| Radio systems are moving toward forming heterogeneous wireless networks: collaborations of multiple radio access networks, which access to the all-IP based common core networks through the all-IP technology. As one of the key technologies in the convergence of heterogeneous wireless networks, load balancing is a significant method to achieve the resource sharing over heterogeneous wireless networks, and it can improve resource utilization, reduce transport delay, enlarge system capacity, as well as provide better services for users. Load balancing based on dividing IP flow is a new technology, it can use the resource of heterogeneous wireless networks more efficiently than the traditional hard load balancing, it can also bring gains for traffic transport using the feature that different network can bears different load.Bringing grid into heterogeneous wireless networks, we propose a hierarchical semi-centralized architecture (HSCA). For HSCA, the signaling flow among function entities is given, and the arithmetic expression of integrated reliability and signaling overhead are derived. Simulation results indicate that HSCA can improve the system reliability and reduce the signaling overhead effectively. The proposed network architecture has properly solved the problem of low reliability in centralized load balancing and high overhead in distributed load balancing.The traditional hard load balancing can not realize the maximum utilization of resources over heterogeneous wireless networks, and the existing load balancing methods based or dividing IP flow are less universal. To solve the above problems, we present a bandwidth allocation based load balancing algorithm by dividing IP flow (BALBD). BALBD takes bandwidth as the resource used by wireless networks to serve subscribers, and calculates the optimal flow-dividing ratio for subscribers. When there is a new call or handove: requirement, BALBD divides subscriber's traffic into sub flows according to the optima flow-dividing ratio, and accesses the sub flows to the corresponding networks. Comparec with the existing load balancing methods based on dividing IP flow, BALBD is mon universal. Simulation results show that BALBD can balance the load among heterogeneou: wireless networks effectively, and it can reduce the blocking rate, as well as improve the system throughput.Considering the mobility of subscribers and the time-varying of wireless environment, dynamic load balancing algorithm by dividing IP flow (DLBD) is proposed. We assume tha all of the wireless access networks adopt OFDM technology, and take the two-dimensioi resource unit as the basic resource allocation unit, which is composed of a time slot in tim domain and a sub-channel in frequency domain. DLBD provides a general method fo calculating the optimal flow-dividing ratio. In the whole process from a subscriber require to access to system to he ends the call, DLBD calculates the optimal flow-dividing ratio fo him in real time, and adjusts the rate of sub flows dynamically according to the optima flow-dividing ratio. Although BALBD has good performance, it has some disadvantages:it computing method for optimal flow-dividing ratio is limited into two wireless networks, and it can not adjust the rate of sub flows dynamically. Fortunately, DLBD solves these problems. Simulation results indicate that the load balancing ability of DLBD is 45.1% higher than that of the traditional hard load balancing methods (MLB), while the blocking and call drop rate of DLBD is 31.6% lower than that of MLB. In addition, DLBD can reduce the packet loss rate and increase the system throughput.The work and results of this paper provide a reference for the research of load balancing based on dividing IP flow, and to some extent, fill the domestic blank in the field of load balancing based on dividing IP flow. |
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