In wireless speech communication systems several measures are taken to provide the required audio quality at the receiver. Besides speech and channel coding, algorithms for speech enhancement are applied to cope with the impairments resulting from acoustic background noise, telephone frequency characteristics, and residual bit errors. In the literature, advanced techniques for noise suppression, artificial bandwidth extension, and error concealment are treated as independent (sub-)disciplines of adaptive speech signal processing. However, these three approaches of speech enhancement are actually based on the same mathematics of conditional Bayesian estimation. In this contribution, a common view and recent developments in these three areas are presented.
Peter Vary was the leader of the winning industrial team (Philips, IBM) which designed the GSM full-rate codec in 1988. Since 1990 he and his group at RWTH University have a continuing tradition in contributing to international speech codec standards (GSM, UMTS, ITU). Furthermore, he made numerous original proposals in the field of digital speech transmission which have opened new directions of academic research and industrial applications (e.g. combined echo cancellation and noise reduction, wideband extension, soft decision source decoding, iterative source-channel decoding). The textbook "Digital Speech Transmission" (Wiley, 2005, together with Rainer Martin) is one of the first books which covers the fundamentals of the complete speech signal processing chain of modern cell phones.