Off-diagonal Beamforming with Fully Connected RIS
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Solution Overview
Problem
Current reconfigurable intelligent surface (RIS) technologies in advanced wireless communication systems face limitations in optimizing signal propagation due to the lack of multi-directional and fully connected load impedance networks, leading to sub-optimal channel gains and increased computational complexity.
Innovation Solution
A multi-directional and fully connected RIS with a load impedance network that allows each element to be connected to every other element, enabling off-diagonal beamforming techniques for routing signals and applying phase shifts to enhance signal reception and system performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a fully connected load impedance network is implemented in RIS, then signal routing flexibility and channel gain are improved, but device complexity increases
Solution Approach 1:
The RIS is divided into multiple independently controllable elements, each capable of receiving feedback and determining its own routing information. This segmentation allows the complex fully connected network to be managed through distributed control, where each element handles local routing decisions based on channel quality information, reducing overall system complexity while maintaining routing flexibility.
Solution Approach 2:
The load impedance network is made dynamically reconfigurable, allowing each RIS element to adapt its connections and phase shifts in real-time based on received feedback. This dynamic capability enables the system to optimize signal routing for different channel conditions without requiring a fixed complex structure, achieving versatility through adaptive reconfiguration rather than static complexity.
2Reliability
If off-diagonal beamforming with multi-element routing is used, then channel gain is improved, but computational complexity increases
Solution Approach 1:
Channel quality information is obtained in advance through feedback from transmitting or receiving devices before routing decisions are made. This preliminary acquisition of channel state information allows the RIS controller to pre-determine optimal routing paths and phase shifts, enabling off-diagonal beamforming to achieve high channel gain without requiring complex real-time computations during signal transmission.
Solution Approach 2:
Each RIS element autonomously determines its routing information based on received feedback, eliminating the need for centralized complex computations. The elements self-configure their phase shifts and routing paths independently, reducing the overall computational burden while maintaining the channel gain benefits of coordinated multi-element signaling.
3Reliability
If feedback-based routing determination is implemented, then signal reception quality is improved, but loss of time occurs due to feedback processing
Solution Approach 1:
Feedback is obtained periodically rather than continuously, with the RIS controller determining routing information at regular intervals based on channel quality measurements. This periodic feedback mechanism balances signal reception quality with time efficiency, allowing the system to adapt to channel changes while avoiding excessive feedback processing delays.
Solution Approach 2:
The system uses partial feedback information sufficient for determining routing decisions without requiring complete channel state knowledge. By obtaining only the necessary channel quality information needed for routing determination rather than full channel characterization, the system achieves good signal reception quality while minimizing feedback processing time and overhead.
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 improves signal reception and system performance by allowing flexible routing of signals and phase shifts, achieving higher channel gains and lower bit error rates compared to singularly connected RIS designs, while maintaining passive operation.
Implementation Method 1
The signal may be phase-shifted while being routed from the ingress element to the egress element
Data Source
AI summary
A reconfigurable intelligent surface (RIS) may include a multi-directional and fully connected load impedance network may be provided. The RIS may include a plurality of elements that are each configured to receive and/or transmit signals. Each element of the RIS may be connected to each of the other elements of the RIS via a multi-directional and fully connected load impedance network. The RIS may receive feedback that comprises channel quality information for a channel between the RIS and another device. The RIS may determine routing information for the RIS based on the feedback. The routing information may comprise a mapping of ingress signals to egress signals. A first signal may be received via an ingress element. The RIS may route and phase shift the first signal to an egress element based on the determined routing information. The RIS may transmit the phase shifted first signal via the second element.