Research On Load Balancing And Signaling Simulation For Lte Network

All traditional load balancing policies are on how to balance the amount of data for users, which are all concentrated at the access network side, and are not up to the core network. In the LTE wireless communication system, the signaling interaction between eNB and the core network is controlled by the MME via S1interface, so MME plays an important role in the LTE system. While in the MME resource pool mode in LTE system, MME load balancing is also particularly important. This thesis firstly introduces the whole network architecture of LTE system, including the protocol stack of user plane and control plane. Then it introduces S1and X2interfaces. Meanwhile, through the anlaysis of the signaling procedures of load balancing on S1and X2interfaces, the main manners and steps of MME load balancing can be obtained. According to the key technologies of the interface consistency test for LTE network interface, a test system based on GTR was set up, including the test environment structure, the scripting language "TTCN3" of the test system, and the components of the test system. And through three important signaling procedures of UE’s attachment, this thesis mainly explains the specific templates of the signaling message, the behavior functions of MME and the test cases. Besides, it also explains how to use TTCN3and GTR simulation platform to test the different signaling procedures.Finally, in this thesis, with the analysis of the existing mainstream NNSF algorithm, it is informed that the the NNSF algorithm is a static algorithm. When the MMEs of the pool region have been unable to meet the service demand and have to extend the capacity, the pre-set capacity factor must be modified artificially, because this static algorithm can not automatically adjust the capacity factor of the MME. By analyzing the available capacity of the MME, a new MME load balancing algorithm which is based on the proportion of "attachment to service" is proposed in this thesis. This new algorithm not only takes it into account that how to allocate the UEs accessed to the eNB without causing a single MME overload in the early stage of system operation, but also considers that how to balance the loads of the MMEs when all MMEs in the pool are saturated after the system is running a long time. The simulation results also show that with the UEs’accessing one by one, this designed "attachment to service" algorithm can be able to reduce the blocking rate much better and be able to reduce the loss of the signaling, and to make the system transmit the signaling effectively under high load condition.