Nearly Passive RIS Unit Cell Selection for Coherent Radio Signals
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Solution Overview
Problem
The reliability and quality of service in wireless communication links are predominantly governed by the capabilities of end-nodes, such as transmitters or receivers, and there is a need for improving wireless channel quality independent of these limitations.
Innovation Solution
Employing a Reconfigurable Intelligent Surface (RIS) with programmable sub-wavelength unit cells to manipulate electromagnetic signals, using a nearly passive RIS structure with fixed phase-shifts and selective unit cell activation to enhance signal coherence at the receiver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional RIS systems with adjustable phase-shifts are used, then signal coherence and communication reliability are improved, but device complexity and control overhead increase
Solution Approach 1:
The patent transitions from static fixed phase-shifts to dynamic adjustable phase-shifts across different operational scenarios. The RIS device can adapt its phase-shift configuration based on channel conditions, traffic patterns, and service requirements, enabling optimal performance in both near-field and far-field regions without requiring complex real-time control mechanisms for each scenario.
Solution Approach 2:
The patent changes the phase-shift parameter from fixed to adjustable based on operational region. In the near-field region, fixed phase-shifts simplify the channel model and reduce control overhead, while in the far-field region, adjustable phase-shifts enable precise beamforming and signal coherence. This parameter adaptation resolves the contradiction by matching system complexity to operational requirements.
2Device complexity
If fixed phase-shifts with selective unit cell activation are used, then device complexity and control overhead are reduced, but signal manipulation flexibility decreases
Solution Approach 1:
The patent segments the RIS surface into distinct near-field and far-field operational regions, each with tailored phase-shift characteristics. This segmentation allows the system to apply simplified fixed phase-shifts in the near-field where complexity should be minimized, while reserving adjustable phase-shifts for the far-field where signal manipulation flexibility is more critical, thus resolving the contradiction between complexity reduction and flexibility maintenance.
Solution Approach 2:
The patent applies different phase-shift strategies to different spatial regions: fixed phase-shifts for near-field unit cells and adjustable phase-shifts for far-field unit cells. This local quality approach ensures that each region receives the appropriate level of control complexity, reducing overall device complexity while maintaining necessary signal manipulation flexibility in regions where it provides the most benefit.
3Reliability
If a large number of unit cells are deployed, then signal coherence and channel control are improved, but manufacturing complexity and cost increase
Solution Approach 1:
The patent employs partial action by activating only the necessary subset of unit cells for each operational scenario rather than requiring all unit cells to be fully functional and controlled. This approach achieves sufficient signal coherence using a manageable number of active elements, reducing manufacturing complexity and cost while maintaining the reliability benefits of having multiple unit cells available for selective activation.
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 enhances wireless communication reliability and spectral efficiency by optimizing signal reflection without complex phase control, reducing overhead and maintaining performance comparable to conventional RIS systems with adjustable phase-shifts.
Implementation Method 1
Reconfigurable Intelligent Surface (RIS) is a generic term used for meta-surfaces that may improve the wireless channel quality between a transmitter and a receiver by manipulating the impinging electromagnetic signals
Implementation Method 2
using a nearly passive RIS structure with fixed phase-shifts and selective unit cell activation to enhance signal coherence at the receiver
Data Source
AI summary
Reconfigurable Intelligent Surface devices, RIS, may be used to improve receipt of radio signals received by wireless transmit-receive units, WTRUs, in a given area. In such area, WTRUs may receive radio signals directly from the transmitter, and indirectly, via reflection of the radio signals from the transmitter by the RIS device. A RIS may consist of programmable sub-wavelength sized unit cells placed in close proximity. Each unit cell behaves like a scatterer. Embodiments of a new RIS structure are described here, being based on a nearly passive reflecting platform. In a Nearly-Passive RIS structure according to embodiments, NP-RIS, each unit cell is programmed to have a constant invariable phase-shift. Embodiments of a unit cell selection method are described, to control the reflected wave by selecting a subset of unit cells whose reflection could assist coherent alignment of the reflected wave with the main direct signal at the WTRU.