Wideband speech coding with hybrid digital-analog transmission

Abstract

Efficient digital transmission of speech requires source coding which comes at the price of unavoidable quantization errors. Thus, even in clear channel conditions, the quality of the decoded speech signal is limited due to the quantization errors. Hybrid Digital-Analog (HDA) codes circumvent this limitation by additionally transmitting the quantization error with quasi-analog methods (discrete-time, quasi-continuous-amplitude) with neither increasing the total transmission power, nor the occupied frequency bandwidth on the radio channel. So far, the HDA concept has mainly been applied to random parameters. In this paper, the HDA concept is adapted to the transmission of wideband speech signals using PCM and ADPCM coding. By experimental verification it is shown that the HDA concept may outperform conventional purely digital transmission systems at all channel qualities while additionally eliminating the quality saturation effect.