On Detection Issues in the SC-Based Uplink of a MU-MIMO System with a Large Number of BS Antennas

This paper deals with Single Carrier (SC)/Frequency Domain Equalization (FDE) within a Multi-User (MU)-Multi-Input Multi-Output (MIMO) system where a large number of Base Station (BS) antennas is adopted. In this context, we consider either a linear or a low-complexity iterative Decision-Feedback (DF) detection technique which does not require matrix inversion operations. We include a detailed evaluation of Bit Error Rate (BER) performances for uncoded 4-Quadrature Amplitude Modulation (4-QAM) schemes and a MUMIMO channel with uncorrelated Rayleigh fading. The accuracy of performance results obtained through selected semi-analytical simulation methods is assessed by means of parallel conventional Monte Carlo simulations; these results are discussed in detail, with the help of selected performance bounds. From our performance results, we conclude that a moderately large number of BS antennas is enough to closely approximate the Single-Input Multi-Output (SIMO) MatchedFilter Bound (MFB) performance, especially when using the low-complexity iterative DF technique. We also emphasize the achievable ”massive MIMO” effects, even for strongly reduced-complexity linear detection techniques, provided that the number of BS antennas is much higher than the number of antennas which are jointly employed in the terminals of the multiple autonomous users.