Mobile Service Continuity in a Heterogeneous Wireless Network Environment

摘要

Mobile devices such as laptops and smartphones are currently equipped with multiple network interfaces, allowing them to reach the Internet via multiple paths. When a running application connects to a service in a remote computer host through the Internet, it leverages on transport and network protocols such as those in the TCP/IP stack expecting continuous, fluent connectivity regardless of which network the mobile device uses. The current state-of-the-art transport protocol that dominates in the Internet is TCP; however, TCP does not allow continuous connectivity when a mobile device leaves the network coverage of an access point. It is expected from a typical device that can connect to both WiFi and cellular networks that it can automatically hand over to an available cellular network once WiFi coverage disappears, and vice-versa. Multipath TCP is a recently proposed transport protocol, backward compatible to TCP, that allows for seamless handovers when new Internet paths appear. This work studies the performance of MPTCP to truly achieve service continuity, with handovers whenever new Internet paths are available, in highly mobile scenarios, such as vehicles engaged into VANET configurations. There may be situations, however, when handovers lead to performance degradation because the newly discovered Internet paths have poor network characteristics. This thesis also addresses the problem of path selection in MPTCP when mobile devices are configured to use at most one network interface prioritizing battery performance; this is the default configuration in smartphones. In all, this thesis advocates for the use of Multipath TCP to truly achieve service continuity for end-to-end connections in both static and highly dynamic mobile settings. It does not consider MPTCP as a substitution to TCP but a natural evolution from the Internet it was designed for to Internet today.