A multi-digit incremental coding of speech for low bit rate transmission

An improved waveform coding technique able to produce a good quality of speech in the vicinity of 16 Kb/s is presented. The proposed scheme generates an output code word, which consist of a binary and a ternary digit. This is achieved by modifying the basic step size compared to the other systems, and hence, provide a more accurate reproduction of the waveform. Besides, it is able to respond to very fast changes in the input due to the wide range of step changes. Simulation results indicate that, the proposed algorithm yields about an 8-dB signal to noise ratio and a 5-10 dB dynamic range improvement compared to other schemes. Further, the effects of channel errors have been studied and its channel error tolerance is satisfactory (0.15%).