Improving TCP performance with fast adaptive congestion control during soft vertical handoff

Recently, the research on the interworking between 3G cellular networks and WLANs is actively being constructed. To integrate these two technologies, there are many issues such as the network architecture, mobility management, and security which should be solved. During vertical handoff, some undesirable phenomena may mistakenly trigger TCP congestion control operations and thus degrade TCP performance. In this paper, we propose an approach that can quickly estimate available bandwidth when a mobile node (MN) handoff occurs. A sender updates the adaptive slow-start threshold (ssthresh) and congestion window size (cwnd) to improve TCP performance during soft vertical handoff in hybrid mobile networks. Our scheme requires only minor modifications of the transport layer of the end hosts. Simulation results show that our scheme effectively improves the TCP performance.