Bandwidth-efficient Mixed Pseudo Analogue-Digital speech transmission

Today´s speech coding and transmission systems are either analogue or digital, with a strong shift from analogue systems to digital systems during the last decades. In this paper, both digital and analogue schemes are combined for the benefit of saving transmission bandwidth, complexity, and of improving the achievable speech quality at any given signal-to-noise ratio (SNR) on the channel. The combination is achieved by transmitting pseudo analogue samples of the unquantized residual signal of a linear predictive digital filter. The new system, Mixed Pseudo Analogue-Digital (MAD) transmission, is applied to narrowband speech as well as to wideband speech. MAD transmission over a channel modeled by additive white Gaussian noise (AWGN) is compared to the GSM Adaptive Multi-Rate speech codec mode 12.2 kbit/s (Enhanced Full-Rate Codec), which uses a comparable transmission bandwidth if channel coding is included.