RIS Beam Steering for Longer-Range THz LoS MIMO Links
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Solution Overview
Problem
Establishing reliable terahertz (THz) communication links is challenging due to high atmospheric attenuation and free-space losses, which limits the transmission range and makes it mostly line-of-sight (LoS), and existing solutions like ultra-massive MIMO systems face issues with power consumption and complexity.
Innovation Solution
The use of reconfigurable intelligent surfaces (RIS) to assist LoS MIMO systems at THz frequencies, optimizing beam-steering reflection matrices through singular value decomposition of channel matrices, and strategically placing RIS to extend communication range while maintaining channel stability and reducing the need for active relays.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If ultra-massive MIMO systems are used to extend transmission range at THz frequencies, then coverage is improved, but power consumption and system complexity increase significantly
Solution Approach 1:
The patent introduces reconfigurable intelligent surfaces (RIS) as intermediary elements that passively reflect and steer THz signals between transmitter and receiver. These RIS surfaces act as mediators that extend coverage without requiring active signal processing, thereby avoiding the power consumption and complexity issues of ultra-massive MIMO systems while still achieving coverage extension
2Area of stationary object
If ultra-massive MIMO systems are deployed to extend transmission range, then coverage is improved, but power consumption increases
Solution Approach 1:
The RIS surfaces serve as passive intermediaries that redirect THz signals using only passive reflection with programmable phase shifts. This eliminates the need for active amplification and signal processing at intermediate nodes, dramatically reducing power consumption compared to active relay systems or ultra-massive MIMO deployments while still achieving coverage extension
Solution Approach 2:
The patent employs multiple low-cost, simple RIS surfaces that can be strategically placed throughout the environment. Each RIS unit is a low-complexity, low-power device that provides localized beam steering capability, replacing the need for expensive, power-hungry ultra-massive MIMO infrastructure while achieving comparable or superior coverage extension
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 extends the communication range at THz frequencies, reduces the number of required nodes, and provides efficient, low-cost, and energy-efficient solutions for maintaining high data rates and channel stability in wireless communication systems.
Implementation Method 1
Each RIS is configured to redirect an incident electromagnetic (EM) signal toward an antenna array of an intended receiver
Implementation Method 2
improving a beam-steering reflection matrix (Φ) of the RIS system based on a singular value decomposition of channel matrices
Data Source
AI summary
A method, implemented by a processor connected to a reconfigurable intelligent surface (RIS) system that includes one or more RISs, includes detecting one or more wireless control signals from a transmitter. The method includes identifying a channel state and one or more phases based on the detected wireless control signals; improving a beam-steering reflection matrix (Φ) of the RIS system based on a singular value decomposition of channel matrices; and configuring the RIS system based on the Φ. Among the RISs, each RIS is configured to redirect an incident signal toward an antenna array of an intended receiver. The incident signal is received from the transmitter. Locations of the RIS and transmitter differ by a height placement value (hRIS). In a horizontal plane, the location of the RIS is a first distance (DTX-RIS) from the transmitter and a second distance (DRX-RIS) from the receiver.