Gui Zhou's research while affiliated with Friedrich-Alexander-University of Erlangen-Nürnberg and other places

Publications (37)

Preprint
In this paper, we adopt a three-stage based uplink channel estimation protocol with reduced pilot overhead for an reconfigurable intelligent surface (RIS)-aided multi-user (MU) millimeter wave (mmWave) communication system, in which both the base station (BS) and the RIS are equipped with a uniform planar array (UPA). Specifically, in Stage I, the...
Article
Full-text available
An intelligent reflecting surface (IRS) is proposed to enhance the physical layer security in the Rician fading channel wherein the angular direction of the eavesdropper (ED) is aligned with a legitimate user. A two-phase communication system under active attacks and passive eavesdropping is considered in this scenario. The base station avoids dire...
Preprint
Full-text available
This paper investigates reconfigurable intelligent surface (RIS)-assisted secure multiuser communication systems subject to hardware impairments (HIs). We jointly optimize the beamforming vectors at the base station (BS) and the phase shifts of the reflecting elements at the RIS so as to maximize the weighted minimum secrecy rate (WMSR), subject to...
Article
Rate-splitting (RS) has recently been recognized as a promising physical-layer technique for multi-antenna broadcast channels (BC). Due to its ability to partially decode the interference and partially treat the remaining interference as noise, RS is an enabler for a powerful multiple access, namely rate-splitting multiple access (RSMA), that has b...
Article
Reconfigurable intelligent surface (RIS) or intelligent reflecting surface (IRS) has recently been envisioned as one of the most promising technologies in the future sixth-generation (6G) communications. In this paper, we consider the joint optimization of the transmit beamforming at the base station (BS) and the phase shifts at the RIS for an RIS-...
Preprint
Full-text available
Reconfigurable intelligent surface (RIS) or intelligent reflecting surface (IRS) has recently been envisioned as one of the most promising technologies in the future sixth-generation (6G) communications. In this paper, we consider the joint optimization of the transmit beamforming at the base station (BS) and the phase shifts at the RIS for an RIS-...
Preprint
Full-text available
In the past as well as present wireless communication systems, the wireless propagation environment is regarded as an uncontrollable black box that impairs the received signal quality, and its negative impacts are compensated for by relying on the design of various sophisticated transmission/reception schemes. However, the improvements through appl...
Preprint
Full-text available
This paper provides a theoretical framework for understanding the performance of reconfigurable intelligent surface (RIS)-aided massive multiple-input multiple-output (MIMO) with zero-forcing (ZF) detectors under imperfect channel state information (CSI). We first propose a low-overhead minimum mean square error (MMSE) channel estimator, and then d...
Preprint
Full-text available
Optimally extracting the advantages available from reconfigurable intelligent surfaces (RISs) in wireless communications systems requires estimation of the channels to and from the RIS. The process of determining these channels is complicated by the fact that the RIS is typically composed of passive elements without any data processing capabilities...
Preprint
Full-text available
Channel estimation in the RIS-aided massive multiuser multiple-input single-output (MU-MISO) wireless communication systems is challenging due to the passive feature of RIS and the large number of reflecting elements that incur high channel estimation overhead. To address this issue, we propose a novel cascaded channel estimation strategy with low...
Article
In practice, residual transceiver hardware impairments inevitably lead to distortion noise which causes the performance loss. In this paper, we study the robust transmission design for a reconfigurable intelligent surface (RIS)-aided secure communication system in the presence of transceiver hardware impairments. We aim for maximizing the secrecy r...
Article
A fundamental challenge for millimeter wave (mmWave) communications lies in its sensitivity to the presence of blockages, which impact the connectivity of the communication links and ultimately the reliability of the network. In this paper, we analyze a mmWave communication system assisted by multiple reconfigurable intelligent surface (RISs) for e...
Preprint
Full-text available
In practice, residual transceiver hardware impairments inevitably lead to distortion noise which causes the performance loss. In this paper, we study the robust transmission design for a reconfigurable intelligent surface (RIS)-aided secure communication system in the presence of transceiver hardware impairments. We aim for maximizing the secrecy r...
Preprint
Full-text available
In millimeter wave (mmWave) systems, it is challenging to ensure the reliable connectivity of communications due to its sensitivity to the presence of blockages. In order to improve the robustness of the mmWave system under the presence of the random blockages, multiple reconfigurable intelligent surfaces (RISs) are deployed to enhance the spatial...
Preprint
Full-text available
In this paper, we investigate the robust outage constrained transmission design for an intelligent reflecting surface (IRS) aided secure communication system. We assume that a single-antenna legitimate receiver (Bob) served by a multi-antenna base station (BS) is overheard by multiple single-antenna eavesdroppers (Eves), and the artificial noise (A...
Preprint
Full-text available
A fundamental challenge for millimeter wave (mmWave) communications lies in its sensitivity to the presence of blockages, which impact the connectivity of the communication links and ultimately the reliability of the entire network. In this paper, we analyze a reconfigurable intelligent surface (RIS)-aided mmWave communication system for enhancing...
Article
Intelligent reflection surface (IRS) has recently been recognized as a promising technique to enhance the performance of wireless systems due to its ability of reconfiguring the signal propagation environment. However, the perfect channel state information (CSI) is challenging to obtain at the base station (BS) due to the lack of radio frequency (R...
Preprint
Full-text available
In this paper, intelligent reflecting surface (IRS) is proposed to enhance the physical layer security in a Rician fading channel scenario where the angle direction of the eavesdropper is aligned with a legitimate user. In this scenario, this paper considers a two-phase communication system under the active attacks and passive eavesdropping. In par...
Article
Full-text available
Perfect channel state information (CSI) is challenging to obtain due to the limited signal processing capability at the intelligent reflection surface (IRS). This is the first work to study the worst-case robust beamforming design for an IRS-aided multiuser multiple-input single-output (MU-MISO) system under the assumption of imperfect CSI. We aim...
Article
Full-text available
Intelligent reflecting surface (IRS) has recently been envisioned to offer unprecedented massive multiple-input multiple-output (MIMO)-like gains by deploying large-scale and low-cost passive reflection elements. By adjusting the reflection coefficients, the IRS can change the phase shifts on the impinging electromagnetic waves so that it can smart...
Preprint
Full-text available
Intelligent reflection surface (IRS) has recently been recognized as a promising technique to enhence the performance of wireless systems due to its ability of recon-figuring the signal propagation environment. However, the perfect channel state information (CSI) is challenging to obtain at the base station (BS) due to the lack of radio frequency (...
Preprint
Full-text available
Rate-splitting (RS) has recently been recognized as a promising physical-layer technique for multi-antenna broadcast channels (BC). Due to its ability to partially decode the interference and partially treat the remaining interference as noise, RS is an enabler for a powerful multiple access, namely rate-splitting multiple access (RSMA), that has b...
Preprint
Full-text available
Perfect channel state information (CSI) is challenging to obtain due to the limited signal processing capability at the intelligent reflection surface (IRS). In this paper, we study the robust beamforming design for the IRS-aided multiple-user multiple-input single-output (MU-MISO) systems under the assumption of imperfect CSI. We aim for minimizin...
Preprint
Full-text available
Intelligent reflecting surface (IRS) has recently been envisioned to offer unprecedented massive multiple-input multiple-output (MIMO)-like gains by deploying large-scale and low-cost passive reflection elements. By adjusting the reflection coefficients, the IRS can change the phase shifts on the impinging electromagnetic waves so that it can smart...
Preprint
Full-text available
Intelligent reflecting surface (IRS) has recently been envisioned to offer unprecedented massive multiple-input multiple-output (MIMO)-like gains by deploying large-scale and low-cost passive reflection elements. By adjusting the reflection coefficients, the IRS can change the phase shifts on the impinging electromagnetic waves so that it can smart...

Citations

... On the other hand, reconfigurable intelligent surface (RIS)aided communications have attracted significant attention in recent years [7]- [9]. In [10], a centralized joint precoding framework was proposed to improve network capacity for wideband RIS-aided cell-free networks. ...
... Deploying an RIS provides additional degrees-of-freedom (DoF) that can be used to reconfigure the wireless propagation environment, which brings tremendous benefits for the wireless systems. To reap the benefits promised by RIS, accurate channel state information (CSI) is required [7]- [9], which is challenging to achieve for the following two reasons. First, an RIS equipped with passive elements typically does not have a receiver, so does not process complex baseband signals, which means that traditional channel estimation approaches cannot be adopted in RIS-aided systems. ...
... In general, different methods for estimating different channel parameters lead to different types of parameter estimation errors [22]. Besides, the radio positioning parameter estimation is a new challenge due to the passive property of RIS [23]. Therefore, it is essential to investigate different RIS-aided positioning systems based on the different types of radio positioning parameter estimation errors. ...
... In [14], the authors analyzed the outage performance for RIS-aided non-orthogonal multiple access systems with HWI, where both near-field and far-field users were considered. Most recently, robust transceiver design for RIS-aided communication systems was studied in [15], where both imperfect CSI and HWI were taken into account. The semidefinite programming was proposed to solve the robust problem. ...
... In [11], a multiple input single output broadcast downlink network consisting of two users was investigated and it was highlighted that RSMA generalizes OMA, NOMA, space division multiple access and multicasting. Moreover, in [12], the spectral and energy efficiency tradeoff of RSMA was studied in a multiuser multi-antenna downlink network. Furthermore, in [13], an optimization problem was studied aiming to maximize the sum-rate under both rate and successive interference cancellation (SIC) constraints in a downlink RSMA network. ...
... With the help of IRS, the spectrum efficiency, energy efficiency and security of wireless communications can be improved without significantly increasing the deployment cost of the system novel deep reinforcement learning (DRL) approach to optimise the base station's (BS) beamforming and the IRS's reflecting beamforming under the quality of service (QoS) requirements and time-varying channel conditions. Unlike most existing studies which focus on the case of a single authorised user or eavesdropping node, Bereyhi et al. [9] and Zhou et al. [10] discuss the optimal design with multiple authorised receivers and eavesdropping nodes, respectively. Furthermore, artificial noise (AN) is first introduced at the base station for suppressing the eavesdropping in [11]. ...
... In particular, the initial technique works [20], [21] theoretically unveiled that the received power at the user is capable of scaling quadratically with the number of reflecting elements. Motivated by such a promising power scaling law, IRS has been extensively studied in the recent literature under various applications for different design objectives, such as non-orthogonal multiple-access (NOMA) [22], [23], multi-cell networks [24], massive MIMO [25], physical-layer security [26], [27], and wireless-powered communications networks [28]- [30], among others. In addition to the aforementioned applications, the IRS is also appealing for improving the task offloading efficiency of the MEC network by exploiting its high passive beamforming gain. ...
... From the signal processing perspective, RIS systems bring interesting challenges to the design of the large-dimensional passive beamforming matrices at the RIS surfaces. For example, [22] investigates the design of low-complexity and energyefficient RIS beamforming algorithms, [23] designs robust RIS beamforming solutions, and [24]- [26] develop techniques for the joint basestation-RIS beamforming design problem. One main critical challenge for the operation of these systems is the high training overhead associated with the channel acquisition, especially if these surfaces are nearly passive. ...