Exploiting the Tolerance of Massive MIMO to Incomplete CSI for Low-Complexity Transmission

In this paper we explore low-complexity transmission in massive multiple-input multiple-output (MIMO) systems by exploiting their tolerance to incomplete channel state information (CSI). We propose a strategy to exploit the transmit antenna correlation that arises in the deployment of size-constrained massive base stations (BSs). The feasibility of acquiring the instantaneous CSI for a subset of antennas and then using averages of the acquired CSI for the remaining array elements is studied. In particular, we focus on determining the influence that the percentage of inactive antennas during the CSI acquisition stage has over the signal processing (SP) complexity and the system performance. The presented results show that the proposed approach significantly reduces the computational complexity of size-constrained BSs while approximately preserving the performance of massive MIMO systems with complete CSI.