First International Conference on Spoken Language Processing (ICSLP 90)

Kobe, Japan
November 18-22, 1990

11.2 kb/s LCELP Speech Codec for Digital Cellular Radio

Yoshihiro Unno (1), Makio Nakamura (1), Toshifumi Sato (1), Toshiki Miyano (2), Kazunori Ozawa (2)

(1) Mobile Media Terminals Div. , NEC Corporation, Kanagawa, Japan
(2) C&C Information Technology Research Labs., NEC Corporation, Kanagawa, Japan

A 11.2 kb/s speech codec for digital cellular radio has been developed. The speech coder uses an LCELP (Learned Code Excited LPC Coding) speech coding algorithm operating at 8 kb/s. In LCELP, the excitation signal is efficiently quantized by a two-stage vector quantizer with a learned codebook and a stochastic codebook. LCELP can provide excellent speech quality in the absence of channel errors. In order to maintain good speech quality in the presence of transmission bit errors, 3.2 kb/s of forward error correction and detection coding is applied. Further, improved speech interpolation and extrapolation techniques have been developed. The speech codec has been implemented on a real time hardware using two 16 bit fixed-point DSP chips. The speech quality of the codec is good even under bit errors, and it is equivalent to 40 kb/s ...-law PCM at 1 % bit error rate.

Full Paper

Bibliographic reference.  Unno, Yoshihiro / Nakamura, Makio / Sato, Toshifumi / Miyano, Toshiki / Ozawa, Kazunori (1990): "11.2 kb/s LCELP speech codec for digital cellular radio", In ICSLP-1990, 121-124.