Mobile Cellular Communications with Base Station Antenna Arrays: Spectrum Efficiency, Algorithms and Propagation Models

This thesis deals with the problem of increasing the spectrum efficiency of cellular systems, by the use of antenna array base stations. The focus of the thesis is on downlink transmission in frequency division duplex systems, i.e., systems with different up and downlink carrier frequency. In a short summary the thesis: * Proposes five reasonable propagation models. * Uses these models to design and analyze three different beamformers: The maximum desired power (MDP the summed interference to carrier ratio minimizing (SCIR) and the generalized-SCIR beamformer. * Introduces three capacity enhancement approaches: same sector frequency reuse (SSFR), reduced cluster size without nulling (RCS-WON) and reduced cluster size with nulling (RCS-WIN). * Proposes channel allocation, power control, and beamforming algorithms for these approaches. * Estimates the “outage probability” (probability of insufficient quality), for SICR-SSFR, SICR-RCS-WON and SICR-RCS-WIN, using simulations as well as analytical analysis, as a function of critical parameters. Investigates the capacity enhancement achieved with the base station antenna array as a function of angular spreading and the number of antennas for SICR-SSFR, SICR-RCS-WON and SICR-RCS-WIN. * Partially verifies the system simulation assumptions using real data. * Combines simulation and experimental results to make likely that three to tenfold capacity enhancement is realistic using $3-18$ antenna elements per 120-degree sector (in comparison with a system employing a single antenna per sector). * The higher capacity enhancements are obtained using the more complex approaches. * Makes a detailed proposal of a simple and robust downlink beamforming algorithm for realizing RCS-WON in GSM (the MDP beamformer) . * Simulates this beamformer under realistic network conditions, using simulated as well as real data.