Modeling, Analysis and Optimization of Vertical Handover Schemes in Heterogeneous Wireless Networks

Abstract

Modeling, Analysis and Optimization of Vertical Handover Schemes in Heterogeneous Wireless Networks Vertical handover has emerged as a key component in the development of seamless con- nectivity framework for today’s heterogeneous wireless network environment with diverse access technologies. This work aims at enhancing the vertical handover experience for a multi-interface mobile node in a heterogeneous network environment and involves op- timization of both handover execution and pre-execution preparation. In this endeavor, we have (i) come-up with a new technique for handover execution, (ii) developed a new handover necessity estimation method for a mobile node moving into a WLAN cell, (iii) mathematically modeled handover triggering condition estimation for a mobile node mov- ing out of a WLAN coverage area, (iv) surveyed various techniques used for target network selection in a heterogeneous network environment, (v) surveyed and categorized handover execution techniques, (vi) suggested a criteria metrics for evaluation of handover execution techniques and (vii) analyzed the proposed handover execution technique against some of the parameters of the evaluation criteria metrics using NCTUns simulator. Finally, we have looked into some bleeding-edge vertical handover optimization techniques; particularly the utilization of RF coverage maps in handover decision process. The proposed vertical handover execution technique is an end-to-end, self-reliant scheme for a multi-interface mobile node, roaming in a heterogeneous network environment. The scheme neither requires rerouting nor the tunneling. Despite end-to-end signaling, the ser- vice disruption time is few milli-seconds as compared to hundreds of milli-seconds for existing techniques. The designed handover necessity estimation model, based on angle of arrival with respect to tangent, for limiting the unnecessary handovers and handover failures provides much better control than the existing model. Even at higher velocities, the deviation from the desired level is five times lower than the existing model. The sug- gested analytical model for handover triggering condition estimation for maximizing the connectivity with the preferred network, as opposed to existing models, does not make assumptions about the shape of the exit region and thus makes it more general. Perfor- mance of this model is identical to the existing model, which reveals that the choice of pdf of exit angle does not affect the performance of handover triggering condition estimationalgorithm. The study of target network selection schemes considers traditional horizon- tal schemes, their adaptation in a heterogeneous network environment, more sophisticated schemes and also the fuzzy logic and neural network based schemes. The information re- quired for each of the handover pre-execution decisions is identified and the methods for information collection are also studied. The detailed survey of vertical handover execution techniques is used for classification and identification of pros and cons associated with these diverse approaches. Use of RF coverage maps in handover decisions is a novel idea. Timely execution of the vertical handover with the help of RF coverage maps can ensure an uninterrupted communication for a multi-interface mobile node traversing the black spots. It has been demonstrated that this can help improve communication and optimize the handover process.