U.S. Philips Corporation

Paul J Stein

Diana M Ball

Rodney W Gibson

Peter J Mabey

Christopher K Davis

John P Parker

A transceiver for a packet radio network comprises a plurality of independently tunable receivers (RX1-RX4) and a single transmitter (TX) tunable to the frequencies of the receivers. Messages on different frequencies of the network can thus be simultaneously received by respective receivers, increasing message handling capacity; additionally or alternatively, one or more of the receivers can be used as an auxiliary channel for one or more functions other than standard reception of data packets. Three auxiliary channel modes are described: Voice Net mode for direct voice communication, Time Division Multiplex Repeater mode for a long-range voice link or bulk data transfer to a single destination, and inter-network gateway mode for transmitting messages to an adjacent network.

Packet radio

A method by which substations in a multiple access communication system, such as a mobile radio system, may access the base station. Access is determined by the base station in accordance with any of a plurality of operating modes during successive message time frames, the particular mode being determined by the base station from an estimate of prevailing traffic conditions. The selected operating mode during any frame is signified by a code and parameters transmitted by the base station in an Aloha invitation message which establishes such mode and the dynamic operation of the substations in that mode. The operating modes include a light traffic mode, a dynamic frame-length mode, a hybrid mode in which subsets of the population of the substations are formed, and a polling mode.

Multiple access communications system

A multiple-access communications system for an unlimited user population wherein a system controller continuously transmits Aloha signals on a slot-by-slot basis giving an updated number of time slots available whereby a calling party can select any one of the designated time slots at random. The calling party checks the time slot immediately preceding its selected time slot to ascertain if the current Aloha number is zero (or an equivalent thereof). If it is zero then the calling party reverts to listening for a time slot containing an Aloha number greater than zero. Alternatively if it is not zero the calling party apparatus sends a signal to the system controller in its selected time slot. Multipurpose signalling in each time slot can be carried out by the system controller thereby reducing the overhead on the system and speeding-up the setting-up of calls which may be off-air or non off-air.

Multiple-access communications system

A multi-tone sequential call signal detector in which a microcomputer is used to detect the tones of a received signal by simulating digitally the response of analogue tuned circuits. The detector includes a limiter for producing a square wave signal from a tone signal, a differentiator for producing interrupt pulses, and a microcomputer which responds to the interrupt pulses to activate a visual display and a call lamp of an output circuit when it detects all the received tones of the signal. The microcomputer performs an algorithm by which it measures the period between successive interrupt pulses, determines which tone frequency has this period, starts a number count which represents the 'rise' response of a tuned circuit for that tone frequency, and determines when the number count reaches a threshold number which represents the resonant condition of the tuned circuit.

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Crawley, United Kingdom

Paul J Stein