Method of codec operation control by the call control protocol in 3GPP mobile station

Types of codec for the 3GPP UE are presented but it is not clear which protocol entity performs codec controls such as the activation, start, stop and deactivation of codec functions and when the codec is controlled. So a normal telephony service is not guaranteed because a call might be established while the codec is not normally worked, and unnecessary resource wastage is happening because a call might be cleared while the operation of codec functions is continued Therefore, it is required that the codec is controlled depending on the call state. In this paper, it is proposed that the codec in the UE is controlled by the call control protocol which administers the call state by execution of call control procedures, and preventing normal call control procedures being executed even in case of abnormal codec operation, call control procedures are executed depending on the result of codec controls. Due to methods proposed in this paper, the establishment of a call guarantees the normal operation of codec functions and the call clearing guarantees stopping of the operation of codec functions.