Macroscopic diversity applications of multi-input multi-output (MIMO) systems for broadband mobile communication
Scope and method of study. This dissertation analyzes the evolution of mobile cellular communication technology and identifies the necessity of implementing the multi-input multi-output (MIMO) structure in future generation mobile systems. The properties and implementation issues of MIMO systems in wireless fading environments are studied. The effects of large-scale shadowing components are intensively investigated. It is found that the shadowing components have a substantial influence on the capacity of MIMO systems and make other capacity improvement schemes much less effective. Macroscopic selection diversity (MSD), which is well-known for combating deep shadowing effects, is implemented in MIMO systems to overcome this capacity degradation. By using the characteristic function (c.f.) method, the exact capacity representation of MSD-MIMO systems is derived. In addition, two base station (BS) selection algorithms are presented and analyzed. The first algorithm is optimal in the sense of giving the highest capacity. The second algorithm is suboptimal, but requires much less complexity. The proofs of optimality and suboptimality are also provided with a performance comparison of the two algorithms.
Findings and conclusions. This dissertation shows that macroscopic diversity in MIMO systems gives another dimension to optimize the system performance and it brings special benefits to the MIMO system design. Both of the proposed BS selection schemes give significant capacity improvements at the region of interest in the capacity distribution curves under all circumstances considered. These capacity improvements are quantified by using the c.f. method. Given a wireless environment, specific data rates, and outage requirements, engineers can use the methods provided in this dissertation to quickly evaluate different cell designs and BS deployment schemes. This evaluation method, together with link budget design and cell planning, will help to realize the system design to meet the most critical requirements. It is expected that macroscopic diversity MIMO systems are going to play important roles in the future broadband 4G systems.