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GSM / UMTS conformance testing

An overview or tutorial about the basics of GSM and UMTS cellular phone conformance testing and the way that GSM and UMTS testing is handled by organisations such as GCF, PTCRB, TIA, etc.

The process for conformance testing for GSM and UMTS is well defined and operates well. The conformance test approval process is run by the industry itself and is effectively self regulating. However the overall GSM / UMTS conformance testing process works well, and the fact that all phone designs have to pass the conformance test process means that the number of problems discovered with phones is very low. Additionally as all phones conform to the same standards, it is possible to roam from one network in one country to another network in another country with no problems, provided that there are agreements betweent he oerpators. This has been one of the major reasons fort he global success of GSM, and much of this can be attributed to the conformance test process.

For GSM these test cases were written in prose, and they described the test itself, the set-up conditions as well as the applied stimuli and of course the pass and fail criteria. It was then possible for each test equipment manufacturer to implement these tests on their equipment. However to ensure that the tests are a faithful implementation of the original intent, a validation and certification process has been set up. The conformance test cases were originally defined by ETSI (European Telecommunications Standards Institute) for GSM, but they are now controlled by 3GPP (Third Generation Partnership Project).

Once the manufacturer is satisfied that the test operates satisfactorily he provides it to an independent validation organisation that will test it and for conformance with the original test case. Assuming that the test case satisfactorily passes this process then it is presented to an industry body for certification. Once it has achieved this status then it can then be used for formal handset testing and certification.

The organisation that has overall control of the test cases for GSM and UMTS is 3GPP. However changes are handled by the GERAN (GSM Enhanced Radio Access Network) working Group for GSM and a group known as the T1 group for UMTS. The validation and approval of the implemented test cases is then handled by the GCF (Global Certification Forum).

The North American version of GSM running in the 1900 MHz band is often referred to as PCS (Personal Communications System) and there is another allocation at 850 MHz. A group known as PVG (PCS Validation Group) handles the approvals and their results are ratified by PTCRB (PCS Type Certification Review Board). Phones are then tested against the test cases which if successful are certified by CTIA. To achieve CTIA certification, it is necessary for phones to be tested in CTIA approved laboratories.

As might be expected, experience gained on GSM has been reflected into improvements for the new third generation UMTS system. One of the main changes is that the protocol test cases, are initially written in prose and then converted into TTCN (Tree and Tabular Combined Notation) to be made available to the industry. This language enables the test cases to be compiled into a format that can be run directly on the target test equipment. This approach saves time for the industry as a whole and reduces costs because generating the test cases is far easier to achieve. The main advantage is that it gives far more consistency across the industry as tests are no longer open to the same level of interpretation that they were before. This also saves time in the validation process.

The TTCN test cases have been prepared by a team of industry experts based at ETSI working on behalf of 3GPP. They prepared the basic TTCN code that was reviewed within the 3GPP community using email reflectors. By reviewing the software in this way at the beginning of the process, the individual test cases do not need to be reviewed each time they are submitted by a test equipment manufacturer for validation.

To test a new handset, the manufacturer generally approaches a qualified test house who will possess a variety of different test systems. They will then run the required certified test cases and be able to present a case for a handset being suitable for use on the available networks.

By Ian Poole

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