We investigate the performance-complexity tradeoff for vector perturbation (VP) precoding in the downlink of multiuser multiple input multiple output (MU-MIMO) systems. To this end, we introduce a VP design that applies a performancedetermined threshold to the desired norm of the precoded signal, to reduce the search through multiple candidate perturbation vectors by the sphere encoder. Once this threshold is met, the search for the perturbation vectors finishes thus saving significant computational burden at the transmitter. Contrary to conventional VP which performs a computationally intense sphere search to find the absolute minimum of the transmit signal norm, the proposed scheme can trade off error rate performance for a much reduced complexity of precoding. The presented analysis and results show that the proposed thresholded VP (TVP) offers a complexity reduction of up to 90% in a 4 x 4 and 99% in a 10 x 10 MIMO, for a moderately increased error rate.
Multiple-input multiple-output (MIMO) systems are still attracting the attention of many researchers and designers for their promising improvements in performance and bandwidth efficiency. This paper presents a low-complexity precoding technique which aims to maximise the MIMO diversity at the receiver. The proposed technique achieves maximum diversity by matching the transmitted data symbols with a suitable precoding matrix from a list of predetermined precoding matrices at the transmitter. This paper shows that significant performance improvements can be obtained with this technique and without any bandwidth degradation.
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