Research On Multiple Attribute Decision Making Algorithm In Heterogeneous Networks

Since wireless access technologies have experienced great success over the past few years. There have emerged a range of wireless access networks which can be divided into two broad categories:the wide area access and the local area access. Services are ubiquitously delivered over multiple wireless access technologies in a heterogeneous wireless network environment. A significant issue is the ranking of the alternative access networks and the selection of the most efficient and suitable one in order to meet the Quality of Service (QoS) requirements of a specific service. The key to solve this issue is to provide a feasible and efficient vertical handover algorithm. However, decisions on which network to connect are usually difficult to be reached. The main problem is the lack of feasible and efficient vertical handoff algorithms in vertical handover technology, this paper focus on the research of this problem and proposes an improved algorithm and studies another improved algorithm.First, for the problem of multiple attributes decision making in weight calculation, such as arbitrarily specified or weights based on human preferences, the paper proposes a new vertical handoff algorithm which comprehensive considers the current type of service and the conditions of the network itself to get the weight. First we calculate out subjective weight of service preferences by using AHP method, and then we get the objective weight based on the mean and differences in the variance of each criterion, at last we combine the subjective weight and objective weight to get the final weight which is dynamic. Through simulation we could see that compared with the algorithm based on RSS, the proposed method could reduce the number of handoffs and the system call drop probability, meanwhile improve the system performance in terms of higher throughput.Secondly, for the deficiencies of the MAX-PRSS algorithm based on the maximum predicted value of received signal strength (PRSS) and hysteresis margin, for example, the number of handoffs is too much, and the algorithm consider only the received signal strength as a single handoff criteria etc, the paper studies a novel algorithm based on the PRSS combined with Multiple Attribute Decision Making. First GPA-MADM algorithm using the gray prediction algorithm (GPA) to predict the value of the RSS, according to the current service is a real-time or non-real-time, by using dynamic dwell timer and the PRSS value to update the candidate networks. And then use the available bandwidth, cost and user preferences as the criteria to select the final handoff network. Simulation results show that GPA-MADM algorithm handoff more timely, and effectively reduce the number of handoffs and handoff call dropping probability, and improve the utilization of the WLAN/WiMAX network.