GB1389611A - Time-division-multiplexing multiple-access communication systems - Google Patents

Abstract

1389611 Multiplex pulse code signalling FUJITSU Ltd 27 March 1972 [27 March 1971] 14319/72 Heading H4L In a time division multiple access communication system comprising a plurality of stations communicating via channels allotted on a demand assignment basis, some of the channels are arranged for use with digital speech interpolation (DSI) and the number of channels available for DSI is increased when the traffic on the remaining channels is low. The arrangement is described in relation to a satellite communication system, Fig. 1, in which audio signals from a transmission trunk TRK are converted to PCM at PCM-COD and fed in time division multiplex via a DSI control unit DSIU-T to a unit CRU-T which converts the signals to the signal speed in the satellite circuits. The signals are then converted into a burst at BSU-T and the normal control signals for synchronization &e. are added, the burst signals being PSK modulated and transmitted to the satellite. Signals received from the satellite are PSK demodulated and supplied to BSU-R in which the control signals are extracted from the burst, the timing of the transmitted burst being regulated in dependence on phase relationships with the received bursts. The communication signals are supplied to CRU-R which converts the signal speed to that of the PCM decoder PCM-DEC, the DS1 control unit DS1U-R for the receiving section ensuring that the signals are allotted to the correct channels. A stored programme central processing unit CPU performs the demand assignment control via unit T1U. As described some of the channels operate under DSI conditions and others do not the arrangement being varied according to traffic conditions. In the transmitting section a reversible counter detects whether speech is taking place or not and a first storage unit stores the counted values for each channel and also stores satellite channel numbers which are used with DSI. A second storage unit stores information indicating station channels as being used or not used for DSI and also stores address information of the station channels. The information in the first storage unit is read out on the basis of the information stored in the second unit and a satellite channel is re-allocated to another station channel if the count for a station channel falls below a predetermined level by re-writing the information stored at the relevant address in the second storage unit.