Iterative Sparse Channel Estimation and Decoding for Underwater MIMO-OFDM

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The authors propose a block-by-block iterative receiver for underwater MIMO-OFDM that couples channel estimation with Multiple-Input Multiple-Output (MIMO) detection and Low-Density Parity-Check (LDPC) channel decoding. In particular, the channel estimator is based on a compressive sensing technique to exploit the channel sparsity, the MIMO detector consists of a hybrid use of successive interference cancellation and soft Minimum Mean-Square Error (MMSE) equalization, and channel coding uses non-binary LDPC codes. Various feedback strategies from the channel decoder to the channel estimator are studied, including full feedback of hard or soft symbol decisions, as well as their threshold-controlled versions.