The Methods Of Autonomic Downlink Coverage Optimization And Autonomic Load Balancing In Radio Access Network

Recently, the development of radio access network shows the features such as large scale, complex, open, heterogeneous, and dynamic. The requirements for the service of radio access network rise too. In such networks, business goal, system structure, operating environment and user requirements vary, so the network should be able to meet the changes dynamically, so as to provide high class service for users. To fulfill this objective, the network is configured, optimized, healed and reconfigured manually in existing system, but it will result in huge operational expenditure. In order to reduce the cost caused by manual involvement, and to improve the operation efficiency and operation quality, the concept of SON (Self-Organizing Networks) is introduced in future radio access network.Future radio access network is supposed to have SON function, which is composed of 3 function domains:self-configuration, self-optimization and self-healing, each function domain can be divided in to several use cases. Downlink coverage is one of the key performance indicators of radio access network, and load balance can improve the network capacity in hot-spot area, and guarantee the quality of service. Currently, downlink coverage optimization and load balancing in radio access network is done in manual manner, so autonomic downlink coverage optimization and autonomic load balancing are considered to be 2 most important use cases in self-optimization function domain of SON, so the research on the realizing of the former use cases will help to improve the operation quality of radio access network and reduce the operational expenditure.The method of implementing SON function of RAN by means of autonomic network management is researched in this dissertation. The research focus on the implementation of autonomic downlink coverage optimization and autonomic load balancing functions.The main contributions of this dissertation are:Simulated Annealing Automated Coverage Optimization Scheme (SAACOS) was proposed, which can be used to optimize wireless down link coverage in various kinds of radio access networks (such as, WCDMA, TD-SCDMA, and LTE). SAACOS can take effect without manual intervention. Records in measurement report of mobile stations are used to estimate condition of wireless down link coverage and generate appropriate scheme. Simulation results show that, in both weak coverage and excessive coverage situation, quality of wireless downlink coverage is improved by SAACOS; the indicators of coverage can achieve objective reference value.A centralized autonomic load balancing management scheme—Game theoretic Diffluence Autonomic Load Balance scheme (GDALB) is proposed based on autonomic management techniques and game theory. The scheme is suitable for TD-SCDMA radio access network. The scheme balances traffic load while optimizes the coverage by adjusting base station parameters (such as the element coefficients of the antenna array). It is proved that the key algorithms are convergent and the optimum local solution can be gained. Simulation results show that, comparing with existing schemes, GDALB results in larger system capacity, and can address the problems such as uncontrollable overlap area; it also can avoid the holding back of balance action caused by handover scheme.A distributed autonomic load balancing scheme, T-AFWBM (Autonomic Flowing Water Balancing Method applying to TD-LTE) is proposed. The scheme is designed based on the flat network structure of LTE radio access network; it works by T-AFWBM management module in E-UTRAN NodeB (eNB). The eNBs with T-AFWBM management modules can detect their load conditions by self-monitoring actions. It is proved that the key algorithms are convergent and the optimum local solution can be gained. Simulation results demonstrated that by T-AFWBM, load of eNBs can be balanced, when there's hot-spot in the network, system capacity can be improved significantly, and the coverage overlaps between base stations are proper.Based on the T-AFWBM that is suitable for TD-LTE, Autonomic Flowing Water Balancing Method applying to LTE (L-AFWBM) is proposed to fit LTE (including TD-LTE and FD-LTE). By adjusting the hand over margin and using the hand over mechanism, load is balanced. Simulation results showed that the proposed scheme can balance the load of hot-spot area, and improve the total system capacity.