The UKs’ communications regulator, Ofcom, released a whitepaper in collaboration with Queen Mary University of London looking into the potential use of reflective surfaces to expand the coverage of wireless broadband and mobile networks. 

The reflective surfaces, or “Reconfigurable Intelligent Surfaces” (RIS), are non-amplifying devices that add advantageous signal paths, known as multipath diversity, between wireless terminals under non-line of sight conditions.

“Reflective surfaces are currently an area of active research. Standardisation in this area is still in its infancy and may be shaped by existing relay and repeater technologies,” said the report. 

The study primarily focused on frequencies below 6GHz, including bands compatible with 5G technology. It found that when they were positioned at a distance from the original signal, the wireless signal was enhanced. 

Although the research suggests that the observed behaviours could be relevant to higher frequencies, use cases targeting even higher millimetre-wave frequencies were not explored.

While the active research in this field is still in the early stages, the attraction behind it lies in its potential as a cost-effective, low complexity solution to expand network coverage. 

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However, some potential issues were highlighted in the report. Firstly there were unwanted scattering effects, which led to increased interference and degraded terminal performance. Another worry is that while redirecting wireless coverage with reflective surfaces, enhancing one area may weaken coverage in another. Finally, reflective surfaces can alter the propagation conditions of out-of-band frequencies, potentially impairing existing services. 

“While we recognise that reflective surfaces may have potential benefits, we believe that further work is required by field experts to understand the regulatory implications for their deployment, especially in environments where multiple independent networks and services coexist,” read the paper.