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Hierarchical Codebook Design for RIS-Based Transmit Arrays
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DOI：10.1109/TWC.2026.3703723.png)
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Abstract
En 中文
This paper investigates hierarchical codebook design for Reconfigurable Intelligent Surface based Transmit Arrays (TA-RIS) architectures operating under practical hardware constraints. We consider a transmissive RIS illuminated by one or more feeders, where the elements can only implement phase shifts and cannot be deactivated, i.e., cannot absorb the signal. A two-dimensional hierarchical codebook tailored to this architecture is proposed to enable efficient beam management and user localization without explicit channel state information estimation. To generate the codewords, we formulate a beampattern optimization problem that supports both wide and narrow beams and present two discrete-phase implementations: direct quantization of an unquantized interior-point solution and a Genetic Algorithm (GA) that operates natively in the discrete domain. A symmetry-based strategy is also introduced to reduce codebook storage requirements. Simulation results evaluate the performance of the algorithms considering 1, 2 and 3 bits phase quantization, and show that for RIS with a moderate number of elements and quantized phase shifts, GA emerge as a promising alternative to implement the desired codewords and construct a hierarchical codebook.
Keywords:
Transmit array
RIS
hierarchical codebook
beampattern optimization
Journal
IF:
10.7
Papers:
1.3W
Citations:
5.3W