RIS Beam Discovery for Non-Line-of-Sight THz Links
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Solution Overview
Problem
High-frequency wireless communications above 100 GHz face challenges due to significant over-the-air attenuation and the need for line-of-sight paths, which limits data transfer rates and reliability, especially when obstacles block direct communication between user equipment and wireless access points.
Innovation Solution
A reconfigurable intelligent surface (RIS) with an array of antenna elements is used to reflect wireless signals, adjusting phase and amplitude responses to optimize signal beams and maintain communication even when a line-of-sight path is blocked, employing a control RAT for discovery and configuration with phased antenna arrays at the access point and user equipment.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If higher frequency radio-frequency signals are used to increase data rates, then data transfer capability is improved, but signal attenuation increases significantly
Solution Approach 1:
A reconfigurable intelligent surface (RIS) is introduced as an intermediary device between the wireless access point and user equipment. The RIS reflects and redirects high-frequency signals around obstacles, enabling the signals to reach their destination without direct line-of-sight while maintaining signal strength and reducing attenuation losses.
Solution Approach 2:
The system transitions from traditional two-dimensional signal propagation (direct line-of-sight paths) to three-dimensional signal routing by utilizing the RIS surface positioned in spatial dimension. This allows signals to bounce off the RIS and reach destinations that are geometrically blocked, effectively adding a vertical/reflection dimension to signal paths.
2Reliability
If line-of-sight paths are required for high-frequency communications, then signal quality is maintained, but communication reliability deteriorates when obstacles block the path
Solution Approach 1:
The RIS is designed with reconfigurable properties that allow it to dynamically adjust its reflection characteristics. The RIS can change its orientation, active surface area, and reflection phase shifts in real-time to adapt to moving obstacles or changing environmental conditions, maintaining reliable communication links despite dynamic blockages.
Solution Approach 2:
The system changes the operational parameters of signal propagation by using the RIS to alter signal direction, phase, and amplitude. By adjusting the RIS configuration parameters, the system can optimize signal paths around obstacles, transforming the fixed line-of-sight requirement into a flexible multi-path capability.
3Reliability
If reconfigurable intelligent surface is used to reflect signals around obstacles, then communication reliability is improved, but system complexity increases
Solution Approach 1:
The RIS system is segmented into multiple independent antenna elements arranged in a grid pattern. Each element can be independently controlled to adjust phase and amplitude, allowing the overall complex function to be achieved through simple, modular units. This segmentation makes the complex RIS manageable and controllable.
Solution Approach 2:
The system incorporates feedback mechanisms where the wireless access point or user equipment communicates with the RIS to determine optimal configuration settings. Based on received signal quality metrics and channel state information, the RIS adjusts its reflection properties to maximize communication reliability, creating a closed-loop control system that manages complexity through intelligent adaptation.
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 RIS enables reliable and high-data-rate wireless communication beyond line-of-sight conditions by effectively redirecting and amplifying wireless signals, enhancing communication performance and reducing the need for complex and power-intensive components in user equipment and access points.
Implementation Method 1
The RIS may include an array of discrete antenna elements, where an impinging electro-magnetic (EM) wave is re-radiated with a respective phase and amplitude response
Implementation Method 2
One way of achieving the per-element phase and amplitude response of the antenna elements is by adjusting the impedance of the antenna elements, thereby controlling the complex reflection coefficient
Data Source
AI summary
A user equipment (UE) device may communicate with an access point (AP) at greater than 100 GHz via a reconfigurable intelligent surface (RIS). The AP may perform a control RAT discovery with the RIS and then a data transfer RAT discovery, during which the AP uses the control RAT to control the RIS to sweep over different RIS beams. The AP may transmit radar waveforms while concurrently sweeping over different AP beams. The AP may gather performance metric values from the radar waveforms after reflection off the RIS during the sweep. The AP may identify an optimal RIS beam that produced the best performance metric values. The AP may use the optimal RIS beam to identify the orientation of the RIS, which the AP may use to select AP and/or RIS beams for conveying wireless data between the AP and the UE via the RIS.