Active RIS vs. Passive RIS: Which Will Prevail in 6G?

Zhang, Zijian; Dai, Linglong; Chen, Xibi; Liu, Changhao; Yang, Fan; Schober, Robert; Poor, H. Vincent

doi:10.48550/arxiv.2103.15154

Cited by 29 publications

(69 citation statements)

References 38 publications

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“…. , a t } with all entries equal to or greater than 1 [41]. In this manner, the SE of CPSC-RIS and CPSC-RIS-IM can be further improved by encoding partial information (up to R log 2 (t) bits) into the amplitude coefficients, and a multi-ring PSK constellation is observed at the receiver.…”

Section: Im-empowered Cpsc-ris Systemmentioning

confidence: 99%

Cyclic-Prefixed Single-Carrier Transmission for RIS-Empowered Broadband Wireless Systems

Li¹,

Wen²,

Başar³

et al. 2022

Preprint

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In this paper, a cyclic-prefixed single-carrier (CPSC) transmission scheme with phase shift keying (PSK) signaling is presented for broadband wireless communications systems empowered by a reconfigurable intelligent surface (RIS). In the proposed CPSC-RIS, the RIS is configured according to the transmitted PSK symbols such that different cyclically delayed versions of the incident signal are created by the RIS to achieve cyclic delay diversity. A practical and efficient channel estimator is developed for CPSC-RIS and the mean square error of the channel estimation is expressed in closed-form. We analyze the bit error rate (BER) performance of CPSC-RIS over frequency-selective Nakagami-m fading channels. An upper bound on the BER is derived by assuming the maximumlikelihood detection. Furthermore, by resorting to the concept of index modulation (IM), we propose an extension of CPSC-RIS, termed CPSC-RIS-IM, which enhances the spectral efficiency. In addition to conventional constellation information of PSK symbols, CPSC-RIS-IM uses the full permutations of

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Section: Im-empowered Cpsc-ris Systemmentioning

confidence: 99%

Cyclic-Prefixed Single-Carrier Transmission for RIS-Empowered Broadband Wireless Systems

Li¹,

Wen²,

Başar³

et al. 2022

Preprint

Self Cite

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Section: Introductionmentioning

confidence: 99%

“…On the other hand, more recent attention has focused on facilitating active reflecting elements at RISs to attain significant performance gains, which lays the groundwork for further research in RIS-aided transmission schemes [35]- [39]. In [35], achievable channel capacity of a single-input single-output (SISO) system assisted by an RIS, whose reflecting elements are equipped with additional controllable power amplifiers to simultaneously amplify and reflect signals, has been elaborately analyzed through experimental measurements. Subsequently, in follow-up studies, channel capacity and energy efficiency of fully active RIS [37] and partially active RIS-aided systems [38] have been compared to the earlier benchmark studies of conventional specular reflection and fully passive RIS-aided systems.…”

Section: Introductionmentioning

confidence: 99%

“…In other words, the main motivation of this study is to combine the attractive advantages of IM and active RIS systems in a clever scheme in which the RIS operates a part of the transmitter and directly transmits information. In the proposed HRM scheme, we assume that the RIS elements are equipped with electronically controllable phase shifters and reflectiontype amplifiers [35], which enable to simultaneously perform reflection and amplification functions. While the integrated phase shifters are dynamically adjusted to supply convenient phase shifts, the available power amplifiers can be turned ON and OFF according to incoming information bits to avoid excessive power consumption.…”

Section: Introductionmentioning

confidence: 99%

“…Moreover, we perform a detailed theoretical analysis to obtain achievable rate expressions using an information theoretic approach, and derive an upper bound for the analytical bit error probability (ABEP) of the system. Furthermore, we carry out a comprehensive numerical analysis to illustrate the performance improvement of the HRM scheme over the prior RIS-aided benchmark schemes considering fully active [35] and fully passive [1], [32] RISs.…”

Section: Introductionmentioning

confidence: 99%

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Hybrid Reflection Modulation

Yigit¹,

Başar²,

Wen³

et al. 2021

Preprint

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Reconfigurable intelligent surface (RIS)-empowered communication has emerged as a novel concept for customizing future wireless environments in a cost-and energy-efficient way. However, due to double path loss, existing fully passive RIS systems that purely reflect the incident signals into preferred directions attain an unsatisfactory performance improvement over the traditional wireless networks in certain conditions. To overcome this bottleneck, we propose a novel transmission scheme, named hybrid reflection modulation (HRM), exploiting both active and passive reflecting elements at the RIS and their combinations, which enables to convey information without using any radio frequency (RF) chains. In the HRM scheme, the active reflecting elements using additional power amplifiers are able to amplify and reflect the incoming signal, while the remaining passive elements can simply reflect the signals with appropriate phase shifts. Based on this novel transmission model, we obtain an upper bound for the average bit error probability (ABEP), and derive achievable rate of the system using an information theoretic approach. Moreover, comprehensive computer simulations are performed to prove the superiority of the proposed HRM scheme over existing fully passive, fully active and reflection modulation (RM) systems.

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Ergodic rate analysis and power allocation schemes for a novel active simultaneous transmission and reflection reconfigurable intelligent surface‐aided wireless network

Maheswara Rao Ukyam,

Kumar Gurrala

2024

Int J Communication

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SummaryIn this work, we propose the ergodic rate analysis and power allocation schemes for a novel active simultaneous transmits and reflects reconfigurable intelligent surface (STAR‐RIS) aided downlink wireless network. Here, the system model comprises of a single antenna source node (S) that uses the ES protocol to broadcast information to two users (T user and R user) via active STAR‐RIS. Each active STAR‐RIS element can function simultaneously in transmission and reflection modes owing to this ES protocol. We first derive the closed‐form analytical expressions for the system's ergodic rate. An optimization problem is formulated with a total power constraint to enhance the ergodic rate of the proposed system. A computationally inexpensive particle swarm optimization‐based power allocation (PSO‐PA) scheme and the Lagrange multiplier method (LMM) are adopted to solve the described optimization problem and to find the optimized power allocation factors for the source node and the active STAR‐RIS that can enhance the ergodic rate. Additionally, a comparison of the suggested PSO‐PA scheme, the LMM approach, and the equal power allocation (EPA) scheme is shown in terms of ergodic rate. Our results unveil that the proposed active STAR‐RIS system outperforms the passive STAR‐RIS and conventional RIS (transmitting/reflecting) aided systems. Further, the ergodic rate can be significantly improved with the proposed PSO‐PA and LMM schemes over the EPA scheme.

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Active RIS vs. Passive RIS: Which Will Prevail in 6G?

Cited by 29 publications

References 38 publications

Cyclic-Prefixed Single-Carrier Transmission for RIS-Empowered Broadband Wireless Systems

Cyclic-Prefixed Single-Carrier Transmission for RIS-Empowered Broadband Wireless Systems

Hybrid Reflection Modulation

Ergodic rate analysis and power allocation schemes for a novel active simultaneous transmission and reflection reconfigurable intelligent surface‐aided wireless network

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