A seamless vertical handoff scheme

In the last decade, many new wireless communication systems have been proposed and developed. These communication systems have different extends of network coverage and form a hierarchical overlay network. A vertical handoff is thus occurred when moving between these different communication systems. In this paper, we propose a new vertical handoff scheme: VHOST (Vertical Hand-Off through Seamless TCP-migration). In VHOST, we first design the mechanism to detect an ongoing handoff. Then, on the basis of TCP-migration, we show how a connection is migrated from the old communication system to the new one. Finally, VHOST includes a handoff-aware TCP adaptation mechanism for link adaptation to accommodate with the different network characteristics. To verify the feasibility of our approach, we implement a prototype system on Linux. The experimental results show that the vertical handoff time is short and acceptable for most applications. Besides, TCP performance is improved by our proposed handoff-aware adaptation scheme. For example, the TCP throughput by proposed adaptation scheme is 1.8 times the original TCP without adaptation.