Importance

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Abstract

A data communications system is described that covers a geographic area divided into a plurality of non-overlapping zones and includes a general communications controller (GCC), a plurality of channel communications modules (CCM) and associated transmitters and receivers, and a plurality of portable radios. Message signals carrying alphanumeric information are communicated between the GCC and the portable radios by way of a radio channel. Each CCM has at least one transmitter and receiver for covering at least one zone. Each CCM receiver has a coverage area overlapping the coverage area of at least two other CCM receivers and at least a predetermined minimum probability P of successful reception of a transmission from a data radio located in its coverage area, such that the joint probability P.sub.J of successful reception of the transmission from the portable radio by at least one of the CCM receivers is expressed by the equation, P.sub.J =1-(1-P).sup.3. Each CCM takes a signal strength measurement every time it receives a message signal from a portable radio. The GCC gathers the signal strength measurements from the CCM receivers receiving the same message signal and computes an adjusted signal strength for each zone. The GCC then selects the zone having the largest adjusted signal strength for determining the location of the portable radio that transmitted the message signal. Whenever the GCC transmits a message signal to a portable radio, the CCM transmitter is used that covers the zone having the largest adjusted signal strength for the last transmission from that portable radio.

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First Claim