Adaptive Modulation and Channel Coding Using Reliability Information

A classical strategy for optimizing digital communication systems is the minimization of the error rate. In this paper we propose a new paradigm: Our main goal is the estimation of the error rate. This alternative strategy offers us (i) to use iterative demodulation and decoding techniques (e.g. turbo codes), (ii) to optimize adaptive modulation and adaptive source and channel coding techniques (e.g. adaptive multi-rate speech codecs) with respect to the average data throughput given a target error rate, and (iii) motivates a “soft-decision” Monte Carlo simulation technique. These three principles are applied here to obtain an adaptive mobile radio system operating near Shannon’s capacity bound. Furthermore, the reliability information (i) may be used for blind detection of the modulation and coding scheme, (ii) may be used as a stop criterion for iterative processing, and (iii) makes error detection coding unnecessary. Keywords— Adaptive modulation, mobile radio, APP decoding, reliability information, Monte Carlo simulation, soft-decision simulation.