During the last decade CELP coding  of speech has been the most popular and promising scheme for producing high quality speech at medium to low bit-rates. Computational complexity of CELP however, has been its main disadvantage. For mobile systems where power and transmission bandwidth are at premium and channel conditions are severe, computational complexity of the speech coding algorithm, its robustness to channel errors, power consumption and the cost of implementation are the main design considerations. In this paper we present a CELP coder implemented using a single AT&T DSP32C. In addition to encoding and decoding in one DSP, we have implemented a forward error control scheme to increase its robustness to channel errors. The coder operates at gross bit rates of 6. 4 and 9. 6 kb/s and produces very high quality speech. A security algorithm to protect against the hardware/software piracy has also been included.
Bibliographic reference. Suddle, M. R. / Atungsiri, S. A. / Kondoz, A. M. / Evans, B. G. (1991): "A secure and robust CELP coder for land and satellite mobile systems", In EUROSPEECH-1991, 813-816.