have to mean roughly the same thing for all units. Remember, even the signal processing used to determine the leading edge has been (until now) considered beyond the scope of the standard.

14. doc.: IEEE 802.15-05-0514-00-004a Submission September, 2005 Brethour, Time DomainSlide 14 So we have a question: Do we want to support positioning with heterogeneous networks? Are we willing to define a consistent meaning for a figure of merit that all vendors must achieve?