A Uniform Planar Array is a configuration of multiple antenna elements arranged in a two-dimensional plane with regular spacing between adjacent elements. This type of antenna array is characterized by a systematic and consistent arrangement of antennas in both the horizontal and vertical directions. This type of antenna array is employed in various applications, particularly in systems where directional sensitivity, beamforming, and control of the radiation pattern are crucial design considerations.

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RIS-aided mmWave Beamforming for Two-way Communications of Multiple Pairs

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Millimeter‑wave (mmWave) communications is a key enabler towards realizing enhanced Mobile Broadband (eMBB) as a key promise of 5G and beyond, due to the abundance of bandwidth available at mmWave bands. An mmWave coverage map consists of blind spots due to shadowing and fading especially in dense urban environments. Beamformingemploying massive MIMO is primarily used to address high attenuation in the mmWave channel. Due to their ability in manipulating the impinging electromagnetic waves in an energy‑efficient fashion, Reconfigurable Intelligent Surfaces (RISs) are considered a great match to complement the massive MIMO systems in realizing the beamforming task and therefore effectively filling in the mmWave coverage gap. In this paper, we propose a novel RIS architecture, namely RIS‑UPA where the RIS elements are arranged in a Uniform Planar Array (UPA). We show how RIS‑UPA can be used in an RIS‑aided MIMO system to fill the coverage gap in mmWave by forming beams of a custom footprint, with optimized main lobe gain, minimum leakage, and fairly sharp edges. Further, we propose a configuration for RIS‑UPA that can support multiple two‑way communication pairs, simultaneously. We theoretically obtain closed‑form low‑complexity solutions for our design and validate our theoretical findings by extensive numerical experiments.

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Shaping mmWave Wireless Channel via Multi-Beam Design using Reconfigurable Intelligent Surfaces

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Millimeter-wave (mmWave) communications is considered as a key enabler towards the realization of next-generation wireless networks, due to the abundance of available spectrum at mmWave frequencies. However, mmWave suffers from high free-space path-loss and poor scattering resulting in mostly line-of-sight (LoS) channels which result in a lack of coverage. Reconfigurable intelligent surfaces (RIS), as a new paradigm, have the potential to fill the coverage holes by shaping the wireless channel. In this paper, we propose a novel approach for designing RIS with elements arranged in a uniform planar array (UPA) structure. In what we refer to as multi-beamforming, We propose and design RIS such that the reflected beam comprises multiple disjoint lobes. Moreover, the beams have optimized gain within the desired angular coverage with fairly sharp edges avoiding power leakage to other regions. We provide a closed-form low-complexity solution for the multi-beamforming design. We confirm our theoretical results by numerical analysis.

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