interoperation
terminal number in the foreign network. A kind of prefi x may be needed in order to dial direct. A second tactical patch scenario is to interconnect
overlapping networks from diff erent organizations (see diagram at the foot of the preceding page). In this case, users working in diff erent radio networks may need to communicate with each other during an incident or event. Authorization for co-operation is typically granted by the offi cer in charge within the control room of the regional or nationwide network. Some examples are:
collaboration between public and private fi re brigades during a large-scale incident or disaster. Private fi re brigades are typically deployed by airports, tunnel operators and large industrial plants.
communication between security personnel and public safety offi cers during incidents in sports stadiums, airports, shopping malls.
communication between armed forces and police offi cers. Military personnel operating on a private system at a military base or compound can interoperate with public safety offi cers during events or incidents.
communication between fi re brigades, police and medical services during a large-scale incident or disaster, where these agencies operate their own independent networks.
connecting a rapid-deployment radio system to the regional or countrywide network to scale up capacity during a large- scale incident or disaster. Here, both networks are supervised by the same user group. In these scenarios, group calls are basically the only means
of communication. T e tactical patch connects two (or more) normally unrelated talk groups within two separate networks.
Scenario 2: expand coverage To expand coverage of an existing radio network by deploying additional networks requires multiple radio
Individual call Group call
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Issue 2 February - April 2011 TE TRA TODAY IP network
Left: expanding coverage by deploying
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additional networks – a challenging problem for current technologies
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networks to act as one single radio network. T is is challenging, because all current radio networks are based on proprietary architectures and thus cannot be integrated easily. T e need for this scenario (see diagram below) is obvious.
It provides choice for the end user when there is a need to expand coverage or capacity. T e user need no longer rely on the original supplier only and can thus avoid vendor lock-in. With TETRA, the terminals should be able to work in
both networks without reprogramming. T is means that the Mobile Country Code (MCC) and Mobile Network Code (MNC) must match, and the same subscriber database must be shared by both networks. In practice, this is possible only if the networks are operated by the same agency. Support of a rich set of functionalities will also be expected.
T ese may include group calls, individual calls, text and status messaging, roaming, effi cient cell handover, packet data gateways, encryption, authentication, and supplementary services such as calling line identifi cation, talking party identifi cation, pre-emptive priority etc.
Scenario 3: migration to another network T is scenario is very similar to mobile phone roaming to a foreign cellular network. When the radio is moved beyond the coverage area of its
home network, it starts searching for other radio networks. If the foreign network indicates that it supports migration, the radio terminal will attempt to register on it as a visitor. Using an authentication-based handshake mechanism, authorized radio terminals will be granted access as visitors to the foreign network. In TETRA, this scenario is referred to as migration. T e objective of this scenario is identical to that of the
TETRA Inter System Interface (ISI). But because the ISI is currently limited to supporting individual calls and SDS and
MS 2 MS 3
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