Study On Load Balancing Method In Heterogeneous Wireless Networks

The evolution trend of current mobile and wireless communication networks is heterogeneous wireless network which consists of several different radio access networks (RAN). Because of the diversity and complementation of different RAN in architecture, performance and operation scheme, joint load balancing methods must be used to schedule and assign services among the RAN in order to improve the resource utilization efficiency of the heterogeneous wireless network.A load metric of heterogeneous wireless packet networks is given. A load balancing index basing on load threshold is studied, and the load balancing algorithm consisting of admission control and the vertical handoff is under investigation. The given load metric can measure the load of the network without considering the difference of various radio access networks and is helpful to the load balancing of heterogeneous wireless networks. Simulation results show that the load balancing index basing on load threshold and the load balancing algorithm consisting of two stages can effectively improve the non-satisfaction index of the users.For the purpose of load balancing, a balancing GAP (General Assignment Problem) algorithm and a vertical utility GAP algorithm which base on the basis GAP algorithm are proposed. The basis GAP algorithm refers as assigning N calls to M RAN. The core concept of the balancing GAP algorithm is to choose the RAN of the largest remaining capacity when assigning a call. While the vertical utility GAP algorithm assigns calls by the vertical utility value of different RAN and chooses the RAN of the largest vertical utility value. Simulation results show that both the balancing GAP algorithm and the vertical utility GAP algorithm can balance the load, decrease the call blocking probabilities, increase the throughput of the network and effectively improve the resource utilization efficiency of the heterogeneous wireless networks.Considering the different features of various RAN, load balancing algorithm basing on analytic hierarchy process (AHP) and multiple attribute decision making (MADM) is studied. According to the preference to network features of different services, the weight factors of network attributes are calculated by AHP, and then the network attributes are normalized. The decision factors for each wireless networks can be calculated by simple additive weighting (SAW) method of MADM and the RAN with largest decision factor is to be chosen. Simulation results indicate that load balancing algorithm basing on AMP and MADM can effectively balance the load of networks, consider several attributes of the network (including the load of the network), decrease the call blocking probabilities and increase the throughput of the system.