How to build radio coverage in complex environments
Ensuring reliable radio communications in tunnels and underground environments is one of the most demanding challenges in modern communications infrastructure.
These environments are inherently complex, often requiring multiple communication technologies to coexist and operate seamlessly. For projects of this kind, it is a significant advantage to work with a specialist who understands different radio technologies, frequency bands and the technical requirements needed to create a robust and future-proof solution.
Distributed Antenna Systems (DAS)
To maintain strong and reliable radio coverage in tunnels, Distributed Antenna Systems (DAS) are commonly used. A DAS typically consists of strategically placed antennas and leaky feeder cables designed to provide consistent coverage throughout the tunnel environment.
The system is usually fed from multiple signal sources through fibre-connected repeaters within a Fibre DAS architecture.
By distributing signals from multiple sources through a common antenna infrastructure, redundancy is built into the network, resulting in a more resilient and reliable solution. The system can support multiple communication technologies, including cellular networks, TETRA and DMR radio systems.
Each technology has unique characteristics and operational requirements, making integration a significant technical challenge.
Cellular Networks
Cellular networks are essential for ensuring that passengers, workers and contractors can use mobile devices for voice and data communications underground. Providing reliable mobile coverage in tunnels is challenging because radio signals cannot easily penetrate thick concrete structures and surrounding ground materials. Overcoming these challenges requires advanced technology, careful planning and specialised expertise.
When properly designed, however, the result is reliable mobile coverage even deep underground.
TETRA (Terrestrial Trunked Radio)
TETRA is primarily used by public safety organisations and emergency services through systems such as Rakel.
In emergency situations, secure and reliable communications are critical. TETRA networks deployed in tunnels must therefore be designed to operate under demanding conditions while maintaining the highest levels of availability and resilience.
DMR (Digital Mobile Radio)
DMR is commonly used to coordinate daily operations between work teams in tunnels and construction sites.
The technology enables efficient collaboration between multiple teams and contractors, helping ensure safe and effective project execution.
Communication as a Lifeline
Radio communications in tunnels are about far more than everyday conversations. They are a vital safety component for everyone working underground. Tunnel environments present risks such as structural failures, gas leaks and fire. In these situations, reliable communications can be the difference between life and death. This is why systems such as Rakel must function flawlessly throughout the tunnel infrastructure.
For project owners, it is therefore essential to engage an experienced communications contractor capable of managing feasibility studies, design, implementation and project management while documenting and quality-assuring every stage of the process.
Verifying Coverage and Performance
Through comprehensive PIM and VSWR measurements, every part of the passive network can be validated and optimised.
These measurements ensure that unwanted reflections and interference do not impact network performance, helping maintain strong and reliable communications throughout the system.
Continuous Network Monitoring
To further ensure operational reliability and safety, communication systems should be continuously monitored throughout the construction phase.
This allows any issues to be identified and resolved quickly, giving workers confidence that the communications system will perform when it is needed most.
Designing and implementing a DAS capable of supporting multiple communication technologies is a complex technical challenge. It requires a deep understanding of radio communications as well as the specific challenges that arise in demanding environments such as tunnels.
Long-Term Reliability
Designing and implementing a DAS capable of supporting multiple communication technologies is technically complex. It requires extensive expertise in radio engineering as well as a deep understanding of the challenges associated with tunnel environments.
The goal is not only to integrate cellular networks, TETRA and DMR into a unified communications platform, but also to ensure that the system is ready for future technologies and evolving standards.
One of the greatest challenges in tunnel projects is maintaining reliable communications throughout construction periods that may extend over many years as tunnels are excavated and worksites continue to expand. Real-time monitoring systems are therefore essential to ensure that all components remain fully operational at all times.
Two Major Tunnel Projects
Tunnel construction sites are dynamic and constantly changing environments where effective communication is essential for both operational efficiency and safety.
The Stockholm Metro expansion is one example of a major project where these requirements are critical. Another significant ongoing project is the Varberg Tunnel, where excavation is taking place simultaneously from both ends of the tunnel.
