On the Trade-Off between Energy Efficiency and Spectral Efficiency in RIS-Aided Multi-User MISO Downlink

Zhang, Meng; Tan, Le Thanh; Huang, Kelin; You, Li

doi:10.3390/electronics10111307

Cited by 11 publications

(5 citation statements)

References 35 publications

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“…In RIS based transmission systems, it is assumed that RIS has perfect knowledge of channel phases of BS-RIS-U k link, which represents the best case scenario for system operation and serves as a performance benchmark for real-world applications [3], [6]. In this configuration, the RIS can adjust its phases with respect to a single user at a given point of time [35]. In such a RIS assisted downlink system, the optimal choice of φ l that maximizes the instantaneous signal to noise ratio (SNR) of U k is given by φ l = θ h l + θ g l,k .…”

Section: A Ris Assisted Downlink Modelmentioning

confidence: 99%

RIS Partition-Assisted Non-Orthogonal Multiple Access (NOMA) and Quadrature-NOMA With Imperfect SIC

Chauhan

Ghosh

Jaiswal

2023

IEEE Trans. Wireless Commun.

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Reconfigurable intelligent surface (RIS)-assisted power-domain non-orthogonal multiple access (PD-NOMA) system has emerged as a revolutionary technology to enhance the spectrum efficiency for future wireless networks. This work introduces two novel RIS systems, namely, RIS partition-assisted (RISP) PD-NOMA (RISP-PD-NOMA) and RISP-Quadrature-NOMA (RISP-Q-NOMA), to improve the signal quality of all users by dedicating fixed RIS units to each user for phase cancellation. The closed-form expressions of average sum-rate, outage probability, and diversity order of both systems are evaluated under the Rician fading channel for perfect and imperfect successive interference cancellation (SIC). Further, the performance of both systems is compared with RIS-division PD-NOMA (RISD-PD-NOMA) system where the RIS subsurface assigned to one user is not exposed to another user. It is noticed from the analysis that under perfect SIC, RISP-PD-NOMA outperforms RISP-Q-NOMA and RISD-PD-NOMA. However, under imperfect SIC, RISP-Q-NOMA demonstrates superior performance than other systems, due to lesser number of SIC operations that lead to less stringent constraints on the power allocation, reduce detection delay, and improve SIC stability. Furthermore, the analytical expression for bit error rate (BER) of RISP-PD-NOMA and RISP-Q-NOMA is derived, and then closed-form expression of average-BER is evaluated. Numerical results demonstrate that RISP-Q-NOMA is superior to RISP-PD-NOMA and RISD-PD-NOMA.

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Section: A Ris Assisted Downlink Modelmentioning

confidence: 99%

RIS Partition-Assisted Non-Orthogonal Multiple Access (NOMA) and Quadrature-NOMA With Imperfect SIC

Chauhan

Ghosh

Jaiswal

2023

IEEE Trans. Wireless Commun.

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“…Considering the rays between different users and the BS follow i.i.d. distribution, E(ξ) and Var(ξ) are converted to (9) and (10). Therefore, we need to derive E(w * ms ), E(w ms ), and E(w * ms w m s ) in ( 9) and (10) to get E(ξ) and Var(ξ), where E φ 0 (•) is the expectation operator for mean azimuth AOAs of different users.…”

Section: Statistical Property Analysis Under Generalized Angle Distri...mentioning

confidence: 99%

“…[1][2][3]. To meet the above requirements, one of the most promising solutions is massive MIMO, which can further utilize the spatial resource [4][5][6][7][8][9].…”

Section: Introductionmentioning

confidence: 99%

A Theoretical Analysis of Favorable Propagation on Massive MIMO Channels with Generalized Angle Distributions

Zhang

et al. 2022

Electronics

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Massive MIMO obtains the multiuser performance gain based on the favorable propagation (FP) assumption, defined as the mutual orthogonality of different users’ channel vectors. Until now, most of the theoretical analyses of FP are based on uniform angular distributions and only consider the horizontal dimension. However, the real propagation channel contains full dimensions, and the spatial angle varies with the environment. Thus, it remains unknown whether the FP condition holds in real deployment scenarios and how it impacts the massive MIMO system performance. In this paper, we analyze the FP condition theoretically based on a cluster-based three-dimensional (3D) MIMO channel with generalized angle distributions. Firstly, the FP condition’s unified mathematical expectation and variance expressions with full-dimensional angular integral are given. Since the closed-form expressions are hard to derive, we decompose generalized angle distributions, i.e., wrapped Gaussian (WG), Von Mises (VM), and truncated Laplacian (TL) into the functions of Bessel and Cosine basis by introducing Jacobi-Anger expansions and Fourier series. Thus the closed-form expressions of the FP condition are derived. Based on the above, we theoretically analyze the asymptotically FP condition under generalized angle distributions and then compare the impact of angular spreads on the FP performance. Furtherly, the FP condition is also investigated by numerical simulations and practical measurements. It is observed that environments with larger angle spreads and larger antenna spacing are more likely to realize FP. This paper provides valuable insights for the theoretical analysis of the practical application of massive MIMO systems.

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“…wireless network architecture [20][21][22][23][24] Single RIS; multi-RIS collaboration; based on spectrum sharing; based on non-spectrum sharing; 3D beamforming; combination with different networks, such as MIMO, OFDM.…”

Section: Design Of Ris-basedmentioning

confidence: 99%

An Innovative Infrastructure Based on Shape-Adaptive RIS for Smart Industrial IoTs

Wang

Peng

et al. 2022

Electronics

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Industrial Internet of Things (IoTs) applications will have higher demands in terms of system capacity and wireless transmission performance in the future. Reconfigurable intelligent surfaces (RIS) for the wireless transmission environment reconstruction is currently a research hotspot in the field of wireless communication. In this paper, RIS is applied to industrial IoTs scenarios, and an innovative infrastructure based on shape-adaptive RIS suitable for smart industrial IoTs is proposed. Based on the many advantages of RIS, the proposed infrastructure can meet the significant demands of industrial IoTs in terms of network coverage, system capacity, transmission rate, and communication security. Further, in order to achieve flexible RIS phase adjustment in wider ranges, in this paper, a shape-adaptive RIS mechanism is proposed to regulate RIS-reflected waves in the shape domain, which can be achieved by scalable RIS unit sizes and macroscopically changeable physical shapes. This mechanism can reduce the requirements for RIS-controller and artificial-unit design and expand the spatial distribution of reflected beams, whereas this is difficult to achieve by conventional regulations in the spatial, time, and frequency domains. The simulation results show that, in terms of system-coverage probability, the system performance of RIS is better than that of general communication systems, and the performance of the deformable RIS-based system is the best. In terms of channel gain, the performance of the deformable RIS is related to its surface size. Moreover, the path loss caused by the long-distance transmission of wireless signals can be compensated for by increasing the RIS surface area.

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On the Trade-Off between Energy Efficiency and Spectral Efficiency in RIS-Aided Multi-User MISO Downlink

Cited by 11 publications

References 35 publications

RIS Partition-Assisted Non-Orthogonal Multiple Access (NOMA) and Quadrature-NOMA With Imperfect SIC

RIS Partition-Assisted Non-Orthogonal Multiple Access (NOMA) and Quadrature-NOMA With Imperfect SIC

A Theoretical Analysis of Favorable Propagation on Massive MIMO Channels with Generalized Angle Distributions

An Innovative Infrastructure Based on Shape-Adaptive RIS for Smart Industrial IoTs

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