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GPS-enabled, location-based services are the next big thing in mobile handsets. But how is the new function most efficiently tested? In this article, we learn the key test careabouts.
November 27, 2006
URL:http://drdobbs.com/mobile/testing-gps-functionality-on-gsm-mobile/196502851
GPS-enabled, location-based services hold out considerable promise as a valuable revenue generator for wireless carriers. Their extension beyond the realms of the emergency services and into the commercial arena looks set to open up a significant opportunity for wireless carriers to provide their subscribers with value-added applications and services utilising location-based functionality.
Consequently, they are becoming a powerful motivator in the development of new mobile handsets that incorporate high accuracy Assisted GPS (A-GPS) technology. But, as always, time-to-market and cost-to-market are critical.
Reducing development time is fundamental to ensuring rapid deployment of new mobile handsets with location features. Needless to say, however, this conflicts with the testing complexity that results from a constantly evolving LBS feature set and the requirement for compliance testing before a new mobile handset can be launched.
Out of the lab, into the field
Until recently, handset testing has taken place mostly in the laboratory. But the rapidly emerging development and conformance test requirements for A-GPS based mobile handsets, as well as time-to-market pressures and the need for field trials has created a pressing need among OEMs for in-field testing of mobile handsets.
The solution must provide GSM/(E)GPRS network emulation, a well-proven technology platforms, and software environments for development and conformance testing,
Typical of such test platform's is Aeroflex's fully integrated A-GPS test solution. It is based on its well-proven 6103 AIME and 6103 AIME/CT mobile handset test systems.
The integrated 12 channel NLC"L1"AGPS Constellation Simulator' from Navigation Laboratories is widely used in global avionics, defence, and space applications.
The platform emulates the entire 24 satellite GPS constellation and provides high performance modelling of all associated GPS satellite and vehicle effects, to provide a complete environment for developing and testing A-GPS devices, and this functionality is included in Aeroflex's A-GPS solution.
The systems support MS-Based and MS-Assisted positioning methods, and provide analysis of the pseudo-range and latitude/longitude location response for the unit under test.
Support for control and user plane techniques using RRLP allows simulation of the standard A-GPS call flow location requests for Control Plane, and for User Plane the capability to support TCP/IP interface and SUPL (Secure User Plane). RF minimum Performance testing of the GPS receiver is also a key test requirement. Aeroflex is currently participating at 3GPP GERAN meetings as the Minimum performance test specifications are being developed.
The standard real time logging and decoding of the protocol signalling messages between mobile and simulated network has been enhanced to support the control and user plane messaging. A complete decode of the A-GPS message content is provided in an exclusive application window.
The test environment
The A-GPS functionality should be a fully scaleable upgrade that can be added to both the basic test platform such as the 6103 AIME and 6103 AIME/CT systems. This allows the OEM to support the development lifecycle of A-GPS devices from initial R&D through to conformance test.
Development: R&D requirements must focus on state machine debugging, protocol stack design and regression testing. In addition, a scripting environment and powerful API such as that found in the AIME platform provide complete testing flexibility.
Scripts can easily be created to run development test simulations for specific A-GPS elements of a mobile handset's operation through to complex simulations that emulate a field environment. Example test scripts include access to each Layer of the protocol structure including the RRLP messaging and the ability to define any RRLP protocol message such as the configuration of the Assistance Data content
An intuitive user interface such as the 6103 AIME's can provide a number of features designed to support A-GPS test requirements such as real time logging, decoding of detailed protocol signalling messages between the mobile handset and network, A-GPS results analysis of the device under test and the generation of log files to allow off-line protocol analysis.
It also includes the colour coding of information to improve readability, the ability to synchronise traffic (Layer 2, Layer 3 including RRLP protocol frames) and an exposed COM based API allowing example scripts to be written in any COM compliant language.
Conformance: The 6103 AIME/CT + Navigation Laboratories NLC-L1-AGPS GPS Constellation Simulator, platform 69 at the Global Certification Forum (GCF) and PCS Type Certification Review Board (PTCRB), can easily be upgraded from a 6103 AIME system. This upgrade enables the user to execute validated 3GPP conformance test cases. Conformance testing is required during the latter stages of the development lifecycle of a GSM device in order to verify that the implementation is fully compliant with the 3GPP standards prior to formal certification at an independent test laboratory.
Within the conformance environment, the automated report generator and analysis software produces detailed results analysis defined in accordance with the associated conformance standards.
Test Cases
A-GPS conformance testing requires a fully compliant test cases as listed in 3GPP TS51.010 section 70. Test cases are currently being validated and will be submitted within the next month to GCF and PTCRB. These test cases can be run in any combination or in a campaign of GSM, (E)GPRS, AMR, DTM, DARP and GAN test cases for use in terminal regression test plans.
The test cases are fully automated ensuring that the network emulator hardware and the GPS simulator are configured to the user's requirements. In the development environment, test cases are user modifiable allowing parameters to be changed for testing beyond the test standards. In the conformance environment, test cases are not modifiable to ensure that every test run complies with the appropriate test standard.
Test case options are:
6103G-695 - 3GPP TS51.010 section 70.7.x Assisted GPS Network Induced Tests
6103G-696 - 3GPP TS51.010 section 70.8.x and 70.9.x Assisted GPS Mobile Originated/Terminated Tests
The GPS simulator
The GPS simulator provides a feature rich emulation environment that supports the complete modelling of the complex effects required for verification and evaluation of all characteristics of GPS equipment performance.
It combines and integrates an RF signal generator, with scenario development and modelling software within a Windows operating system. The flexible but intuitive user interface ensures that the software meets the needs of operators of varying levels of experience.
The simulator is supplied with pre-written GPS scenarios, developed to 3GPP minimum performance standards. The scenarios include GPS Accuracy (moving and stationary), GPS Sensitivity, GPS Dynamic Range and GPS Multipath
The Scenario Generation operating mode (such as the one optionally supplied with Aeroflex's the development solution) provides an operator interface that allows modification of the configuration, environmental and dynamic vehicle modelling in addition to the GPS system functions.
The 3GPP GPS referenced scenarios are file based and can be deterministically executed. The graphical user interface provides simple to use pull-down menu bars and buttons within the modelling and scenario generation software to allow the operator to modify or develop their own scenarios to test above and beyond the conformance standards.
About the author
Daniel Quant is the Product Marketing Manager for the Wireless Division of Aeroflex Test Solutions, Slough, Berkshire, UK.
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