Beyond Cell-Free MIMO: Energy Efficient Reconfigurable Intelligent Surface Aided Cell-Free MIMO Communications

Zhang, Yutong; Di, Boya; Zhang, Hongliang; Lin, Jian; Xu, Chenren; Zhang, Daqing; Li, Yonghui; Song, Lingyang

doi:10.1109/tccn.2021.3058683

Cited by 129 publications

(78 citation statements)

References 37 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…In [16] and [18], to reduce the impact of the channel estimation overhead, the authors have investigated the design of RISassisted communications in the presence of statistical CSI. As far as the integration of Cell-Free Massive MIMO and RIS is concerned, recent works have formulated and solved optimization problems with different communication objectives under the assumption of perfect (and instantaneous) CSI [22]- [26]. Recent results in the context of single-input single-output (SISO) and multi-user MIMO systems have, however, shown that designs for the engineered scattering elements of the RIS that are based on statistical CSI may be of practical interest and provide good performance [18], [27]- [29].…”

Section: Introductionmentioning

confidence: 99%

Reconfigurable Intelligent Surface-Assisted Cell-Free Massive MIMO Systems Over Spatially-Correlated Channels

Chien

Ngo

Chatzinotas

et al. 2022

IEEE Trans. Wireless Commun.

134

View full text Add to dashboard Cite

Cell-Free Massive multiple-input multiple-output (MIMO) and reconfigurable intelligent surface (RIS) are two promising technologies for application to beyond-5G networks. This paper considers Cell-Free Massive MIMO systems with the assistance of an RIS for enhancing the system performance under the presence of spatial correlation among the engineered scattering elements of the RIS. Distributed maximum-ratio processing is considered at the access points (APs). We introduce an aggregated channel estimation approach that provides sufficient information for data processing with the main benefit of reducing the overhead required for channel estimation. The considered system is studied by using asymptotic analysis which lets the number of APs and/or the number of RIS elements grow large. A lower bound for the channel capacity is obtained for a finite number of APs and engineered scattering elements of the RIS, and closed-form expressions for the uplink and downlink ergodic net throughput are formulated in terms of only the channel statistics. Based on the obtained analytical frameworks, we unveil the impact of channel correlation, the number of RIS elements, and the pilot contamination on the net throughput of each user. In addition, a simple control scheme for optimizing the configuration of the engineered scattering elements of the RIS is proposed, which is shown to increase the channel estimation quality, and, hence, the system performance. Numerical results demonstrate the effectiveness of the proposed system design and performance analysis. In particular, the performance benefits of using RISs in Cell-Free Massive MIMO systems are confirmed, especially if the direct links between the APs and the users are of insufficient quality with high probability.

show abstract

Section: Introductionmentioning

confidence: 99%

Reconfigurable Intelligent Surface-Assisted Cell-Free Massive MIMO Systems Over Spatially-Correlated Channels

Chien

Ngo

Chatzinotas

et al. 2022

IEEE Trans. Wireless Commun.

134

View full text Add to dashboard Cite

show abstract

“…Compared with existing multi-antenna systems [4]- [9], it has been demonstrated that RISaided systems have the potential to achieve better performance in terms of cost and energy consumption [10]- [16]. Recently, RISs have been considered for integration into various communication scenarios, such as terahertz, sub-terahertz, and millimeter-wave systems [17], [18], simultaneous wireless information and power transfer (SWIPT) [19], unmanned aerial vehicle (UAV) communications [20], cell-free systems [21], physical-layer security [22]- [24], mobile edge computing (MEC) [25]- [27], device-to-device (D2D) communications [28], [29] and so on. Furthermore, the effectiveness of RIS-aided systems in the presence of practical imperfections has been demonstrated in [30]- [34].…”

Section: Introductionmentioning

confidence: 99%

Statistical CSI-Based Design for Reconfigurable Intelligent Surface-Aided Massive MIMO Systems With Direct Links

Zhi

Pan

Ren

et al. 2021

IEEE Wireless Commun. Lett.

111

View full text Add to dashboard Cite

This paper investigates the performance of reconfigurable intelligent surface (RIS)-aided massive multiple-input multiple-output (mMIMO) systems with direct links, and the phase shifts of the RIS are designed based on the statistical channel state information (CSI). We first derive the closed-form expression of the uplink ergodic data rate. Then, based on the derived expression, we use the genetic algorithm (GA) to solve the sum data rate maximization problem. With low-complexity maximal-ratio combination (MRC) and low-overhead statistical CSI-based scheme, we validate that the RIS can bring significant performance gains to the traditional mMIMO systems.

show abstract

“…For example, the researchers in [29] considered a RIS-aided MISO system to maximize the energy efficiency of wireless systems. Furthermore, the energy efficiency maximization problem for cooperative MIMO was discussed in [30], while the same problem for the RIS-aided CF network with limited backhaul was investigated in [31]. To maintain fairness among users, [32] proposed algorithm to enhance the energy efficiency of the worst user in the CF network.…”

Section: A Prior Workmentioning

confidence: 99%

On Energy Efficiency of Wideband RIS-Aided Cell-Free Network

et al. 2022

View full text Add to dashboard Cite

Cell-free (CF) network is a favorable technique against inter-cell interferences to improve the network capacity. However, to further improve the network capacity, a large number of base stations (BSs) are required to be deployed with high cost and power consumption. To tackle this problem, an energyefficient technique called reconfigurable intelligent surface (RIS)-aided CF network has been recently proposed. By replacing some of the required power-hungry BSs with low-power RISs, the energy efficiency of CF network can be enhanced with guaranteed performance. To achieve this goal, in this paper, we first formulate a joint active and passive beamforming problem to maximize the energy efficiency of RIS-aided CF networks. Then, we propose an alternate optimization algorithm to solve this problem. Specifically, we decompose the original energy efficiency maximization problem into multiple subproblems and solve them alternatively. Particularly, we adopt the zero-forcing (ZF) beamforming scheme to optimize the active beamforming at BSs, while the sequential programming (SP) method is adopted to realize the passive beamforming at RISs. Moreover, a realistic energy-consumption model for wideband RIS-aided CF networks is provided, and the effectiveness of the proposed scheme is evaluated by simulations. Finally, simulation results verify that, the proposed scheme is able to achieve a higher energy efficiency than the existing benchmark solution.INDEX TERMS Cell-free network, reconfigurable intelligent surface (RIS), beamforming, wideband, energy efficiency.

show abstract

Beyond Cell-Free MIMO: Energy Efficient Reconfigurable Intelligent Surface Aided Cell-Free MIMO Communications

Cited by 129 publications

References 37 publications

Reconfigurable Intelligent Surface-Assisted Cell-Free Massive MIMO Systems Over Spatially-Correlated Channels

Reconfigurable Intelligent Surface-Assisted Cell-Free Massive MIMO Systems Over Spatially-Correlated Channels

Statistical CSI-Based Design for Reconfigurable Intelligent Surface-Aided Massive MIMO Systems With Direct Links

On Energy Efficiency of Wideband RIS-Aided Cell-Free Network

Contact Info

Product

Resources

About