| The long term evolution communication system always faces the problem of radio resource scarcity, how to manage the radio resource efficiently and maximizing system resource utilization rate while ensuring the quality of service for users have been the current research hot spot. Load balancing and admission control, as the key technology of radio resource management, play an important role in improving the resource utilization rate. According to the disadvantage of load balancing and admission control algorithms in existing literatures, two improved algorithms are proposed in this thesis.When the current load balancing algorithms choose the optimal target cell, they only consider one factor and transfer the users in overload cell to the one target cell whose load is the lightest. But these algorithms can easily lead to handover failure and make the target cell become overloaded. Therefore, the algorithm about mobility load balancing based on load pre-allocation has been proposed in the thesis. Firstly, considering multiple factors to choose the optimal target cell by the analytic hierarchy process and getting the user-cell pairs. Secondly, pre-allocating the load the overload cell needs to transfer according to the load capacity of the target cell. Finally, adjusting the cell individual offset by the variable step to transfer some users in overload cell to these target cells until the whole system achieves load balancing. The simulation results show that the proposed algorithm combines the analytic hierarchy process with load pre-allocation, so it can effectively improve the system equilibrium degree and the handover success rate.Existing admission control algorithms always can’t meet the dropping rate requirement, and when the arrival rate of handover call is small, their resource utilization rate is low. Therefore, the dynamic resource reservation admission control algorithm with queuing is proposed in the thesis. By setting the threshold of resource reservation, the system resource is divided into two parts which are shared resource and reserved resource. For the shared resource, new call and handover call can be accessed directly. For the reserved resource, the handover call also can be accessed directly, but the new call only can be accessed with dynamic request probability. When the system resource is used up, the new call is rejected directly while the handover call can be queued, waiting for the system to be idle. The simulation results show that the proposed algorithm can effectively reduce the dropping rate of handover call, improve the resource utilization rate, and the algorithm is less affected by the reserved threshold. |
