Research on Energy Efficiency Optimization of Rotatable Hybrid Intelligent Reflecting Surface Communication

ZHANG Guangchi; GUO Xuan; WANG Luyao; CUI Miao; FU Hao

doi:10.11999/JEIT260119

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ZHANG Guangchi, GUO Xuan, WANG Luyao, CUI Miao, FU Hao. Research on Energy Efficiency Optimization of Rotatable Hybrid Intelligent Reflecting Surface Communication[J]. Journal of Electronics & Information Technology. doi: 10.11999/JEIT260119

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ZHANG Guangchi, GUO Xuan, WANG Luyao, CUI Miao, FU Hao. Research on Energy Efficiency Optimization of Rotatable Hybrid Intelligent Reflecting Surface Communication[J]. Journal of Electronics & Information Technology. doi: 10.11999/JEIT260119

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Research on Energy Efficiency Optimization of Rotatable Hybrid Intelligent Reflecting Surface Communication

doi: 10.11999/JEIT260119 cstr: 32379.14.JEIT260119

Guangdong University of Technology, Guangzhou 510006, China

Funds: Guangdong Basic and Applied Basic Research Foundation (2026A1515011208), Guangdong Science and Technology Plan Project (2022A0505050023)

Accepted Date: 2026-04-23
Rev Recd Date: 2026-04-23

Available Online: 2026-05-16

Abstract

Abstract

Objective With the evolution of 6G communication networks, reconfigurable intelligent surfaces (RIS) have emerged as a pivotal technology for reshaping wireless environments and enhancing spectral efficiency. However, conventional fixed RIS architectures face two critical challenges in practical deployment: the “angle mismatch” loss, where the effective aperture significantly diminishes when users are located at large angles from the RIS normal, and the “energy consumption bottleneck,” caused by the high cumulative power consumption of radio frequency (RF) circuits and static control elements in large-scale arrays. Existing research often treats mechanical rotation and element switching in isolation, lacking a unified framework to balance the trade-off between mechanical/circuit energy consumption and communication gain. To address these limitations, this paper investigates a rotatable and switchable hybrid RIS (H-RIS) assisted downlink communication system. The primary objective is to maximize the system’s energy efficiency (EE) by jointly optimizing the base station transmit power, subarray activation states, physical rotation angles, and electronic phase shifts. This approach aims to introduce mechanical rotation degrees of freedom to compensate for path loss and employ dynamic switching mechanisms to reduce redundant power consumption, thereby achieving sustainable green communication. Methods A joint optimization framework is established for the H-RIS aided single-user multiple-input single-output (MISO) system. The system model explicitly accounts for the dynamic power consumption induced by mechanical rotation and the static power consumption of active subarrays. The resulting optimization problem is formulated as a non-convex mixed-Integer non-linear programming (MINLP) problem, involving coupled binary variables (activation status) and continuous variables (power, angles, phases). To solve this challenging problem, a block coordinate descent (BCD)-based alternating optimization (AO) algorithm is proposed to decouple the variables into three sub-problems.Firstly, to tackle the exponential complexity caused by binary switching variables, a channel contribution-based ranking strategy is developed. By performing eigenvalue decomposition on the cascaded channel correlation matrix, the priority of each subarray is quantified, reducing the search space from exponential to linear.Secondly, for the power allocation sub-problem, the non-convex fractional objective function is transformed into a parametric subtractive form using the Dinkelbach algorithm, which is then solved via the interior-point method.Thirdly, for the physical rotation and electronic phase optimization, the problem is decomposed into single-variable sub-problems. A Golden Section Search algorithm is employed to iteratively find the optimal rotation angle and phase shift for each subarray within bounded constraints, ensuring the monotonic convergence of the objective function. Results and Discussions Extensive simulations are conducted to evaluate the performance of the proposed H-RIS scheme compared with benchmark schemes, including “Only-Rotation” (always on), “Only-Switching” (fixed angle), and “Conventional” (fixed and always on).The simulation results regarding the maximum transmit power P_max(Fig. 2 and Fig. 3) demonstrate that the proposed method achieves the highest energy efficiency across the entire power range. Specifically, in the low power regime, the proposed algorithm intelligently turns off redundant subarrays where the rate gain cannot offset the circuit power cost, thereby significantly outperforming the “Only-Rotation” scheme which suffers from high static power consumption.The impact of user distance is also analyzed (Fig. 4 and Fig. 5). Results indicate that the proposed scheme maintains high spectral efficiency comparable to the “Only-Rotation” scheme by dynamically adjusting the rotation angles to align with the Line-of-Sight (LoS) path, effectively compensating for the angle mismatch loss observed in the “Only-Switching” and “Conventional” schemes.Furthermore, the activation pattern of the subarray varies in a “U” shape with distance (Table 1), which allows for flexible adjustment of array size and orientation according to user-RIS geometry. Conclusions This paper proposes an energy-efficient transmission scheme for H-RIS aided communication systems by integrating mechanical rotation and dynamic switching capabilities. A low-complexity BCD-based algorithm is developed to jointly optimize the transceiver design. The results confirm that introducing mechanical rotation significantly mitigates the angle mismatch loss, while the proposed channel contribution-based switching strategy effectively eliminates redundant energy consumption. The proposed H-RIS architecture offers a superior trade-off between spectral efficiency and energy efficiency compared to traditional fixed RIS architectures, providing a viable solution for future green 6G networks.
- Reconfigurable Intelligent Surface (RIS),
- Hybrid RIS (H-RIS),
- Energy Efficiency,
- Switch Control,
- Alternating Optimization

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References(20)

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