Method for a communication unit to maintain a data base of system services

In a trunking communication system that comprises a plurality of communication units, a limited number of communication resources that are transceived via a predetermined number of repeaters, and a communication resource allocator that allocates the limited number of communication resources among the plurality of communication units, wherein a communication unit of the plurality of communication units has been assigned to perform at least some of a plurality of communication system services, a method for the communication unit to reduce control channel traffic by maintaining a database of communication system services that it can perform, the method comprises the steps of:

• a) selecting a service of the plurality of communication services to produce a selected service;
• b) verifying, from the database, that the selected service is one that the communication unit can perform;
• c) transmitting a request to perform the selected service when the selected service has been verified that it is one that the communication unit can perform, otherwise, the request to perform the selected service is not transmitted;
• d) receiving, from the communication resource allocator, a response to the request to perform the selected service;
• and
• e) updating the database based upon the response from the communication resource allocator.