RIS Codebook Design for Near-Field Beamforming
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Solution Overview
Problem
In wireless communication systems, particularly in 5G NR and beyond, the use of Reconfigurable Intelligent Surfaces (RIS) faces challenges in achieving low power consumption and low cost while maintaining high signal-to-noise ratio (SNR) and reducing electromagnetic signal leakage due to near-field radiation array limitations, especially when using low phase shift accuracy and existing DFT codebooks for beamforming and precoding.
Innovation Solution
A method involving a codebook design for RIS that determines initial phases and offset information based on position information, including distance and angle between the RIS and terminals, to improve SNR and reduce grating lobes and side lobes, using a combination of Fresnel diffraction principle and DFT codebooks to enhance beamforming accuracy and reduce noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If higher RIS matching accuracy is used to improve SNR, then signal quality improves, but power consumption and cost increase
Solution Approach 1:
The patent changes the parameter of phase shift accuracy from high precision to low precision (1-bit or 2-bit quantization), accepting lower matching accuracy to reduce power consumption and cost while maintaining acceptable communication performance in near-field scenarios
2Device complexity
If DFT codebook is used for beamforming with low phase shift accuracy, then device complexity is reduced, but periodic quantization errors cause increased side lobe level and grating lobes
Solution Approach 1:
The patent segments the codebook design into two parts: a base codebook for coarse beam direction and an offset codebook for fine adjustment. This segmentation allows low-complexity 1-bit/2-bit phase quantization while using offset compensation to reduce quantization errors and suppress grating lobes
Solution Approach 2:
The patent introduces offset information as an intermediary element between the base codebook and the final beamforming weights. This offset compensation mechanism mediates the trade-off between low phase quantization accuracy and high beamforming performance, reducing quantization errors without requiring high-precision phase shifters
3Productivity
If larger scale radiation array is used to improve SNR for ultra-high-speed communication, then communication capacity increases, but near-field radiation range increases causing more interference
Solution Approach 1:
The patent applies local quality by using position information to determine different codebook configurations for different spatial regions. The sending device adjusts the codebook selection and offset information based on the terminal's position, optimizing beamforming performance locally while suppressing grating lobes and side lobes in specific directions to reduce electromagnetic signal leakage
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 effectively improves the SNR of the near-field radiation range, suppresses interference from grating lobes, and reduces electromagnetic signal leakage, thereby enhancing the performance and flexibility of wireless communication systems.
Implementation Method 1
by introducing a certain phase shift to RIS, focused beam transmission in any direction in space can be achieved
Implementation Method 2
as the working frequency band of the wireless communication network system increases and the scale of the radiation array increases, the near-field radiation range of the radiation array also increases
Data Source
AI summary
Provided in the present disclosure are a terminal and a sending device in a communication system. The sending device includes: a receiving unit, which is configured to receive position information of a terminal, and a control unit, which is configured to determine a first codeword in a first codebook and offset information according to the position information. The first codeword indicates initial phases of at least some array elements in a reconfigurable intelligent surface (RIS). The offset information indicates an offset relative to the at least one of the at least some array elements, the initial phases, and a reference position of the RIS.