Considering Fading Effects for Vertical Handover in Heterogenous Wireless Networks

Considering Fading Effects for Vertical Handover in Heterogenous Wireless Networks Over the years, vertical handover has attracted the interest of numerous researchers. Despite the attractive benefits of integrating different wireless platforms, mobile users are confronted with the issue of detrimental handover. As a mobile node (MN) moves within a heterogeneous environment, satisfactory quality of service (QoS) is desired by ensuring efficient vertical handover. This demands not only the efficient execution of vertical handover, but also optimized pre-handover decisions, such as: handover necessity estimation (HNE), handover triggering condition estimation (HTCE) and handover target selection (HTS). The existing works on HNE and HTCE optimization considered the coverage region of a point of attachment to be circular, ignoring the fading effect. This paper considers the effect of shadow fading and used extensive geometric and probability analysis in modelling the coverage area of a WLAN cell. Thus, presents a realistic and novel model with an attempt to ensure optimal handover as a mobile node (MN) traverses a heterogeneous wireless environment. In the proposed HNE approach, the dwell time is estimated along with the threshold values to ensure an optimal handover decision by the MN, while the probability of unnecessary handover and handover failure are kept within tolerable bounds. The proposed HTCE approach estimates the optimal handover triggering point at which an MN will need to initiate a handover in order to avoid connection breakdowns as well as maximize the usage of the preferred access network. In the proposed HTS approach, Grey Relational Analysis (GRA) algorithm was applied on two different case studies and used to select an optimal access network to perform a handover based on certain performance criteria. Monte-Carlo simulations were carried out to show the behaviour of the proposed HNE and HTCE models. Results were validated by comparing the proposed models with existing works.