Proposals for increasing the user capacity of the British post office public radiophone system

Abstract

The public radiophone system presently uses 55 VHF channels 25 kHz spaced. It is manually operated and will soon be channel limited in London. Forecasts indicate a need for greatly increased capacity to cater for growth before further bandwidth is likely to be made available. Tests demonstrate that 12½ kHz spaced channels could be used, and traffic statistics show that over half of the used "air time" is taken up by operation and switching procedures. This paper proposes a new type of automatic system, using 12½ kHz spaced channels, in which all call set-up procedures are conducted by fast data transmission over a common channel. The traffic channels are thereby used for successful calls only and the capacity would be more than quadrupled; additional advantages are that the base stations would be used much more effectively, hence yielding a minimum-cost solution.