WIDEBAND SPEECH CODINGWITH HYBRID DIGITAL-ANALOG TRANSMISSION

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 quanti-zation errors. Hybrid Digital-Analog (HDA) codes circum-vent this limitation by additionally transmitting the quanti-zation error with quasi-analog methods (discrete-time, quasi-continuous-amplitude) with neither increasing the total trans-mission power, nor the occupied frequency bandwidth on the radio channel. So far, the HDA concept has mainly been ap-plied 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. Index Terms — Hybrid Digital-Analog (HDA) transmis-sion, lattice ADPCM speech coding 1