Rail Tunnel

Take wireless connectivity underground with no compromises

We make fast, reliable wireless connectivity in rail tunnels a reality so you can accelerate to 5G and securely deliver all commercial and mission-critical communications services in the safest, most effective and affordable way possible. With more than four decades of experience designing and delivering innovative wireless solutions for rail tunnels, including more than 40% of the world’s metros, we can confidently say our solutions overcome the toughest in-tunnel communications challenges.

Challenges

Environment and cost

Rail tunnels are hostile environments where space is tight and ventilation is often poor. Telecom infrastructure deployments typically occur at night, during short time periods, and require specially trained personnel to ensure secure, long-lasting deployments. These challenges increase deployment costs, which means you can’t afford to get it wrong.

Radio signal propagation

Outdoor wireless coverage can’t penetrate into rail tunnels, but there are very limited locations to install antennas and repeaters in these ultra-confined spaces. Tunnel curves and signal blockages due to passing trains compound propagation challenges. It takes significant RF expertise to ensure mission-critical rail systems have continuous access to highly reliable wireless connectivity.

In-train wireless coverage

Radio signals must also penetrate into trains packed with passengers while compensating for the losses caused by train materials and human bodies. With complex RF designs to implement, but relatively few locations where equipment can be installed, only solutions that are precision-engineered for optimal performance can reduce total cost of ownership (TCO).

Indutry Trends

One wireless solution for all services

Rail operators can’t afford to deploy and maintain multiple wireless solutions. For cost-effective flexibility, rail operators need a single, ultra-broadband wireless solution that’s 4G- and 5G-ready. This multi-operator, multi-service shared infrastructure:

Supports all commercial and mission-critical services in 3GPP bands up to 4200 MHz
Simplifies spectrum rebanding and refarming projects
Optimizes throughput to lower TCO

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Extreme reliability

Rail operators rely on mission-critical TETRA and GSM-R radio systems for safe and efficient operations. To keep these systems operating at peak performance at all times, connectivity solutions must be:

Optimized for communications at frequencies under 1 GHz
Flexible and robust to ensure continuous wireless coverage
Field-proven to reliably perform for decades in harsh tunnel conditions

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5G in tunnels

To fully leverage the benefits of 5G, rail operators know they need to take advantage of 3.5 GHz spectrum and accelerate to 5G in tunnels. To get there, they need a multiband connectivity solution that:

Optimizes support for high-capacity 2x2, 4x4 and higher MIMO applications
Is proven to deliver clear advantages over SISO solutions

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Fire safety

Fire safety in rail tunnels is paramount to protect lives. All cabling used in wireless connectivity solutions must:

Meet International Electromechanical Commission (IEC) standards for low smoke, flame and fire retardance
Achieve best-in-class Construction Products Regulation (CPR) ratings for burning droplets (d0), low smoke emission (s1) and corrosivity (a1)

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RFS Solutions

RADIAFLEX® Radiating Cables

RFS RADIAFLEX is the industry’s most advanced portfolio of 5G-ready radiating cables for contoured wireless coverage in buildings and underground. RADIAFLEX cables support all services up to 6 GHz with high performance, making them ideal for multiband, multi-operator applications in any indoor environment. With a variety of different bending radii, performance levels and outer conductor types to choose from, there’s a RADIAFLEX radiating cable for even the most challenging coverage requirements.

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RADIAFLEX® Radiating Waveguide

The RFS RADIAFLEX radiating waveguide is a distributed antenna system for tunnels, mines, large building complexes and other challenging locations. The broadband solution simultaneously supports multiple one-way and two-way communications systems, so a single waveguide can be used for all applications. A specialized manufacturing and longitudinal seam welding process developed by RFS ensures optimal electrical performance and good bending properties.

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CELLFLEX® Coaxial Cables and Jumpers

RFS CELLFLEX coaxial cables and jumpers combine industry-leading electrical performance with remarkable flexibility and strength. These premium attenuation, low-loss cables support all frequencies from low MHz ranges to 6 GHz, and are available in 20 models ranging from 1/4-inch to 1 5/8-inch in diameter. The CELLFLEX portfolio also includes CELLFLEX Lite, lighter weight coaxial cables that are ideal when fluctuating copper prices rise and in areas where copper theft is an issue.

Connectors and Accessories

RFS OMNI FIT™ Premium and OMNI FIT Standard connectors are well-known for their precision-engineered performance, ease of installation and long life in the field. They can be used with copper and aluminum cables, and are the perfect complement to our CELLFLEX and CELLFLEX Lite coaxial cables. The connectors support all frequencies up to 6 GHz, making them ideal for smooth evolution to 5G globally. A comprehensive range of adapters, grounding kits, hangers, clamps and tools complete the portfolio.

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Passive RF Components

RFS passive RF components operate in all frequency bands from 555 MHz to 6 GHz and provide optimal passive intermodulation (PIM) performance to reduce interference and support the highest throughput levels end-to-end. Our comprehensive portfolio includes all components required for an end-to-end, 5G-ready distributed antennas system, including: combiners, hybrid combiners and couplers, directional couplers, diplexers and triplexers, power splitters, loads and attenuators.

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References

Grand Paris Express

France | 2 Phases, 2021-2030

HELIFLEX®: Designed and produced by RFS for over 70 years, our HELIFLEX solutions have been installed across the globe. Here, Gerd Bohnet, Product Line Manager Waveguide & Air Dielectric Cable at RFS talks us through the solution and how it is used.

Read blog about HELIFLEX

Follobanen

Norway | 2019-2020

RFS RADIAFLEX radiating cables set a new world record for download speeds in tunnels in 2018 with a unique 4x4 MIMO configuration that reached 560 Mbps in a Follobanen tunnel. The innovative RADIAFLEX solution for the high-speed railway project combines “perfect match” vertically and horizontally polarized radiating cables to take advantage of cross-polarization effects and optimize MIMO conditions in tunnels.

Metro Rio De Janeiro

Brazil | 2020

RFS RADIAFLEX radiating cables are bringing 4G multiband, multi-operator communications to the latest in-tunnel wireless network deployments along the Metro Rio De Janeiro. The projects follow RFS’ success providing high-performance wireless connectivity solutions at the legendary Maracanã Stadium for FIFA World Cup 2014 and at several main venues for the 2016 Olympic Games in Rio de Janeiro.

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TAKE 5G INTO TUNNELS

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