Radio Communication for Communications-Based Train Control (CBTC): A Tutorial and Survey

Abstract

Abstract-Over the last decade, railway industry has seen a huge transition from conventional railway signalling systems to modern, communication-based signalling systems. Communications-Based Train Control (CBTC) is a modern communication-based system that uses radio communication to transfer timely and accurate train control information. CBTC is the choice of mass-transit railway operators today, with over a hundred systems currently installed worldwide. The safetyrelated, time-critical applications such as train control impose stringent reliability and availability requirements on the radio communication technology used. IEEE 802.11 Wi-Fi, despite being originally developed for stationary users within a limited area, has prevailed as the de-facto radio technology for CBTC. Unfortunately, very limited literature is publicly available on this topic due to the highly competitive nature of the railway industry. We believe that this paper fills the much-needed gap. It aims to present a comprehensive tutorial, as well as a survey of the stateof-the-art, of CBTC and the role of radio communication in it. The operation and fundamental components of a CBTC system are discussed. A summary of the evolution of the communication technologies used for modern railway signalling is presented. The benefits and drawbacks of using a radio communication technology, particularly Wi-Fi, and the challenges it introduces, are discussed. Best practices in the design of a CBTC radio network and the measures to optimize its availability are discussed, while using the currently in-progress Copenhagen Strain CBTC project as a reference. An overview of the CBTC standardization efforts, as well as the IEEE CBTC standardfrequently overlooked due to its limited scope-is included. The paper is concluded by providing a number of potential directions for future work.

A Multimedia Streaming System for Urban Rail Environments

“…In communication-based signaling, a radio communication technology is used to transfer trains control information between a train and the train control center. Nearly all of the modern CBTC systems use IEEE 802.11, widely known as Wi-Fi [6], as the radio technology, mainly owing to its costeffectiveness [7]. IEEE 802.11a or 802.11g are the most commonly used versions of this technology, supporting data rates of up to 54 Mbps.…”

“…CBTC data, which consists of train control messages typically sent about every 500 milliseconds, itself does not require high bandwidth. Typical data rate ranges up to maximum 100 kbps [7]. This leaves with plenty of excessive bandwidth to be used for other purposes.…”

Performance Evaluation of a Multi-radio, Multi-hop Ad-hoc Radio Communication Network for Communications-Based Train Control (CBTC)

“…A sharp increase in the popularity of the CBTC systems is currently being witnessed among masstransit railway operators. Despite its short range and lack of support for mobility, the IEEE 802.11 WLAN, also known as Wi-Fi, has prevailed as the radio technology of choice for CBTC systems, mainly due to its cost-effectiveness [1].…”

“…Therefore, complex roaming algorithms are employed by CBTC systems to solve this problem. Often different roaming algorithms are employed for train's front and rear antennas due to different alignments with respect to the antennas on the trackside APs [1]. Nonetheless, roaming results in delays in communication and limits the supported train speed as well.…”

“…For a more detailed version, refer to [1]. In CBTC, radio communication is used to exchange train control information between the train and the wayside, enabling Automatic Train Control (ATC) functions.…”