RIS Space-Time Block Coding for Adaptive Information Transfer
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Solution Overview
Problem
Current techniques for passive beamforming and information transfer using reconfigurable intelligent surfaces (RIS) are limited, particularly in managing interference, positioning, and early detection of link failures.
Innovation Solution
Implementing channel-adaptive space time block codes (STBCs) to enable reconfigurable intelligent surfaces to encode and reflect information bits, adjusting STBC size based on channel correlation metrics, and transmitting parameters to network entities and user equipment (UE) for accurate data identification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a fixed STBC size is used for encoding information bits on RIS, then the encoding process is simple, but the system cannot adapt to varying channel conditions leading to reduced reliability
Solution Approach 1:
The patent implements dynamic STBC configuration where the network entity selects different STBC sizes (e.g., 2x2, 4x4, 8x8) based on channel correlation metrics. The RIS divides its N elements into K subarrays where K corresponds to the STBC size, allowing the system to adapt to varying channel conditions while maintaining manageable complexity through standardized STBC selections.
Solution Approach 2:
The system changes the STBC size parameter based on channel conditions. The network entity receives channel correlation metrics from the RIS, determines an appropriate STBC size from a set of predefined sizes, and configures the RIS accordingly. This parameter adjustment optimizes information transfer reliability under different channel correlation scenarios.
2Productivity
If the RIS encodes more information bits using larger STBC, then the information transfer capacity increases, but the detection complexity at the UE increases
Solution Approach 1:
The patent uses partial action by selecting STBC sizes that match the actual channel correlation characteristics. Rather than always using the maximum possible STBC size, the system selects the appropriate level of encoding complexity based on measured channel conditions, achieving sufficient information transfer capacity without unnecessary detection complexity.
Solution Approach 2:
The system implements feedback through channel correlation metric measurements. The RIS measures channel correlations, reports metrics to the network entity, which then selects an appropriate STBC size. This feedback loop ensures the encoding complexity matches the actual channel conditions, optimizing the balance between information transfer capacity and detection complexity.
3Adaptability or versatility
If the RIS uses multiple subarrays for STBC encoding, then the channel adaptation capability improves, but the system complexity increases
Solution Approach 1:
The patent segments the RIS into K subarrays, where each subarray corresponds to a column in the STBC matrix. This segmentation enables the RIS to implement different phase shifts for different groups of elements, providing channel adaptation capability. The number of subarrays K is selected from a predefined set based on channel correlation metrics, managing complexity while maintaining adaptability.
Solution Approach 2:
The RIS is designed to support multiple STBC sizes (2x2, 4x4, 8x8, etc.) using the same fundamental mechanism of dividing elements into subarrays. This universal approach allows the system to adapt to different channel conditions without requiring fundamentally different hardware configurations, reducing overall system complexity while maintaining versatility.
Data Source
AI summary
Methods, systems, and devices for wireless communications are described. Generally, the techniques described herein may enable information transfer via channel-adaptive space time block codes (STBCs) over reconfigurable intelligent surfaces (RISs). For example, a network entity may transmit a control message indicating a set of parameters associated with an STBC of multiple STBCs associated with a RIS, where the set of parameters includes a size of the STBC. The network entity may transmit, to the RIS, a downlink message and the RIS may encode one or more information bits on the downlink message according to the parameters associated with the STBC. Additionally, the RIS may reflect the downlink message to a UE based on the set of parameters, where the reflected message includes the one or more information bits, and the UE may identify the one or more information bits based on a detection procedure associated with the set of parameters.