METHOD FOR IMPROVING THE QUALITY OF SOUND BY USING A DUAL CODEC IN A SUBSCRIBER-BASED RINGBACK TONE SERVICE, ESPECIALLY CONCERNED WITH PROVIDING A SPECIFIC RINGBACK TONE SOUND, REGISTERED BY A CALLED SUBSCRIBER, TO A CALLING SUBSCRIBER WITH A MORE ENHANCED TONE QUALITY

摘要

PURPOSE: A method for improving the quality of sound using a dual codec in a subscriber-based ringback tone service is provided to regenerate a ringback tone sound source at a better tone quality by releasing channel coding, such as an EVRC(Enhanced Variable Rate Codec) method, a QCELP(Qualcomm Code Excited Linear Prediction) method, etc., and executing sound source regeneration through a traffic channel suitably for the one-way transmission of a ringback tone sound source. CONSTITUTION: If a calling-side MSC(26) transmits a call connection request to a called-side MSC(22) as a calling mobile terminal(12) attempts call origination for a called mobile terminal(10), channel coding for a called-side BSC(18) is released. The called-side BSC(18) executes coding, suitable for the one-way transmission of ringback tone data, for a ringback tone sound source, registered by the subscriber of the called mobile terminal(10), and sends it to the calling mobile terminal(12). If the call connection between the two mobile terminals is made, the called-side BSC is transferred to a channel coding state so that a voice call can be initiated.