TETRA Trunk Wide Area System solution is presented in crypto and non-crypto formats to users listed below;
- Demanding use in a wide area,
- In need of data communication very often,
- In need of a system management centre due to requirements such as audio / data traffic and tracking radio locations,
- Have high number of user groups and the call frequency,
- It is important to use Time-Division Multiple Access (TDMA) because it is important to efficiently allocate the frequency in the region where the communications will take place,
- Generally located in towns and city centres.
ASELSAN, provides infrastructure (base stations and switching unit) and integration / installation solutions for Tetra Trunk Wide Area architecture.
In TDMA technology, while a call is on the physical channel, another user may initiate a call and continue two different calls on the same physical channel while a physical channel determined in the FDMA technology (e.g., a channel with a bandwidth of 12.5 kHz) is available only by the caller initiating a call. When the number of time slots is increased, the number of calls that can be performed on the same physical channel increases. Since TETRA communication protocol has four time slot TDMA structure, four different calls can be made in the same physical channel and thus ensuring frequency efficiency.
In the trunk system architecture, each base station has "control channel (time slot)" and "traffic channels". All radios within the range of the base station wait on the control channel. If there is a call in any of the radio groups, all the radios in that group move from the control channel to the traffic channel assigned for that call. [The term "channel" here refers to the logical channel. Since the TETRA protocol has 4 time slots (TDMA with 4 time slots), each repeater radio supports 4 logical channels in 1 physical channel. Other groups continue to wait on the control channel. If there are calls in the waiting radio groups, a new traffic channel is assigned for this call. The higher the number of traffic channels, the more number of users can serve the same group of users. If all the traffic channels in the base station are occupied, this call is queued, if a new call is to be initiated, and this call is made in this traffic channel if any of the traffic channels is again eligible.