Cell Coverage Control And Optimization Based On Pattern Synthesis Of Antenna Arrays

Cellular communication systems are the most widely used mobile communication systems. The proper coverage of a cell/sector is a prerequisite for the cellular communication system to provide users with high-quality services. Aiming at improving the utilization and performance of the system, controlling and optimizing cell coverage according to the actual environment is a long-term yet important task.With the aforesaid purpose, in this thesis we focus on the research of coverage control and optimization based on pattern synthesis of antenna arrays.Firstly, the algorithms of pattern synthesis for antenna arrays are studied. The principles and implementation steps of three typical algorithms, namely Woodward-Lawson method, Least Squares Error algorithm and Minimax Design algorithm, are analyzed first of all. The performance of each of theses algorithms is derived when synthesizing some typical desired field patterns. The applicable scenes, advantages/disadvantages, and characteristics of the three algorithms are obtained by analyzing a number of pattern parameters. Further, the impact of the number of array elements on pattern properties is discussed as well, whereby the relationship between the number of array elements and the locations of the discontinuous points of the desired patterns, the impact of the number of array elements on the radiation characteristics of the actual field patterns, and the relationship between the parity of the number of array elements and the radiation characteristics of the actual field patterns are derived.Secondly, the approach of controlling cell coverage taking advantage of pattern synthesis of antenna arrays is studied. For the purpose of coverage control, the mathematical expression of the desired pattern of antenna arrays is derived, and the relationship among the desired pattern, the size of the target coverage area, and the propagation loss is thus obatined. In order to get the accurate desired pattern, an engineering applicable method for measuring the propagation loss including path loss and the shadowing is introduced. With the obtained desired pattern, the method for coverage control utilizing pattern synthesis is proposed and analyzed in detail. The performance of the methods with and without considering the propagation loss is compared via simulation in terms of the coverage effect. The simulation result shows that a better coverage effect can be achieved by the former approach in terms of reducing the area of weak coverage and over coverage.Finally, in order to achieve an overall improved coverage effect on a target multi-cell/multi-sector area, a multi-cell/multi-sector joint optimization approach is proposed. In particular, the coverage effects of three strategies, optimizing the transmit power of each cell/sector merely, individually optimizing the transmit power as well as antenna parteen for each cell/sector, and jointly optimizing the transmit power as well as antenna parteen for each cell/sector, are compared. Simulation results show that the last strategies achieve the best performance.