Rethinking Soft Interference Cancellation (IC) for MIMO: A Hard-Decision IC Inspired Recursive Scheme

Multiple-input multiple-output (MIMO) technology has been regarded as one of the most important technologies to enable emerging applications in current and next generation wireless communication systems, for which signal detection methods have been endowed with higher requirements, such as finer bit-error ratio (BER) performance, lower complexity, and smaller memory. Existing detectors mainly include hard-decision-based ordered successive interference cancellation (HD-OSIC) schemes with relatively simple implementation, and linear-minimum-mean-squareerror-based iterative soft interference cancellation (LMMSE-ISIC) schemes exhibiting near-optimal BER performance, whose advantages are combined by the detector developed in this paper. Specifically, we first elaborate that the LMMSE-ISIC scheme is the extension of the HD-OSIC counterpart, via comparing our proposed reordered description based on the equivalent channel matrix for the LMMSE-ISIC detection process with the other. Then, we propose a recursive scheme with speed advantage and memory saving for LMMSE-ISIC by extending that for HDOSIC, where the LMMSE-ISIC estimate and the filtering bias are updated highly efficiently. Compared to the existing best low-complexity LMMSE-ISIC scheme, theoretically, the required computations and memory units in each iteration of our proposed scheme decrease by at least 87.50% and 80.00%, respectively, and simulation results demonstrate that our proposed scheme always yields identical BER performance.