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Wall to Wall explain the benefits of digital over analogue radio equipment

25 May 2012

With so much confusing information available on two way digital radios, mostly favouring specific manufacturers, Wall to Wall Communications have provided some useful information if you are contemplating switching from analogue to digital two-way radio systems.

According to UK regulators Ofcom, (Office of Communications), the supply of available Private Mobile Radio (PMR) channels is virtually exhausted in some areas. Undoubtedly, the radio comms industry needs more capacity for its current and future developments. The way forward is to adopt spectrum-efficient digital modes.

Digital standard is here to stay. Digital two way radios are available in both licenced and licence-free forms. They digitise speech like mobile phones and transmit using radio waves, whereby analogue two-way radios use audible speech. Digital radios have received global recognition, being capable of voice, data and a whole range of other features and applications in conventional and trunking mode.

Current protocols used to transmit digital signals are Time Division Multiple Access, (TDMA) and Frequency Division Multiple Access, (FDMA).

Two of the biggest benefits of digital radios compared to analogue include a better clarity of voice through the use of coders and other techniques, with digital processing more consistent in screening out noise and re-constructing signals from degraded transmissions and doubled capacity in existing licenced channels.

TDMA retains the 12.5kHz channel width and divides it into two alternating 30ms timeslots, where each timeslot acts as a separate communication path or channel.

FDMA narrowband technology slices the signal in length and uses 2 x 6.25kHz channels which allows twice the amount of users on the radio spectrum, for example, two simultaneous independent calls on one channel.

Both standards can be also used for reverse-channel signalling for improved control of the system operator.

•    reduced equipment and licencing cost – doubled capacity also means that less system equipment is needed in order to gain the same coverage for the same number of radio users
•    wider coverage and better performance at the edge of coverage area – no scratchy noises until the signal is completely gone beyond the communication footprint
•    longer battery life and greater power efficiency – this is achieved as the radio transmits only half of the time every other 30 msec (TDMA) and for FDMA the reduced noise components (with the narrower channel bandwidth) improve receiver sensitivity, which makes the radio transmit at a reduced power as well
•    backwards spectrum compatibility with legacy analogue systems – all digital equipment works in mixed mode (analogue and digital), therefore old analogue radios can still be used
•    easier integration with IP-based data applications, text messaging, telemetry or external tools like GPS and telephone interconnect – it is possible to separate voice and data streams into different communication paths in order to improve quality of service and utilize a computer to control the whole system via sophisticated software
•    (last but not least) secure connection – digital signal encryption is much easier to implement and more secure (as opposed to “scrambling” with analogue)

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