Massive Spatial Multiplexing Using Large Aperture Antenna Arrays

The ever-growing demand for higher wireless data rates has driven the exploration of novel methods to harness spatial degrees of freedom in multiple input multiple output (MIMO) systems. This thesis investigates the potential of both fixed and movable antenna arrays in line-of-sight (LoS) and multipath rich environments to optimize spatial multiplexing performance in narrowband and wideband settings. First, fixed dual-polarized planar antenna arrays are considered, and their spatial configuration is optimized to maximize the MIMO channel rank and condition number. Through careful optimization of antenna spacing, it is shown that the MIMO rank can grow quadratically with the carrier frequency, enabling data rates well beyond 1 Tbps. Analytical and numerical results confirm that strategically designed sparse arrays can deliver superior spectral efficiency, even within physically compact apertures. Building on this, arrays of movable antenna (MA) are examined for their ability to dynamically adapt antenna positions to changing channel conditions. While theoretically powerful, real time optimization of MA systems is computationally intensive and practically challenging. To address this, a pre-optimized irregular array (PIA) design is introduced, where antenna positions are fixed based on statistical knowledge of the coverage area. Using particle swarm optimization, PIAs are shown to achieve performance close to that of fully dynamic MA systems, without the need for real-time repositioning. Finally, MA systems are analyzed in wideband MIMO scenarios, where hardware impairments and multipath richness present additional challenges. A novel wideband system model is developed that incorporates hardware non-idealities, and antenna positions are optimized to maximize the average sum rate across subcarriers. Results reveal that the performance benefits of MA systems over fixed arrays are highly dependent on factors such as transceiver quality, channel richness, and the number of subcarriers. Overall, this work presents a unified exploration of spatial array design, spanning from optimized fixed geometries to adaptive movable configurations in both narrowband and wideband systems. The insights gained offer practical guidelines for deploying next generation high capacity MIMO communication networks.