Trunked Systems

Wall to Wall Radio Communications is proud to be working with Fylde Micro Ltd, co founders and current world leader in the design and manufacture of MPT1327 trunked radio networks.

Delivering the first ever true MPT1327 system to BT back in 1986 this was installed on the Post Office Tower in London. This was closely followed by the first multi-site trunked radio systems.

Today, we work with Fylde Micro Ltd and are successfully utilising networks with a 3rd generation product to meet modern day voice and data communications challenges.

Multi-channel radio systems need to be planned properly if they are to be efficient. This is even more important if the systems include multiple base stations and have a large number of mobile radios as shown in the picture.

There are many criteria that need to be considered when designing a radio system. These include deciding:

  • the number of handhelds and/or mobile radio users
  • whether users will be grouped, e.g. managers, drivers, staff, security, and cleaners
  • the typical radio activity of each group of users, e.g. low (5%), medium (25%), and high (50%)
  • whether the low radio activity of individual groups may enable them to share a single channel
  • whether higher radio activity groups will require their having a single dedicated channel or perhaps multiple dedicated channels, e.g. to ensure that a vacant channel is available immediately if required
  • whether it is essential for groups with their own channel(s) to be able to communicate with groups on other channels, e.g. all-call messages during an emergency.

The problems with some multiple-channel multiple-site systems include:

the system is not spectrally efficient, e.g. more channels are used than necessary (NB: also resulting in the licensee paying higher fees than necessary)
groups of users may not be able to communicate with all other groups
all channels transmit simultaneously when one channel is accessed.

Spectrum efficiency may be enhanced by using a trunked radio system. Trunked radio systems are based on access to a pool of radio channels. This system includes the following benefits:

the use of comparatively lower number of channels required more closely matches the probability of calls being made and the duration of those calls (using Erlang B theory), e.g. fewer channels may be needed for 100 short calls within an hour compared with 25 long calls, and probably many fewer than each user group having its own channel(s)
a control channel (CCH) manages access to the traffic channels
a free traffic channel (TC) may be accessed by any user immediately
the control channel can become a temporary traffic channel during peak activity
a well planned 7-channel trunked system may accommodate 3000 mobiles.

Trunked systems can vary in size from on-site to wide-area multi-site. Multi-site systems may be connected using cable, fibre, or microwave links. The control channel frequencies at each site will be different. This enables a mobile radio to automatically establish the strongest, and usually nearest, base station and communicate through it. This method should ensure that the mobile remains within range of the base station for the duration of the call.

There are digital system equivalents to the analogue trunked system standard (MPT1327).

Wall to Wall Radio Communications will be pleased to discuss your multi-channel radio system requirements and design, install, commission, demonstrate, and maintain the best analogue or digital solution to meet your requirements.

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