November 2005doc.: IEEE /1079r0 Stuart GoldenNovember Notice: This document has been prepared to assist IEEE 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 grants a free, irrevocable license to the IEEE to incorporate material contained in this contribution, and any modifications thereof, in the creation of an IEEE Standards publication; to copyright in the IEEE’s name any IEEE Standards publication even though it may include portions of this contribution; and at the IEEE’s sole discretion to permit others to reproduce in whole or in part the resulting IEEE Standards publication. The contributor also acknowledges and accepts that this contribution may be made public by IEEE Patent Policy and Procedures: The contributor is familiar with the IEEE 802 Patent Policy and Procedures, including the statement "IEEE standards may include the known use of patent(s), including patent applications, provided the IEEE receives assurance from the patent holder or applicant with respect to patents essential for compliance with both mandatory and optional portions of the standard." Early disclosure to the Working Group of patent information that might be relevant to the standard is essential to reduce the possibility for delays in the development process and increase the likelihood that the draft publication will be approved for publication. Please notify the Chair as early as possible, in written or electronic form, if patented technology (or technology under patent application) might be incorporated into a draft standard being developed within the IEEE Working Group. If you have questions, contact the IEEE Patent Committee Administrator at. Key Issues about WIFI Location Date: Authors :

November 2005doc.: IEEE /1079r0 Stuart GoldenNovember Abstract –In this presentation, we present three key issues that need to be addressed for adding location to WLAN. The issues are AP database management, location measurements, and control mechanisms for measurement rate.

November 2005doc.: IEEE /1079r0 Stuart GoldenNovember Key Issues AP Database Management –Is AP Location Information Correct? Location Measurements –Signal Strength (SS) & Time Based (TOA, TDOA) Control Mechanism for Measurement Rate –Who controls how often measurement is performed?

November 2005doc.: IEEE /1079r0 Stuart GoldenNovember Location Measurement Location measurements are needed for all WLAN location approaches Proposal: –Support Signal Strength (SS), Time-of-Arrival (TOA), and Time- Difference-of-Arrival (TDOA) measurement exchange between stations RCPI – supports SS TSD (Time Stamp Differences) – supports TOA & TDOA Timestamp Difference (TSD) Definition: –Time-difference between the time that the acknowledgement of a frame is sent/received minus the time that the frame was originally sent/received. The timestamp difference is always measured on a single station.

November 2005doc.: IEEE /1079r0 Stuart GoldenNovember TOA Timing Diagram The Mobile’s timestamp difference and the AP’s timestamp difference are used to determine propagation delay

November 2005doc.: IEEE /1079r0 Stuart GoldenNovember TDOA Timing Diagram Responding AP’s timestamp difference and observer’s (non-responding AP’s) timestamp difference are used to compute a hyperbolic loci of possible locations of the client

November 2005doc.: IEEE /1079r0 Stuart GoldenNovember TOA Ranging Performance Multiple ranges were calculated from a single AP node to multiple locations of mobile located on red line

November 2005doc.: IEEE /1079r0 Stuart GoldenNovember AP Location Database Integrity Mobile location depends on accurate AP location Is AP Database Valid? –AP moved or default location still present in AP –Will Emergency services (E911) be sent to wrong location? Proposal: –AP Distributed Database with validity metric Distributed -- AP owns its own location Validity Metric –AP periodically and at start up validates its own location –Validation performed by AP to AP communication, GPS, etc …

November 2005doc.: IEEE /1079r0 Stuart GoldenNovember Control Mechanism for Measurement Rate Enable a WiFi location service that co-exists with data services –Too many mobiles overloading network by requesting location updates –Priorities: Emergency services, etc… During emergency, location has higher priority over data; otherwise data has higher priority Proposal Options: –(1) Use normal access procedures Mobiles or APs perform measurements when channel is clear –(2) Centralized/Infrastructure spectrum management mechanism Manage priorities for all WiFi-provided services (data, location, other) Mobiles request when and how often they can make measurements –(3) “STA managed” mechanism Location measurements allowed when channel utilization below threshold or emergency Or STA can scale-down measurement rate and/or degrade to less accurate mechanism depending on channel load –Report location of associated AP as location of mobile (“cell id” approach)

November 2005doc.: IEEE /1079r0 Stuart GoldenNovember Straw Polls 1) Use TSD and SS for location measurements? (Yes/No) 2) Include validity metric with AP location information? (Yes/No) 3) Channel access mechanism? (Normal/Centralized/STA)