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Method and apparatus for direct communication between mobile stations

  • US 5,995,500 A
  • Filed: 07/18/1997
  • Issued: 11/30/1999
  • Est. Priority Date: 07/18/1997
  • Status: Expired due to Term
First Claim
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1. A communication system that provides duplex communication between mobile stations over at least one RF channel divided into a plurality of time slots during which information are communicated in a duplex manner, comprising:

  • a calling and a called mobile stations that communicate with each other in one of two communication modes, a direct mode, when the calling and called mobile stations engage in a direct duplex communication with each other, and an indirect mode, when the calling and called mobile stations communicate with each other through at least one base station; and

    a controller that before a call set up, determines whether the calling and called mobile stations are in-range or out-of-range from each other, wherein the mobile stations communicate in direct mode if they are in-range and communicate in indirect mode if they are out-of-range, wherein the controller, in response to an in-range condition, allocates a first time slot during which the calling mobile station transmits the information to the called mobile station, while the called mobile station receives the transmitted information from the calling mobile station, and a second time slot during which the called mobile station transmits the information to the calling mobile station, while the calling mobile station receives the transmitted messages from the called mobile station, and wherein, when the mobile stations communicate in direct mode, the controller performs a direct mode test to determine whether direct communication between the mobile stations should be maintained or not.

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