CBTC DCS Based on LTE Unlicensed Wireless Access: Assessment of Coexistence Performance With Wi-Fi

As the existing communication technologies which for about a decade have supported railway operations and the huge transition from conventional to modern communication-based signaling approach the extent of their performance capabilities, the railway industry strives to migrate to a proven solution aiming to support the new and diverse broadband services and reduce cost. Long Term Evolution (LTE) radio access technology has been globally accepted because of the unparalleled performance, off-the-shelf convenience, and well-developed standardization. An LTE solution, however, brings both the opportunities and challenges to a Data Communication System (DCS) underlying a Communication-Based Train Control (CBTC) system. The presented research targets one of the main LTE deployment challenges; the spectrum availability. To cope with the increasing scarcity of spectrum resources, LTE/LTE-A has envisaged an extension to the unlicensed band which is already heavily populated with incompatible legacy systems such as the immensely popular Wi-Fi networks. In this paper, a design framework is established to dimension the LTE system according to the CBTC DCS sub-system level requirements. Furthermore, the LTE/Wi-Fi coexistence performance is evaluated and studied in a train control application’s context by using a Markov chain analysis approach.