Adapting TCP for Vertical Handoffs in Wireless Networks

With the growing use of multiradio mobile terminals a vertical handoff between different wireless access technologies is becoming increasingly common. The vertical hand-off may result in a significant change in the access link characteristics that can affect the performance of TCP dramatically as its behaviour depends on the end-to-end path properties that also change consequently. We propose a number of simple enhancements to the TCP sender algorithm which make use of explicit information about the change in the link characteristics due to handoff. We study the effectiveness of the enhancements in a simulated WLAN-GPRS environment with different handoff scenarios. The enhancements are shown to improve TCP performance significantly