Access point deployment optimisation in communication-based train control systems

Through the use of new communication-based train control (CBTC) systems, modern metro railways have been able to provide a more efficient, more reliable and more eco-friendly transport services. The main advantages of the CBTC systems are achieved by utilising modern communication technologies. The performance of the communications network is dependent on a well-designed access point (AP) deployment, as this determines the overall communication capability and impacts the cost. In this thesis, a systematic methodology is proposed for formulating and solving AP deployment planning (ADP) problems in two scenarios: (i) a tunnel section area; and (ii) a real-world metro system. Different mathematical models are presented for modelling the ADP problem in these two scenarios. In addition to mathematical models, an exhaustive search and a customized search algorithm, which uses a multi-objective evolutionary algorithm based on decomposition (MOEA/D), are proposed for solving the ADP optimisation problems. The methodologies are applied to the scenarios mentioned above. To evaluate the optimisation results, the optimised AP deployments are tested on a simulation platform integrating a railway network simulator and a communication network simulator. The test result shows that with the optimised AP deployments the DCS can achieve a better performance while using fewer APs

A cognitive control approach to interference mitigation in communications-based train control (CBTC) co-existing with passenger information systems (PISs)

As a key component of urban rail transit systems, communications-based train control (CBTC) is an automated train control system using train-ground communications to ensure efficient operation of rail vehicles. In addition to CBTC systems, passenger information systems (PISs) are adopted in urban rail transit systems to improve quality of service (QoS) offered to customers. The interference between CBTC systems and PISs is an important factor impacting QoS of both CBTC systems and PISs. With recent advances in cognitive dynamic systems, in this paper, we take a cognitive control approach to interference mitigation considering the co-existence of CBTC systems and PISs. In our cognitive control approach, the notion of information gap is adopted to quantitatively describe effects of interference on CBTC. The wireless channel is modeled as a finite-state Markov chain with multiple state transition probability matrices, which are derived from real field measurements. Simulation results show that the proposed cognitive control approach can significantly improve performance of CBTC train-ground communications under interference from

Towards safer level crossings: existing recommendations, new applicable technologies and a proposed simulation model

Every year,more than 400 people are killed in over 1,200 accidents at road-rail level crossings in the European Union. Together with tunnels and specific road black spots, level crossings have been identified as being a particular weak point in road infrastructure, seriously jeopardizing road safety. In the case of railway transport, level crossings can represent as much as 29% of all fatalities caused by railway operations. Up to now, the only effective solution appears to involve upgrading level crossing safety systems even though in more than 90% of cases the primary accident cause is inadequate or improper human behavior rather than any technical, rail-based issue. This article provides results of research done on possible technological solutions to reduce the number of accidents at level crossings and demonstrate the effectiveness of the latter. Elements of these recommendations and related research activities constitute the main focus of the research work described in this paper. It is organized as follows: In Section 2, we consider statistical data related to LX accidents in certain given European countries. These statistics as well as a European Commission Directive related to safety targets are analyzed and the main trends are drawn. The study was carried out on the basis of the classification by the European Railway Agency of active LXs and passive LXs. These results form the foundation for the work described in Section 3. Section 3 focuses on advanced technology to improve LXs safety. The main thrust of the study is to evaluate low-cost, standard technology that can contribute to a direct decrease in the number of accidents, at an affordable cost. Existing surveillance technologies already used in rail or road transport are first considered. To facilitate LX bimodality, special emphasis is put on technical solutions which have already demonstrated high efficiency in both environments. In Section 4, the mode of operation of each potential solution is modeled and evaluated considering several operational scenarii, in order to evaluate the aggregate benefits of all the input. Setting models to describe the dynamics surrounding the LX environment will prepare a basis to support the decision making process of a joint rail and road sector strategy on how to control LXs. Finally, section 5 brings the study to a close with a list of the main areas in which to concentrate our future work

Leaky Waveguide for Train-to-Wayside Communication-Based Train Control

In guided urban automated transportation systems, the maintenance of a high-quality broadband train-to-wayside communication at all locations along the track poses a major problem. Several techniques are currently used. However, to achieve sufficient rates, a communication frequency range of 2-6 GHz is widely in use. At these frequencies, the natural propagation in tunnels usually works efficiently, but the communication through a leaky waveguide that, is continuously laid along the track has several advantages. Over the required communication ranges of several hundred meters, between stations, such waveguides provide low longitudinal attenuation and remain of reasonable size. They also provide predictable communication ranges that could offer significant advantages over the natural propagation approach. This paper will theoretically and experimentally describe such a technical solution. Using ray-optical modeling of the radio propagation in a railway-type tunnel, the radiation characteristics of such a system will be evaluated. At the same operating frequencies, it will be compared with a conventional base solution using antennas separated a few hundred meters apart. An example of a recently operational implemented system will be presented