On the System Design and Optimization of Relay-Assisted Cellular Networks

• Main Authors: Lin, Shiang-Jiun, 林香君
• Other Authors: Huang, Chia-Chi
• Format: Others
• Language: en_US
• Published: 2010
• Online Access: http://ndltd.ncl.edu.tw/handle/54314468087806888426

博士 === 國立交通大學 === 電信工程研究所 === 98 === Deploying fixed relay stations (RSs) in traditional mobile cellular networks is widely recognized as a promising technology in next generation mobile communication systems to improve cell coverage, user throughput and system capacity, to save transmit power of a mobile station (MS) in the uplink, and to provide a low cost deployment for coverage extension. One crucial step toward developing such a relay-assisted cellular network is to fully evaluate its performance from both theoretical and practical points of view. In this dissertation, we aim to explore the system design and the optimization of relay-assisted cellular networks in multi-cell environment by considering general system configurations. In the first part of this dissertation, we aim to investigate the downlink performance limits of a general relay-assisted network with optimized system parameters in a multi-cell environment. Two types of quality of end-user experience (QoE), i.e., fixed bandwidth allocation and fixed throughput allocation, along with two path selection methods, i.e., spectral-efficiency based and signal-to-noise-plus-interference ratio based are investigated. A genetic algorithm (GA) based method is proposed for joint optimization of system parameters, including the number of RSs and their locations, frequency reuse pattern, path selection and resource allocation so as to maximize the system spectral efficiency. Numerical results show that significant improvement on the system spectral efficiency and the user throughput are achieved in the relay-assisted cellular network. In the second part, the aim is to study the uplink performance of a relay-assisted cellular network. Two performance measures, average power consumption of mobile stations and uplink system spectral efficiency, are optimized by jointly considering the system parameters of RSs’ locations, reuse patterns, path selections and resource allocation. GA-based method along with a method of MAI (multiple access interference) estimation is applied to solve the optimization problem. Numerical results show that with proper deployment of RSs both power consumption of MSs and the system capacity are remarkably improved in the uplink. In the third part, we investigate the important issue of resource scheduling for multi-hop relay networks in the Manhattan-like environment. New resource scheduling methods are proposed for the multi-hop relay network with directional antennas equipped at both the base station and relay stations. By taking advantage of the effect of high degree shadowing in the Manhattan-like environment, the system throughput can be largely increased by the proposed methods as compared to the system with omni-directional antennas. In this dissertation, the theoretical performance in both downlink and uplink with general configurations in relay-assisted cellular networks is presented. The practical issues of resource scheduling of relay-assisted cellular networks in the Manhattan-like environment is also addressed. With comprehensively evaluations, we can conclude that a relay-assisted cellular system is with the benefits to improve the system capacity and the user throughput, to save transmit power of an MS in the uplink, and to provide better coverage in the Manhattan-like environment with the optimized system parameters.