Ofcom's Report on 'Reflective Surfaces in Wireless Networks'

The Office of Communications, commonly known as Ofcom, is the government-approved regulatory and competition authority for the broadcasting, telecommunications and postal industries of the United Kingdom. Ofcom has wide-ranging powers across the television, radio, telecoms and postal sectors. It has a statutory duty to represent the interests of citizens and consumers by promoting competition and protecting the public from harmful or offensive material. Some of the main areas Ofcom regulates are TV and radio standards, broadband and phones, video-sharing platforms online, the wireless spectrum and postal services.

Ofcom announced this week that they have undertaken a piece of technology foresight work in collaboration with Queen Mary University of London on the potential role of reflective surfaces in future wireless communications. 

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 within 3GPP. Reflective surfaces are primarily envisaged as non-amplifying devices and limited to adding advantageous signal paths, referred to as multipath diversity, between wireless terminals under non-line of sight (NLOS) conditions. The driving attraction behind reflective surfaces is to provide a potentially low-cost and low-complexity solution to extend the coverage of wireless networks.

On the basis of the work that we have undertaken, we consider there are potential technical challenges associated with the adoption of reflective surfaces, which may have regulatory implications and require further attention from field experts. In particular, the use of reflective surfaces as a common solution for extending wireless coverage at ‘a large-scale’ deployment may raise concerns if their use blocks or alters the propagation environment for services and networks in neighbouring frequencies and creates performance dependencies between multiple networks and services. In addition, mobile terminals behind reflective surfaces may suffer from shadowing losses due to high reflectivity, preventing them from accessing critical wireless services. Shadowing effects depend on the frequency range, geometrical design and the levels of diffraction and edge scattering effects of reflective surfaces. 

Another effect that may potentially arise in high user density areas is that the reflected images of mobile terminals on a given reflective surface may be equivalent to having many terminals in close proximity. Unless the number of the reflected terminals is limited on a given reflective surface, additional interference may occur due to intrinsic effects related to mutual electromagnetic coupling, edge scattering, spurious sidelobes and lack of spatial isolation between independent beams. As a result, network terminals may require complex design changes to handle such unwanted effects. Additionally, reflective surfaces require implementing secure functions and interfaces to allow them to integrate with the network over the air to authenticate, obtain and process network control information, forward user traffic, and operate efficiently.

As set out above, this report does not necessarily represent Ofcom’s concluded position on the potential role of reflective surfaces in future wireless communications. We will continue to engage with stakeholders and monitor any relevant development of this technology, including any standardisation development.

I find this paper useful as it covers important discussion topics that I have mentioned a few times for RIS to succeed. PDF version of report is available here.

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