Underground broadband: design of a reliable WLAN gap filler solution

Nowadays on-board wireless broadband connectivity in mass transport vehicles, like trains and light rails, are being trialed around the world. These solutions depend on existing mobile network or satellite coverage to maintain a broadband internet connection to these vehicles. However these technologies lack coverage in underground areas or tunnels, and an alternative "gap filler" technology is needed to keep the train connected. In this paper we discuss the architecture and design of a WLAN based gap filler network solution for rail vehicles, which is able to provide a reliable broadband connection, even at high speed