Abstract
Latest 3G and 4G technologies have made it possible for mobile users to use real time applications anytime, anywhere. The use of real time applications like VoIP by mobile users is increasing day by day. To achieve uninterrupted and better service, mobile users should be able to maintain continuous and seamless connectivity with the corresponding node. In this paper, we study the impact of Vertical Handovers (VHOs) on performance of VoIP using existing multimedia protocols. Results show that use of existing protocols like Real time Transport Protocol (RTP) and TCP Friendly Rate Control (TFRC) do not meet the Quality of Service (QoS) requirements of VoIP during VHOs. We propose a scheme, Adaptive Vertical Handover Rate Control (AVHRC), that meets the QoS requirements of VoIP during Vertical handovers. AVHRC acquires the information of next possible access technology during vertical handovers and provide effective rate control mechanism to cater for the effect of vertical handovers. We also determine the lower bound of link stability for AVHRC that meets the QoS requirements of VoIP. Our results show that for various mobility scenarios AVHRC provides significant improvement in terms of throughput, packet loss and handover latency as compared to RTP and TFRC.