Published on October 9th, 2013 | by Juan Roman0
ETCS AND CBTC CONVERGENCE OVER LTE RADIO LAYER
A general propensity in modern Train Control Systems is the use of increasingly similar hardware platforms to implement different applications. Increasingly, the on-board equipment needed to deploy a mass transit CBTC system is, if not the same, at least equivalent to the equipment used for ETCS Level 2 roll-outs.
A similar process is taking place trackside, with Eurobalises being adopted for CBTC and Zone Controllers or Interlockings being revamped into RBCs. It is mostly at the application level where these systems begin to differ, as if CBTC systems were about to become a series of customised ATO solutions on top of what basically is a generic ETCS-like ATP system.
This integration trend begs a question: what will happen with the radio layer? Today, most ETCS Level 2 systems use GSM-R as their radio carrier technology. At the same time, nearly all CBTC systems use radio networks based on IEEE 802.11 (Wi-Fi). The main reason for this difference is historical – with GSM-R being developed by European authorities as part of the ERTMS specification, and Wi-Fi being chosen as a “cheap and dirty” unlicensed band solution for railways that are mostly underground.
There is a growing interest to move away from those radio layers not only because GSM-R and Wi-Fi are becoming obsolete, rather because they are limiting the capacity and capabilities of train control systems. Innovations requiring high-data rates, such us a simple video surveillance of a train cabin, can’t be implemented using mobile technologies of the past century.
Nowadays, LTE is the technology that, according to technical and market trends, appears to be the logical successor to GSM-R and the best alternative to replace Wi-Fi in safety critical applications. Vendors are already offering LTE products for railway environments, and becoming increasingly reluctant to support out dated products for a relatively small market niche.
The railway market appears ready to embrace the change, notwithstanding the transitional challenges associated with existing platforms in adopting a new radio layer.
However, it seems that Europe is committed to continue its GSM-R deployment up to 2025 and beyond, in line with the efforts and investments made over the past. Back in the late 1980´s, it took almost five years for European authorities to select GSM as the base of a European railway standard. Subsequently, ten years later the first version of the ERTMS specifications was released. The first GSM-R was deployed in 2003, and the first ERTMS L2 application in service on December 2005.
On the other hand, there is strong pressure from operators of mass transit systems based on CBTC and railways in countries outside Europe to move to LTE. Will Europe, ironically being the architect of modern and interoperable railway systems, remain fixed on GSM-R while the rest of the world is already deploying CBTC and ETCS based systems over LTE?
Historically the railway industry has evolved slowly when compared to others such as airspace, telecommunications and computing industries. The LTE question heralds an exciting and challenging situation in the next few years and we wait in anticipation to see if this is finally the time that train control system’s providers will seize the initiative by committing to a “state-of-the-art” solution.
This article is extracted from a White Paper of the same name, written by Rodrigo Alvarez and Juan Roman for the IRSE technical meeting to be held in Perth, Australia, on 19 October, 2013. Follow Titan ICT on Linkedin to be notified of the release of the full Technical Paper after the conference.