Trunking Advantages of TETRA
Trunking techniques have been used for many years in switched telephone networks. The first trunked mobile radio communication systems were deployed as early the 70s’ in North America with proprietary signalling protocols and shortly afterwards in Europe using analogue MPT1327 technology.
The main benefit of trunking is normally seen as spectrum efficiency, or more radio users per RF channel for a given Grade of Service (GoS), brought about by the automatic and dynamic assignment of a small number of communication channels shared amongst a relatively large number of users.
From a radio users point of view, spectrum efficiency does not mean anything. What users want is to solve all the operational problems associated with conventional PMR, yet still retain the simplicity of conventional open channel ‘all informed net’ operation. The fundamental element of trunking that solves these conventional PMR problems is the use of a control channel to enable the automatic and dynamic assignment of voice traffic channels amongst mobile radio users.
Additional Services and Facilities
As the control channel acts as a signalling communications link between the Trunking Controller and all mobile radio terminals operating on the system, the Trunking Controller knows the status of the system at any moment in time as well as its historic usage, which is stored in its memory. For example, the Trunking Controller knows:
- The individual and group identity of all radio units registered on the system
- The individual identity and time radio units registered on the system
- The individual identity and time radio units de-registered from the system
- The individual and group identity, time and duration of all messages
With additional intelligence in both the radio terminals and the trunking controller the advantages and benefits of trunking can be increased. For example, the length of the control channel signalling messages can be increased by a set amount to accommodate a variety of new services and facilities. Also, the trunking controller can be programmed to handle calls in a variety of ways as required by the operator of the system.
Source: TETRA Association