(A) study on ADPCM systems with improved error control

Abstract

A new method of improving the performance of ADPCM in noisy channel is proposed. The proposed system employs a robust quantizer, and transmits the information regarding the maximum step size periodically. Also, a most significant bit correction scheme is used in the receiver buffer. According to our extensive computer simulation with real speech, a remarkable performance improvement in noisy channel could be obtained with the proposed method. In addition, a new delayed decision algorithm is proposed that is suitable for ADPCM coding of speech. It can yield an improvement of 2 dB per sample delay in signal-to-noise ratio over the conventional ADPCM system at 32 kbps.