Confined Space Radio Design


Confined Space Radio Design

From a radio communications perspective a confined space is anywhere where a reasonable line of sight cannot be maintained between radio devices and a transmitting mast. Confined space radio design is an important activity which should be completed well in advance of the system build. 

This could refer to very cramped and restricted spaces, including those underground such as road tunnels, underground railways, utility tunnels and mines. However, it also covers spaces that may in themselves be relatively large and open, but are nevertheless cut off from major masts by complex layouts or obstacles such as thick concrete.



Every confined space engineering project needs to begin with an in depth understanding of the existing communications technologies that are currently in place and any that are planned for the future, along with a comprehensive understanding of the user requirements.

This information should be defined following a requirements gathering exercise carried out through user group workshops. It should include areas such as the identification of the parties involved in the project, its purpose/aim, all technical requirements, special features and an agreement on acceptance documentation and stakeholder sign-off.

Following this, a comprehensive survey of the environment in question should be carried out.
The survey determines factors including:

• Precise cable routes: cables must generally bend as little as possible, and larger diameter cables cannot always be threaded through a complex route
• Mounting requirements: cables must be mounted away from other fixtures such as lighting and other metal structures
• Historical or other key features that must be avoided or preserved

• Building structure and fabric: this affects both antenna signal and cabling routes
• Handling and delivery: long runs of cable may be supplied on drums weighing over 1000kg and up to 3m in diameter so careful handling and delivery to the installation site is essential

For spaces that are cut off, rather than cramped an additional antenna or antennas can be installed within the confined space, to create a kind of signal ‘hotspot’. This is therefore a common technique in settings such as the turbine hall at a power station.

Alternatively sophisticated radiating cables can be used in a ‘leaky feeder’ approach allowing the radio signal to radiate out in a pre-calculated manner for the frequency ranges in use by the system.