Users have morechoices when selecting radio communications systems than ever before. Itshould consider which system architecture should be implemented to meettechnical, operational, and environmental requirements.
Thereis a range of two-way radio technologies, systems, and types. There arefamilies of radio types and each family has differing sub-groups and specificradio models.
Increasingdemands on frequency spectrum, a finite resource, force users to look for morespectrum-efficient systems, in addition to increased features. System planners(especially those in public safety agencies) may need to conduct a wide rangeof comparative analyses to determine the type of system that is mostappropriate for their environment and requirements.
In general, Land Mobile Radio (LMR) systems are designed using one of threearchitectures: conventional, trunked, or hybrid of the two. The selection ofone over the others is based on a range of factors. It includes spectrum,technical features, operational requirements, and cost considerations.
Conventional radiosoperate 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-channelsystems channels are used for separate purposes. For instance, Channel 1 can be allocated to road crews to talk toroad maintenance office and Channel 2 can be assigned to talk to state highwaydepartment crews.
At the present timethe land mobile frequency spectrum is very crowded and additional frequenciesare difficult to obtain. For this reasonthere has been a great deal of work in developing new techniques to conservespectrum. Trunking is one of these conservation systems.
The trunked radio systems differ from the conventional radio systems. Trunkedradios are much more complex controlled radio systems where the use of a poolof channels is made available for different groups of users known as talk groups.In contrast, conventional radio system provides communications between userswithin a given geographic coverage area.
In terms of spectrum used, trunking is more efficient than the conventionalsystem as it has the ability to switch between multiple radio channels. Thisallows less congestion and can accommodate greater number of users to a numberof radio channels.
The quantity of simultaneous conversations is limited by the number of discretechannels, minus one. Trunking does not increase the number of possibleconcurrent radio conversations beyond the quantity of discrete radio channels.Rather, trunking permits the discrete channels to be dynamically assigned in amanner that is more efficient than non-trunked systems.
Trunked radiotechnology addresses some specific business problems, however it has majordrawbacks. Sales tactics are aggressive and countless systems are sold toclients that would be better off without them.
Trunking allows a system to serve more userswith the same amount of spectrum or less.Since spectrum has become a scarce resource, this property of trunkingwill drive its use in the future.
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