WiMAX Role on CBTC Systems

The recent progresses in mobile telecommunications technologies have allowed railway telecommunications technology to go a step forward, and, in the same way, the railway control systems. In this sense, while the mobile telecommunications technology evolved from the first generation of analogue mobile communication systems to what is known today as B3G (Beyond 3G), the same occurred with the telecommunication systems used in railways, from those based on analogue telecommunications, to the most recent ones based on 2G such as GSM-R or TETRA. Till recently, there was a technological gap regarding high mobility environments, high transmission rate and high interactivity (low latency). However, new emerging telecommunications technologies have shortened this gap significantly. This way, the train control systems will be affected by the availability of telecommunications technologies capable of offering earth-train broadband communications in real time. This article presents a telecommunications network architecture based on WiMAX (Worldwide Interoperability for Microwave Access) mobile technology (IEEE 802.16e) that fulfils the telecommunications needs in the railway environment. The WiMAX mobile technology most relevant features are: transmission rates up to 30Mbps at 15 km distance; mobility support up to 200km/h; QoS, security, low latency, fast, scalable and cost effective deployment, mainly compared to GSM-R deployment. In the mobile node design of this network telecommunications architecture, the multipath fading effect, and the Doppler effect, present in high speed mobility scenarios, have been taken into account. An improvement in the handoff between BSs, through a neighbouring and predictive mobility algorithm, is included. The architecture proposed supports the functional and system requirements identified in the UIC Project EIRENE (European Integrated Railway Radio Enhanced Network), and demanded to GSM-R technology. Measures on a real testbed and a model developed with the discrete event simulation tool, Opnet, have been employed in this work.