28 ||| 1556-6072/14/$31.00©2014IEEE IEEE VEHICULAR TECHNOLOGY MAGAZINE | MARCH 2014 Digital Object Identifier 10.1109/MVT.2013.2295072 Date of publication: 6 February 2014 End-to-End Multipath Technology T he migration of railway signaling systems based on circuit switching toward Internet protocol (IP) is on the way. Conse- quently, new strategies to promote reliability in packet- switching networks must be studied. In this article, we propose the use of multipath technology to enhance the availability and reliability of these communications. To our knowledge, this is the first time that multipath strategies are customized for the railway train-control domain. We present the basic requirements that a mul- tipath protocol must fulfill to increase the reliability and evaluate dif- ferent related multipath proposals and provide our own customized protocol, the reliable multipath transmission control protocol (RMPTCP). Finally, we demonstrate the availability improvement that our proposed multipath strategy introduces. Railway control and signaling systems are the core of railway op- erations. Historically, each country has deployed its own signaling system independently. Nevertheless, because of the increase in in- ternational services, the necessity to harmonize different national train control systems emerged. In Europe, this need is intensified by the evolution of European cross-border economic and social relation- ships. Therefore, the European Rail Traffic Management System (ERT- MS) was introduced as the European standard for train control and signaling systems in European railway networks and to increase track utilization by dynamic train control (moving blocks). Because there are risks to human lives involved, train control sys- tems must fulfill specific requirements regarding reliability, availability, maintainability, and safety (RAMS). These requirements are specified in the railway RAMS standard EN50126/IEC62278 [1] and have been ap- plied to the ERTMS in [2] to achieve a fault-tolerant system with safety integrity level 4. Meeting these requirements over the railway commu- nication channels has always represented a challenge, due to the harsh, electrically noisy disturbances, high mobility, and continuous hando- vers. To solve this issue, traditionally, the communication architecture Enhancing Availability and Reliability in Next-Generation Packet-Switched Train Signaling Systems Igor Lopez, Marina Aguado, and Eduardo Jacob ©PHOTODISC