Beamforming on Reconfigurable Intelligent Surface: A Codebook Design for Spatial Coverage with Beam Squint Effect
Beamforming on Reconfigurable Intelligent Surface: A Codebook Design for Spatial Coverage with Beam Squint Effect
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DOI：
10.1109/iccworkshops57953.2023.10283606
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发表时间：
2023-05
期刊：
影响因子：
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通讯作者：
Xinyi Lin;Yihong Liu;Lei Zhang;Anvar Tukmanov;Q. Abbasi;M. Imran
中科院分区：
文献类型：
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作者：
Xinyi Lin;Yihong Liu;Lei Zhang;Anvar Tukmanov;Q. Abbasi;M. Imran
在本文中，我们提出了一种新的可重构智能表面（RIS）码本设计，利用半功率波束宽度（HPBW）概念利用光束斜视。特别是波束斜视效应会导致RIS在不同频率下的阵列响应方向变化。我们的目标是设计RIS相移，使不同RIS权重产生的斜视光束能够平铺在RIS的整个空间域中而不重叠。为了量化宽频系统的空间覆盖性能，在宽频覆盖定义的基础上引入了宽频覆盖（W-HPBW）一词。导出了W-HPBW角信息的封闭表达式。为了进一步减少RIS权值的切换，降低信道估计中的导频开销，研究了波束展宽技术。这种设计大大减少了RIS相位调整次数和对精确信道估计的要求。仿真结果表明，所设计的码本能够有效地实现W-HBPW准则下的空间覆盖。
In this paper, we propose a novel reconfigurable intelligent surface (RIS) codebook design by leveraging beam squint with the help of half-power beamwidth (HPBW) concept. In particular, the beam squint effect incurs the array responses' direction change of RIS under different frequencies. We aim to design the RIS phase shifts such that the beams with squint generated by different RIS weights could tile over the entire spatial domain of the RIS without overlapping. To quantify the spatial coverage performance in wideband systems, a new term — wideband-HPBW (W-HPBW), is introduced based on the definition of HPBW. The closed-form expression of the angular information of W-HPBW is derived. To further reduce RIS weights switching and realize lower pilot overhead in channel estimation, a beam broadening technique is then investigated. This design largely reduces the times of RIS phase adjustments and the requirement for accurate channel estimation. Simulation results show that the designed codebook can effectively realize spatial coverage under the W-HBPW criterion.