Wireless mmW communications for Railway – mmW4Rail

The mmW4Rail project is organised into five interconnected Work Packages. The resolution of scientific challenges involved simulations and experiments. WP1 consisted of characterising and modelling radio propagation channels in specific railway areas for T2T and T2I communications. Channel characterisation was carried out at the Railway Test Centre (CEF) in Petite Forêt (59). Specific railway vehicles on the tracks will be considered. WP2 focused on the integration of antennas in the specific context. In WP3, we defined the requirements for T2I and T2T wireless communications in the railway context based on existing documents. Deployment solutions for millimetre wave 5G were proposed, as well as codebook-type algorithms for performance improvement.

Numerous results have been obtained. As part of WP1, a channel sounder was developed and tested. Tests were carried out at the Railway Test Centre. A large amount of data was recorded. Based on the 3GPP model, the statistical parameters of the measured data were calculated and compared with the parameters of the standardised models. The results were found to be quite different, confirming the need to take railway environments into specific account. This work resulted in Nicholas Atwood's thesis, defended in December 2024. Additional work was carried out on the detection of pylons along the track based on the analysis of the measured data.

Two approaches were taken in WP2. First, we studied the possibility of designing and producing a specific reflective surface to facilitate deployment. In addition, we proposed the design and development of an antenna adapted to several standards and multiple ports for FRMCS and other systems in the millimetre band. Specific antennas were also designed and built. This work was partly carried out as part of Jibran Pandit Zahor's thesis, which has not yet been defended.

With regard to the task of designing improvements to the physical layer for T2T/T2I communication, an algorithm for managing radio resources in a heterogeneous multi-hop railway communication network was proposed, and performance evaluations were carried out. With regard to the task of system-level simulation and evaluation of technologies for millimetre wave railway radio, a specification of the deployment, simulation scenario and detailed parameters was drafted. Two in-depth state-of-the-art reviews of physical layer enhancement techniques and the latest beamforming codebook designs were conducted and published in journals. Several codebook algorithms were then evaluated in a 3GPP-type railway channel. This work on codebooks led to Sameh Mabrouki's thesis defence in September 2025. Finally, work on the introduction of RIS in railway tunnels using a ray tracing tool was carried out and resulted in Aline Habib's thesis defence in december 2025.

The mmW4Rail project has already yielded several important results that have been presented at conferences and in journals. It has also opened up numerous prospects:

- Improvement of the existing channel sounder to obtain information on arrival and departure angles

- Carrying out new measurements with other scenarios - Comparing the 3GPP model obtained from measurements with ray tracing simulation in the environment

- Testing the algorithms developed in the 3GPP channel model based on measurements in a railway environment

- Development of other algorithms to improve the physical layer in railway environments

- Continued work on RIS in tunnels or along tracks for 6G applications

- Introduction of ISAC in the railway sector

1. S. Mabrouki, I. Dayoub, Q. Li and M. Berbineau, «Codebook Designs for Millimeter-Wave Communication Systems in Both Low- and High-Mobility: Achievements and Challenges,« in IEEE Access, vol. 10, pp. 25786-25810, 2022, doi: 10.1109/ACCESS.2022.3154016.
2. Q. Li, J. -C. Sibel, M. Berbineau, I. Dayoub, F. Gallée and H. Bonneville, «Physical Layer Enhancement for Next-Generation Railway Communication Systems,« in IEEE Access, vol. 10, pp. 83152-83175, 2022, doi: 10.1109/ACCESS.2022.3192971.
3. Marion Berbineau, Nicholas Attwood, François Gallée, Patrice Pajusco, Quianrui Li, Hervé Bonneville, Semah Mabrouki, Iyad Dayoub, Divitha Seetharamdoo, « Millimetric waves communications for Railways », Accepted for oral presentation at TRA2022, Lisbon, September
4. ATTWOOD Nicholas, GALLEE François, PAJUSCO Patrice, BERBINEAU Marion, MmW channel sounder for dynamic SIMO measurement, Journée URSI France,
5. Q. Li, A. Charaf, N. Gresset, H. Bonneville, “Radio Resource Management in Next-Generation Railway System with Heterogeneous Multi-hop Relaying Deployment”. In International Workshop on Communication Technologies for Vehicles (pp. 59-70), 2021, November, Madrid.

Trains are entering the era of full automation thanks to wireless systems shifting control functions from the human driver to computers. High data rate, robustness, high reliability and ultra-low latency are required. The Future Railway Mobile Communication System (FRMCS) is under development at European level. It will be IP based, multi-bearer and resilient to technology evolution and interferences.
One of the main problems for railway control and command applications is spectrum scarcity. Only very small bands are allocated in the 900 MHz, 1900 MHz band and 5.9 GHz, but mainly reserved for urban rail. This motivates the exploration of the millimeter-wave (mmW) frequencies in the 5G developments. This band can answer specific needs for railways in addition to or for complementing the current telecommunication standards. This is foreseen in well-defined and restricted areas (e.g. train stations, shunting yards, high-speed lines), while possibly sharing existing infrastructures, and for specific use cases such as virtual coupling of trains, platooning, remote driving of trains, downloading maintenance data, etc. The objective in considering mmW is to improve the communication system adaptability for full bearer independency.
The bands foreseen for 5G NR standard are located at 28-30 GHz, 38-40 GHz, the free-licensed band 57–64 GHz, extended to 71 GHz. The 60 GHz band is of great interest for railway in case of very high data rate and very low latency requirements. The environment (ballast, cutting, tunnels, high voltage near the antennas, dust, interferences, etc.) as well as the constraints (vibrations of the trains, non-line of sight situations, crossing of trains, cohabitation with other systems, etc.) are very specific and will impact the performances of the wireless links for both Train-to-Infrastructure (T2I) and Train-to-Train (T2T). The propagation conditions and channel behaviour have to be well known to avoid communication outages particularly in the context of mobility. Dedicated channel models for mmW in railway environments are needed.
Solutions to enhance T2T and T2I performances in the mmW band should be developed and analysed. Optimization of radio resources management considering the train-specific security, latency and reliability constraints; deployment enhancement and radio condition monitoring in the mmW band, are important topics to study. Optimization of the wireless link thanks to integration of multiple antenna array with different potential application (beamforming, diversity and/or spatial multiplexing) should also to be considered taking into account the impact of integration on antenna performances with the specification and the definition of new models for antenna.
The mmW4Rail project focuses on three fundamental research topics: in the mmW band characterization and modelling of radio channels for dynamic scenarios, antenna specification; design and prototyping; and enhancement of reliability of the communications at Physical layer. We will consider three typical and representative use cases:
• T2I links along high speed line with infrastructure sharing;
• T2I links in specific areas for remote driving of trains;
• T2T links for virtual coupling and platooning applications.
The mmW4Rail results will contribute actively to the development of wireless communications in mmW to answer specific needs for railways. The mmW communication system will be deployed to complement current standards, improving the system adaptability in view of full bearer independency as foreseen by railway operators. The consortium will disseminate the results at international level, at 3GPP, ETSI and UIT-R. The proposed works in the mmW4Rail project are in line with Shift2Rail multi annual plan and they should provide a foundation for future developments and deployments of alternative communication systems.