Reconfigurable Intelligent Surfaces Challenge

Until recently, hardware for the forthcoming 6G Communications has been relatively ignored, with most effort going into non-hardware aspects often of great obscurity and sophistication. However, if new physics, software and systems are the head of 6G, hardware is the neck and the hardware needs to be much more than a simple improvement of 5G hardware. For example, reconfigurable intelligent surfaces RIS will be essential. Researchers do us no favours by using about six other terms for the same thing. RIS are not core to 5G but without widely deployed RIS enhancing the feeble propagation paths of the higher frequencies of 6G and optimising the necessary ultra-massive UM-MIMO base stations, 6G will fail. The Zhar Research image here shows the dream and reality. Pleasingly, there is now much work on RIS but we are a long way from practicality and affordability on the grand scale and the clock is ticking.

For example, nearly all of the RIS for first generation 6G from 2030 using 0.1-0.3THz will be semi-passive, simply polarising, collimating and redirecting beams to get them further and in the required direction. It will not amplify or focus beams, nor will it enable simultaneous wireless information and power transmission SWIPT permitting unpowered client devices on the system. Maybe that comes around 2035 with active RIS everywhere in Phase 2 of 6G. Maybe.

Technologies exist to make the initial semi-passive RIS for little more than one dollar per square meter when vast areas are purchased. However, how much does it cost in time and money to get permission to put them across high rise building facades etc., rent that space, install and maintain them? Here is a clue. When you see that gantry over the freeway with its huge signage, vehicle monitoring radar and lighting, bear in mind that the cost of the permitting process, steelwork, installation and gantry maintenance dwarfs that of the glamorous electronics and electrics.

The definitive report on all this is shown below.