Modified-rate-quantization algorithm for multiple-input multiple-output systems under imperfect channel knowledge

摘要

In this paper, a modified-rate-quantization algorithm for multiple input multiple output (MIMO) systems is proposed using singular-value decomposition (SVD). This low complexity scheme adapts the subchannel transmit power and spectral efficiency in the spatial and temporal domains under transmit power and instantaneous bit error rate (BER) constraints. It is shown that with five discrete-rate levels, the proposed scheme reaches a spectral efficiency performance similar to the scheme with a continuous rate. The robustness of the proposed scheme to channel state information (CSI) imperfections is also studied. The obtained results show that the spectral efficiency is unaffected up to a certain level, but the bit error rate (BER) performance is particularly sensitive to these imperfections, especially at high SNR levels. Indeed, this ideally designed MIMO system over-estimates the subchannels, which leads to a deterioration of the BER performance. A new version of this algorithm, which is suitable for vertical Bell Labs layered space–time (V-BLAST) systems, is also presented. Through simulation results, it appears that the extended algorithm allows to reach a better performance in terms of spectral efficiency than other known schemes, but it is more sensitive to imperfect CSI than the first version.