Distributed RIS Role Control for Higher-Rank Wireless Channels
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Solution Overview
Problem
Existing wireless communication systems using reconfigurable intelligent surfaces (RIS) face limitations in spatial multiplexing due to low rank propagation channels, particularly at high frequencies, which restrict the number of user terminals that can be served with sufficient quality, especially when RISs are in line of sight with the base station.
Innovation Solution
A method for controlling a set of RISs, including selecting at least one surface as an intermediate and one as a main surface, determining and applying phase shifts to optimize communication performance, allowing dynamic role assignment to RISs based on geographical areas and user terminal dynamics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If a single RIS is used to extend coverage in degraded propagation areas, then coverage extension is achieved, but the rank of the propagation channel matrix is limited, restricting spatial multiplexing performance
Solution Approach 1:
The system divides the RIS deployment into multiple independent RISs instead of using a single large RIS. Each RIS is positioned at different locations and can be independently controlled, allowing the system to serve multiple geographical areas simultaneously while increasing the overall channel rank through diverse propagation paths.
Solution Approach 2:
The patent transitions from a single-point RIS solution to a multi-point distributed RIS architecture. By adding spatial dimensionality through multiple RISs deployed across different locations, the system increases the rank of the propagation channel matrix, enabling better spatial multiplexing while maintaining coverage extension capabilities.
2Productivity
If multiple RISs are deployed to increase channel rank and improve spatial multiplexing, then more user terminals can be served, but the system complexity and computational load increase
Solution Approach 1:
The patent implements autonomous role assignment where RISs automatically determine their own roles (intermediate or main) based on their geographical positions and the distribution of user terminals. This self-organizing capability eliminates the need for complex centralized control algorithms, reducing computational load while enabling multiple RISs to work together effectively for serving more user terminals.
3Power
If RISs are positioned in line of sight with the base station, then signal reflection is efficient, but the propagation channel rank remains low, limiting spatial multiplexing gain
Solution Approach 1:
The patent assigns different functional roles to different RISs based on their local characteristics and positions. Intermediate RISs positioned in line of sight with the base station are optimized for efficient signal reflection, while main RISs positioned to serve specific geographical areas are optimized for providing diverse propagation paths. This local optimization allows the system to maintain high reflection efficiency while achieving high channel rank through the collective contribution of multiple RISs with different local qualities.
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
Enhances communication performance by increasing the rank of propagation channels, enabling efficient data transmission to various geographical areas within a communication cell, adapting to user terminal distribution and dynamics, and reducing computational load.
Implementation Method 1
By modifying the reflection properties of each element of the RIS, for example by individually modifying the phase shift introduced by each of these reflection elements, it is possible to influence the way in which the incident radio signals are reflected by the RIS and, ultimately, to influence the propagation channel taken by these radio signals.
Data Source
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AI summary
The invention relates to a method for controlling a set E of reconfigurable intelligent surfaces (20_1, 20_2, 20_3, 20_4), said method comprising steps of: - selecting (E10), from the set E, at least one surface as "intermediate surface" and at least one surface as "main surface", the selection being carried out so as to optimize a determined communication performance criterion for antennas located in the geographical area served by each main surface, - determining (E20) phase shifts of reflection elements of said at least one selected intermediate surface and at least one selected main surface, - controlling (E30) the reflection elements of said at least one selected intermediate surface and at least one selected main surface by means of the determined phase shifts.