Bypass Decoding: A Reduced-Complexity Decoding Technique for LDPC-Coded MIMO-OFDM Systems

In this paper, we propose a simple reduced-complexity decoding technique called bypass decoding for low-density parity-check (LDPC)-coded multiple-input-multiple-output (MIMO) orthogonal frequency-division multiplexing (OFDM) systems. Employing the bypass decoding technique, the receiver of an LDPC-coded MIMO-OFDM system decodes a codeword in two steps based on the log-likelihood ratios (LLRs) of coded bits. The hard decisions are first made on the coded bits whose LLRs have magnitudes above a certain threshold, and the rest of the coded bits will next be decoded by using an iterative receiver. We show that, as long as the threshold is properly selected, the bypass decoding technique not only delivers considerable complexity reductions but also maintains a comparable performance in LDPC-coded MIMO-OFDM transmissions. We also provide a selection rule for choosing a suitable threshold and show its effectiveness by simulations.