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December 19, 2011

New Wi-Fi tech for the Paris underground

Alcatel-Lucent has been working on the French Metro to not only integrate a driverless train system, but integrating new wi-fi technology to stream data on safety and security, as well as video for passengers on the Paris Metro Line 1, Paris' busiest.

By Allan Swann

The French-American company collaborated with RATP, the French public transport operator and the world’s fifth largest urban transport operator to introduce a range of broadband communications services.

"The key feature to highlight is the use of Wi-Fi technology. Wi-Fi is normally associated with more ‘sedate’ or slow mobility applications, such as people walking around with laptops, tablets or smartphones within a very small area. Paris Métro trains move at an average of 20km/h – and up to a maximum 80km/h over many kilometres," says Olivier Andre, Alcatel-Lucent’s Vice President of Business Development – Transport.

"It is a particular challenge to ensure highly reliable, uninterrupted, high-speed communications over Wi-Fi under these conditions. However, our solutions does just that, allowing video and data transmission in real-time between trains and operations centres," Andre added.

Paris Metro
Paris Metro image courtesy of Mike_fleming on Flickr.

As a result of the work, Line 1 metro trains now benefit from real-time video train control, video surveillance and operational data transfer between trains and the control center, all transmitted wirelessly.

This enhances passenger safety and optimises operational and maintenance efficiency, as part of the long term goal to transform Métro line 1 into a fully-automated ‘driverless’ system.

Line 1 is the busiest on the subway system and runs from Château de Vincennes in south-east Paris to La Défense, the main business district. The line also serves major tourist destinations such as the Louvre museum, and carries an average of 725,000 passengers every day.

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The project has been three years in the making. The tender was launched in June 2007, Alcatel-Lucent was awarded the contract and began work in 2008, and the system went online in November 2011.

Building the system was no easy task, as Line 1 had to maintain full operational capacity during the work.

"Much of the work was done overnight between 1am and 5am when the Paris Métro is closed. This included all the Wi-Fi installation work as well as testing with trains running. Testing actually began in July 2011, so we had several months to validate the installation and demonstrate continued reliability before the service opened to the public in November," said Andre.

TDST (Transmission de Données Sol Train, or in English, ground-to-train data transmission) is the name of the project given by the RATP. It refers to the complete end-to-end system comprising ground infrastructure (i.e. antennae, Wi-Fi access points), equipment on-board the trains (antennae, Wi-Fi clients, routers and CPUs) through to an application layer that guarantees a permanent IP connection, regardless of changes in Wi-Fi conditions.

"The TSDT network delivers full Wi-Fi coverage over 18km of track and enables a ground to train connection even when the train travels up to 60 km/h. This infrastructure can stream real-time video at 6Mb/s, improving passenger security with on-board surveillance cameras in each carriage, as well as at the front and back of each train. Information for the on-board systems of the train is conveyed at the same speed, reducing response and repair time as well as enhancing efficiency across the service. The system can also offer services to passengers, such as TV shows, advertisements and information for tourists in Paris," says Andre.

However, despite the heavy use of Wi-Fi in the system, there will be no internet connectivity offered to passengers. However, the RATP has recently launched a project to provide 3G mobile coverage in the Paris Métro.

"In the future it is very likely that urban rail operators like the RATP will operate a unified LTE network to serve all their radio needs, both operational and passenger," says Andre.

Ofcom in the UK has announced that 4G/LTE of any kind will not be available until 2015, let alone on the underground.

Every carriage on the train will also be covered by CCTV, which is monitored in real time. This will act as a deterrent for criminals, and give passengers added piece of mind.

"In the event of an incident, it is not always possible for a passenger to raise an alarm quickly – this is no longer an issue as the video transmitted is monitored at one of the RATP’s operations centres. Security services can be alerted and dispatched immediately," says Andre.

The new system also has cameras on the front and rear of the trains, allowing remote monitoring in real-time. Staff in the operations centres can see immediately if there is a problem on the track and halt the train, and have important visibility as trains arrive and leave platforms. In the event of any accidents, footage can be reviewed to give valuable insight into the possible causes, similar to the UK’s driverless systems.

This kind of real time data collection is extremely useful for maintenance also, and ensures that any malfunction is flagged immediately and trains can be stopped remotely if necessary.

"Even if immediate action is not required, maintenance teams are alerted to issues so that the performance and safety of the trains themselves can be maintained efficiently," he says.

Andre wouldn’t comment on any questions concerning costs of construction (or any Government subsidies involved), or the long term financial benefits to the line or indeed Alcatel-Lucent’s bottom line.

Technical Features now in action on Paris Metro Line 1

Wi-Fi technology for train to ground communications using 5.2 GHz to 5.8 GHz band (for indoor and outdoor environments)

Access Points installed along the line in order to provide seamless roaming (for the train) with the central WLAN Control system

Required performance is 6Mbps minimum per train (3 trains can be in the same area) (-76 db level required)

300 ms buffering capability in case of temporary loss of communication

Compliance with train environment requirements: rugged equipment (temperature, immunity, smoke and fire) tested in an official lab environment.

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