Hybrid Relay-Reflecting Intelligent Surface-Assisted Wireless Communications

Nguyen, Nhan T.; Vu, Doanh; Lee, Kyungchun; Juntti, Markku

doi:10.1109/tvt.2022.3158686

Cited by 87 publications

(81 citation statements)

References 57 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…We assume that Bob's channel state information (CSI) is perfectly known by himself through channel estimation [10]. Following (4), Bob's covert rate in the HR-RIS-aided covert communication system can be expressed as [8]…”

Section: B Transmission From Alice To Bobmentioning

confidence: 99%

“…Thus, the traditional RIS cannot outperform a half-duplex relay when the number of the elements in the RIS is not sufficiently large [7]. This implies that if a few passive elements of the RIS are replaced by active ones, the traditional RIS becomes a hybrid relay reflecting intelligent surface (HR-RIS) [8], which may lead to that the HR-RIS is able to significantly improve the assisted system performance. Therefore, in this work we propose a HR-RIS-based covert communication scheme, which applies active beamforming by adding some relaying elements at the traditional RIS to mitigate the limitation of the passive reflecting.…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Hybrid Relay-Reflecting Intelligent Surface-Aided Covert Communications

Hu¹,

Shi²,

Yan³

et al. 2022

Preprint

View full text Add to dashboard Cite

In this paper, we propose to use a hybrid relayreflecting intelligent surface (HR-RIS) to enhance the performance of a covert communication system. Specifically, the HR-RIS consists of passive reflecting elements and active relay elements to manipulate the wireless signals from a transmitter to a desired receiver while ensuring the covertness of the transmission via avoiding such signals being detected by a warden. To fully explore the benefits offered by the HR-RIS, we first formulate the joint design of the transmit power and relay/reflection coefficients of the HR-RIS as an optimization problem to maximize the covert rate subject to a covertness constraint. To tackle the solution to this optimization problem, we then derive a closedform expression for an upper bound on covert rate, based on which we develop an alternate algorithm to solve the formulated optimization problem. Our examination shows that the HR-RIS outperforms the traditional RIS in term of achieving a higher covert rate. Interestingly, we also observe the major part of the performance gain brought by the HR-RIS can be obtained by a small number of active relay elements (e.g., 5) and further increasing this number does not improve the covert communication performance.

show abstract

Section: B Transmission From Alice To Bobmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Hybrid Relay-Reflecting Intelligent Surface-Aided Covert Communications

Hu¹,

Shi²,

Yan³

et al. 2022

Preprint

View full text Add to dashboard Cite

show abstract

“…It is worth highlighting that although there exists another type of HRNs where few of the UCs at the RIS are connected to RF chains and act as relays [9], the focus of this article is on detached HRNs where the relay and the RIS are spatially separated.…”

Section: Hybrid Relaying Architecturesmentioning

confidence: 99%

Cooperative Hybrid Networks with Active Relays and RISs for B5G: Applications, Challenges, and Research Directions

Abdullah¹,

Kisseleff²,

Martins³

et al. 2022

Preprint

View full text Add to dashboard Cite

Among the recent advances and innovations in wireless technologies, reconfigurable intelligent surfaces (RISs) have received much attention and are envisioned to be one of the enabling technologies for beyond 5G (B5G) networks. On the other hand, active (or classical) cooperative relays have played a key role in providing reliable and power-efficient communications in previous wireless generations. In this article, we focus on hybrid network architectures that amalgamate both active relays and RISs. The operation concept and protocols of each technology are first discussed. Subsequently, we present multiple use cases of cooperative hybrid networks where both active relays and RISs can coexist harmoniously for enhanced rate performance. Furthermore, a case study is provided which demonstrates the achievable rate performance of a communication network assisted by either an active relay, an RIS, or both, and with different relaying protocols. Finally, we provide the reader with the challenges and key research directions in this area.

show abstract

“…Despite the conventional RIS has shown to be a promising technology to enable secure and intelligent radio environments, it has been proved that a very large number of reflecting elements of a passive RIS is needed to outperform the performance of decode-and-forward relaying [9]. Therefore, hybrid relay-RIS (HR-RIS) scheme was introduced in [10] to leverage the benefits from both passive RIS and relay. Specifically, Nguyen et al proposed employing a single or few active elements in the RIS to provide the signal amplification gain for a significant improvement in the system spectral efficiency.…”

Section: Introductionmentioning

confidence: 99%

Secrecy Capacity Maximization for a Hybrid Relay-RIS Scheme in mmWave MIMO Networks

Egashira¹,

Osorio²,

Nguyen³

et al. 2022

Preprint

Self Cite

View full text Add to dashboard Cite

The hybrid relay-reflecting intelligent surface (HR-RIS) has been recently introduced as an efficient solution to overcome the double path loss and limited beamforming diversity of the conventional fully passive reflecting surface. This motivates us to investigate the application of the HR-RIS in improving the secrecy capacity of millimeter wave multiple-inputmultiple-output (MIMO) systems with the presence of multiantenna eavesdropper. The joint optimization of the transmit beamformer and the relay-reflecting coefficients at RIS is tackled via alternating optimization. In the proposed solution, a closedform expression for the optimal transmit beamformer at the transmitter is derived, and a metaheuristic solution based on particle swarm optimization is proposed to optimize the active and passive elements at the HR-RIS. The simulation results verify that under various scenarios, the HR-RIS provides significant improvement in the secrecy capacity with respect to the conventional passive reflecting surface.

show abstract

Hybrid Relay-Reflecting Intelligent Surface-Assisted Wireless Communications

Cited by 87 publications

References 57 publications

Hybrid Relay-Reflecting Intelligent Surface-Aided Covert Communications

Hybrid Relay-Reflecting Intelligent Surface-Aided Covert Communications

Cooperative Hybrid Networks with Active Relays and RISs for B5G: Applications, Challenges, and Research Directions

Secrecy Capacity Maximization for a Hybrid Relay-RIS Scheme in mmWave MIMO Networks

Contact Info

Product

Resources

About