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One of the most important issues in wireless and mobile communication technologies is the mobility management when a mobile node moves between different access networks. Many alternative ways to realize mobility management have been proposed on different layers. In this paper we discuss the vertical handoff behavior when a mobile node moves from IEEE 802.11network to IEEE 802.16 network and vice versa using Session Initiation Protocol (SIP) in order to support real-time communication in a more efficient way in application layer. A new approach named Enhanced Mid-call Mobility SIP(EMSIP)which provides better billing procedures during handoff for real-time operator environment is proposed. Bandwidth and received signal strength (RSS)are used as metrics. Real-time application (streaming video) is taken into consideration. We are using NS2 to measure handoff latency and packet loss in two cases. Varying the speed of Mobile Node(MN) keeping other parameters viz., video packet size constant. Varying the size of video packet keeping the speed of MN constant and the performance characteristics of EMSIP are studied.

One of the recent research issues in IP Multimedia Subsystem (IMS) based heterogeneous internetworking environment is to provide secure handover when a mobile node (MN) moves between different access networks. Various security schemes are available in literature but most of the schemes provide security but degrades the Quality of Service (QoS). The objective of this work is to provide secure and efficient handover in an IMS based Worldwide Interoperability for Microwave access (WiMAX)/ Long Term Evolution (LTE) integrated networks by using the proposed Secure Context Transfer Model (SCTM). New Session Initiation Protocol (SIP) messages are introduced in the proposed SCTM for transferring the context securely from old Proxy-Call session control function (P-CSCF) server to new P-CSCF server during handover. SCTM is verified using NS-2 simulator and analyzed based on Queuing theory. The results show that when compared with previous approaches, SCTM shows an improvement of 23% in terms of handover delay and packet loss providing security and guaranteed QoS to mobile users.