Efficient Iterative Source-Channel Decoding Using Irregular Index Assignments

We present a system for iterative source-channel decoding (ISCD) using irregular index assignments: The concept of irregular codes is applied to the index assignment of a scalar quantizer. The optimization performed in the EXIT chart enables near optimum transmission. The irregular index assignments are constructed by using high-rate block codes. This construction allows to use a very simple stopping criterion at the receiver and thereby to potentially reduce the number of iterations. We demonstrate the performance of this system by means of a simulation example over an AWGN channel with hard decision at the output. Furthermore we present simple yet effective measures for the case that no channel state information (e.g., instantaneous bit error rate) is available.