Connectivity is a key stage in the implementation of Line 18, for which the Société des grands projets is the contracting authority. For TDF, the challenge is to set up a multi-operator network of distributed antennas (DAS - Distributed Antenna System) in stations, tunnels, trenches and viaducts along the 35 kilometers of the line, including 21 kilometers underground and 14 kilometers overhead.
Indoor mobile coverage: a challenge for large-scale projects
Indoor mobile coverage is a central issue in major transport projects, as it guarantees passengers a reliable and continuous connection, even in underground or confined spaces. Ensuring this quality of service is essential to meet growing user expectations and support the modernization of mobility networks.
To ensure optimum quality of service throughout Line 18, TDF has installed a mobile coverage system (known as "indoor") comprising almost 400 antennas and 100 repeater zones to amplify the range of operators' signals.
One of the special features of the project is the DAS that TDF is deploying outside the tunnels, over a distance of 14 kilometers, to cover the overhead sections, including the 6.7-kilometer viaduct. This summer, several telecom masts were installed on this viaduct to reinforce the line's coverage. This outdoor DAS solution, already successfully used by TDF on the Nouvelle Route du Littoral in La Réunion, is a first in mainland France.
In addition to installing the antenna system, TDF is also building two technical premises (known as "BTS Hôtels") outside the metro line, measuring around one hundred square metres, to house the network heads and technical racks for the telecom operators. This work is being carried out in parallel, over several months.
Together with TDF's partners and service providers, nearly a hundred people are working on the metro's mobile coverage project.
A technical challenge in a complex environment
This project is particularly complex because of the sheer scale of the metro project. It involves the construction of all the infrastructure and the coordination of numerous players within a tight schedule.
On site, TDF's system coexists with many other systems, such as the subway control system, or the operator's private cell phone network, dedicated solely to the agents working on site. The stakes are high, as the mobile connectivity solution designed by TDF has to be technically integrated with all the other telecommunications systems.
Line 18 of the Grand Paris Express will be commissioned in three stages. The first section, between Massy - Palaiseau and Christ de Saclay stations, is scheduled to open to the public at the end of 2026. By 2030, line 18 will link Orly airport (Val-de-Marne) to Versailles - Chantiers (Yvelines) in just 33 minutes, compared with over an hour by public transport today!
Karim El Naggar, Chief Executive Officer of TDF, said:
"The connectivity worksite on Line 18 of the Grand Paris Express fully embodies our commitment to meeting major infrastructure challenges to offer users a reliable, high-performance and continuous mobile service throughout their journey. This project mobilizes the expertise of our teams to guarantee optimal coverage, particularly indoors, while providing operators with a robust, scalable network. Our ambition is clear: to build today indoor infrastructures capable of meeting the needs of travelers and operators alike, for a high-performance connected mobility experience."