Moving bits from 3G to metro-scale WiFi for vehicular network access: An integrated transport layer solution

Abstract

We investigate a transport layer protocol design that integrates 3G and WiFi networks, specifically targeting vehicular mobility. The goal is to move load from the expensive 3G network to the less expensive WiFi network without hurting the user experience. As the test platform we choose a nationwide 3G network and a commercially operated metro-scale WiFi network. We exploit the often complementary characteristics of these networks for a hybrid design at the transport layer. To this end, we modify the stock Linux SCTP implementation to support `striping' across multiple interfaces and the ability to handle frequent path failures and recovery in a seamless fashion. Instead of simply striping data over two network connections, we develop a utility and cost-based formulation that decides the right amount of load that can be put on the 3G network to maximize the user's benefit. We develop and experiment with a transport level scheduler to do this. We call the new SCTP design as oSCTP, meaning `SCTP to be used for offloading.' We demonstrate the effectiveness of oSCTP and show that it is able to deliver superior network throughput and user experience, while significantly reducing the load on the 3G network.