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Wireless Assisted GPS

Personal Location for GSM and GSM

Evolution

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Introduction

Wireless Assisted GPS (WAG) Definition

How it operates

GSM Standards-Based Messaging

Requirements

WAG Performance

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WAG

Wireless Assisted GPS (WAG) Definition

How it operates

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WirelessInformation is

obtained from the

wireless

infrastructure,

wireless handset, or

via wireless

messages from a

Location Server.

This information iscalled assistance

information, and it is

used by the WAG

receiver

AssistedThe assistance

information received,

or derived from, the

wireless network isused to aid the

WAG receiver by

providing data that

would normally be

derived by

timeconsuming

demodulation of

GPS satellite signals

demodulation is

difficult and

sometimesimpossible in certain

common wireless

environments.

GPSA proven system for

world-wide

positioning and

navigation used forpersonal,

commercial,

business, and

government

applications.

Commercial

implementations

have been in place

for close to 10

years, though the

system has been inplace over 20

years

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WAG Architecture

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Why WAG ?

Very rapid acquisition--100 to 1000 times faster thanconventional GPS.

Extremely fast positioning in almost all conditions

Operation in difficult environments (blocked signals,fading, etc.) Very sensitive for given acquisition time

Can withstand >20 dB signal attenuation due to buildingblockage, etc.

Works indoors

Excellent accuracy/reliability through cooperationbetween MS client and server

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Why WAG? (Cont)

A single server supports roaming across differentnetworks and different geographies

Other than one Server, no special infrastructureequipment is needed

Accuracy of WAG supports emergency services andenables a much larger number of location serviceapplications

Cost of implementation decreases over time as

handset integration increases WAG can be combined with other terrestrial

radiolocation methodologies

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How it Works?

WAG receiver obtains aiding data from theserver and/or extracts key information from thewireless network

Using this aiding data, WAG receiver processessmall amounts of GPS satellite signals

Then

MS-Assisted: Sends data to Server for positioncalculation

MS-Based: Calculates position in the handset

WAG splits the workload into a very efficient,quick, and accurate client/server structure

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Client/Server Structure

=0 (v-us)/(v-uo)

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GSM Standards-BasedMessaging

Requirements

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GSM Architecture

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Existing Technologies

Cell ID

Locates user in a sector at most.

Easy to implement

Low cost

Low accuracy

E-OTD

Cant be used in WCDMA (specific to GSM/GPRS)

High costs involved due to additional LUs

Accuracy better than Cell-Id OTDOA

Used only in WCDMA

Cost between Cell-Id and EOTD

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Cell-Id

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E-OTDEnhanced Observed Time Difference

3 T

Measurementsto measure

distance.

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OTDOA

WCDMA version of EOTD

Little Cheaper than EOTD due to LU

implementation only at Base Stations.

Uses RTT

Observed Time Difference of Arrival

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LBS Architecture onGSM/GPRS

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WAG Implementation onWCDMA

Stand-alone Assisted-GPS SMLC

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GSM LCS Methodologies

Two Mobile Station Location Methodologies MS-Assisted = Location Computation in Network MS-Based = Location Computation in MS

Two Location Transaction Modes Broadcast mode

Periodic Short Message Service Cell Broadcast (SMSCB) onBroadcast Control Channel (BCCH)

Point-to-Point messaging mode (request/response)

Standalone Dedicated Control Channel (SDCCH) in idle mode Fast Associated Control Channel (FACCH) in dedicated mode Slow Associated Control Channel (SACCH) in dedicated

mode

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GSM Point-to-Point Mode

GPS Assistance Data Element providesseveral information elements Reference Time (optional)

GPS Time Assistance information (optional) Nominal size - 3 bytes per satellite Produces ~3dB sensitivity improvement Allows LMU-independent GPS time dissemination

Reference Location (optional) DGPS Corrections (optional) Navigation Message Bits (optional) Acquisition Assistance (optional)

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GSM Broadcast Mode

Broadcast SMSCB messages with four dataelements Reference Time (mandatory)

GSM Time (optional)

GPS Time (mandatory) Reference Location (mandatory) Differential (DGPS) Corrections (optional) Navigation Message Bits (optional)

Produces ~3 dB additional sensitivity improvement Allows LMU-independent GPS time dissemination capability Incremental means for Navigation Model update

Reduces requirements for point-to-point messages

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Scenario1: GSM Broadcast

Handset listens to broadcast messages to Receive navigation message bits for GPS SVs (satellites

in view)

Acquire one or more GPS SVs

Determine/maintain GPS time Software-based method utilizing navigation message bits

Incrementally update Navigation Model

Ready for location requests from user or network

Supports MS-based or MS-assisted solutions

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Scenario2: Point-to-PointMode

Handset is powered on Scenario 1 operation commenced Location request initiated by user or network Resident GPS assistance data evaluated If data insufficient, point-to-point mode

entered

Required assistance data requested/received Required location request performed Transition back to Scenario 1

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MS Assisted Sample GSM CallFlow

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MS Based GSM Call Flow

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WAG Performance

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WAG PerformanceExpectations

High Performance High Sensitivity (inside, urban canyons, etc.)

Rapid First Fix (

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Global Validation

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Conclusion

Cell-ID meets cost objectives, supports roaming, but provides generallypoor performance and poor ROI,

E-OTD provides good performance, but has severe roaming limitations,is expensive, is limited to GSM networks and provides poor ROI,

OTDOA provides average performance, but has severe roaminglimitations, is expensive, is limited to WCDMA networks and provides

poor ROI, A-GPS provides very good performance, is relatively inexpensive,

supports roaming, can be used on all networks and provides good ROI, A-GPS hybrid combinations of A-GPS + Cell-ID provide very good

performance, support roaming, optimize yield, minimize the cost of thehybrid implementation and provide ROI on par with A-GPS solutions,

A-GPS hybrid combinations with spot deployments of E-OTD or OTDOAare also viable, but the complexity and cost of these implementationsincreases over the A-GPS + Cell-ID hybrid because of the need forLMUs in the network to support E-OTD/OTDOA, which can decreasethe ROI.

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Hybrid Technology

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References

Andrew S. Tenenbaum, Computer Networks. http://isi.edu Location Based Services, A Strategic Analysis of Wireless Technologies, Markets, and

Trends; Frank Viquez, AnnaLee Dragon, Tim Archdeacon; Allied Business Intelligence;1Q, 2001

Ready or Not, Mobile Location Technology is Here!; Allen Nogee; Cahners In-Stat Group;March 2001

European Wireless Location Services; Jake Sanders, Jamie Moss, Stephan Beckert; TheStrategis Group; March 2000 Synchronous vs. Asynchronous Deployment of WCDMA Effect on Communication

System Performance; QUALCOMM; publish date September 2001 GSM Mobile Location Systems; Omnipoint Technologies, Inc.; Document #0710009-00B,

1999 Determining Location Using Wireless Networks; Gunter W. Hein, Bernd Eissfeller, Jon O.

Winkel, and Veit Oehler; GPS World; March 2001

Synergies Between Satellite Navigation and Location Services of Terrestrial MobileCommunication, Gunter W. Hein, Bernd Eissfeller, Jon O. Winkel, and Veit Oehler;Institute of Navigation; September 2000 Conference Proceedings, September 2000.

http://www.fcc.gov/e911 ; FCC mandate for Docket 94-102 http://gullfoss2.fcc.gov/cgi-bin/websql/prod/ecfs/comsrch_v2.hts ; Carrier Filings on

performance relative to FCC mandate 94-102

http://isi.edu/http://www.fcc.gov/e911http://gullfoss2.fcc.gov/cgi-bin/websql/prod/ecfs/comsrch_v2.htshttp://gullfoss2.fcc.gov/cgi-bin/websql/prod/ecfs/comsrch_v2.htshttp://www.fcc.gov/e911http://isi.edu/

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Thank You