A Low Complexity Adaptive Scheme for Massive MIMO Systems with MRC Receiver

Abstract

This paper evaluates a low-complexity Multiuser Adaptive Modulation (MAM) scheme for an uplink massive multiple input and multiple output (MIMO) systems with maximum-ratio combining linear receivers, which requires only slow-varying large-scale shadowing information for the users. For a channel that includes both small-scale and large-scale fading, the probability density function of signal-to-interference-plus-noise ratio is analytically calculated for the first time and verified by simulation. Also, closed-form expressions are derived for the average spectral efficiency and bit error outage. Since, the MRC is desirable in low transmit power, the previous expression is approximated at low power values. Moreover, the paper investigates different users’ arrangements around the base station to achieve the maximum possible bit rate. For MAM with joint power control, optimal power adaptation strategy switching thresholds are also acquired. Compared to the research literature, the proposed adaptive scheme by the MRC receiver, gives similar performance as a proper adaptive method at low power transmission.