TCP Mobility Enhancement for Vertical Handovers

TCP is not designed to be used in a wireless mobile environment. It lacks the capability to handle issues caused by handover, especially those between heterogeneous networks. In this paper a mobility enhancement is proposed for TCP to handle these mobility issues. This enhancement does not change the behaviour of TCP in all normal situations and is only evoked when a vertical handover actually occurs. A series of adaptation actions are defined to guide the handed-over TCP flow through phases of handover detection, new network probing, loss recovery and the final state adjustment, so that the flow can adequately settle down in the new network without the aforementioned penalties. The enhancement can handle various vertical handover scenarios and the overall improvement over the original TCP is clearly proven by simulation results.