Adaptive window size to reduce the influence of heterogeneous mobility on TCP performance

The proliferation of wireless access technologies and the growth of demand for mobile services pose the need for seamless mobility across heterogeneous networks. Moreover, the widespread use of the TCP/IP protocol stack clearly reinforces the need to enhance its performance in such scenarios. In this paper we present an experimental evaluation of the influence of the so called heterogeneous (vertical) mobility on the behavior TCP protocol, and we propose a cross-layer solution to reduce this impact in future mobile environments. The described solution is based on the dynamic adaptation of the window size for a TCP connection, based on the related mobility conditions. We have evaluated this solution using the BIB3R testbed, which emulates the inter-working between commercial wireless technologies (e.g., UMTS, Wi-Fi, WiMAX, etc). The results showed that by adjusting the window size before the vertical handover process, TCP connections can reduce the adaptation time between 30 and 40 percent depending on the mobility scenario (heterogeneous links).