Roaming

Need for cooperation
The world is changing towards one where both people and organisations need to communicate across wider regions than before and that is setting new requirements to the interoperability of communications systems. European Public Safety community has recognised the need for efficient cooperation across the national borders to be able to respond to the challenges of an evolving operating environment. Cross-border cooperation of European police forces and customs has been officially agreed and defined in the documents of the Schengen Agreement between 13 European countries. Additional information concerning the Schengen agreement can be found for example via the following EU web pages titled ‘Abolition of internal borders and creation of a single EU external frontier’.

Equally important in some regions is the capability of fire, rescue and ambulance services to provide mutual aid to their neighbours when needs arise. Neighbours can in these cases be in the next town, another province or neighbouring country, but the basic need for efficient joint operations remains the same.

Users have taken the initiative
The Three-Country Pilot between the Belgian, Dutch and German ministries has been working together for several years to define tactical scenarios, to test the operational procedures and to define operational requirements for the radio systems. Recently the project has also been expanded to include the French government and the name of the project is changing accordingly. Please see www.3countrypilot.com.

TETRA Inter-System Interface gives the tools
The technical means for providing cross-border cooperation and roaming between networks are provided by the TETRA Inter-System Interface (ISI). The TETRA ISI standards define common protocols to support all the important services between interconnected networks:
   – roaming and mobility management of radios between networks
       (roaming is called ‘migration’ in the TETRA standards)
   – security, i.e. authentication and encryption
   – individual calls in visited network and between networks
   – group calls in visited network and between networks
   – supplementary services to support e.g. emergency calls
   – status and short data messaging

It should also be noted that interconnection of IP packet data services is defined in other TETRA standards and IP gateway solutions are available today.

Interoperable implementations of the TETRA ISI functionality are specified in the TETRA Interoperability Profile (TIP) specifications produced by the TETRA Association and those are already available for manufacturers.  The relevant Test Plan documents for ISI certification test sessions are currently being prepared, the plans for ISI Individual Call and ISI Mobility management were completed late 2005. The first Interoperability Certificates have been issued in accordance with the Air Interface Migration TIP that specifies the air interface signalling for roaming.

To summarise, TETRA roaming solutions are a reality today and certified TETRA ISI interfaces are keenly expected by an increasing number of users. 

See also Mobile Country Codes for TETRA