IRS-enabled NOMA communication systems: A network architecture primer with future trends and challenges
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Abstract
https://doi.org/10.1016/j.dcan.2023.09.002
... The study in [14], revealed that IRS can provide a novel vehicular communication paradigm, enabling secure and efficient Vehicle to Vehicle (V2V) and Vehicle-to-Infrastructure (V2I) communications with massive connectivity in 6G ITS. In [15,16] and [17], the authors have discussed the IRS channel estimation techniques, machine learning-based solutions, and hardware designs for IRS. Authors in [18] have discussed the enabling technologies and various application scenarios for IRS-assisted wireless communications for 6G networks. ...
6G incorporates Intelligent Reflecting Surfaces (IRS) and Unmanned Aerial Vehicles (UAVs) as effective solutions to overcome the limitations of terrestrial networks in terms of coverage and resource constraints. Compared to communications with conventional UAV networks which face restricted battery longevity, fluctuating channel conditions, and paucity of resources, IRS-assisted UAV communications is seen as an attractive strategy. In this paper, we present an extensive survey on IRS-assisted UAV communications for 6G networks. We highlight various application scenarios and key technologies for integrating IRS and UAVs in 6G architecture. We discuss primary issues along with their solutions and put forward the open research challenges that could serve as a potential area for further investigation in the related discipline. Key findings encompass an in-depth exploration of diverse application scenarios and pivotal technologies crucial for seamless integration of IRS and UAVs within the 6G architecture, providing valuable insights into optimizing communication efficiency and addressing network challenges. This survey serves as a valuable resource for scholars, practitioners, and policymakers in the fields of integrated UAV and IRS communication. It provides insights for making well-informed decisions and driving advancements to meet the constantly evolving demands of our connected world.
... In order to serve several users simultaneously, on a frequency, or in a code block, the NOMA system divides radio resource blocks into distinct power levels [3]- [6]. Recently, there has been an increase in scientific interest in combining NOMA with current technologies such as Multiple-Input Multiple-Output (MIMO), cognitive radio, cooperative communications, and Intelligent Reflecting Surfaces (IRSs) [7]- [9]. Due to its potential to take advantage of spatial diversity, cooperative relay transmission has drawn a lot of interest. ...
... Similarly, with the introduction of the Internet of Things (IoT) [5] and machine-to-machine (M2M) communications [6], various application requirements are increasing at a faster rate. The 5G communication systems are progressively developing to meet rising capacity demands [7]. In the previous generations of wireless systems, different conventional orthogonal multiple access (OMA) schemes have been successfully used [8]. ...
Reconfigurable intelligent surface (RIS) has stimulated their potential applications for improving the performance of wireless communication networks. In this paper, the performance of RIS aided non‐orthogonal multiple access (NOMA) networks with hardware impairments over Rician fading channels is investigated. More specifically, the exact and asymptotic expressions of outage probability for a pair of users, that is, the nearby user n and distant user m are derived, where the imperfect successive interference cancellation (ipSIC) and perfect SIC (pSIC) are taken into consideration. According to the approximate analyses, the diversity orders of user n with ipSIC/pSIC and user m are obtained in the high signal‐to‐noise radio regime. It indicates that the diversity orders are in connection with reflecting elements and Rician factors except the channel ordering. The impact of these parameters on outage behaviors of RIS‐NOMA networks is also analysed. In addition, the system throughput of RIS‐NOMA networks with ipSIC/pSIC is surveyed in detail. Monte Carlo simulations are present to verify the correctness of theoretical analyses that: (1) The outage probability of user n with pSIC is superior to that of orthogonal user, while the outage probability of user m is inferior to that of orthogonal user and (2) as the number of reflecting elements and Rician factors increases, the outage behaviors of RIS‐NOMA networks are enhanced carefully.
This paper investigates the use of the reconfigurable dual-functional surface to guarantee the full-space secure transmission in non-orthogonal multiple access (NOMA) networks. In the presence of eavesdroppers, the downlink communication from the base station to the legitimate users is safeguarded by the simultaneously transmitting and reflecting reconfigurable intelligent surface (STAR-RIS), where three practical operating protocols, namely energy splitting (ES), mode selection (MS), and time splitting (TS), are studied. The joint optimization of power allocation, active and passive beamforming is investigated to maximize the secrecy energy efficiency (SEE), taking into account the imperfect channel state information (CSI) of all channels. For ES, by approximating the semi-infinite constraints with the
$\mathcal {S}$
-procedure and general sign-definiteness, the problem is solved by an alternating optimization framework. Besides, the proposed algorithm is extended to the MS protocol by solving a mixed-integer non-convex problem. While for TS, a two-layer iterative method is proposed. Simulation results show that: 1) The proposed STAR-RIS assisted NOMA networks are able to provide up to 33.6% higher SEE than conventional RIS counterparts; 2) TS and ES protocols are generally preferable for low and high power domain, respectively; 3) The accuracy of CSI estimation and the bit resolution power consumption are crucial to reap the SEE benefits offered by STAR-RIS.
The demanding objectives for the future sixth generation (6G) of wireless communication networks have spurred recent research efforts on novel materials and radio-frequency front-end architectures for wireless connectivity, as well as revolutionary communication and computing paradigms. Among the pioneering candidate technologies for 6G belong the reconfigurable intelligent surfaces (RISs), which are artificial planar structures with integrated electronic circuits that can be programmed to manipulate the incoming electromagnetic field in a wide variety of functionalities. Incorporating RISs in wireless networks have been recently advocated as a revolutionary means to transform any wireless signal propagation environment to a dynamically programmable one, intended for various networking objectives, such as coverage extension and capacity boosting, spatiotemporal focusing with benefits in energy efficiency and secrecy, and low electromagnetic field exposure. Motivated by the recent increasing interests in the field of RISs and the consequent pioneering concept of the RIS-enabled smart wireless environments, in this paper, we overview and taxonomize the latest advances in RIS hardware architectures as well as the most recent developments in the modeling of RIS unit elements and RIS-empowered wireless signal propagation. We also present a thorough overview of the channel estimation approaches for RIS-empowered communications systems, which constitute a prerequisite step for the optimized incorporation of RISs in future wireless networks. Finally, we discuss the relevance of the RIS technology in the latest wireless communication standards, and highlight the current and future standardization activities for the RIS technology and the consequent RIS-empowered wireless networking approaches.
https://authors.elsevier.com/a/1gV7Z6gDRXhTyb
Intelligent reconfigurable surfaces (IRSs) provide a new way to manipulate the propagation properties of electromagnetic (EM) waves, and thus realize dynamical controls of their reflection, transmission, and scattering features. Recent researches have envisioned numerous applications based on IRSs to facilitate the development of wireless communication technology, with their iconic skills such as wavefront manipulations as well as information modulations. In this chapter, we will detail the general hardware architecture of IRS, from the concept to the operation mode, to demonstrate a clear framework to help researchers better understand it.
Large intelligent surface/antennas (LISA), a two-dimensional artificial structure with a large number of reflective-surface/antenna elements, is a promising reflective radio technology to construct programmable wireless environments in a smart way. Specifically, each element of the LISA adjusts the reflection of the incident electromagnetic waves with unnatural properties, such as negative refraction, perfect absorption, and anomalous reflection, thus the wireless environments can be software-defined according to various design objectives. In this paper, we introduce the reflective radio basics, including backscattering principles, backscatter communication, reflective relay, the fundamentals and implementations of LISA technology. Then, we present an overview of the state-of-the-art research on emerging applications of LISA-aided wireless networks. Finally, the limitations, challenges, and open issues associated with LISA for future wireless applications are discussed.
This letter theoretically compares the active reconfigurable intelligent surface (RIS)-aided system with the passive RIS-aided system. For a fair comparison, we consider that these two systems have the same overall power budget that can be used at both the base station (BS) and the RIS. For active RIS, we first derive the optimal power splitting between the BS’s transmit signal power and RIS’s output signal power. We also analyze the impact of various system parameters on the optimal power splitting ratio. Then, we theoretically and numerically compare the performance between the active RIS and the passive RIS, which demonstrates that the active RIS would be superior if the power budget is not very small and the number of RIS elements is not very large.
As a prominent member of the next generation multiple access (NGMA) family, non-orthogonal multiple access (NOMA) has been recognized as a promising multiple access candidate for the sixth-generation (6G) networks. This article focuses on applying NOMA in 6G networks, with an emphasis on proposing the so-called "One Basic Principle plus Four New" concept. Starting with the basic NOMA principle, the importance of successive interference cancellation (SIC) becomes evident. In particular, the advantages and drawbacks of both the channel state information based SIC and quality-of-service based SIC are discussed. Then, the application of NOMA to meet the new 6G performance requirements, especially for massive connectivity, is explored. Furthermore, the integration of NOMA with new physical layer techniques is considered, followed by introducing new application scenarios for NOMA towards 6G. Finally, the application of machine learning in NOMA networks is investigated, ushering in the machine learning empowered NGMA era.
Reconfigurable intelligent surfaces (RISs) and nonorthogonal multiple access (NOMA) have been recognized as key enabling techniques for the envisioned sixth generation (6G) of mobile communication networks. The key feature of RISs is to intelligently reconfigure the wireless propagation environment, which was once considered to be fixed and untunable. The key idea of NOMA is to utilize users’ dynamic channel conditions to improve spectral efficiency and user fairness. Naturally, the two communication techniques are complementary to each other and can be integrated to cope with the challenging requirements envisioned for 6G mobile networks. This survey provides a comprehensive overview of the recent progress on the synergistic integration of RISs and NOMA. In particular, the basics of both techniques are introduced first, and then, the fundamentals of RIS-NOMA are discussed for two communication scenarios with different transceiver capabilities. Resource allocation is of paramount importance for the success of RIS-assisted NOMA networks, and various approaches, including artificial intelligence (AI)-empowered designs, are introduced. Security provisioning in RIS-NOMA networks is also discussed as wireless networks are prone to security attacks due to the nature of the shared wireless medium. Finally, the survey is concluded with detailed discussions of the challenges arising in the practical implementation of RIS-NOMA, future research directions, and emerging applications.
For the last few decades, wireless communication has been facing a technological revolution. High data rate and continuous connectivity are the necessities because the technology has turned from simple voice communication to newly high interactive multimedia applications. Also, the demands for mobile devices are growing tremendously. Researchers are developing fifth-generation (5G) and beyond fifth-generation (B5G) wireless communication networks to fulfill the needs in the future. Non-orthogonal multiple access (NOMA) can be a promising scheme to meet the demands of an enormously growing number of users, connectivity requirements, low-cost requirements, limited bandwidth requirements, and high coverage requirements for future wireless communication networks. NOMA-assisted wireless communication networks have to face several challenges along with several benefits. In the previous survey papers, the main focus of the researchers was on the concepts of NOMA, its comparison with other techniques, and issues related to NOMA. This paper presents a thorough survey on NOMA and future 5G and B5G wireless communication networks. We have arranged the paper in such a way that conveys all the aspects of 5G and B5G networks and NOMA’s application in 5G and B5G. This paper includes the study of existing survey papers, comparison with our paper, our contribution, uniqueness, and benefits of our paper. It includes requirements and technologies for 5G and B5G, channel modeling, the role of NOMA in 5G and B5G, types of NOMA, NOMA’s network architecture, mobility management (MM) in NOMA, asynchronous and synchronous operations in NOMA, energy and green aspects of NOMA in 5G and B5G, NOMA’s challenges, solutions to these challenges, NOMA’s performance indicators. This paper also includes the problems of resource allocation in 5G and B5G, role of NOMA in improving resource allocation and future research directions for next-generation wireless communication networks. This paper also discusses cloud virtualization (CV), fog networking (FN), and edge networking (EN), enterprise and industry 4.0 perspectives, the importance of standardization of NOMA, third generation partnership project (3GPP) standards for NOMA. This paper also highlights the security, blockchain aspects, practicality, and industry acceptance for NOMA in 5G and B5G.