RADIO COMMUNICATION SYSTEM

摘要

A radio communication system has a random access channel for the transmission of data (214) from a secondary station to a primary station. Such a channel is intended for use by secondary stations having packets of data (214) to transmit to a primary station while not actually engaged in a call. A problem with known systems of this type is that a secondary station requesting access also specifies which of a plurality of channels it wishes to access. If that channel is busy access is denied, even if other suitable channels are available. In the present system the primary station transmits a random access channel availability (AV) message (302) once per frame to inform secondary stations about the resources currently available. Hence a secondary station can select a channel known to be free. If no channels are available the secondary station can avoid a wasted access attempt.