Algorithmic Vertical Handoff Decision and Merit Network Selection across Heterogeneous Wireless Networks

Abstract: -Next generation wireless networks must be able to coordinate services between heterogeneous networks through multi-mode mobile terminals. Such heterogeneity poses a challenge to seamless handover since each access network has different operations. In this paper, the policies of multiple metrics for handoff to permit connectivity across UMTS and WLAN/WiMAX are designed. Moreover, how to select an optimal target network is an important issue to balance against the network condition and user preference. The considered metrics for handoff initiation include the predicted received signal strength (RSS) of neighbor networks and dwell time. The RSS is predicted by back propagation neural network which is beneficial to perform handoff early. Dwell time value depends on the user speed and moving pattern. The policy for triggering a handoff is that the RSS conditions are consistently true during dwell time, so that unnecessary handoffs are avoidable. The predictive RSS and current RSS conditions have different policies for real time and non-real time services in different networks. Policies in the merit function are presented to select an optimal network. The weighting factors in the merit function are dynamic to neighbor networks. To evaluate the algorithm, RSS prediction, network selection performance and handoff decision performance are considered. The results indicate that the proposed vertical handoff decision algorithm and network selection outperforms the other two approaches in performing handoff earlier and reducing the number of vertical handoffs, connection dropping, Grade of Service (GoS) while increasing the average utilization per call of WLAN/WiMAX networks