A TOLL QUALITY 8-KB S SPEECH CODEC FOR THE PERSONAL COMMUNICATIONS-SYSTEM (PCS)/

A toll quality speech codec at 8 Kb/s suitable for the future personal communications system is presented. The codec is currently under stan dardization by the ITU-T (successor of CCITT) where the codec terms of reference were mainly determined considering PCS application. The enc oding algorithm is based on algebraic code-excited linear prediction ( ACELP) and has a speech frame of 10 ms. Efficient pitch and codebook s earch strategies, along with efficient quantization procedures, have b een developed to achieve toll quality encoded speech with a complexity implementable on current fixed-point DSP chips. Formal subjective lis tening tests, performed by ITU-T SG 12, showed that the codec quality is equivalent to that of G.726 ADPCM at 32 Kb/s in error-free conditio ns and it outperforms G.726 under error conditions. The codec performs adequately under tandeming conditions, and can support a frame erasur e rate up to 3% with a degradation in its performance that is still wo rse than the ITU-T requirements, and this is one subject of study for the next phase. The algorithm has been implemented on a single fixed-p oint DSP for the ITU-T subjective test, and required about 29 MIPS. A recent optimized version, however, requires 24 MIPS without any speech quality degradation,