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1
Wang, Wenhe, and Kang Song. "Hybrid Active–Passive Reconfigurable Intelligent Surface for Cooperative Transmission Systems." Applied Sciences 14, no. 1 (December 27, 2023): 231. http://dx.doi.org/10.3390/app14010231.
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Reconfigurable intelligent surfaces (RISs) are acknowledged as one of the key technologies for the next-generation communications systems due to their low cost, high-energy efficiency, and the ability to intelligently control the wireless propagation environment. In this paper, we present a hybrid active–passive reconfigurable intelligent surface (HAPR) for cooperative transmission system, where HAPR can intelligently change its operating mode according to the channel environment, eliminating the “multiplicative fading” effect of traditional passive RIS (P-RIS) and higher power consumption of active RIS (A-RIS), and combining the advantages of both to effectively improve the system performance. First, we investigate the ideal reflection coefficient of RIS reflecting elements (REs) under the condition of a limited power budget. Using the compound Simpson formula, the closed-form approximation expression for the system outage probability (OP) has been derived. Finally, Monte Carlo simulation is used to confirm the accuracy of the expression. The simulation results demonstrate that HAPR has a better performance than both A-RIS and P-RIS, which can achieve a lower OP.
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Rana, Biswarup, Sung-Sil Cho, and Ic-Pyo Hong. "Parameters and Measurement Techniques of Reconfigurable Intelligent Surfaces." Micromachines 13, no. 11 (October 27, 2022): 1841. http://dx.doi.org/10.3390/mi13111841.
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Reconfigurable intelligent surface (RIS)-aided wireless communications systems are one the promising wireless communication system where the wave can be guided by the RIS. It is envisioned that beyond-5G/6G communication will have a low-cost, high spectral efficiency, high energy efficiency, and smart wireless environment. In this paper, initially, different measurement techniques of the RIS have been discussed, which are available in the literature. Then, a new type of RIS has been proposed. Finally, a different parameter measurement technique for our proposed RIS has been presented. A low-cost FR4 substrate with a height of 1.6 mm was considered to design the RIS in the sub-6 GHz frequency band. Another important thing is that our proposed IRS is a single-layer substrate backed by a copper plate. The area of each unit cell was 42 mm × 42 mm. The RIS was designed to operate at the central frequency of the 3.5 GHz frequency band. The novelty of the proposed RIS is that it is a polarization-independent structure. Thus, polarization-related losses can be overcome using this structure. A 10×10-unit cell array was designed to check the radiation performance. The magnitude of the reflection coefficients was measured in our laboratory for the proposed configuration.
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Ni, Li, Yonggang Zhu, and Wenlong Guo. "Controllable Multiple Active Reconfigurable Intelligent Surfaces Assisted Anti-Jamming Communication." Electronics 12, no. 18 (September 18, 2023): 3933. http://dx.doi.org/10.3390/electronics12183933.
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Traditional anti-jamming techniques such as frequency hopping (FH) and direction-sequence spread spectrum (DSSS) are easily targeted by jammers. Inspired by the significant advantages of reconfigurable intelligent surfaces (RIS), and in order to overcome “double fading”, controllable multiple active RISs are proposed to explore anti-jamming communication in this paper. To verify the feasibility of active RIS, the anti-jamming performance of active RIS is analyzed through theoretical derivation and simulation and compared with passive RIS. Furthermore, to solve the optimization problem of active RIS, a controllable multi-active RIS assisted anti-jamming algorithm based on BCD is proposed. Theoretical analysis and simulation results show that in small-scale deployment scenarios of RIS, the anti-jamming performance of active RIS is better than that of passive RIS, and the complexity and optimization performance of the proposed algorithm are better than those of semidefinite relaxation (SDR) algorithms.
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Nguyen, Nhan Duc, Minh-Sang Van Nguyen, and Munyaradzi Munochiveyi. "Empowering Reconfigurable Intelligent Surfaces for Security of Downlink NOMA." Wireless Communications and Mobile Computing 2022 (May 25, 2022): 1–15. http://dx.doi.org/10.1155/2022/1498918.
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Reconfigurable intelligent surfaces (RIS) and non-orthogonal multiple access (NOMA) are promising techniques to develop next-generation wireless systems. While RIS has huge potential to create massive device connectivity, NOMA exhibits its spectrum efficient communication among multiple access approaches. RIS is a passive device made up of low-cost meta-surfaces which can control the propagation of radio waves, and it is easily deployable in lots of applications in the Internet of Things. The full-duplex nature of RIS has also been a major reason for its consideration of major emerging and trending technologies. In this paper, we aim to investigate the secrecy performance of the RIS-NOMA-assisted Internet of Things (IoT) systems in the presence of two legitimate users who belong to a cluster, and those devices are associated with the existence of an eavesdropper situated close to such a cluster. This paper considers the devices in the presence of RIS and an eavesdropper. As main performance metrics, the closed-form expressions for secrecy outage probability (SOP) and strictly positive secrecy capacity (SPSC) are derived to evaluate the performance of legitimate users. Simulations are performed in support of the Monte-Carlo method, and the obtained results show that in most of the cases, the number of meta-surfaces in RIS and signal-to-noise ratio (SNR) levels at the source also plays a pivotal role in influencing the secure performance of the system.
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UmaMaheswari, Kaveti, Arjun Chakravarthi Pogaku, Dinh-Thuan Do, Anh-Tu Le, and Munyaradzi Munochiveyi. "Improving Performance of User Pair Using Reconfigurable Intelligent Surfaces." Wireless Communications and Mobile Computing 2021 (December 23, 2021): 1–12. http://dx.doi.org/10.1155/2021/2036778.
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With the given scope for new use cases and the demanding needs of future 6th generation (6G) wireless networks, the development of wireless communications looks exciting. The propagation medium has been viewed as a randomly behaving entity between the transmitter and the receiver since traditional wireless technology, degrading the quality of the received signal due to the unpredictable interactions of the broadcast radio waves with the surrounding objects. On the other hand, network operators could now manipulate electromagnetic radiation to remove the negative impacts of natural wireless propagation due to the recent arrival of reconfigurable intelligent surfaces (RIS) in wireless communications. According to recent findings, the RIS mechanism benefits nonorthogonal multiple access (NOMA), which can effectively deliver effective transmissions. For simple design, of RIS-NOMA system, fixed power allocation scheme for NOMA is required. The main system performance metric, i.e., outage probability, needs to be considered to look at the efficiency and capability of transmission mode relying on RIS and NOMA schemes, motivated by the potential of these developing technologies. As major performance metrics, we derive analytical representations of outage probability, and throughput and an accurate approximation is obtained for the outage probability. Numerical results are conducted to validate the exactness of the theoretical analysis. It is found that increasing the higher number of reflecting elements in the RIS can significantly boost the outage probability performance, and the scenario with only the RIS link is also beneficial. In addition, it is desirable to deploy the RIS-NOMA since it is indicated that better performance compared with the traditional multiple access technique.
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Liu, Yiping, Jianwu Dou, Yijun Cui, Yijian Chen, Jun Yang, Fan Qin, and Yuxin Wang. "Reconfigurable Intelligent Surface Physical Model in Channel Modeling." Electronics 11, no. 17 (September 5, 2022): 2798. http://dx.doi.org/10.3390/electronics11172798.
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Reconfigurable intelligent surfaces (RISs) are one of the potential technologies for 6th generation (6G) mobile communication systems with superior electromagnetic (EM) wave-steering capability to effectively control the phase, amplitude, and polarization of the incident EM wave. An implementation-independent physical RIS model with key EM characteristics is especially crucial to RIS channel modeling considering the trade-off between complexity and accuracy. In this paper, a reflective RIS physical model is proposed to facilitate channel modeling in a system simulation. Based on the impinging EM wave of the last bounce to the RIS, the scattering field intensity of the target point is obtained using geometric optics and the electric field surface integration method of physical optics. The feasibility of the model is verified by a comparison of the simulation and test results.
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Patra, Radhashyam, and Arunanshu Mahapatro. "Reconfigurable Intelligent Surface-based Propagation Control in FBMC/OQAM Systems." Journal of Telecommunications and Information Technology, no. 1 (February 28, 2024): 83–90. http://dx.doi.org/10.26636/jtit.2024.1.1326.
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In this paper, transmission of filter bank multi-carrier (FBMC) modulated signal through reconfigurable intelligent surfaces (RIS) is proposed as an assuring technique for future wireless communication. RIS deliberately alters phases of incident signals to enhance quality of the received signal. Simulation outcomes show that it is possible to establish RIS-based FBMC communications in which RIS functions as an intelligent reflector with information concerning channel phases. It is observed that RIS-based FBMC transmissions may be a prospective solution for beyond 5G communication.
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Demmer, David, Francesco Foglia Manzillo, Samara Gharbieh, Maciej Śmierzchalski, Raffaele D’Errico, Jean-Baptiste Doré, and Antonio Clemente. "Hybrid Precoding Applied to Multi-Beam Transmitting Reconfigurable Intelligent Surfaces (T-RIS)." Electronics 12, no. 5 (February 27, 2023): 1162. http://dx.doi.org/10.3390/electronics12051162.
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In this work, we study hybrid precoding techniques applied to multi-user Transmitting Reconfigurable Intelligent Surface (T-RIS) systems. The T-RIS considered here is a large array of electronically reconfigurable antenna elements illuminated by a small set of active sources. When it comes to digital signal-processing techniques applied to T-RIS systems, it is necessary to consider realistic models to bridge the gap with theoretical results. For this reason, we propose a multi-beam T-RIS propagation model with strong phase quantization constraints and limited beam codebooks. First, the proposed model is validated by characterizing a Ka-band T-RIS. Then, we optimize the quad-beam T-RIS structure by tuning the focal distance between the lens and the focal sources according to two metrics: (i) the per-user antenna gain (analog-only approach), and (ii) the per-user average rate (hybrid digital/analog approach). For both indicators, the system performance is evaluated in a multi-user scenario by assuming imperfect channel state information. We show that considering only the analog precoder is sufficient to optimize the T-RIS. However, the fully hybrid precoding scheme is required to deal with inter-user interference. We propose a codebook-aware optimization that improves the aperture efficiency of the T-RIS system.
9
Rana, Biswarup, Sung-Sil Cho, and Ic-Pyo Hong. "Passive Type Reconfigurable Intelligent Surface: Measurement of Radiation Patterns." Micromachines 14, no. 4 (April 5, 2023): 818. http://dx.doi.org/10.3390/mi14040818.
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The demand for unprecedented data and ubiquitous wireless connections have led to the adoption of new types of transmitters and receivers. Additionally, different new types of devices and technologies need to be proposed for such demand. Reconfigurable intelligent surface (RIS) is going to play a very significant role in the upcoming beyond-5G/6G communications. It is envisioned that not only the RIS will be deployed to assist and create a smart wireless environment for the upcoming communications, but also the receiver and transmitter can be fabricated using RIS to make a smart and intelligent transmitter and receiver. Thus, the latency of upcoming communications can be reduced very significantly using RIS, which is a very important factor. Artificial intelligence assists communications and shall be adopted widely for the next generation networks. In this paper, radiation pattern measurement results of our previously published RIS have been provided. This work is the extension work of our previously proposed RIS. The polarization-independent passive type of RIS working in the sub-6 GHz frequency band using low-cost FR4-substrate was designed. Each unit cell with dimensions of 42 mm × 42 mm had a single-layer substrate backed by a copper plate. A 10 × 10-unit cell array was fabricated to check the performance of the RIS. Such types of unit cells and RIS were designed to set up initial measurement facilities in our laboratory for any kinds of RIS measurements.
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Goh, Chi Yen, Chee Yen Leow, and Rosdiadee Nordin. "Energy Efficiency of Unmanned Aerial Vehicle with Reconfigurable Intelligent Surfaces: A Comparative Study." Drones 7, no. 2 (January 31, 2023): 98. http://dx.doi.org/10.3390/drones7020098.
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Unmanned aerial vehicles (UAVs) and reconfigurable intelligent surfaces (RIS) are the promising emerging technologies proposed for the 6th-Generation (6G) network to improve the capacity, reliability, and coverage of wireless communications. By integrating the UAV with RIS (RIS-UAV), the three-dimensional (3D) mobility of the UAV can be leveraged to establish strong line-of-sight links with the ground nodes, while the RIS intelligently reflect the signals toward the desired directions. However, the existing literature on RIS-UAV systems mainly assumes the use of passive elements, which suffers from the double path-loss problem. The use of active elements in RIS, which could improve the reflected link performance at the cost of increased energy consumption, has not been considered for the RIS-UAV system. Further, the energy efficiency of a RIS-UAV with active elements remains as an open direction because there is a need to investigate the feasibility of either an active or hybrid RIS-UAV implementation. This paper proposes active and hybrid RIS-UAVs and investigates the energy efficiencies of active and hybrid RIS-UAVs in comparison with existing passive RIS-UAVs and conventional UAV relays. The numerical results reveal that the proposed hybrid and active RIS-UAV relaying schemes can provide up to 14 times and 26 times improvement as compared to the passive RIS-UAV, respectively. As opposed to the active RIS-UAV that requires a larger power budget, half-duplex UAV relays that have a lower spectral efficiency, and full-duplex UAV relays that suffer from self-interference, the hybrid RIS-UAV emerges as a promising option to assist the ground communication system.
11
Alanazi, Faisal. "Enhanced physical layer security using reconfigurable intelligent surfaces (RIS)." International Journal of Sensor Networks 36, no. 4 (2021): 229. http://dx.doi.org/10.1504/ijsnet.2021.117485.
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Alanazi, Faisal. "Enhanced physical layer security using reconfigurable intelligent surfaces (RIS)." International Journal of Sensor Networks 36, no. 4 (2021): 229. http://dx.doi.org/10.1504/ijsnet.2021.10040555.
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Chiti, Francesco, Ashley Degl’Innocenti, and Laura Pierucci. "Secure Networking with Software-Defined Reconfigurable Intelligent Surfaces." Sensors 23, no. 5 (March 2, 2023): 2726. http://dx.doi.org/10.3390/s23052726.
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Reconfigurable intelligent surfaces (RIS) are considered of paramount importance to improve air–ground and THz communications performance for 6G systems. Recently, RISs were proposed in Physical Layer Security (PLS), as they can (i) improve the secrecy capacity due to the controlled directional reflections’ capability of RIS elements and (ii) avoid potential eavesdroppers, redirecting data streams towards the intended users. This paper proposes the integration of a multi-RISs system within a Software Defined Networking (SDN) architecture to provide a specific control layer for secure data flows forwarding. The optimisation problem is properly characterised in terms of an objective function and an equivalent graph theory model is considered to address the optimal solution. Moreover, different heuristics are proposed, trading off complexity and PLS performance, to evaluate the more suitable multi-beam routing strategy. Numerical results are also provided, focusing on a worst case scenario which points out the improvement of the secrecy rate from the increase in the number of eavesdroppers. Furthermore, the security performance is investigated for a specific user mobility pattern in a pedestrian scenario.
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Matos, Randy, and Nezih Pala. "A Review of Phase-Change Materials and Their Potential for Reconfigurable Intelligent Surfaces." Micromachines 14, no. 6 (June 16, 2023): 1259. http://dx.doi.org/10.3390/mi14061259.
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Phase-change materials (PCMs) and metal-insulator transition (MIT) materials have the unique feature of changing their material phase through external excitations such as conductive heating, optical stimulation, or the application of electric or magnetic fields, which, in turn, results in changes to their electrical and optical properties. This feature can find applications in many fields, particularly in reconfigurable electrical and optical structures. Among these applications, the reconfigurable intelligent surface (RIS) has emerged as a promising platform for both wireless RF applications as well as optical ones. This paper reviews the current, state-of-the-art PCMs within the context of RIS, their material properties, their performance metrics, some applications found in the literature, and how they can impact the future of RIS.
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Li, Kainan, Siyuan Zhou, and Guoping Tan. "Performance Analysis of a Reconfigurable-Intelligent-Surfaces-Assisted V2V Communication System." Electronics 12, no. 11 (May 24, 2023): 2383. http://dx.doi.org/10.3390/electronics12112383.
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Novel reconfigurable Intelligent Surfaces (RISs) area technology can improve the communication performance by changing the wireless transmission environment. Introducing RIS technology into Vehicle-to-Vehicle (V2V) communication environments can enhance the communication reliability by creating Line-of-Sight (LoS) communication links, thereby effectively improving the communication performance. However, in RIS-assisted V2V large-scale communication networks, the stochasticity of network nodes and random interference can impact performance. In this article, we examine the outage communication transmission performance of an RIS-assisted V2V communication network. We select the signal transmission mode based on the obstacle presence between vehicles and use the stochastic geometry theory to calculate the probabilities of the two modes: direct mode and RIS-assisted mode. By deriving the communication distance distribution and the aggregate interference distribution, we evaluate V2V communication in the direct mode to assess its transmission performance in two scenarios and obtain the overall outage probability. The numerical results demonstrate a better performance in RIS-assisted V2V networks, with an improved optimal phase shift scheme over that of the original V2V network. Monte Carlo simulation validated our analytical findings.
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Frimpong, Emmanuel Obeng, Bong-Hwan Oh, Taehoon Kim, and Inkyu Bang. "Physical-Layer Security with Irregular Reconfigurable Intelligent Surfaces for 6G Networks †." Sensors 23, no. 4 (February 7, 2023): 1881. http://dx.doi.org/10.3390/s23041881.
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The goal of 6G is to make far-reaching changes in communication systems with stricter demands, such as high throughput, extremely low latency, stronger security, and ubiquitous connectivity. Several promising techniques, such as reconfigurable intelligent surfaces (RISs), have been introduced to achieve these goals. An RIS is a 2D low-cost array of reflecting elements that can adjust the electromagnetic properties of an incident signal. In this paper, we guarantee secrecy by using an irregular RIS (IRIS). The main idea of an IRIS is to irregularly activate reflecting elements for a given number of RIS elements. In this work, we consider a communication scenario in which, with the aid of an IRIS, a multi-antenna base station establishes a secure link with a legitimate single-antenna user in the presence of a single-antenna eavesdropper. To this end, we formulate a topology-and-precoding optimization problem to maximize the secrecy rate. We then propose a Tabu search-based algorithm to jointly optimize the RIS topology and the precoding design. Finally, we present simulation results to validate the proposed algorithm, which highlights the performance gain of the IRIS in improving secure transmissions compared to an RIS. Our results show that exploiting an IRIS can allow additional spatial diversity to be achieved, resulting in secrecy performance improvement and overcoming the limitations of conventional RIS-assisted systems (e.g., a large number of active elements).
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AL-Shaeli, Intisar, Lsmail Sharhan Hburi, and Ammar A. Majeed. "Reconfigurable intelligent surface passive beamforming enhancement using unsupervised learning." International Journal of Electrical and Computer Engineering (IJECE) 13, no. 1 (February 1, 2023): 493. http://dx.doi.org/10.11591/ijece.v13i1.pp493-501.
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<p><span lang="EN-US">Reconfigurable intelligent surfaces (RIS) is a wireless technology that has the potential to improve cellular communication systems significantly. This paper considers enhancing the RIS beamforming in a RIS-aided multiuser multi-input multi-output (MIMO) system to enhance user throughput in cellular networks. The study offers an unsupervised/deep neural network (U/DNN) that simultaneously optimizes the intelligent surface beamforming with less complexity to overcome the non-convex sum-rate problem difficulty. The numerical outcomes comparing the suggested approach to the near-optimal iterative semi-definite programming strategy indicate that the proposed method retains most performance (more than 95% of optimal throughput value when the number of antennas is 4 and RIS’s elements are 30) while drastically reducing system computing complexity.</span></p>
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Yang, Fengyuan, Prakash Pitchappa, and Nan Wang. "Terahertz Reconfigurable Intelligent Surfaces (RISs) for 6G Communication Links." Micromachines 13, no. 2 (February 10, 2022): 285. http://dx.doi.org/10.3390/mi13020285.
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The forthcoming sixth generation (6G) communication network is envisioned to provide ultra-fast data transmission and ubiquitous wireless connectivity. The terahertz (THz) spectrum, with higher frequency and wider bandwidth, offers great potential for 6G wireless technologies. However, the THz links suffers from high loss and line-of-sight connectivity. To overcome these challenges, a cost-effective method to dynamically optimize the transmission path using reconfigurable intelligent surfaces (RISs) is widely proposed. RIS is constructed by embedding active elements into passive metasurfaces, which is an artificially designed periodic structure. However, the active elements (e.g., PIN diodes) used for 5G RIS are impractical for 6G RIS due to the cutoff frequency limitation and higher loss at THz frequencies. As such, various tuning elements have been explored to fill this THz gap between radio waves and infrared light. The focus of this review is on THz RISs with the potential to assist 6G communication functionalities including pixel-level amplitude modulation and dynamic beam manipulation. By reviewing a wide range of tuning mechanisms, including electronic approaches (complementary metal-oxide-semiconductor (CMOS) transistors, Schottky diodes, high electron mobility transistors (HEMTs), and graphene), optical approaches (photoactive semiconductor materials), phase-change materials (vanadium dioxide, chalcogenides, and liquid crystals), as well as microelectromechanical systems (MEMS), this review summarizes recent developments in THz RISs in support of 6G communication links and discusses future research directions in this field.
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Ramamoorthi, Yoghitha, Riku Ohmiya, Masashi Iwabuchi, Tomoaki Ogawa, and Yasushi Takatori. "Resource Allocation and Sharing Methodologies When Reconfigurable Intelligent Surfaces Meet Multiple Base Stations." Sensors 22, no. 15 (July 27, 2022): 5619. http://dx.doi.org/10.3390/s22155619.
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The 6G wireless systems are expected to have higher capacity, reliability, and energy efficiency than the existing cellular systems. Millimeter-wave (mmWave) frequencies offer high capacity at the cost of high attenuation and blockage losses. Reconfigurable intelligent surface (RIS) assisted mmWave networks consist of smaller antenna elements that control the propagation channel between the base station (BS) and the user by appropriately tuning the phase and the reflection of the incident electromagnetic signal. The deployment of RIS is considered to be an energy efficient solution to improve the coverage of regions with high blocking probability. However, if every BS is associated with one or more dedicated RIS, then the density of RIS increases proportionally with the density of BSs. Hence in this work, we propose RIS sharing mechanisms where multiple BSs share one RIS. We formulate resource allocation of RIS sharing in terms of time and the RIS elements as an optimization problem, and we propose heuristics to solve both. Further, we present detailed simulation results to compare time and the element based RIS sharing methods for various scenarios with the benchmark and the RIS system without sharing. The proposed time and element based RIS sharing methods improve throughput upto 53% and 25%, respectively, compared to the RIS system without sharing in specific scenarios.
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Almamori, Aqiel, and Mohammed Adil Abbas. "Channel state information estimation for reconfigurable intelligent surfaces based on received signal analysis." International Journal of Electrical and Computer Engineering (IJECE) 13, no. 2 (April 1, 2023): 1599. http://dx.doi.org/10.11591/ijece.v13i2.pp1599-1605.
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<p>Recently, reconfigurable intelligent surfaces have an increasing role to enhance the coverage and quality of mobile networks especially when the received signal level is very weak because of obstacles and random fluctuation. This motivates the researchers to add more contributions to the fields of reconfigurable intelligent surfaces (RIS) in wireless communications. A substantial issue in reconfigurable intelligent surfaces is the huge overhead for channel state information estimation which limits the system’s performance, oppressively. In this work, a newly proposed method is to estimate the angle of arrival and path loss at the RIS side and then send short information to the base station rather than huge overhead as in previous research. The estimated channel state information is used to beamform the downlink waveform toward users accurately. The simulation results indicate that the proposed algorithm calculated the angle of arrival of users, admirably especially at a high signal-to-noise ratio. Moreover, a considerable spectral efficiency enhancement is obtained as compared to the traditional methods.</p>
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Ramamoorthi, Yoghitha, Masashi Iwabuchi, Tomoki Murakami, Tomoaki Ogawa, and Yasushi Takatori. "Resource Allocation for Reconfigurable Intelligent Surface Assisted Dual Connectivity." Sensors 22, no. 15 (August 1, 2022): 5755. http://dx.doi.org/10.3390/s22155755.
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The next generation 6G wireless systems are envisioned to have higher reliability and capacity than the existing cellular systems. The reconfigurable intelligent surfaces (RISs)-assisted wireless networks are one of the promising solutions to control the wireless channel by altering the electromagnetic properties of the signal. The dual connectivity (DC) increases the per-user throughput by utilizing radio resources from two different base stations. In this work, we propose the RIS-assisted DC system to improve the per-user throughput of the users by utilizing resources from two base stations (BSs) in proximity via different RISs. Given an α−fair utility function, the joint resource allocation and the user scheduling of a RIS-assisted DC system is formulated as an optimization problem and the optimal user scheduling time fraction is derived. A heuristic is proposed to solve the formulated optimization problem with the derived optimal user scheduling time fractions. Exhaustive simulation results for coverage and throughput of the RIS-assisted DC system are presented with varying user, BS, blockage, and RIS densities for different fairness values. Further, we show that the proposed RIS-assisted DC system provides significant throughput gain of 52% and 48% in certain scenarios when compared to the existing benchmark and DC systems.
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Singh, Khushboo, Mondeep Saikia, Karthick Thiyagarajan, Dushmantha Thalakotuna, Karu Esselle, and Sarath Kodagoda. "Multi-Functional Reconfigurable Intelligent Surfaces for Enhanced Sensing and Communication." Sensors 23, no. 20 (October 18, 2023): 8561. http://dx.doi.org/10.3390/s23208561.
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In this paper, we propose a reconfigurable intelligent surface (RIS) that can dynamically switch the transmission and reflection phase of incident electromagnetic waves in real time to realize the dual-beam or quad-beam and convert the polarization of the transmitted beam. Such surfaces can redirect a wireless signal at will to establish robust connectivity when the designated line-of-sight channel is disturbed, thereby enhancing the performance of wireless communication systems by creating an intelligent radio environment. When integrated with a sensing element, they are integral to performing joint detection and communication functions in future wireless sensor networks. In this work, we first analyze the scattering performance of a reconfigurable unit element and then design a RIS. The dynamic field scattering manipulation capability of the RIS is validated by full-wave electromagnetic simulations to realize six different functions. The scattering characteristics of the proposed unit element, which incorporates two p-i-n diodes have been substantiated through practical implementation. This involved the construction of a simple prototype and the subsequent examination of its scattering properties via the free-space measurement method. The obtained transmission and reflection coefficients from the measurements are in agreement with the anticipated outcomes from simulations.
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Tran, Huu Q., Nguyen Trong Duy, and Huynh Phan Hieu Nghia. "Collaborative Relay Radio Network Using Reconfigurable Intelligent Surface." ICST Transactions on Mobile Communications and Applications 7, no. 3 (September 21, 2022): e2. http://dx.doi.org/10.4108/eetmca.v7i3.2716.
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In this paper, we have studied a model of a relay radio network system using Reconfigurable Intelligent Surface (RIS). Specifically, we used a relay network that uses RIS when there is an extra direct link from the Source (S) to the Destination (D). Next, an approximate closed-form expressions of the Outage Probability (OP) and Ergodic Capacity (EC) are considered. Based on the simulation results of OP and EC, the results show that our proposed system is more optimal than the system using supported RIS without direct link and the system without using RIS. In addition, changing the number of the RIS reflecting elements and the RIS’s location near (S) or (D) has a significant impact on the performance of the system. The analytical expression match the simulation results through the Monte Carlo simulation method. Furthermore, the simulation results of energy efficiency (EE) also show that when the target spectral efficiency (SE), Rth, is high (more than 5.45 b/s/Hz), the system using supported RIS with direct link will help reduce the transmit power and optimize the most energy compared to the other two systems.
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Lian, Xuanhao, Xinwei Yue, Xuehua Li, Xiang Yun, Tian Li, and Dehan Wan. "Reconfigurable Intelligent Surface Assisted Non-Terrestrial NOMA Networks." Wireless Communications and Mobile Computing 2022 (September 19, 2022): 1–13. http://dx.doi.org/10.1155/2022/8494630.
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This paper considers the application of reconfigurable intelligent surface (RIS) to non-terrestrial non-orthogonal multiple access (NOMA) networks. More specifically, the performance of a pair of non-orthogonal users for RIS assisted non-terrestrial NOMA networks is investigated over large-scale fading and Nakagami- m fading cascaded channel. The exact and asymptotic expressions of outage probability are derived for the nearby user and distant user with the imperfect successive interference cancellation (SIC) and perfect SIC schemes. Based on the approximated results, the diversity orders of these two users are obtained in the high signal-to-noise ratios. The simulation results are used to verify the theoretical derivations and find that: 1) The outage behaviors of RIS assisted non-terrestrial NOMA networks outperforms than that of orthogonal multiple access; 2) By increasing the number of reflecting elements of RIS and Nagakami- m fading factors m ′ and Ω , RIS-assisted non-terrestrial NOMA networks are able to achieve the enhanced outage performance.
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Odeyemi, Kehinde, Pius Owolawi, and Oladayo Olakanmi. "Reconfigurable Intelligent Surface in Wireless-Powered Interference-Limited Communication Networks." Symmetry 13, no. 6 (May 28, 2021): 960. http://dx.doi.org/10.3390/sym13060960.
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The commercialization of future wireless communication systems faces crucial problems in terms of reduced network cost of deployment and high power consumption. As a result, reconfigurable intelligent surfaces (RIS) have been suggested as a promising approach to overcome these existing challenges. In this paper, the performance of RIS in a wireless-powered interference-limited communication network is investigated. In this network, an energy-constrained access point (AP) is powered by a dedicated multiantenna power beacon (PB) and communicates to a destination limited-interference node via the RIS. It is assumed that the RIS experiences generalized-K fading distribution while the PB and interferers links are subjected to Nakagami-m fading distributions. To evaluate the system performance, the analytical closed-form expression of the probability distribution function (PDF) for the concerned system is derived. Through this, the exact closed-form expressions of the systems outage probability, average delay-tolerance throughput and average bit error rate are obtained. The analysis quantifies the effects of the number of reflecting elements in the RIS, number of interferer nodes, fading parameters on the AP and interferer links and number of antennas on the PB. It is deduced from the results that there is a kind of symmetry relationship between the analytical and simulation results. Additionally, the results illustrate that the proposed system with an RIS outperforms the conventional system without an RIS. Finally, the accuracy of the derived analytical expressions is validated through a Monte-Carlo simulation.
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Jaafar Qassim Kadhim and Adheed H. Sallomi. "Design and Implementation Unit Cell for 6G Reconfigurable Intelligent Surface Application." International Journal of Online and Biomedical Engineering (iJOE) 19, no. 05 (April 27, 2023): 163–71. http://dx.doi.org/10.3991/ijoe.v19i05.37585.
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This article presents a model through which the reflection coefficient amplitude as well as phase of reflective intelligent surfaces can be estimated accurately. The reconfigurability of the surface was achieved by incorporating the varactor diodes into the surface of the cell unit. The manipulation of the phase of the reflection coefficient can be achieved by making adjustments to the biasing state of the varactors. The model, which makes use of a physics-based methodology and is based on a transmission-line circuit description of the Reconfigurable Intelligent surfaces (RIS) unit cells, considers every pertinent electrical and geometrical characteristics of the proposed surface. With the method proposed in this paper, fast and accurate RIS-based communication lines can be created. The recommended accuracy of the proposed method was confirmed through the use of a CST microwave studio full-wave simulations.
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Yang, Qiangqiang, Yufeng Chen, Zhiyu Huang, Hongwen Yu, and Yong Fang. "Low-Resolution Optimization for an Unmanned Aerial Vehicle Communication Network under a Passive Reconfigurable Intelligent Surface and Active Reconfigurable Intelligent Surface." Electronics 13, no. 10 (May 8, 2024): 1826. http://dx.doi.org/10.3390/electronics13101826.
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This paper investigates the optimization of an unmanned aerial vehicle (UAV) network serving multiple downlink users equipped with single antennas. The network is enhanced by the deployment of either a passive reconfigurable intelligent surface (RIS) or an active RIS. The objective is to jointly design the UAV’s trajectory and the low-bit, quantized, RIS-programmable coefficients to maximize the minimum user rate in a multi-user scenario. To address this optimization challenge, an alternating optimization framework is employed, leveraging the successive convex approximation (SCA) method. Specifically, for the UAV trajectory design, the original non-convex optimization problem is reformulated into an equivalent convex problem through the introduction of slack variables and appropriate approximations. On the other hand, for the RIS-programmable coefficient design, an efficient algorithm is developed using a penalty-based approximation approach. To solve the problems with the proposed optimization, high-performance optimization tools such as CVX are utilized, despite their associated high time complexity. To mitigate this complexity, a low-complexity algorithm is specifically tailored for the optimization of passive RIS-programmable reflecting elements. This algorithm relies solely on closed-form expressions to generate improved feasible points, thereby reducing the computational burden while maintaining reasonable performance. Extensive simulations are created to validate the performance of the proposed algorithms. The results demonstrate that the active RIS-based approach outperforms the passive RIS-based approach. Additionally, for the passive RIS-based algorithms, the low-complexity variant achieves a reduced time complexity with a moderate loss in performance.
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Wang, YuanYuan, Feng Zhou, and Rugang Wang. "Transmission Design in Secure URLLC Network Assisted by Reconfigurable Intelligent Surfaces." Wireless Communications and Mobile Computing 2022 (June 1, 2022): 1–10. http://dx.doi.org/10.1155/2022/8718279.
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In this work, we focus on the secure transmission in reconfigurable intelligent surface- (RIS-) aided ultrareliable low-latency communications (URLLC) network. Specifically, we investigate the average effective secrecy rate (AESR) optimization via jointly designing the transmit beamforming, the artificial noise covariance at the transmitter (Tx), and the phase shifter at the RIS. Particulary, the AESR in URLLC network contains not only the commonly used information rate expression based on long codewords but also two penalty terms about the decoding error probability introduced by finite block-length coding. Thus, the AESR is a nonconcave objective. In addition, the unit modulus constraint of the reflecting coefficient at the RIS is nonconvex, which makes the formulated problem difficult to handle. To solve the formulated highly nonconvex problem, we first decouple the complicated objective into a linear function by introducing several slack variables. Then, we address the nonconvex constraints by the first-order expression and the penalty concave-convex procedure (PCCP) technique. Thus, an alternating optimization (AO) technique is proposed to solve the reformulated problem, where the convergence can be guaranteed by rigorous proof, and the computational complexity is a polynomial function of the main system parameters. Simulation results demonstrated the performance of the proposed design as well as the superiority of RIS in improving the secrecy performance when comparing with other baselines.
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Touati, Sami, Musaed Alhussein, and Rachid Sammouda. "Dual hop relaying using CDMA and reconfigurable intelligent surfaces (RIS)." International Journal of Sensor Networks 36, no. 2 (2021): 79. http://dx.doi.org/10.1504/ijsnet.2021.10039016.
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Touati, Sami, Rachid Sammouda, and Musaed Alhussein. "Dual hop relaying using CDMA and reconfigurable intelligent surfaces (RIS)." International Journal of Sensor Networks 36, no. 2 (2021): 79. http://dx.doi.org/10.1504/ijsnet.2021.115887.
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Song, Wei, and Bing Guan. "Reconfigurable Intelligent Surface-Based Space-Time Block Transmission on 6G." Wireless Communications and Mobile Computing 2021 (December 16, 2021): 1–9. http://dx.doi.org/10.1155/2021/5569006.
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Reconfigurable intelligent surface (RIS) is considered to be a new technology with great potential and is being studied extensively and deeply. And the application extension of STBC in the RIS-aided scheme provides a new train of thought for the research of channel coding. In this paper, we propose we extend the scheme of using the RIS to adjust the phase and reconfigure the reflected signal and propose the design of the RIS-aided QO-STBC scheme and the RIS-aided QO-STBC scheme with interference cancellation. Particularly in the RIS-aided QO-STBC scheme with interference cancellation, the design can achieve the transmission of the full rate and full diversity using an auxiliary reflection group to eliminate the influence of interference term. Also, the advantages and disadvantages of the schemes are analyzed in the paper, and the decoding algorithms with different complexity used in the proposed schemes are described. The simulation results show that the performance of the RIS-aided QO-STBC scheme with interference cancellation is better than that of the RIS-aided QO-STBC scheme and the RIS-aided Alamouti scheme by about 5 dB and 7 dB at 1 0 − 3 BER because of diversity gain and coding gain.
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Hong, Ic-Pyo. "Reviews Based on the Reconfigurable Intelligent Surface Technical Issues." Electronics 12, no. 21 (November 1, 2023): 4489. http://dx.doi.org/10.3390/electronics12214489.
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Reconfigurable intelligent surfaces (RISs) are programmable metasurface structures that can control the propagation of electromagnetic waves by changing the electrical and magnetic properties of the surface. They can be used to intelligently reconfigure the wireless environment to improve the capacity and coverage of wireless networks. In recent years, numerous theoretical innovations and prototype tests have demonstrated that the RIS has the advantages of low cost, low power consumption, and easy deployment, and creates many potential opportunities and broad application prospects in 5G and future 6G networks. In this paper, starting from the technological development of RISs, we discussed the technical issues of RISs. The standardization of RISs, types of RISs according to operation modes, channel modeling, considerations for hardware implementation, differences from existing communication modules and the need for active RIS implementation, noise and power characteristics to ensure the efficiency of RISs, and performance parameters of RISs and field test results of RISs in indoor and outdoor environments were reviewed. By resolving the current technical issues of RISs, it is expected that RISs will be successfully used for B5G/6G communication through commercialization.
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Sharma, Teena, Abdellah Chehri, and Paul Fortier. "Reconfigurable Intelligent Surfaces for 5G and beyond Wireless Communications: A Comprehensive Survey." Energies 14, no. 24 (December 7, 2021): 8219. http://dx.doi.org/10.3390/en14248219.
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With possible new use cases and demanding requirements of future 5th generation (5G) and beyond cellular networks, the future of mobile communications sounds promising. However, the propagation medium has been considered a randomly acting agent between the transmitter and the receiver. With the advent of the digital age of wireless communications, the received signal quality is degrading due to the uncontrollable interactions of the transmitted radio waves with the surrounding artifacts. This paper presents a comprehensive literature review on reconfigurable intelligent surfaces (RISs) and assisted application areas. With the RIS, the network operators can control radio waves’ scattering, reflection, and refraction characteristics by resolving the harmful properties of environmental wireless propagation. Further, the RIS can effectively control the wavefront, such as amplitude, phase, frequency, and even polarization, without requiring complex encoding, decoding, or radio wave processing techniques. Motivated by technological advances, the metasurfaces, reflectarrays, phase shift, and liquid crystals are potential candidates for implementing RIS. Thus, they can be considered the front runner for realizing the 5G and beyond network. Furthermore, the current research activities in the evolving field of wireless networks operated by RIS are reviewed and discussed thoroughly. Finally, to fully explore the potential of RISs in wireless networks, the fundamental research issues to be addressed have been discussed.
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Puspitasari, Annisa Anggun, and Byung Moo Lee. "A Survey on Reinforcement Learning for Reconfigurable Intelligent Surfaces in Wireless Communications." Sensors 23, no. 5 (February 24, 2023): 2554. http://dx.doi.org/10.3390/s23052554.
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A reconfigurable intelligent surface (RIS) is a development of conventional relay technology that can send a signal by reflecting the signal received from a transmitter to a receiver without additional power. RISs are a promising technology for future wireless communication due to their improvement of the quality of the received signal, energy efficiency, and power allocation. In addition, machine learning (ML) is widely used in many technologies because it can create machines that mimic human mindsets with mathematical algorithms without requiring direct human assistance. Meanwhile, it is necessary to implement a subfield of ML, reinforcement learning (RL), to automatically allow a machine to make decisions based on real-time conditions. However, few studies have provided comprehensive information related to RL algorithms—especially deep RL (DRL)—for RIS technology. Therefore, in this study, we provide an overview of RISs and an explanation of the operations and implementations of RL algorithms for optimizing the parameters of RIS technology. Optimizing the parameters of RISs can offer several benefits for communication systems, such as the maximization of the sum rate, user power allocation, and energy efficiency or the minimization of the information age. Finally, we highlight several issues to consider in implementing RL algorithms for RIS technology in wireless communications in the future and provide possible solutions.
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Zhao, Shanshan, Biao Xie, Ziwei Liu, and Jirui An. "Reconfigurable Intelligent Surface-Assisted Radar Deception Electronic Counter-Countermeasures." Remote Sensing 15, no. 21 (October 27, 2023): 5149. http://dx.doi.org/10.3390/rs15215149.
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A reconfigurable intelligent surface (RIS) is a promising technology for wireless communication and radar detection, owing to its superior ability to realize smart radio environments. Inspired by previous studies on RISs, this study deals with the use of RISs for radar electronic counter-countermeasures (ECCMs) in deception jamming scenarios. At first, a RIS was applied to a monostatic radar, constructing a virtual multi-radar system combined with multi-beam receiving technology. Then, a data-fusion-based deception ECCM method for the proposed virtual multi-radar system was studied to discriminate the active false targets generated by deception jamming. A theoretical analysis of the target discrimination probability was derived. Because the location of RISs is the key to determining the target discrimination ability, the location optimization of the RIS was considered based on the theoretical analysis. Simulation results corroborate the deception ECCM ability of the proposed RIS-assisted virtual multi-radar system, enhancing the survivability of a radar system in a complex electromagnetic environment.
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Martín-Martín, Alberto, Rubén Padial-Allué, Encarnación Castillo, Luis Parrilla, Ignacio Parellada-Serrano, Alejandro Morán, and Antonio García. "Hardware Implementations of a Deep Learning Approach to Optimal Configuration of Reconfigurable Intelligence Surfaces." Sensors 24, no. 3 (January 30, 2024): 899. http://dx.doi.org/10.3390/s24030899.
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Reconfigurable intelligent surfaces (RIS) offer the potential to customize the radio propagation environment for wireless networks, and will be a key element for 6G communications. However, due to the unique constraints in these systems, the optimization problems associated to RIS configuration are challenging to solve. This paper illustrates a new approach to the RIS configuration problem, based on the use of artificial intelligence (AI) and deep learning (DL) algorithms. Concretely, a custom convolutional neural network (CNN) intended for edge computing is presented, and implementations on different representative edge devices are compared, including the use of commercial AI-oriented devices and a field-programmable gate array (FPGA) platform. This FPGA option provides the best performance, with ×20 performance increase over the closest FP32, GPU-accelerated option, and almost ×3 performance advantage when compared with the INT8-quantized, TPU-accelerated implementation. More noticeably, this is achieved even when high-level synthesis (HLS) tools are used and no custom accelerators are developed. At the same time, the inherent reconfigurability of FPGAs opens a new field for their use as enabler hardware in RIS applications.
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Wu, Qi, Jian Zhang, and Jia-Ning Guo. "Position Design for Reconfigurable Intelligent-Surface-Aided Indoor Visible Light Communication Systems." Electronics 11, no. 19 (September 27, 2022): 3076. http://dx.doi.org/10.3390/electronics11193076.
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As an emerging technology, reconfigurable intelligent surfaces (RISs) have been investigated to apply to visible light communication (VLC) systems to enhance the transmission capability of the systems, recently. However, the optimization of RIS location in VLC has not been studied. In this study, we first investigated RIS positioning design in VLC. Specifically, we set two indoor VLC scenarios with a VLC RIS composed of a mirror array. We set the achievable rates in different scenarios as the utility functions to optimize the position of the RIS array according to the placement of the access point (AP) and user. We found that the problems are nondeterministic polynomial (NP)-hard. Aiming at the different optimization problems, the particle swarm optimization (PSO) algorithm was used to confirm the optimal position of the RIS array. Unlike the traditional algorithm, we added an adaptive mutation mechanism to the algorithm to guarantee the randomness of the particle to search for the optimal solution. Finally, our simulation results showed that the proper position design of the RIS array can improve the communication performance to a greater degree, while the computational complexity required to solve the position optimization problems through the PSO algorithm can be significantly reduced compared with that required for the exhaustive search method in the case where both of the algorithms find the optimal solution.
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Soumana Hamadou, Abdel Nasser, Ciira wa Maina, and Moussa Moindze Soidridine. "Cross-Tier Interference Mitigation for RIS-Assisted Heterogeneous Networks." Technologies 11, no. 3 (June 9, 2023): 73. http://dx.doi.org/10.3390/technologies11030073.
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With the development of the next generation of mobile networks, new research challenges have emerged, and new technologies have been proposed to address them. On the other hand, reconfigurable intelligent surface (RIS) technology is being investigated for partially controlling wireless channels. RIS is a promising technology for improving signal quality by controlling the scattering of electromagnetic waves in a nearly passive manner. Heterogeneous networks (HetNets) are another promising technology that is designed to meet the capacity requirements of the network. RIS technology can be used to improve system performance in the context of HetNets. This study investigates the applications of reconfigurable intelligent surfaces (RISs) in heterogeneous downlink networks (HetNets). Due to the network densification, the small cell base station (SBS) interferes with the macrocell users (MUEs). In this paper, we utilise RIS to mitigate cross-tier interference in a HetNet via directional beamforming by adjusting the phase shift of the RIS. We consider RIS-assisted heterogeneous networks consisting of multiple SBS nodes and MUEs that utilise both direct paths and reflected paths. Therefore, the aim of this study is to maximise the sum rate of all MUEs by jointly optimising the transmit beamforming of the macrocell base station (MBS) and the phase shift of the RIS. An efficient RIS reflecting coefficient-based optimisation (RCO) is proposed based on a successive convex approximation approach. Simulation results are provided to show the effectiveness of the proposed scheme in terms of its sum rate in comparison with the scheme HetNet without RIS and the scheme HetNet with RIS but with random phase shifts.
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Khaleel, Sherif A., Ehab K. I. Hamad, Naser Ojaroudi Parchin, and Mohamed B. Saleh. "Programmable Beam-Steering Capabilities Based on Graphene Plasmonic THz MIMO Antenna Via Reconfigurable Intelligent Surfaces (RIS) for IoT Applications." Electronics 12, no. 1 (December 29, 2022): 164. http://dx.doi.org/10.3390/electronics12010164.
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The approaching sixth-generation (6G) communication network will modernize applications and satisfy user demands through implementing a smart and reconfigurable system with a higher data rate and wider bandwidth. The controllable THz waves are highly recommended for the instantaneous development the new technology in wireless communication systems. Recently, reconfigurable intelligent surfaces (RIS), also called codded/tunable programmable metasurfaces, have enabled a conspicuous functionality for THz devices and components for influencing electromagnetic waves (EM) such as beam steering, multi-beam-scanning applications, polarization variation, and beam focusing applications. In this article, we proposed a graphene plasmonic two-port MIMO microstrip patch antenna structure that operates at a 1.9 THz resonance frequency. An E-shape MTM unit cell is introduced to enhance the isolation of the antenna from −35 dB to −54 dB. An implementation of controllable and reconfigurable surfaces based on graphene meta-atoms (G-RIS) placed above the radiating patches with a suitable separated distance to control the radiated beam to steer in different directions (±60°). The reconfigurable process is carried out via changing the (ON/OFF) meta-atoms states to get a specific code with a certain beam direction. The gain enhancement of the antenna can be implemented through an artificial magnetic conductor (AMC) based on graphene material. The G-AMC layer is located underneath the (MIMO antenna, G-RIS layer) to improve the gain from 4.5 dBi to 10 dBi. The suggested antenna structure results are validated with different techniques CST microwave studio and ADS equivalent circuit model. The results have asymptotic values. So, the proposed design of the MIMO antenna that is sandwiched between G-RIS and G-AMC is suitable for IoT applications.
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Wu, Qi, Jian Zhang, and Jianing Guo. "Capacity Maximization for Reconfigurable Intelligent Surface-Aided MISO Visible Light Communications." Photonics 9, no. 7 (July 12, 2022): 487. http://dx.doi.org/10.3390/photonics9070487.
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This paper investigates the employment of reconfigurable intelligent surfaces (RISs) to improve the asymptotic capacity of the multiple-input single-output (MISO) visible light communication (VLC) system in the case of high signal-to-noise (SNR). For the RIS-aided MISO-VLC system based on mirror array, we regard the high-SNR asymptotic capacity with the input subject to peak-intensity constraints as a goal and formulate an asymptotic capacity maximization problem to find the optimal orientations of mirrors. As for the non-convex optimization problem, we convert it into a quadratic programming (QP) problem with hemispherical constraints and prove that it can be solved by computing the maximum eigenvalue of an equivalent matrix. Simulation results indicate that the asymptotic capacity is able to be improved significantly by adopting RIS in MISO-VLC systems. Meanwhile, we observe that the proper deployment scheme of RIS is able to enhance the degree of improvement through several simulations.
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Do, Dinh-Thuan, and Chi-Bao Le. "Reconfigurable intelligent surfaces assisted wireless communication networks: ergodic capacity and symbol error rate." Indonesian Journal of Electrical Engineering and Computer Science 25, no. 1 (January 1, 2022): 358. http://dx.doi.org/10.11591/ijeecs.v25.i1.pp358-364.
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By enabling reconfigurable intelligent surfaces (RIS), we can deploy intelligent reflecting signals from the base station to destinations. Different from traditional relaying system, RIS relies on programmable metasurfaces and mirrors to improve system performance of destinations. We derive the formulas of main system performance metrics such as ergodic capacity and symbol error rate (SER). Based on types of modulation, we need to demonstrate other parameters which make influence to system performance. We show analytically that the number of reflecting elements along with the transmit power at the source can improve system performance. Moreover, we check the exactness of derived expressions by matching Monte-Carlo with analytical simulations. Finally, we find the best performance can be achieved at specific parameters and results are verified by explicit simulations.
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M M, Yamuna Devi, Amalorpava Mary Rajee S, Ahila A, and Indira N. R. "Reconfigurable Intelligent Surface aided Indoor and Outdoor User Distribution in Heterogeneous Network." International Journal of Computer Network and Information Security 14, no. 4 (August 8, 2022): 89–97. http://dx.doi.org/10.5815/ijcnis.2022.04.07.
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Millimeter wave communication suffers from static blockages such as trees, buildings and so on. Reconfigurable Intelligent Surfaces (RISs) has been adapted to solve this blockage problem and enable the urban environment user to choose mmW enabled small cells as their source transmitter or to choose macro cells in case of non-line of sight exists. RIS is a promising network technology to improve the quality of service parameters such as spectral efficiency and energy efficiency by artificially reconfiguring the propagation environment of electromagnetic waves. An indoor user can be connected with mmW band if the line of sight (LOS) link exists. Otherwise, the system utilizes RIS transmission model to have reliable and low-latency communication. It reflects the capability of RISs to enable enhanced communications in challenging environments. An optimization problem is formulated to maximize the sum data rate of an indoor user by phase shift optimization at the RIS. The outage probability of the proposed scheme is analyzed under Rician fading channel. The proposed RIS enabled method targets to enhance the overall performance in terms of average spectral efficiency and achievable data rate in the presence of blockages and system imperfections. The data rate is increased by three fold times than that of the transmission without RIS. The utility of this framework is discussed for both indoor and outdoor environments.
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Wang, Yi, Haibo Wang, and XueWen Jiang. "Performance of Reconfigurable-Intelligent-Surface-Assisted Satellite Quasi-Stationary Aircraft–Terrestrial Laser Communication System." Drones 6, no. 12 (December 8, 2022): 405. http://dx.doi.org/10.3390/drones6120405.
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This paper proposes the use of quasi-stationary aircraft and reconfigurable intelligent surfaces (RIS) to improve the system performance in satellite–terrestrial laser communication downlink. Single-input multiple-output (SIMO) technology is applied to the relay node of a quasi-stationary aircraft. The closed expression of the bit error rate (BER) of an RIS-assisted satellite quasi-stationary aircraft–terrestrial laser communication system (RIS-SHTLC) is derived under the M-distributed atmospheric turbulence model while considering the influence of atmospheric turbulence and pointing errors caused by RIS jitter. The effects of coherent binary frequency shift keying (CBFSK), coherent binary phase-shift keying (CBPSK), non-coherent binary frequency shift keying (NBFSK), and differential binary phase-shift keying (DBPSK) on the performance of an RIS-SHTLC system are simulated and analyzed under weak turbulence. The results show that the RIS-SHTLC system with CBPSK modulation has the best communication performance. Simultaneously, the relationships between the average signal-to-noise ratio (SNR) and BER of the RIS-SHTLC system under different RIS elements are simulated and analyzed, and compared with the traditional SHTLC system. In addition, the influence of the zenith angle, receiving aperture and divergence angle on the performance of the system is studied. Finally, Monte Carlo simulations are used to validate the analytical results.
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Lin, Hai, Wen Yu, Rongxin Tang, Jing Jin, Yumei Wang, Jie Xiong, Yanjie Wu, and Junming Zhao. "A dual-band reconfigurable intelligent metasurface with beam steering." Journal of Physics D: Applied Physics 55, no. 24 (March 18, 2022): 245002. http://dx.doi.org/10.1088/1361-6463/ac5663.
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Abstract In recent years, reconfigurable metasurfaces have become research hotspots since they can manipulate electromagnetic waves dynamically and flexibly. The realisation of cost-effective and energy-efficient wireless communications via reconfigurable intelligent surfaces (RISs) is attractive in various application scenerios. In this work, a + 45 ∘ -polarized dual-band reconfigurable metasurface with beam steering ability is proposed to combat signal attenuation in wireless communications. By varying the bias voltages of the integrated varactors in the specially designed meta-atom, 0 and π phase responses have been excited around both 2.4 and 5.8 GHz. Taking advantage of this unique feature, we proposed a one-bit coding RIS device which provides dual-band application. To validate the proposed concepts, a reconfigurable metasurface composed of 16 × 16 elements was fabricated and measured. The measurement results agree well with the simulation, so the proposed prototype is a promising candidate for future intelligent communications.
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AL-Shaeli, Intisar, and Lsmail Hburi. "Spectral Efficiency Enhancement for Reconfigurable Intelligent Surface Assisted MIMO System." Wasit Journal of Engineering Sciences 10, no. 2 (July 1, 2022): 57–68. http://dx.doi.org/10.31185/ejuow.vol10.iss2.286.
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Reconfigurable intelligent surfaces (RISs) have emerged as promising contenders for enabling sixth-generation (6G) physical wireless platforms. RISs fine-tune wireless networks to optimize the spectrum and energy use. This article explores the design challenge of a joint beamforming strategy for increasing throughput at the AP and RIS sides. To address this challenging problem, we created an iterative algorithm, that makes use of the Duality Theory and the Alternating Optimization technique called the DAO algorithm. Due to the given problem's non-convexity and difficulty with variable coupling, the proposed Algorithm divides the optimization problem of the coupled variables into four distinct optimization sub-problems by introducing new supporting variables. The alternate optimization strategy handles the issue sequentially by iteratively updating these new variables, the active beamformer, and the non-active beamformer. Finally, the simulation results indicate that we achieve about a 30% spectrum boost over the standard network without RIS for a certain system and circumstances scenario.
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Nguyen, Nhan Duc, Chi-Bao Le, and Munyaradzi Munochiveyi. "Uplink Multiple Access for Reconfigurable Intelligent Surface-Aided Wireless Systems." Wireless Communications and Mobile Computing 2022 (July 21, 2022): 1–14. http://dx.doi.org/10.1155/2022/1932708.
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The integration of reconfigurable intelligent surface- (RIS-) aided wireless communication and multiple access is an attractive and promising scheme for next-generation wireless networks. In this research work, separate uplink RIS-aided nonorthogonal multiple access (NOMA) and uplink relay-assisted NOMA schemes are studied, where the RIS and relay devices are deployed to enhance the coverage of an obstructed single-antenna far user by assisting it to communicate with a single-antenna base station. In each scenario, both perfect successive interference cancellation (pSIC) and imperfect successive interference cancellation (ipSIC) operations are considered in the proposed multiple access network. To characterize the system performance, the associated residual interference caused by ipSIC and relay loop self-interference is characterized using the Rayleigh fading model; subsequently, new channel statistics are derived based on the Gauss-Laguerre polynomial. Consequently, the closed-form approximate outage probability expressions are derived for each scenario in the high signal-to-noise ratio (SNR) regime. To gain further insight, the system throughput in the delay-limited transmission is also obtained for each scenario. The formulated expressions are validated via Monte-Carlo simulations. Finally, the obtained simulation results demonstrate and validate the superiority of the RIS system over the relay device under several system parameters of interest despite the limitation of ipSIC.
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Youn, Janghyuk, Woong Son, and Bang Chul Jung. "Physical-Layer Security Improvement with Reconfigurable Intelligent Surfaces for 6G Wireless Communication Systems." Sensors 21, no. 4 (February 19, 2021): 1439. http://dx.doi.org/10.3390/s21041439.
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Recently, reconfigurable intelligent surfaces (RISs) have received much interest from both academia and industry due to their flexibility and cost-effectiveness in adjusting the phase and amplitude of wireless signals with low-cost passive reflecting elements. In particular, many RIS-aided techniques have been proposed to improve both data rate and energy efficiency for 6G wireless communication systems. In this paper, we propose a novel RIS-based channel randomization (RCR) technique for improving physical-layer security (PLS) for a time-division duplex (TDD) downlink cellular wire-tap network which consists of a single base station (BS) with multiple antennas, multiple legitimate pieces of user equipment (UE), multiple eavesdroppers (EVEs), and multiple RISs. We assume that only a line-of-sight (LOS) channel exists among the BS, the RISs, and the UE due to propagation characteristics of tera-hertz (THz) spectrum bands that may be used in 6G wireless communication systems. In the proposed technique, each RIS first pseudo-randomly generates multiple reflection matrices and utilizes them for both pilot signal duration (PSD) in uplink and data transmission duration (DTD) in downlink. Then, the BS estimates wireless channels of UE with reflection matrices of all RISs and selects the UE that has the best secrecy rate for each reflection matrix generated. It is shown herein that the proposed technique outperforms the conventional techniques in terms of achievable secrecy rates.
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P. de Figueiredo, Felipe A. "Unlocking the Power of Reconfigurable Intelligent Surfaces: From Wireless Communication to Energy Efficiency and Beyond." Applied Sciences 13, no. 21 (October 27, 2023): 11750. http://dx.doi.org/10.3390/app132111750.
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Reconfigurable Intelligent Surfaces (RISs) are a class of metamaterials that have gained significant attention in recent years due to their potential to revolutionize wireless communication, sensing, and imaging technologies. RISs consist of a planar array of closely spaced, subwavelengthsized elements that can manipulate electromagnetic waves in a controllable manner. By reconfiguring the geometry, material properties, or phases of the individual elements on the RIS, the surface can be customized to meet specific application requirements. RISs can improve wireless communication by creating virtual channels, reducing interference, and improving overall quality. They can also enhance the efficiency of energy harvesting systems and improve sensing and imaging technologies by manipulating the propagation and scattering of electromagnetic waves. Additionally, RISs could be used to increase privacy and security by selectively blocking or allowing specific frequencies of electromagnetic waves. In this editorial, we provide a brief history of the development of RISs and discuss the design and fabrication of RIS structures. We also discuss RIS technology’s potential applications and benefits, including improved wireless communication, enhanced energy efficiency, advanced sensing and imaging, and increased privacy and security. Finally, we highlight some current research challenges and future directions for RIS technology. Overall, RISs hold great promise for advancing a wide range of technologies and applications, and we expect to see many exciting developments in this area.
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Ayaz, Hina, Muhammad Waqas, Ghulam Abbas, Ziaul Haq Abbas, Muhammad Bilal, and Kyung-Sup Kwak. "Improved Rate of Secret Key Generation Using Passive Re-Configurable Intelligent Surfaces for Vehicular Networks." Sustainability 15, no. 1 (December 26, 2022): 342. http://dx.doi.org/10.3390/su15010342.
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The reconfigurable intelligent surfaces (RIS) is a new technology that can be utilized to provide security to vehicle-to-vehicle (V2V) communications at the physical layer. In this paper, we achieve a higher key generation rate for V2V communications at lower cost and computational complexity. We investigate the use of a passive RIS as a relay, to introduce channel diversity and increase the key generation rate (KGR), accordingly. In this regard, we consider the subsets of consecutive reflecting elements instead of the RIS as a whole in a time slot, i.e., instead of a single reflector, the subsets of reflectors are utilized to redirect the signal to the receiver via passive beam forming. Simulations are conducted for different sizes of RISs and subsets of reflectors per RIS. From the results obtained, it can be seen that when we consider a subset of reflectors instead of the RIS as a single entity, it becomes increasingly difficult to intercept the signal at the eavesdropper. In the proposed scheme, the KGR reaches up to 6 bps per time slot.
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Zeng, Shuhao, Hongliang Zhang, Boya Di, Zhu Han, and Lingyang Song. "Reconfigurable Intelligent Surface (RIS) Assisted Wireless Coverage Extension: RIS Orientation and Location Optimization." IEEE Communications Letters 25, no. 1 (January 2021): 269–73. http://dx.doi.org/10.1109/lcomm.2020.3025345.
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