Trunked Radio Systems - An outline to application

What is a trunked radio system?

Trunking is a spectrally efficient method of utilising a number of individual channels in a cohesive system of radio traffic management. In conventional radio systems, each mobile only has access to one radio channel. However, with trunking, the mobiles operating on the system have access to a pool of channels. When a mobile becomes involved in communications, one of the unused channels is dynamically assigned for use. This assignment lasts for the duration of the call. After this time, the channel is returned to the pool for future use by another mobile.

The efficiency of the system depends on good design based around sound engineering principles, including the grade of service required and the additional facilities which the service may have to cope with. Poorly engineered systems may need more channels than an untrunked system to provide the same level of service e.g. a three channel trunked system with a permanent control, is less efficient than a three channel untrunked system. As such, the granting of trunked systems is not automatic, even if the new system will be using existing channels.

Subject to assessment, as outlined later in this information sheet, many private business radio licensees may find advantage in the use of trunked radio systems.

The Application Process

Applicants requesting trunked assignments are required to submit to the Agency a full technical description of their requirements, both current and future, including statistical details of likely traffic levels. Each application is assessed on its technical merits. When deciding whether or not to assign a trunking system, the Agency will take into account the availability of existing channels in the required operational area as well as the proposed channel loading. This will be weighed against the Agency's need to manage the spectrum for future use as well as present.

It is a matter for the licensee or applicant in association with their equipment supplier to provide the Agency's Private Business Systems Engineering section with a detailed description of the proposed trunking system. This should include details such as system loading, grade of service required, technical parameters and methods of traffic management. The installation should be engineered to provide a system which is at least as efficient as that described in the protocol MPT1327 "A Signalling Standard for Trunked Private Land Mobile Radio Systems".

The engineering study must be submitted to the Agency before any likely assignment can be considered. MPT1318 "Engineering Memorandum on Trunked Systems in the Land Mobile Radio Service" outlines the principles involved, and the parameters on which the report should be based.

If an applicant is requesting more channels than any current assignment, then it is necessary to provide the Agency with the reason why additional channels should be assigned, along with any likely impact affecting the spectrum efficiency of the system.

In the first instance, applications for trunked frequency assignments should be made to one of the Agency's regional offices, using application form RA1. Information sheet RA206 gives the addresses of and areas covered by the Agency's Local Offices. The application will then be forwarded to the Private Business Systems Engineering section of the Agency along with the accompanying engineering study for the proposed system. This will then be considered, in line with the above procedure.

Further Information

If you require further information on trunked radio systems, you should initially contact the Agency's Local Office covering your area. Contact details may be found in information sheet RA206.

Copies of MPT specifications and RA information sheets are available free of charge from:

The Information and Library Service,
Radiocommunications Agency,
Wyndham House
189 Marsh Wall
London
E14 9SX

Telephone: 020 7211 0502 or 0505
Fax: 020 7211 0507

E-mail: library@ra.gsi.gov.uk

Alternatively, some MPT specifications and RA information sheets are available on the Agency web site: www.radio.gov.uk

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