The Research Of Mobility Load Balancing Technology In Long Term Evolution

In the past 20 years, wireless communication technologies have been developed rapidly. With the increase of the importance of data applications every day, users are willing to communicate with others whenever and wherever possible, including voice, email, picture, music, video and so on. In order to satisfy the bandwidth of data application, transmission delay and network coverage, the 3rd Generation Partnership Project (3GPP) has launched the Long Term Evolution (LTE) project.In LTE system, the number and structure of network parameters have become large and complex. To reduce the expenses of operations and maintenances of the network, Self-Organizing Networks (SON) is introduced to LTE, which is considered as the one of the promising area to save operational expenditures. Mobility Load Balancing (MLB) is one of the important use cases in SON, which aims to cope with the unequal loads between different cells. There are some problems in MLB, and this paper researches these problems deeply. The main contributions of this paper are:(1) Proposed a novel scheme to resolve the conflict problem between MLB and Mobility Robustness Optimization (MRO)MRO is another important use case in SON, which is used for coping with the handover problems in LTE. MLB and MRO both choose adjusting handover parameters as optimization actions, the conflict may occur when they are operating at the same time. In the 3rd chapter, this paper analyzes the reason of the conflict problem at first, and then presents a novel scheme which is based on the restriction on operation of MLB to avoid the conflict. The simulation results demonstrate that the proposed scheme can resolve the conflict problem effectively and improve the performances of both functions.(2) Proposed a novel neighbor selection scheme for MLB to achieve the high efficiencyIn the MLB procedure, the overloaded cell needs to select a neighbor to balance the load. If the overloaded cell selects an unsuitable neighbor, the operation of MLB will not achieve the high efficiency. In the 4th chapter, after analyzing the drawback of the neighbor selection scheme which is based on the loads of neighbor cells, this paper proposed a novel neighbor selection scheme which combines the loads of neighbor cells and the load distribution of the overloaded cell itself. The simulation results demonstrate that the operation of MLB can achieve the high efficiency and better performances in the novel scheme.(3) Proposed a multi-hop MLB scheme to resolve the problem which cannot be resolved by the single-hop MLB schemeIn some complex wireless environments, the single-hop MLB scheme cannot deal with the unequal load between different cells. To resolve this problem, the 4th chapter proposed a multi-hop MLB scheme, which expands the single-hop load balancing to multi-hop. In the proposed scheme, the overloaded cell cooperates with neighbor to distribute the load among multi-cells. The simulation results demonstrate that the multi-hop MLB scheme can distribute the load more equally among multi-cells in some particular environments.