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Low cost wide area network for data communication using outbound message specifying inbound message time and frequency

  • US 5,765,112 A
  • Filed: 06/06/1995
  • Issued: 06/09/1998
  • Est. Priority Date: 06/06/1995
  • Status: Expired due to Term
First Claim
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1. A two-way wireless data communication system comprising:

  • an outbound messaging sub-system for sending outbound messages;

    an inbound messaging sub-system consisting of a network of at least two radio frequency base stations for receiving inbound messages, the radio frequency base stations also continuously sampling, at their respective locations, a set of frequency channels in an inbound radio frequency band, to determine an observed frequency availability level for the set of frequencies for each base station;

    at least one remote field unit having an outbound message receiver and a tunable inbound message transmitter; and

    a central control unit, wherein the central control unit uses the outbound messaging sub-system as an outbound link to send an outbound message to the remote field unit, and uses the inbound messaging sub-system as an inbound link to receive an inbound message from the field unit, and wherein the outbound message comprises a time data field and a frequency data field indicating, respectively, an inbound message time and an inbound message carrier frequency at which the field unit is to send an inbound message in response to the outbound message, and wherein the central control unit receives reports of the observed frequency availability levels from the network of radio base stations, and the central control unit selects the time data field and frequency data field such that the inbound message will be received by one or more of the base stations in the inbound messaging sub-system without interference from another communication system.

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