Conventional vs. Trunked Two Way Radios Systems

There is a range of two-way radio technologies, systems, and types. There are families of radio types and each family has differing sub-groups and specific radio models.

Increasing demands on frequency spectrum, a finite resource, force users to look for more spectrum-efficient systems, in addition to increased features. System planners (especially those in public safety agencies) may need to conduct a wide range of comparative analyses to determine the type of system that is most appropriate for their environment and requirements.

In general, Land Mobile Radio (LMR) systems are designed using one of three architectures: conventional, trunked, or hybrid of the two. The selection of one over the others is based on a range of factors. It includes spectrum, technical features, operational requirements, and cost considerations.

Conventional radios operate on fixed RF channels. In the case of radios with multiple channels, they operate on one channel at a time. The proper channel is selected by a user. In multi-channel systems channels are used for separate purposes. For instance, Channel 1 can be allocated to road crews to talk to road maintenance office and Channel 2 can be assigned to talk to state highway department crews.

At the present time the land mobile frequency spectrum is very crowded and additional frequencies are difficult to obtain.  For this reason there has been a great deal of work in developing new techniques to conserve spectrum. Trunking is one of these conservation systems.

The trunked radio systems differ from the conventional radio systems. Trunked radios are much more complex controlled radio systems where the use of a pool of channels is made available for different groups of users known as talk groups. In contrast, conventional radio system provides communications between users within a given geographic coverage area.

In terms of spectrum used, trunking is more efficient than the conventional system as it has the ability to switch between multiple radio channels. This allows less congestion and can accommodate greater number of users to a number of radio channels.

The quantity of simultaneous conversations is limited by the number of discrete channels, minus one. Trunking does not increase the number of possible concurrent radio conversations beyond the quantity of discrete radio channels. Rather, trunking permits the discrete channels to be dynamically assigned in a manner that is more efficient than non-trunked systems.

Trunked radio technology addresses some specific business problems, however it has major drawbacks. Sales tactics are aggressive and countless systems are sold to clients that would be better off without them.

Trunking allows a system to serve more users with the same amount of spectrum or less.  Since spectrum has become a scarce resource, this property of trunking will drive its use in the future.