Multi-RIS Phase Control for Higher Spatial Multiplexing
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Solution Overview
Problem
The use of a single reconfigurable intelligent surface (RIS) to create an indirect path between a base station and a geographical area may not be sufficient to serve multiple user terminals with sufficient quality of service, especially at high frequencies, due to a low rank of the propagation channel matrix, which limits spatial multiplexing gains.
Innovation Solution
Deploy a plurality of RISs, including a main RIS and intermediate RISs, and dynamically assign roles to each RIS based on a communication performance criterion to optimize data transmission, using phase shift control to enhance the rank of the propagation channel matrix.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single RIS is deployed to create an indirect path, then the system complexity is low, but the propagation channel matrix rank is low which limits spatial multiplexing gains
Solution Approach 1:
The patent divides the single RIS into multiple RISs (first RIS, second RIS, third RIS) that work together to form indirect paths. This segmentation increases the propagation channel matrix rank from what a single RIS could achieve, thereby enabling higher spatial multiplexing gains while maintaining manageable system complexity through modular deployment
2Productivity
If multiple RISs are deployed to increase propagation channel matrix rank, then spatial multiplexing gains are improved, but the system complexity increases
Solution Approach 1:
The patent introduces a control device as an intermediary that manages multiple RISs. This control device determines phase shifts for each RIS and coordinates their operation, allowing the system to achieve high spatial multiplexing gains through multiple RISs while centralizing the complexity management rather than distributing it across all components
3Area of stationary object
If RISs are deployed to serve multiple user terminals, then the coverage area is improved, but the energy consumption increases
Solution Approach 1:
The patent replaces active signal transmission (which would require high energy) with passive signal reflection through RISs. The RISs reflect signals from the base station to user terminals without amplification, enabling extended coverage area while consuming minimal energy compared to active transmission systems
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach allows for improved communication performance by increasing the rank of the propagation channel matrix, enabling effective data transmission to multiple geographical areas within a communication cell, adapting to dynamic user terminal distributions and optimizing communication quality.
Implementation Method 1
By modifying the reflective properties of each element of the RIS, for example by individually modifying the phase shift introduced by each of these reflective elements, it is possible to influence the way in which the incident radio signals are reflected by the RIS
Implementation Method 2
a reconfigurable reflective surface, hereinafter referred to as a 'RIS' (Reconfigurable Intelligent Surface)... is intended to reflect incident radio signals in a passive manner
Data Source
AI summary
A method for controlling a set of reconfigurable intelligent surfaces. The method includes: selecting, from among the set, at least one surface as an “intermediate surface”, and at least one surface as a “main surface”, the selection being made so as to optimize a determined communication performance criterion for antennas situated in the geographical area served by each main surface; determining phase shifts of reflective elements of the at least one selected intermediate surface and at least one selected main surface; and controlling reflective elements of the at least one intermediate surface and at least one main surface, both selected by using the determined phase shifts.