The efficient speech coders are required for spectral efficient mobile communication systems such as CDMA IMT-2000 system. These coders have to provide the good speech quality with low bit rate. The G. 729 was accepted as 8kb/s toll quality speech cod...
The efficient speech coders are required for spectral efficient mobile communication systems such as CDMA IMT-2000 system. These coders have to provide the good speech quality with low bit rate. The G. 729 was accepted as 8kb/s toll quality speech coding algorithm by ITU-T. For radio communication application, the G.729B with discontinuous transmission scheme was developed. This algorithm can be operated based on voice activity detection and discontinuous transmission. For IS-95 compatible system, the continuous transmission may be required. I will proposed the variable rate speech coding algorithm through classification of speech frame as voice, unvoice and silence frame. I explain these speech coding algorithms briefly and evaluate the performance by speech quality and bit-rate criterion.