Coverage Planning and Resource Allocation in Broadband Cellular Access : Optimization Models and Algorithms
Sammanfattning: The last two decades have witnessed a booming in the use of cellular communication technologies. Billions of people are now enjoying the benefits of mobile communications. This thesis deals with planning and optimization of broadband cellular access network design and operation. The problem types considered include coverage planning, power optimization, and channel assignment. Mathematical modeling and optimization methods have been used to approach the problems.Coverage planning is a classical problem in cellular network deployment. A minimum-power covering problem with overlap constraints between cell pairs is considered. The objective is to minimize the total power consumption for coverage, while maintaining a necessary level of overlap to facilitate handover. For this coverage planning problem, the thesis develops two integer programming models and compares the models' strength in approaching global optimality. In addition, a tabu search algorithm has been developed for solving the problem in large-scale networks.For High Speed Downlink Packet Access (HSDPA) networks, transmission power is a crucial factor to performance. Minimizing the power allocated for coverage enables significant power saving that can be used for HSDPA data transmission, thus enhancing the HSDPA performance. Exploring this potential power saving, a mathematical model targeting cell-edge HSDPA performance has been developed. In determining the optimal coverage pattern for maximizing power saving, the model also allows for controlling the degree of soft handover for Universal Mobile Telecommunications System (UMTS) Release 99 services. In addition to the mathematical model, heuristic algorithms based on local search and repeated local search are developed.For Orthogonal Frequency Division Multiple Access (OFDMA), which is used in Long Term Evolution (LTE) networks, inter-cell interference control is a key performance engineering issue. The aspect is of particular importance to cell-edge throughput. Frequency reuse schemes for mitigating inter-cell interference at cell-edge areas have received an increasing amount of research attention. In the thesis, a generalization of the standard Fractional Frequency Reuse (FFR) scheme is introduced. The generalization addresses OFDMA networks with irregular cell layout. Optimization algorithms using local search have been proposed to find the frequency reuse pattern of generalized FFR that maximizes the cell-edge area performance.For the problems considered in the thesis, computational experiments of the optimization models and algorithms using data sets representing realistic planning scenarios have been carried out. The experimental results demonstrate the effectiveness of the proposed solution approaches.
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