Up-to-date, expert coverage of topics in wireless voice communications Voice communication is the most important facet of mobile radio service. Even when the predicted surge of wireless data and Internet services becomes a reality, voice will remain the most natural means of human communication. Voice Compression and Communications details issues in wireless voice communications and treats compression, channel coding, and wireless transmission as a joint subject. Part I covers background material, whereas Part II provides detailed information on both proprietary and standardized analysis-by-synthesis codecs, including the speech codecs of virtually all existing wireline-based and wireless systems. Parts III and IV discuss mainly research-based wideband, audio, as well as very low-rate schemes likely to find their way into future standards. Voice Compression and Communications describes fundamental concepts in a non-mathematical way early in the book for those with only a background knowledge of signal processing and communications. More advanced readers will find detailed discussions of theoretical principles, future concepts, and solutions to various specific wireless voice communications problems.

Voice compression and communications : principles and applications for fixed and wireless channels

This paper presents a low delay high quality speech coder at low bit rates. The configuration of the speech coder is mainly composed of a formant filter, a pitch codebook, an excitation joint codebook, and post enhancement filters. The algorithm of the speech coder is briefly described. Two versions of the speech coder have been implemented in real-time with a single: ADSP-21020 chip. Both objective measurement and informal subjective listening tests show that the proposed speech coder has high quality performance.

Implementation of a low delay modified CELP coder at 4.8 kb/s

We propose a low delay speech coder operating at 6 kb/s bit rate in which 4.4 kb/s bit rate is assigned for the low delay speech coding algorithm and 1.6 kb/s bit rate for the error correction algorithm. The main features of the speech coding include the backward short term prediction, the "dual-decision" scheme, and the joint excitation codebook. The forward error correction (FEC) technique is adopted to protect the parameters which need be transmitted in the channel. The proposed coder provides good reconstructed speech quality and is robust to channel errors, while having the coding delay about 2.5 ms only.

A robust 6 kb/s low delay speech coder for mobile communication

Low-delay speech coding has drawn much attention because of its many potential applications. A lot of low delay speech coders have been proposed in the past few years. But almost all of them focus on the speech bit rate between 8 kb/s to 16 kb/s. The authors present a low delay speech coder operating at 4.8 kb/s which provides good speech quality with a coding delay only about 2.5 msec. This new low delay coder uses backward LPC analysis to remove the short-term correlation from speech and adopts a new approach to predict the long term prediction (LTP) coefficients based on a "dual-decision" scheme. At the excitation part, the authors exploit a new excitaton model which contains a sinusoid signal codebook and a stochastic codebook to excite the whole speech system. The synthesized speech of this coder has comparable quality to that of FS-1016 CELP coder while having a delay constraint more than an order of magnitude smaller than that of the FS-1016 coder. >

Hong Shen Wang

Papers

A low delay speech coding system at 4.8 kb/s