Harald Ludwig, chairman of the TCCA Technical Forum, looks at the TETRA Interoperability Certification Process – the basis of TETRA’s ongoing market success.

There are various types of interoperability – organisational, between agencies or people; regional, between regions, across national borders, and technical – between equipment.  When we talk about interoperability in the TETRA market, we are referring to the technical interoperability between the products from different manufacturers.

Our approach to interoperability (IOP) ensures that TETRA equipment from one manufacturer works with TETRA equipment from another manufacturer, and vice versa.

Testing programme

TETRA offers true interoperability achieved through the Interoperability Certification Process, a strict, independent and tightly controlled testing programme, originally developed by the TETRA MoU – now the TETRA + Critical Communications Association (TCCA) – to ensure a truly open multi-vendor market.

The IOP gives TETRA customers and users the confidence that equipment is interoperable, ensures that TETRA is an open standard, and has enabled and continues to drive a multi-vendor TETRA market.

A healthy, competitive market brings proven benefits to users such as choice of equipment and supplier, continuous development of new products, increased product functionality and improved price performance. 

For manufacturers, it eliminates different and incompatible implementations of the TETRA standard, and provides a formal compatibility test forum. Users can be confident that products awarded an IOP certificate have been rigorously tested, and that the functions listed on the certificate fully meet the TETRA standard. This allows users selecting equipment from a number of suppliers to reduce the amount of system integration and testing. 

Each IOP certificate issued is for a specific infrastructure-radio terminal combination. The first IOP certificates awarded in 1999 were to four companies that remain leading forces in the TETRA market – although the names have changed. These first recipients were Marconi (now Selex Elsag), Motorola (now Motorola Solutions), Nokia (now Cassidian), and Simoco (now Sepura). Today more than 740 IOP Certificates have been issued.

The TETRA IOP process is managed by the Technical Forum, a TCCA Working Group. Targets and priorities are set each year in agreement with the Operators & Users Association (OUA). 

ETSI standards

All testing is based on ETSI standards. For each feature that is to be certified, a TETRA Interoperability Profile (TIP) specification is created, together with an Interoperability Test Plan. The Test Plan is a detailed document that ensures that the tests are repeatable and identical in all test sessions. After the TIP and Test Plan have been approved, test sessions can be conducted. 

The IOP Testing verifies the conformance of the signalling (layer 3) of the TETRA Air Interface protocol stack with the TIPs, and is carried out under controlled conditions in a laboratory environment. Testing is done in a specific frequency band and with a specific encryption algorithm, but since the same protocol stack software is used for different frequency bands and encryption algorithms the IOP certificate is valid for all frequency bands and all encryption algorithms.

The TCCA contracts an independent testing house to act as the certification authority for TETRA. This is the Istituto Superiore delle Comunicazioni e delle Tecnologie dell’Informazione (ISCOM), an organisation of the Italian Ministry of Economic Development. Sessions are carried out in a multi-vendor environment, and test the interaction between TETRA terminals – voice and data – on infrastructure from different suppliers. 

After each session, the testing house analyses the test results and issues an official IOP certificate that lists each feature and function that has successfully passed its test. Test schedules and certificates are posted in the public domain on www.tandcca.com.  Detailed test reports are available to TCCA Members.

IOP testing is a voluntary process, but its value is such that every TETRA manufacturer is involved in the programme.  Potential customers can see all the IOP certificates for reassurance that the devices are proven to work on and across all TETRA manufacturers’ infrastructure. With that knowledge, users can concentrate on choosing the terminal that best suits their needs in terms of design, form factor, features, price, and particular requirements such as covert or intrinsically safe. 

The TCCA Technical Forum is currently working on automation of the IOP tests, to speed up testing and increase the test coverage. Phase 1, due for completion by the end of this year, will see 76 of the 1000+ test cases automated, including automatic execution and automatic log file analysis.

Approaching our 15th year of testing, there is no doubt that the TETRA IOP has been a critical enabler for the highly successful multi-vendor TETRA market. Although other PMR technologies have taken the TETRA lead and instigated their own interoperability testing programmes, none is as comprehensive as the TETRA IOP. 
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