Originally published on TrackTalk [December 2015]
With demand for metro services growing as urban populations expand, operators are responding by deploying new technologies to increase network capacity and performance. From communications-based train control (CBTC) to video protection, onboard and station applications, metro operators are successfully extracting more from what they already have.
But this has come at a cost. Traditionally these applications require their own separate network infrastructure. However, this “silo” approach results in significant management and maintenance challenges as well as higher costs. For example CBTC may use a proprietary WiFi network, while operational voice networks and onboard emergency call points use Private Mobile Radio technology based on Tetra or P25 standards. In addition, platform TV could be based either on Wi-Fi or Digital Video Broadcasting.
A single operator may consequently be hosting seven or eight separate networks, which inevitably increases costs. It also prevents upgrades to support next-generation applications, including IP-based services. Indeed the shift to greater automation is increasing the need for more CCTV while passengers expect access to services like onboard WiFi. Unfortunately current network structures are unable to cope with these demands.
The French government is attempting to address this issue through the “Investments for the Future – National Fund for the Digital Society” initiative, or Systuf (SYstem Transport Urban Future) project. This programme is led by Alcatel-Lucent with seven industry partners and is focusing on developing and testing 4G LTE mobile broadband as the foundation of a single integrated radio network. The project includes defining and characterising both traditional and new applications, and developing a new LTE-based end-to-end communications architecture.
LTE is the right platform for this as it can carry voice and data for train control, onboard video surveillance, and passenger information simultaneously on a single IP network, while offering high speeds of up to 150MB/s, enhanced security and large capacity. LTE also offers low latency, with the time a packet of data gets from one to another as low as 10 milliseconds. It also guarantees the segregation of services, which is critical for mission-critical applications like CBTC.
The project initially focused on testing the technology at Alcatel-Lucent’s Transportation Solution Lab from July 2012 to October 2015. This covered network design, radio planning simulation and performance by measuring throughput and response times at various simulated train speeds. The work is now entering the next phase: live testing on the driverless Line 14 of Paris Metro, which will start this month and conclude in spring 2016.
Latency, bandwidth and error bit rate performance will be tested for each application supported by the network during these trials. In addition, the tests will be carried out while the network is fully loaded and with trains passing one another, which offers the biggest chance for interference and overloading radio cells.
Successful completion of the trials, and the research project, will help to establish 4G LTE as the network architecture of choice for metro operators. By deploying 4G LTE they will finally be able to ditch silos in favour of a converged network, which will meet their demand for greater capacity now and well into the future. For more information visit our web site.