Backwards-Compatible One-Shot Access Via RIS-Aware Raster Segmentation
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Solution Overview
Problem
Existing wireless communication systems face challenges in enabling one-shot initial access that is backwards compatible with both legacy and advanced user equipment (UE), particularly when reconfigurable intelligent surfaces (RIS) are involved, as legacy UE may not be able to detect watermarked signals reflected by RIS.
Innovation Solution
A synchronization raster is defined based on the number of RIS beams, allowing UE to indicate a raster index in its uplink reporting, which informs the base station about direct or indirect signal reception, enabling detection of watermarked signals by both legacy and advanced UE.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a synchronization raster is defined based on the number of RIS beams with watermarked signals, then advanced UE can detect RIS-reflected signals, but legacy UE cannot detect these watermarked signals
Solution Approach 1:
The synchronization raster is segmented into multiple subsets, where the first subset contains frequencies for direct base station signals and the second subset contains frequencies for RIS-reflected watermarked signals. This segmentation allows legacy UE to operate on the first subset while advanced UE can access both subsets to detect RIS beams.
Solution Approach 2:
The watermarked signal acts as an intermediary that carries identification information about RIS beams. By embedding this watermark in the synchronization signal, the system enables advanced UE to distinguish RIS-reflected signals from direct signals without preventing legacy UE from receiving standard signals.
2Adaptability or versatility
If legacy UE are supported with standard synchronization frequencies, then backwards compatibility is maintained, but advanced UE cannot distinguish direct signals from RIS-reflected signals
Solution Approach 1:
The system adds a frequency dimension to signal identification. By assigning watermarked synchronization signals to specific frequency offsets in the second subset, advanced UE can identify RIS-reflected signals through frequency analysis without affecting legacy UE operation on standard frequencies.
Solution Approach 2:
The synchronization signal parameters are changed by applying frequency watermarking to RIS-reflected signals. This parameter modification allows advanced UE to distinguish signal paths while maintaining compatibility with legacy UE that use standard synchronization parameters.
3Device complexity
If a single synchronization raster is used for all UEs, then system complexity is reduced, but the ability to support RIS beam identification is lost
Solution Approach 1:
The synchronization raster is divided into multiple subsets with distinct frequency allocations. The first subset handles standard direct signals while the second subset handles watermarked RIS signals, enabling beam identification without substantially increasing overall system complexity.
Data Source
AI summary
Methods, systems, and devices for wireless communication are described. A user equipment (UE) may monitor a plurality of synchronization raster frequencies to identify a frequency of a downlink signal transmitted from a base station, a first subset of the plurality of synchronization raster frequencies corresponding to the UE receiving the downlink signal from the base station and a second subset of the plurality of synchronization raster frequencies corresponding to the UE receiving the downlink signal from the base station via a configurable reflective device. The UE may identify a raster index associated with the frequency, the raster index corresponding to one of receiving the downlink signal from the base station or receiving the downlink signal from the base station via the configurable reflective device. The UE may transmit an uplink signal to the base station indicating the raster index.