Method and apparatus for communicating in a dispatch communication system

A system controller that allocates radio communication resources in support of dispatch communications among a group of communication units as individual communication units of the group travel throughout a plurality of service coverage areas of a dispatch communication system, the system controller comprising:

• a signaling interface coupled to a plurality of base sites that provide communication service to the plurality of service coverage areas;
• and
• a memory device, coupled to the signaling interface, having stored therein a computer program that, when executed, performs the following functions:
• establishes a dispatch communication between the group of communication units;
• determines a first length of time since establishment of the dispatch communication;
• determines whether an event indicative of call reassignment has occurred;
• when the event indicative of call reassignment has occurred, determines, based on the first length of time, a second length of time commencing at a time of the event for maintaining allocation of a radio communication resource assigned to the dispatch communication;
• determines whether call reassignment has occurred within the second length of time;
• and
• when call reassignment has not occurred within the second length of time, terminates the dispatch communication.

A communication unit in a dispatch communication system, the communication unit being one member of a group of communication units that travel throughout a plurality of service coverage areas of the dispatch communication system, the communication unit comprising:

• a transmitter that transmits radio communication resource requests and voice information to at least one base site of a plurality of base sites that provide communication service to the plurality of service coverage areas;
• a receiver that receives radio communication resource allocations and voice information from the at least one base site;
• and
• a memory device, coupled to the transmitter and the receiver, having stored therein a computer program that, when executed, performs the following functions:
• establishes a dispatch communication between the group of communication units;
• determines a first length of time since establishment of the dispatch communication;
• determines whether an event indicative of call reassignment has occurred;
• when the event indicative of call reassignment has occurred, determines, based on the first length of time, a second length of time commencing at a time of the event for maintaining allocation of a radio communication resource assigned to the dispatch communication;
• determines whether call reassignment has occurred within the second length of time;
• and
• when call reassignment has not occurred within the second length of time, terminates the dispatch communication.