Policy-based scanning with QoS support for seamless handovers in wireless networks

Supporting seamless handovers between different wireless networks is a challenging issue. One of the most important aspects of a seamless handover is finding a target network and point of attachment (PoA). This is achieved by performing a so-called channel scanning. In most handovers, such as between universal mobile telecommunications system (UMTS), wireless local area network (WLAN), and worldwide interoperability for microwave access (WiMAX), channel scanning causes severe service disruptions with the current PoA and degrades the quality of service (QoS) during the handover. In this paper, a new architecture for QoS supported scanning that can be generalized to different wireless networks is proposed. It employs two techniques. The first is for determining a policy-based order for the channel scanning sequence.With this technique, depending on the network costs and user requirements, the policy engine determines the channel scanning order for different network types and sets up a scanning sequence of PoAs for a given network type. This policy-based scanning order provides a faster discovery of the target PoA that meets the QoS demands of the user. The second technique consists of a QoS supported dynamic scanning algorithm where the scanning frequency and duration are determined based on the user QOS requirements. Most importantly, the scanning duration is scheduled to guarantee the user QoS requirements while the scan progresses. Simulation results show that the proposed mechanism achieves relatively short service disruptions and provides the desired quality to users during the scanning period.