UMTS to WLAN Handover based on A Priori Knowledge of the Networks

Mobile terminals measurements capabilities are strong limitations that may impede seamless handover from UMTS to WLAN. In this article, we propose an inter-system handover method that does not require in-line measurements on WLAN. It identifies the most probable WLAN Access Point for handover, from coverage point of view, depending on UMTS signal measurements and on a handover probability database. This method can be implemented in the RNC, or in a B3G common controller. Simulation results in a WLAN hot spot deployment show that handover based on a priori knowledge of the networks increases handover success rate, compared to classical blind handover. Its performance can be improved by optimizing the handover probability database. Besides, the proposed method enables to forecast handover's success, and adapt accordingly. Handover based on a priori knowledge of the networks can consequently be integrated into several B3G handover algorithms, to decrease handover delay and complexity.