×

Seamless handoff for radio telephone systems

  • US 5,329,635 A
  • Filed: 05/12/1992
  • Issued: 07/12/1994
  • Est. Priority Date: 05/12/1992
  • Status: Expired due to Fees
First Claim
Patent Images

1. In a time-division duplex radio communication system comprising a plurality of base stations and portable radio units communicating on a plurality of alternating transmit and receive frames, a method for seamless transfer of a communication link from a first base station to a second base station comprising the steps of:

  • at the first base station;

    receiving a communication link request from a calling portable radio unit;

    synchronizing with the calling portable radio unitdetermining whether the calling portable radio unit has handoff authorization;

    connecting received data to a transceiver in the second base station to allow for bit level synchronization to the calling portable radio unit;

    measuring a first RSSI level at the first base station for the calling portable radio unit;

    determining whether the first RSSI level for the calling portable radio unit is below a first handoff threshold;

    determining a second RSSI level for the calling portable radio unit, as measured at the second base station, if the first RSSI level for the calling portable radio unit is below the first handoff threshold,determining whether the second RSSI level for the calling portable radio unit is above a second handoff threshold;

    if the first RSSI level is below the first handoff threshold and the second RSSI level is above the second handoff threshold, alerting the second base station to pick up the communication link;

    at the second base station;

    synchronizing with the calling portable radio unit;

    receiving the alert to pick up the communication link from the first base station; and

    commencing to transmit in a next transmit frame of the second base station following a last transmit frame of the first base station.

View all claims
  • 1 Assignment
Timeline View
Assignment View
    ×
    ×