Coexistence studies on the interference performance between subway CBTC system and portable Wi-Fi devices

Nowadays, Wi-Fi technology, by virtue of its unique advantages such as easier to use, faster transmission speeds and less charge, has been more widely applied. People can create a Wi-Fi hotspot with their mobile phones, laptops or other electronic equipment in any of cellular network coverage areas. But this also brings trouble to the communication networks of public transportation which work in the same frequency band. For example, at the end of 2012, several Shenzhen Metro lines were forced to stop as their Communication Based Train Control (CBTC) systems had been interfered by portable Wi-Fi devices in carriages. Hence, in this paper, we build a coexistence scenario based system model in order to analyze the coexistence problems between CBTC system and portable Wi-Fi devices. we also propose an anti-interference algorithm to reduce the performance loss of CBTC system, and the algorithm means to optimize the procedure of channel selection and access. Simulation results show the improvement of the performance of CBTC system through the algorithm.