Multilevel Coding for Fading Channels

This paper proposes a multilevel coding system with linear mapping for fading channels. The receiver performs multi-stage decoding. Each stage employs the decision-aided successive estimation and decoding method that decouples the channel estimation and decoding without loss of information. As a result, existing codes designed for memoryless channels can be applied directly. The overall system can achieve the constrained capacity of the fading channel with a given input distribution, provided that the memoryless channel codes are capacity achieving and the channel estimator is lossless. This paper uses the block fading channel as example, and derives a low complexity channel estimator. For i.i.d. Gaussian inputs, the estimator is lossless and so the multilevel coding system achieves the mutual information of the channel. For QAM inputs, the same estimator is shown numerically to have good performance.