Cellular communication system with common channel soft handoff and associated method

Abstract

A cellular communications system comprising; a mobile unit which designates an active set of base stations; a base station; and a base station controller which puts the base stations in the active set in common channel soft handoff.

1 . A method comprising: 
 identifying a mobile unit in a coverage area of a base station of multiple base stations in a spread spectrum communication system;    monitoring by said mobile unit a power level of control signals received from said multiple base stations;    identifying by the mobile unit a first set of base stations in said multiple base stations for which the monitored power level of the received control signal exceeds a prescribed level;    sending a power measurement message from the mobile unit to at least one base station in the set that identifies the base stations in the identified first set;    sending to the mobile unit by at least one base station in said multiple base stations a message that specifies a second set of base stations that are permitted to transmit to the mobile unit in soft handoff; communicating a control message to the mobile unit for soft handoff that identifies members of both the first set and the second set;    wherein at least one member of the second set of base stations is determined based on independent soft handoff information other than the information provided by the mobile unit relating to the power level of control signals.    
     
     
         2 . The method as recited in    claim 1    further comprising: 
 performing a soft handoff communication from the base stations that are members of both the first set and the second set.  
 
     
     
         3 . The method as recited in    claim 1    wherein said independent soft handoff information is based on said identifying said mobile unit.