Turbo Source Compression with Jointly Optimized Inner Irregular and Outer Irregular Codes

In this paper, we present a near-lossless compression scheme for scalar-quantized source codec parameters based on iterative source-channel decoding (ISCD). The scheme is comparable to a Turbo source encoder and can inherently incorporate protection against transmission errors. In order to realize a close-to-capacity transmission/compression scheme, we employ irregular redundant bit mappings and irregular inner channel codes. The irregular inner code is composed of (pseudo) randomly punctured convolutional codes of rate > 1, i.e., the compression is performed by strong puncturing of the inner code. The optimization goal is a minimum number of transmitted bits given certain source and channel conditions. We show how the inner and outer component can be jointly optimized resulting in a constrained nonlinear programming problem. An additional successive approximation based on linear programming is also presented. Simulation examples show the advantage over systems employing only a single irregular component.