Controllers for setting reflection phases of elements in a reconfigurable intelligent surface

A system for setting reflection phases of elements of a reconfigurable intelligent surface the system comprising:

• a central controller, the central controller for setting reflection phases of elements of a reconfigurable intelligent surface, the elements being divided into element subsets with at least two elements per element subset, where the reflection phase per each of the elements in each element subset are controlled by a respective local controller of each element subset, the central controller being configured to communicate control messages with the local controllers, the central controller comprising processing circuitry, the processing circuitry being configured to cause the central controller to:
• send a first control message towards a first local controller of the local controllers, wherein the first control message comprises a description of a first reflection phase specific for a first element subset whose reflection phases are controlled by said first local controller;
• and
• at least one local controller for setting reflection phases of elements of a reconfigurable intelligent surface, the local controller being configured to set the reflection phases of elements in a first element subset comprising at least two of the elements, the local controller being configured to communicate control messages with neighbouring local controllers of the reconfigurable intelligent surface, each of the neighbouring local controllers being configured to set the reflection phases of elements in a respective second element subset, with at least two elements per each of the second element subset, the local controller comprising processing circuitry, and the processing circuitry being configured to cause the local controller to:
• receive a first control message, the first control message comprising a description of a first reflection phase specific for the first element subset;
• send a second control message towards a second local controller of the neighbouring local controllers, the second control message comprising a description of a second reflection phase specific for the second element subset of the second local controller, and the second reflection phase being based on the first reflection phase and a geometric relation in the reconfigurable intelligent surface between the first element subset and the second element subset of the second local controller;
• and
• set the reflection phase of each element in the first element subset in accordance with the description of the first reflection phase.

A method for setting reflection phases of elements of a reconfigurable intelligent surface, the method being performed by a local controller of the reconfigurable intelligent surface, the local controller being configured to set the reflection phases of elements in a first element subset comprising at least two of the elements, the local controller being configured to communicate control messages with neighbouring local controllers of the reconfigurable intelligent surface, each of the neighbouring local controllers being configured to set the reflection phases of elements in a respective second element subset, with at least two elements per each of the second element subset, the method comprising:

• receiving a first control message, the first control message comprising a description of a first reflection phase specific for the first element subset;
• sending a second control message towards a second local controller of the neighbouring local controllers, the second control message comprising a description of a second reflection phase specific for the second element subset of the second local controller, the second reflection phase being based on the first reflection phase and a geometric relation in the reconfigurable intelligent surface between the first element subset and the second element subset of the second local controller;
• and
• setting the reflection phase of each element in the first element subset in accordance with the description of the first reflection phase.