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Two Approaches to Combined Source-Channel Coding: A Scientific Competition in Estimating Correlated Parameters

Authors:
Hindelang, T. ,  Heinen, S.Vary, P. ,  Hagenauer, J.
Journal:
(AEÜ)
Volume:
54
Page(s):
364-378
number:
6
Date:
Dec. 2000
Language:
English

Abstract

In digital transmission of speech, audio, images and video signals residual redundancy is often left after source coding due to complexity and delay constraints. In a scientific competition two ways of exploiting this redundancy to improve the end-to-end quality of the transmission over a noisy channel are investigated. On the one hand we present a new class of channel codes, which we call Source Optimized Channel Codes (SOCCs). These codes are designed by an optimization process, which takes into account the source and channel statistics as well as a quality measure. At the receiver we exploit the code redundancy not for error correction, but to support parameter estimation in terms of Soft Bit Source Decoding (SBSD). Designing SOCCs with respect to the Signal to Noise Ratio (SNR) quality measure is considered in detail. On the other hand we show a channel coding scheme using convolutional codes and Unequal Error Protection (UEP) by puncturing considering the influence of each bit of a quantized parameter on the quality after source decoding. This approach is improved by exploiting two kinds of a priori knowledge in channel decoding -- the time correlation and the correlation due to the distribution of a parameter. -- This method we call Source Controlled Channel Decoding (SCCD). Furthermore, we consider the bit-mapping and its effect on decoding. The mutual information as entity for the gain of decoding with a priori information is explained.

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