Performance Evaluation of Massive MIMO Systems

Abstract

THESIS SUMMARY Two timeless truths are evident: first, demand for wireless communications will always grow; second, the quantity of available electromagnetic spectrum will never increase. The fundamental wireless problem is a physical layer problem: how to provide ever-increasing total wireless throughput reliably and uniformly throughout a designated area. Massive MIMO (Multiple-Input-Multiple-Output) makes a clean break with current practice through the use of a very large number of service antennas (i.e., hundreds or thousands) that are operated fully coherently and adaptively. Extra antennas help by focusing the transmission and reception of signal energy into ever-smaller regions of space. This brings huge improvements in throughput, energy efficiency, and spectral efficiency. This thesis presents the analysis and simulation of multi-layer precoding framework, to enable efficient and low complexity massive MIMO operation. A massive MIMO system, operating in Frequency Division Duplexing (FDD) mode of operation, suffers from prohibitively high overhead associated with downlink channel state information (CSI) acquisition and downlink precoding, due to the lack of uplink/downlink channel reciprocity. A heuristic edge-weighted vertex-coloring based pattern division (EWVC-PD) scheme is proposed to reduce the overhead of a two-layer precoding approach, in a practical scenario where the user clusters undergo serious angular-spreading-range (ASR) overlapping, under a constraint of limited number of subchannels. Mathematical analysis as well as numerical simulations reveal the potential solutions for FDD massive MIMO systems to achieve high throughput gains with simplified signal processing.