Simulation based channel hardening of cell-free massive MIMO in mm-Wave

Abstract

In this paper, the spatial distribution of the channel hardening of cell-free massive MIMO array antenna topologies for mm-Wave communications is explored. The simulation of the propagation channels was performed by means of ray tracing computations. The channel hardening is evaluated in two different radio wave propagation channel conditions: first, an indoor office room furnished with desks, chairs and shelters and secondly, the same room without furniture. The spatial distribution of the channel hardening is investigated in both scenarios as a function of the number of antenna elements of the array. The simulation results show that the channel hardening effect is as expected larger in the furnished room as compared with the empty room. Also as expected, the channel hardening increases with the number of antenna elements. An interesting new observation is that the channel hardening is not uniformly distributed within the coverage area. Indeed, for the considered cell-free array antenna topologies and indoor propagation scenarios the channel hardening effect becomes lesser the closer the user gets to the antenna locations and near the walls of the rooms.