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Generalized spatial modulation (GSM) is an attractive transmission technique for multiple-input multiple-output systems because of its spectral efficiency and energy efficiency. The maximum likelihood detector provides the optimal performance for GSM signal detection, but also leads to a high level of detection complexity. In this paper, both hard-decision and soft-decision detectors, which are based on a low-complexity codebook-assisted tree-search algorithm, are investigated. In addition, outer low-density parity-check codes are designed such that the concatenated schemes are able to provide error performances, which are very close to those of the schemes using conventional detectors, but with a much lower level of computational complexity.

In this paper, we propose the use of a convolutional interleaver employing a variety of block delay parameters as the bit interleaver in a multiple-input-multiple-output (MIMO) bit-interleaved coded-modulation (BICM) scheme. The associated iterative decoding-detection algorithm is proposed, and the design criteria for the outer convolutional code are derived. The cases for both the perfect channel-state information (CSI) and the estimated CSI are investigated. In the proposed MIMO-BICM scheme, the MIMO detector and the channel estimator utilize the soft information passed from the sliding-window convolutional decoder within the same iteration, and hence, the convergence speed can be increased. Compared with the conventional scheme using various interleaver designs, the proposed scheme not only achieves better error performance for the first iteration but also has lower decoding latency. Consequently, the proposed scheme is suitable for delay-sensitive applications.