Patent ID: 6292670
Filing Date: 2001-09-18
Classification: H04W

Abstract:
A method for maintaining a group call in a mobile communications system in which in said group call a plurality of mobile stations communicate with each other, said mobile communications system including one or more first base stations and second base stations located around the first base stations, and one or more mobile stations that are able to communicate with said base stations in said group call and a database, said method comprising:a) registering said one or more mobile stations in said mobile communications system;b) activating into said database of said mobile communications system a follow me function for said group call in order for said group call to follow uninterruptedly said mobile station participating in said group call from a first base station to said second base station;c) reserving a traffic channel for said group call from said first base station;d) said mobile station changing over to communicating on said traffic channel reserved from said first base station;e) in response to reserving said traffic channel from said first base station for said group call and in response to said activation of said follow me function, reserving a traffic channel simultaneously from a plurality of desired second base stations adjacent to said first base station for said group call;f) upon changing over to using a second base station adjacent to said first base station, the mobile station participating in said group call changing over to communicating on the traffic channel reserved for said call from said second base station;g) checking, in response to activating said follow me function for said group call, and registering of said mobile station to said second base station, whether a traffic channel has been reserved previously for said group call from all of said desired third base stations adjacent to said second base station;h) reserving a traffic channel for said group call from said desired third base stations adjacent to said second base station from which no traffic channel has been reserved previously for said group call;i) checking among all said desired second base stations which base stations are not included in said desired third base stations adjacent to said second base station whether a mobile station participating in said group call is registered to said base station, or such a base station to which said base station is a desired adjacent base station; andj) canceling said reservation of a traffic channel for said group call regarding said desired second base stations which are not included in said desired third base stations adjacent to said second base station, and to which base stations or base station to which said base station is a desired adjacent base station, none of the mobile stations participating in said group call is registered.