Using link layer information for improving vertical handovers

In this paper we present a common triggering mechanism (cross-layer framework) and logic to gather link state and quality related information from the link layers of different access technologies. This information may he utilized by upper layer protocols and applications to react to changes of the link layer. Examples of such a utilization is movement detection, handover decision and application adaptation. The access technology dependent events and parameters, when necessary, are converted into access technology independent triggers and hints. The presented prototype architecture, link information provider (LIP), is currently tested with the VERHO vertical handover controller, which enables intelligent policy-based handover decisions according to several input parameters from the user, application, link layer, etc. Currently, LIP supports certain general link layer parameters, which can he gathered from the operating system and network interface drivers. The system is designed to be easily extended