Analysis of Ongoing SIP Session with Resource Reservation in Vertical Handover Scenario

Typically, WiFi-to-3G handover is time-critical depending on mobility and speed of mobile host (MH) while 3G-to-WiFi handover is optional for better quality of service and less cost. In this paper, a WiFi-to-3G vertical handover scheme is proposed in order to reduce the total handover delay and keep it within a desirable maximum limit. Our main concern is focused on MH attached currently to WiFi, which tries to move out of WLAN for switching to 3G link. Received signal strength (RSS) is actually an important decision criterion for vertical handover as well as horizontal handover. However, WiFi-to-3G vertical handover cannot be triggered by the signal decay of 3G system since there is no comparable signal strength available to aid the 3G handover decision. During WiFi-to-3G vertical handover, moreover, multimedia session initiation protocol (SIP) session re-setup with resource reservation cannot be completed before network resources along the new path via 3G are successfully reserved. Hence, RSS-based vertical handover algorithm with SIP session re-setup is proposed. From the results, we can know that well-defined or dynamically-adjusted threshold values could result in getting enough time in order to re-setup SIP session with resource reservation.