Research On Network Selection And Joint Call Admission Control In Heterogeneous Wireless Networks

As the rapid development of the wireless mobile communication technologies, the emerging radio access technologies come out one after another. They have different implementation techniques, different control methods, different coverage and different data transmission rate, they complement each other and compete with each other to form the heterogeneous wireless networks. In the heterogeneous wireless networks, how to choose the most suitable access networks for users, and allocate the resources for users rationally, are key issues in the heterogeneous wireless networks. They play an important role in guaranteeing the QoS of users and improving the capacity of systems. Therefore, in this paper, we do a deep research on the network selection and joint call admission control algorithms in the heterogeneous wireless networks.A network selection algorithm based on analytic hierarchy process (AHP) and gray relation analysis (GRA) theory is proposed in this paper. Firstly, The network selection problem is transformed into typical dynamic multi-attribute decision making (DMADM) problem. The dynamic change trend of network parameters is taken into account in the decision model besides user preference, service application and the current level of network parameters. Secondly, the AHP is used to calculate the weight of the network parameters. Then the GRA is used in the dynamic multi-attribute decision making method to calculate the comprehensive evaluation values of the available networks. The simulation results show that this strategy could provide mobile users with reasonable access selection. A joint call admission control algorithm based on bandwidth thresholds is proposed in heterogeneous wireless networks of 3G and WLAN interconnection. The priority access network is selected according to the traffic characteristics of users. Taking into account the priorities of handoff users and users with different traffic class, Multi-level access thresholds are set in 3G and WLAN respectively. A Multi-dimensional Markov chain model is used to analyze the new call blocking probability and handoff call dropping probability of the proposed algorithm. The simulation results show that the proposed algorithm not only satisfies the QoS requirements of users with different services, but also achieves better tradeoff between new call blocking probability and handoff call dropping probability and improves the overall performance of the system.Additionally, a joint call admission control algorithm based on bandwidth degradation is proposed in heterogeneous networks of 3G and WLAN interconnection. Since the transmission rate of video and data services are variable, when 3G or WLAN is at full load and can not access new users, the bandwidth of the connected video or data users in the networks can be degraded to reduce the network load and accept more users. Compared With the fixed bandwidth allocation scheme, the bandwidth degradation scheme reduces the total new call blocking probability and handoff call dropping probability in the heterogeneous systems.