Patent ID: 6081714
Filing Date: 2000-06-27
Classification: H04W

Abstract:
A handoff method for a code division multiple access cellular communication network, wherein a plurality of base stations share a first, common frequency, a first base station of said plurality of base stations has a second frequency in addition to the common frequency, said plurality of base stations being connected to a control station, the method comprising:a) receiving, at a mobile station, a pilot signal from the first base station over the second frequency when the mobile station has established a connection thereto, and transmitting a first handoff request message when field strength of the pilot signal drops below a predefined threshold;b) receiving, at the first base station, the first handoff request message, said first base station returning a change-frequencies command message to the mobile station;c) receiving, at the mobile station, said change-frequencies command message from the first base station for switching to the common frequency and receiving pilot signals from more than one base station over the common frequency, and transmitting a second handoff request message containing a list of field strengths of the pilot signals;d) receiving, at the first base station, the second handoff request message from the mobile station, making a search through the list of field strengths contained in the received message, returning a handoff command message to the mobile station and transferring a connection setup command message to said control station if a second base station appropriate for handoff is found;e) receiving, at the control station, the connection setup command message from the first base station for instructing the second base station to establish a connection to the mobile station;f) receiving, at the mobile station, the handoff command message from the first base station for instructing the second base station to transmit a connection setup complete message to the control station; andg) receiving, at the control station, the connection setup complete message from the second base station for instructing the first base station to clear the connection to the mobile station.