Research On Vertical Handoff-based Load Balancing Algorithm In Heterogeneous Networks

With the rapid development of information technology,users' services present a development trend of diversification and large quantities,while heterogeneous wireless network has become an inevitable choice for the future evolution of wireless networks.In heterogeneous wireless networks,joint radio resource management(JRRM)can dispatch and distribute the radio resources centrally,due to the wireless resources provided by multiple networks,and as one of the key technologies of RRM in heterogeneous wireless networks,load balancing technology can ensure the services' quality of the users,at the same time,optimize the system resources.Therefore,the research of load balancing in heterogeneous wireless networks has important significance.In this thesis,firstly a brief introduction of the load balancing researches' background and significance,research status in the heterogeneous wireless networks is provided.Then,it studies the heterogeneous wireless networks and the joint radio resource management.Finally,the load balancing and its key technology are researched.In addition,based on the research of the existing load balancing algorithms,an improved load balancing algorithm is proposed.Aiming at the problem of frequent handoff and complex handoff decision of the existing load balancing algorithms,a vertical handoff algorithm based on sojourn time is proposed.The candidate target network is determined by the minimum guarantee function,citing the introduction of the concept of sojourn time,it can effectively prevent the unnecessary handoff occurrence,and use the dynamic new call blocking probability to calculating the handoff decision function.Through comparing the calculation value of the handoff decision function to complete the vertical handoff.Compared with the traditional algorithm,the improved algorithm can reduce the average blocking rate and the handoff rate,and can get better bandwidth utilization.Simulation results show that the vertical handoff algorithm based on the sojourn time can utilize the limited wireless resources more effectively.A vertical handoff algorithm based on the total utility is proposed,for the existing load balancing algorithms,the reward of network is considered,while the loss of the handoff is ignored.A reward function is used to capture the network bandwidth and transmission delay,while the blocking probability and the signaling loss is expressed as a cost function.The total utility function is defined as the combination of the reward function and the cost function.While considering the different types of services,the user selects the network which obtaining the maximum total utility function value as the handoff target network.The vertical handoff algorithm based on the total utility can effectively reduce the new call blocking probability and the handoff rate,and provide higher user satisfaction.The simulation results show that the algorithm can improve the throughput of the system and realize the load balancing between the networks.