Abstract: Low density parity check (LDPC) coded multiple-input multiple-output orthogonal frequency division multiplexing (MIMO-OFDM) systems, combined with iterative detection and decoding receivers, are simple and efficient methods for approaching the capacity of MIMO channels in broadband wireless communication systems. In iterative detection and receivers, soft messages should be passed not only between the MIMO detector and the LDPC decoder, but also between the two steps of LDPC decoding. The factor graph of MIMO-OFDM systems is derived and then dual-turbo receivers are proposed, where the MIMO detector and the iterative decoder work concurrently and soft messages are exchanged between them in real time. Compared with the sequential iterative detection and decoding receivers, dual-turbo receivers have lower latency and converge faster. Simulation results show that dual-turbo detection and decoding receivers greatly reduce the SNR required to achieve certain frame error rate (FER) with determined computational complexity, which is beneficial to green communications.

Key words: low density parity check codes, MIMO, OFDM, turbo detection and decoding