RIS Unit-Group Precoding for Far-Field Validity
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Solution Overview
Problem
Existing precoding schemes for reconfigurable intelligent surfaces (RIS) fail to maintain the far-field hypothesis due to the comparable size of the RIS array and propagation distance, leading to inefficiencies and complexity in precoding.
Innovation Solution
The method involves grouping RIS units based on channel information to ensure compliance with the far-field hypothesis, determining precoding matrix indicators (PMI) and additional deflection phase angles for each group, and sending indication information to either the network device or the RIS array to precode each unit group, thereby reducing complexity and ensuring effective signal reflection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the RIS array size is made large to improve coverage area, then the far-field hypothesis cannot be established, but using far-field precoding schemes becomes invalid
Solution Approach 1:
The RIS array is divided into multiple unit groups, where each unit group is small enough to satisfy the far-field hypothesis. This segmentation allows the system to maintain both large coverage area and valid far-field precoding by treating each segment independently
Solution Approach 2:
The patent introduces a grouping dimension to organize RIS units into unit groups based on spatial distribution and channel characteristics. This additional organizational dimension enables the system to reconcile the contradiction between large array size and far-field hypothesis validity
2Strength
If joint precoding design for RIS array and network device is implemented, then signal strength is enhanced, but system complexity increases
Solution Approach 1:
The precoding design is segmented into independent unit group precoding and network device precoding. Each unit group has its own precoding matrix determined separately, which simplifies the overall system complexity while maintaining signal enhancement through coordinated control
Solution Approach 2:
Different unit groups are assigned different precoding matrices tailored to their specific channel characteristics. This local optimization approach enhances signal strength for each group while avoiding the complexity of a single unified precoding design for the entire RIS array
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 maintains the far-field hypothesis, reduces precoding complexity, and enhances signal strength and reliability by accurately directing electromagnetic waves to the intended receiving end.
Implementation Method 1
A reconfigurable intelligence surface (RIS) can reflect a signal incident on its surface to a specific direction through precoding technology
Data Source
AI summary
A method and apparatus for precoding a reconfigurable intelligent surface (RIS) are disclosed, the method is performed by a terminal device, including: determining a precoding matrix indicator (PMI) and an additional deflection phase angle for each RIS unit group in an RIS array according to channel information of the each RIS unit group; and sending first indication information, where the first indication information indicates the precoding matrix indicator and the additional deflection phase angle for the each RIS unit group.