Enhancing the Modelling of Vertical Handover in Integrated Cellular/WLAN Environments

This paper presents a new analytical model to enhance the modelling of vertical handover for integrated cellular/WLAN systems. The WLAN system considered is within the coverage area of cellular network, hence users can have a downward vertical handover to the WLAN and/or an upward vertical handover to the cellular network. Recent work on the modelling of these systems using a two-stage model with feedback encountered some complications in terms of handling certain streams. The possibility of having continuous streams which keep on switching between WLAN and cellular systems, may reduce the practicality of the models. The new analytical model presented in this paper restricts certain flows to make sure that the handover calls from the WLAN to the cellular system are not allowed back to the WLAN. Previously proposed analytical models, which do not nullify these streams may not reflect real systems and the results obtained may not be practically applicable especially for such a configuration of cellular/WLAN interaction. A new model is presented with an extra random variable in order to ensure that Markovian property is not violated. Results are presented to show that the new model is a significant improvement but more work is needed to analyse more complex scenarios.