Performance Evaluation of UWB Massive MIMO Channels With Favorable Propagation Features

Abstract

Radio wave propagation can be characterized by two major sets: empirical and deterministic models. Empirical models rely on the received signals' statistics and thus offer lower precision. Deterministic models have certain physical bases and therefore necessitate a massive amount of geometrical data. For instance, the ray-based technique represents a suitable facility for reliable estimations in indoor schemes. Ultra-wideband (UWB) technology allows transmitting signals over a huge bandwidth, typically in the order of 500 MHz to several GHz enabling the design of communication systems with very high data rates. Massive multiple-input multiple-output (MIMO) is a new technique, utilizing a large number of base station antennas, advancing large system capacities in multiuser schemes, where multiple users are simultaneously served in the same time-frequency resources. We develop a ray-based procedure to investigate the behavior of the downlink UWB massive MIMO channel including the antennas transfer functions under various typical propagation situations. We estimate the magnitude and the phase of the voltage induced at each receiving antenna as a function of frequency (through the reciprocity theorem). We compare the singular value spread (SVS) cumulative distribution function (CDF) of each situation while varying the number of base station antennas. As the number of base station antennas or the inter-user separation increase, both the SVS and the sum-rate improve, the channel becomes more favorable, where better spatial separation is provided, and the disparity of the power values allocated for the users' channels reduces (through water-filling). The attained monotonic sum-rates were verified with the interference-free sum-rate.