RIS Mode Switching for Channel Training Overhead Reduction
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Solution Overview
Problem
In RIS-assisted communication systems, the increasing number of RIS elements leads to longer training durations, reducing effective data transmission time due to increased channel training overheads, which cannot be fully utilized, necessitating a method to reduce these overheads while maintaining communication efficiency.
Innovation Solution
A mode switching method that dynamically configures user transmission modes based on feedback and channel information, utilizing instantaneous and statistical channel state information to select optimal RIS element selection, grouping, or reflection phase design modes, thereby reducing training overheads and improving data transmission rates.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the number of RIS elements is increased to enhance signal strength, then communication reliability is improved, but training duration increases linearly reducing effective data transmission time
Solution Approach 1:
The patent segments the RIS elements into multiple groups and performs channel training for each group separately. This segmentation allows the system to train a subset of RIS elements at a time rather than all N elements simultaneously, thereby reducing the training duration from linear O(N) to a more manageable scale while still utilizing the full RIS array for signal enhancement
Solution Approach 2:
The patent implements dynamic mode switching between different transmission modes (e.g., direct transmission mode, RIS-assisted transmission mode, and hybrid mode). This dynamic adaptation allows the system to select the most efficient transmission path based on current channel conditions, reducing unnecessary training overhead when direct links are available while maximizing RIS element utilization when direct links are blocked
2Reliability
If all RIS elements are activated for transmission to maximize signal strength, then communication reliability is improved, but training overheads increase linearly
Solution Approach 1:
The patent divides the RIS elements into multiple groups and performs sequential or parallel training for each group. This segmentation reduces the training overhead from O(N) to O(N/L) where L is the number of groups, while still enabling all RIS elements to contribute to signal enhancement during data transmission
Solution Approach 2:
The patent employs partial activation of RIS elements during different transmission phases. During channel training, only a subset of RIS elements is activated at a time to reduce training overhead. During data transmission, all RIS elements are activated to maximize signal strength. This partial action during training phase reduces complexity while maintaining full capability during operation
3Loss of time
If RIS elements are grouped to reduce training duration, then training overheads are reduced, but full advantage of RIS elements cannot be taken
Solution Approach 1:
The patent implements dynamic mode switching that adapts to channel conditions. When direct transmission is available, the system uses direct mode with minimal RIS involvement. When direct links are blocked, the system switches to RIS-assisted mode and activates all RIS element groups, thereby maximizing data transmission rate through the RIS while maintaining reduced training overhead through the grouping structure
Solution Approach 2:
The patent combines multiple RIS element groups to work together in RIS-assisted transmission mode. By merging the contributions of all grouped elements through coordinated phase shifting, the system achieves full utilization of all N RIS elements for signal enhancement, thereby maximizing productivity and data transmission rate when RIS assistance is required
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
The method effectively reduces channel estimation and training overheads, especially with a large number of RIS elements, ensuring high data transmission quality and maximizing the use of RIS elements by dynamically switching between modes based on channel conditions and thresholds.
Implementation Method 1
due to passive reflection of an RIS element
Implementation Method 2
signal strength at a target user is enhanced by passive beamforming
Data Source
AI summary
The present disclosure provides a mode switching method for reducing training overheads in a reconfigurable intelligent surface (RIS)-assisted communication system. The system includes one single-antenna base station, one single-antenna user terminal, and an RIS including N reflection elements, the single-antenna user terminal sends data to the single-antenna base station, however, when a direct link of a user-base station is blocked by a blockage, the data can be sent to the single-antenna base station only via the RIS; the RIS determines a proper reflection solution by using a controller, and dynamically adjusts a phase shift thereof to improve an achievable data rate of the system; and necessary information for phase shift adjustment can be obtained at the base station by uplink training, and transmitted to the RIS controller by using a control link.