A novel enhancement of TCP for on-board IP networks with wireless cellular connectivity

Network mobility (NEMO) allows various types of in-vehicle networks (e.g., WLANs inside public transport vehicle) to be seamlessly connected to the Internet. An on-board mobile router (MR) connects the moving network to the Internet by means of high-speed cellular mobile data services. Unlike terminal mobility, where the mobile hosts (MHs) connect to the cellular base station directly, MHs in NEMO encounter an additional wireless link (MR–MH) before they get connected to the Internet. In this paper, we first note the impact of this additional wireless link on the performance of the wireless enhancements of TCP and observe that the existing TCP enhancement schemes designed for conventional terminal mobility are not equally effective in NEMO. So, we propose an extension of TCP, called on-board TCP (obTCP), to effectively address the double wireless link related issues in NEMO. We compare obTCP against a classical scheme, called snoop, known for its effectiveness in terminal mobility, and analytically demonstrate that the performance gain of obTCP over snoop increases linearly with the delays, and non-linearly with the loss probabilities in the wireless links. Finally, we extend these analyses to obtain throughput models for snoop and obTCP in NEMO. The throughput models are validated through ns-2 simulations.