RIS Phase-Change Watermarking for Beam Identification
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Solution Overview
Problem
Existing wireless communication systems face challenges in efficiently determining the best reconfigurable intelligent surface (RIS) beam for communication between a user equipment (UE) and a network entity, especially when line-of-sight links are blocked.
Innovation Solution
The implementation of a phase-change watermarking technique by the RIS on uplink transmissions, allowing the network entity to identify the appropriate RIS beam by recognizing the phase-change pattern associated with the received random access message.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Area of stationary object
If the network entity transmits multiple synchronization signal blocks via different downlink transmit beams, then the coverage area is expanded and more UEs can be reached, but the complexity of identifying the best RIS beam increases
Solution Approach 1:
The RIS applies different phase-change patterns (analogous to color changes) to reflected uplink signals based on which downlink transmit beam the UE received. Each phase-change pattern serves as a unique identifier that allows the network entity to determine which RIS beam configuration is best, without requiring complex beam identification procedures.
Solution Approach 2:
The system implements a feedback mechanism where the RIS observes which downlink transmit beam the UE successfully received (through the received uplink signal characteristics) and then applies the corresponding phase-change pattern to provide feedback about the optimal RIS beam configuration to the network entity.
2Measurement precision
If the RIS applies phase-change patterns to uplink transmissions, then the network entity can identify the best RIS beam more accurately, but the processing complexity at the RIS increases
Solution Approach 1:
The RIS changes the phase parameter of the reflected uplink signal based on the identified downlink transmit beam. Instead of complex beamforming calculations, the RIS simply applies pre-determined phase-change patterns corresponding to each downlink beam, reducing processing complexity while maintaining accurate beam identification.
Solution Approach 2:
The phase-change patterns are pre-configured and associated with specific downlink transmit beams before actual communication occurs. This preliminary preparation allows the RIS to quickly apply the appropriate phase pattern without real-time complex calculations, reducing processing complexity during operation.
3Reliability
If the system uses phase-change watermarking on uplink transmissions, then communication reliability is improved, but the system requires additional signaling overhead
Solution Approach 1:
The phase-change patterns serve multiple functions simultaneously: they act as watermarks for beam identification, provide implicit feedback about the optimal RIS configuration, and enable reliable communication establishment. This multi-functionality reduces the need for separate signaling messages, offsetting the overhead with informational efficiency.
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 communication efficiency by enabling the network entity to accurately determine the best RIS beam, thereby improving signal quality, reducing latency, and increasing the reliability of transmissions between the UE and the network entity.
Implementation Method 1
The RIS may reflect instances of the synchronization signal block (e.g., each synchronization signal block being associated with the same index) in downlink transmit beams that the RIS directs in multiple directions
Implementation Method 2
The RIS may identify a phase-change pattern associated with the received random access message and reflect the random access message to the network entity by applying the identified phase-change pattern to antenna elements of the RIS
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. The method includes a reconfigurable intelligent surface receiving, from a network entity, a synchronization signal block associated with a synchronization signal block index, reflecting the synchronization signal block as a set of multiple instances of the synchronization signal block via a corresponding set of multiple downlink transmit beams, receiving a random access message from a user equipment (UE) during a random access occasion that corresponds with the synchronization signal block index and on an uplink receive beam that corresponds with one of the set of multiple downlink transmit beams, identifying the phase-change pattern of multiple phase-change patterns that corresponds to the uplink receive beam, and reflecting the random access message to the network entity by applying the phase-change pattern to antenna elements of the reconfigurable intelligent surface that reflect the random access message to the network entity.