Submission

doc.: 11-10-1239-00-0wng

Slide 1

802.11 WNG Presentation onLocation Awareness

Date: 2010-11-09

Name Affiliation Address Phone email Jim Lansford CSR, plc 217 Bridle Ln,

Florissant, CO 80816

+1 214 842 3959

jim.lansford@csr.com

Authors:

Nov 2010

Jim Lansford (CSR)

Submission

doc.: 11-10-1239-00-0wng

Abstract

This document has a discussion of location awareness issues in 802.11, to see if there are features in the

802.11 PHY and MAC that need to be added to support location based services for regulatory and

asset tracking purposes.

Slide 2

Nov 2009

Jim Lansford (CSR)

Submission

doc.: 11-10-1239-00-0wng

The Problem & Market• Increasing need for Wi-Fi devices to know position

• TV White Spaces - Mode 2 devices: location +/- 50 meters• Mandatory for FCC certification…also likely to be mandatory for

Ofcom• 5GHz

• Requirement to avoid airport radar• Wi-Fi Direct – complex global regulatory requirements

• E911 – FCC will require AP or handset in VoIP system to know position

• Asset tracking - If an AP or other device knows its location, can it infer location of other devices well enough to track?

• Location will be required for many future Wi-Fi systems– WiFi-based Real Time Location Systems will become an $800

million dollar market by 2012 (ABI Research, 2007)

Jim Lansford (CSR)

Submission

doc.: 11-10-1239-00-0wng

Existing Techniques• For position fixing in a Wi-Fi device:

– If available: GPS (or similar satellite systems)– If available: aGPS/eGPS

• Using CELLID, Wi-Fi AP location databases, or similar– Lots of work on proprietary systems:

• Based on BSS database lookup, TDoA, AoA, or fingerprinting

• Propagating position information around a BSS– 802.11k standardized RSSI measurements– 802.11v is standardizing the formats for sending RSSI +

geolocation (from GPS/aGPS) around the network

Jim Lansford (CSR)

Submission

doc.: 11-10-1239-00-0wng

Use Case 1: AP to APOne or both AP’s can have a known position

Established from database, site survey at installation, or GPS802.11v allows AP’s to distribute this position information to all devices in the BSS

Since many (if not most) AP’s have at least two antennas (for diversity or 2x2 MIMO), could use RF positioning methods to infer approximate position of AP’s with unknown coordinates

Since both AP’s have dual antennas (or 3 or 4 for MIMO) AP’s could collaborate to improve estimates802.11 PHY could also add “Time of Flight” (ToF) to measure range

If no absolute position available, relative position may still be useful for asset tracking

TV White Spaces (802.11af) requires absolute position, however

AoATDoAToF

Jim Lansford (CSR)

Submission

doc.: 11-10-1239-00-0wng

Use Case 2: AP to Device or Device to APIf device has GPS

Could send coordinates to AP using 802.11vAP could infer its position using position fixing (AoA/TDoA/ToF)

If AP knows its coordinates but device does notAP does position fix on device, calculates its approximate coordinates, then sends to deviceThis will be ideal for RF tags, legacy devices, and “dumb” Wi-Fi stations – asset tracking

If both have GPSCan calculate precise range and bearing using 801.11v coordinate exchange

Jim Lansford (CSR)

Submission

doc.: 11-10-1239-00-0wng

Jim Lansford (CSR)

Use Case 3: Device to Device• Wi-Fi Direct doesn’t have a fixed AP• If one device has GPS/aGPS:

– Can distribute its position using 802.11v– If only one antenna, can only give range estimate

• Using RSSI, ToF or fingerprinting– Required for Mode 2 TVWS (802.11af) devices

• If no device has absolute location coordinates– Still useful for asset tracking– Can only get range estimates from single antenna

(RSSI/fingerprinting) using 802.11k or ToF– Can do triangulation if multiple devices have 802.11k RSSI

capability or if ToF were added to 802.11 PHY

Submission

doc.: 11-10-1239-00-0wng

Next Steps

• Where should we go from here?