How to Test A-GPS Capable Cellular Devices and Why Testing ... · and location accuracy in impaired...

How to Test A-GPS

Capable Cellular Devices

and

Why Testing is Required

Presented by:

Agilent Technologies

February 4, 2010

© 2010 Agilent Technologies &

ETS-Lindgren, L.P.

Page 1

Agenda

Introduction to A-GPS

Why Test A-GPS Performance?

Types of A-GPS Testing

February 4, 2010


ETS-Lindgren, L.P.Page 2

Origins of A-GPS:

US FCC E-911 and

EU E-112 Requirements•U.S. FCC mandates that 100% of new digital handsets sold in

the U.S. are Automatic Location Identification (ALI) capable

•Phase II of FCC E-911 implementation requires location

accuracy within 50-300 meters depending on location method

•Wireless carriers are responsible for meeting these

requirements

•Assisted GPS (A-GPS) was developed to optimize coverage

and location accuracy in impaired satellite reception areas such

as inside structures or multipath fading

•European Union requires caller location information to be

shared with emergency authorities when a 112 call is placed

February 4, 2010



GPS vs A-GPS:

Time To First Fix

Up to 12min!

Time To First Fix

< 20secs!

February 4, 2010



A-GPS worldwide deployment

Percentage of phones shipping with integrated GPS receivers

is increasing – 90% of smart phones expected to have GPS by

2014. In 2008, only one in three smart phones had GPS.

A-GPS capability is becoming a standard feature for smart

phones

February 4, 2010



Trends in Applications using A-GPS

•Assisted GPS (A-GPS) has driven growth in

high-precision applications like navigation,

geotagging, and tracking

•Continued trend upward due to wide range of

independently developed applications with

location-based content

•Today’s smart phone applications utilize A-GPS

for everything from social networking and

restaurant searching to mapping and stargazing

February 4, 2010



Overview




February 4, 2010



Why Test A-GPS Performance? Location Based Services

End user satisfaction and safety depend on A-GPS performance

The US wireless carriers tasked the CTIA with developing a test

plan for determining over-the-air (OTA) performance of A-GPS

devices.

• The CTIA currently operates a certification program that determines OTA

performance of cellular radios.

Version 3.0 of the CTIA Over-the-Air Performance Test Plan

requires A-GPS testing.

Wireless Carriers already require phones they purchase to have

A-GPS OTA performance data.

February 4, 2010



Why Test A-GPS Performance? The Link Budget

An over-the-air communication link is usually characterized by

the concept of a link budget.

The quality of the link is a function of:

• The radiated power of the transmitter

• The sensitivity of the receiver

• The quality of the radio channel between transmitter and receiver

– Includes path loss between transmitter and receiver as well as

interference sources

February 4, 2010



Why Test A-GPS Performance? The Link Budget

For traditional cellular networks, carriers have several choices to

improve link quality

• Increase transmitted power (up to regulatory limits)

• Improve receiver sensitivity (up to physical limits)

• Move transmitter and receiver closer together (requires adding more base

stations to increase network density)

• Reduce interference (where they have control over interferers)

For A-GPS, the location and power of the transmitter are fixed

by the design of the satellite network.

Performance can only be improved by improving the

performance of the A-GPS receiver.

February 4, 2010



Why Test Over-the-Air A-GPS Performance? The Antenna Assumption

In practice, this is only a first approximation. Various interaction

factors occur between the radio, antenna, device platform, and

objects found in the near field of the device and alter the

resulting performance of the device. These include:

• Impact of device body on radiation pattern

• Impact of head and hand on radiated performance

• Mismatch between antenna and receiver

• Platform interference (desensitization), including cellular radio

• Cabling effects

Only by testing in a radiated over-the-air test environment can

we be sure to capture the direct impact of all performance

impairments on the A-GPS receiver.

February 4, 2010



Overview




February 4, 2010




Over-the-Air A-GPS

Conformance System

Bench-top Pre-conformance

February 4, 2010



Base Station

Emulator

GPS Simulator

A-GPS Test Systems

DUT

Multi-AxisPositioner

Dual PolarizedMeasurement

Antenna

Fully Anechoic Chamber

RF AbsorberMaterial

MeasurementSignal Path

CommunicationAntenna

CommunicationSignal Path

Base StationEmulator

Signal Conditioning

RF SwitchMatrix

BroadbandSignal Analyzer

SatelliteSimulator

A-GPS OTA Test Setup

(radiated)

A-GPS Design Verification/Functional Test

Setup

(conducted)

February 4, 2010



How do they differ?

DUT

Multi-AxisPositioner

Dual PolarizedMeasurement

Antenna

Fully Anechoic Chamber

RF AbsorberMaterial

MeasurementSignal Path

CommunicationAntenna

CommunicationSignal Path

Base StationEmulator

Signal Conditioning

RF SwitchMatrix

BroadbandSignal Analyzer

SatelliteSimulator

A-GPS OTA Test Setup

(radiated)

Fixed Parameters

• Satellite base location

• Relative power of satellites (sat to sat)

Variable Parameters

• Antenna position

• Satellite power (composite)

February 4, 2010



How do they differ?

Fixed Parameters

•Antenna position (“ideal” antenna)

Variable Parameters

•Satellite Power (composite)

•Relative Satellite power

•Satellite Scenario (base location i.e. Atlanta/Sydney

•Satellite orbital location with respect to mobile station

•Assistance data delivered

•Satellites LOS or multi-path

•Assistance data delivery method (user/control plane)

GS-9000 SW

and/or Location

Server

A-GPS Design Verification/Functional Test Setup

(conducted)

Base Station

Emulator

GPS Simulator

February 4, 2010



Conducted A-GPS Systems

Design Verification System

• Perform “What if” analysis

• Room for design specific tests

• General less expensive

Conformance System

• Parameters are pre-set

• Generally high cost

February 4, 2010



Design Verification/Functional Testing

Location

Satellite Position

Assistance Data

Path Effects

Power

What if?

T0Tn

Time

February 4, 2010



A-GPS Test Solution Overview

User

Assistance Data

Cellular Network

Base Station Emulator

GPS Assistance

Server

Satellite Simulator

Location Server

Emulator

Control Plane mode

User Plane mode

Network Downlink:

Coarse Time

Ephemeris Data

Location, Almanac

Automation

Software

February 4, 2010



What Now?

February 4, 2010



Agilent GS-9000 A-GPS Design Verification

Systems

Scalable systems for R&D engineers who are designing and testing A-GPS

capabilities in chipsets and mobile devices.

R&D Product Life Cycle

Prototype Phase Pre-Certification Certification

GS-9000 Lite

GS-9000 Standard

February 4, 2010



GS9000-Lite Capabilities

3GPP Defined Test Cases 2G/3G (51.010/34.171)

Sensitivity Coarse Time Alignment (70.11.5.1/5.2.1)

Nominal Accuracy (70.11.6/5.3)

Dynamic Range (70.11.7/5.4)

TTFF (time to first fix)

Raw satellite data (Satellite ID, C/No, Doppler, Code

Phase, and Pseudo Range Error)

Reporting of latitude and longitude with mobile based

methodology

2D error calculation and reporting

Multiple GPS scenarios (8)

Individual satellite power control

GPS time advancing

Sensitivity searches

Power Sweeps

User friendly GUI, Test executive, test automation

6

+2

February 4, 2010



GS9000 Standard Capabilities3GPP Defined Test Cases 2G/3G (51.010/34.171)

Sensitivity Coarse Time Alignment (70.11.5.1/5.2.1)

Sensitivity Fine Time Alignment (70.11.5.2/5.2.2)

Nominal Accuracy (70.11.6/5.3)

Dynamic Range (70.11.7/5.4)

Multi-path performance (70.11.8/5.5)

Moving Scenario and Periodic Update (5.6)

SUPL Server Support

TTFF (time to first fix)

Raw satellite data (Satellite ID, C/No, Doppler, Code Phase, and Pseudo Range

Error)

Positions estimation with mobile assisted methodology

Reporting of latitude and longitude with mobile based methodology

2D error calculation and reporting

12+ GPS Satellite Simulation

User defined GPS scenarios

Individual satellite power control

GPS time advancing

Sensitivity searches

Power Sweeps

Complete test executive for test plan creation and execution

11

February 4, 2010



A-GPS Automation Software

Data Viewer

Calibration

Assistance Data Generator

GS-9000 Test Executive with A-GPS Libraries

Protocol Logging

February 4, 2010



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