Cascaded Channel Estimation for RIS Assisted mmWave MIMO Transmissions

Liu, Yushan; Zhang, Shun; Gao, Feifei; Tang, Jie; Dobre, Octavia A.

doi:10.1109/lwc.2021.3092147

Cited by 58 publications

(31 citation statements)

References 8 publications

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“…A deep learning algorithm was proposed in [ 28 ] to set up a relation between CSI and RIS configurations for better optimal communication rate performance. An efficient cascaded channel estimation model for an RIS-assisted mmWave MIMO system, with the wideband effect on the transmission model, was considered in [ 29 ]. A hybrid precoding (HP) design for the RIS-aided multiuser (MU) mmWave communication systems was investigated in [ 30 ].…”

Section: Literature Reviewmentioning

confidence: 99%

Two-Stage Multiarmed Bandit for Reconfigurable Intelligent Surface Aided Millimeter Wave Communications

Mohamed

Hashima

Hatano

et al. 2022

Sensors

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A reconfigurable intelligent surface (RIS) is a promising technology that can extend short-range millimeter wave (mmWave) communications coverage. However, phase shifts (PSs) of both mmWave transmitter (TX) and RIS antenna elements need to be optimally adjusted to effectively cover a mmWave user. This paper proposes codebook-based phase shifters for mmWave TX and RIS to overcome the difficulty of estimating their mmWave channel state information (CSI). Moreover, to adjust the PSs of both, an online learning approach in the form of a multiarmed bandit (MAB) game is suggested, where a nested two-stage stochastic MAB strategy is proposed. In the proposed strategy, the PS vector of the mmWave TX is adjusted in the first MAB stage. Based on it, the PS vector of the RIS is calibrated in the second stage and vice versa over the time horizon. Hence, we leverage and implement two standard MAB algorithms, namely Thompson sampling (TS) and upper confidence bound (UCB). Simulation results confirm the superior performance of the proposed nested two-stage MAB strategy; in particular, the nested two-stage TS nearly matches the optimal performance.

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Section: Literature Reviewmentioning

confidence: 99%

Two-Stage Multiarmed Bandit for Reconfigurable Intelligent Surface Aided Millimeter Wave Communications

Mohamed

Hashima

Hatano

et al. 2022

Sensors

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“…A combined design of federated learning (FL) with mmWave based RIS systems was proposed in [11]. An effective cascaded channel estimation formula for RIS-aided mmWave MIMO system was considered in [12], while the authors in [13] used atomic norm minimization for RIS-aided mmWave channel estimation. A dual proposal of BS's hybrid precoders and RIS's passive precoder to exploit the average spectral efficiency in a RIS-aided mmWave MIMO structure was studied in [14] through manipulating the diverse timescale channel state information (CSI).…”

Section: Literature Reviewmentioning

confidence: 99%

“…Towards that, some searchers investigated the application of RIS to empower mmWave communication, especially in a high blockage environment [8][9][10][11]. Various challenges, including the joint estimation of the cascaded RISaided mmWave channel as well as the joint optimization of antenna PSs of both mmWave BS and RIS relay, were extensively investigated in literature [12][13][14]. Despite the existing literature, this paper considers the problem of finding out the best RIS relay among the deployed ones, which maximizes the achievable data rate at the mmWave user equipment (UE).…”

Section: Introductionmentioning

confidence: 99%

Cost-Effective MAB Approaches for Reconfigurable Intelligent Surface Aided Millimeter Wave Relaying

et al. 2022

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Recently, reconfigurable intelligent surface (RIS) relaying is suggested as a talented technology for extending the millimeter wave (mmWave) coverage. However, finding out the best RIS relay maximizing the achievable data rate is a too time-consuming process due to the beamforming training (BT) procedure needed for adjusting the antenna phase shifts (PSs) of both mmWave base station (BS) and the probed RIS relay. Thus, finding out the best RIS relay with the minimum BT time cost seems challenging. In this paper, a cost-effective online learning approach is proposed by means of multi-armed bandit (MAB) hypothesis to address this problem. In this context, two MAB schemes with time-cost efficiency, MAB-CE1, and MAB-CE2, are proposed. In MAB-CE1, the BT time cost of selecting the RIS relay is included in the exploitation term of the MAB algorithm. However, in MAB-CE2, lower and upper confidence bounds (LCB, UCB) values of the expected RISs' achievable spectral efficiencies are utilized to support the selection of the RIS relay characterized by the minimum BT time cost. Numerical analysis shows the superior performance of the proposed cost-effective MAB schemes for RIS mmWave relaying over other benchmarks in terms of BT time cost and the achievable throughput.

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“…RISs composed of discrete elements make the wireless environment controllable and programmable, and thus bring unprecedented new opportunities to enhance the performance of wireless communication systems [9]- [11]. The channel along the path from the base station (BS) to RIS and then to the user is modeled as the cascading convolution of the BS-to-RIS channel, the diagonal phase shift matrix of the RIS, and the RIS-to-user channel [12]- [14].…”

Section: Introductionmentioning

confidence: 99%

Reconfigurable Intelligent Surface for Near Field Communications: Beamforming and Sensing

Jiang¹,

Gao²,

Jian³

et al. 2022

Preprint

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Reconfigurable intelligent surface (RIS) can improve the communications between a source and a destination. The surface contains metamaterial that is configured to reflect the incident wave from the source towards the destination, especially when there is a blockage in between. Recently, continuous aperture RIS is proved to have better communication performance than discrete aperture RIS and has received much attention. However, the conventional continuous aperture RIS is designed to convert the incoming planar waves into the outgoing planar waves, which is not the optimal reflecting scheme when the receiver is not a planar array and is located in the near field of the RIS. In this paper, we consider two types of receivers in the radiating near field of the RIS: (1) when the receiver is equipped with a uniform linear array (ULA), we design RIS coefficient to convert planar waves into cylindrical waves; (2) when the receiver is equipped with a single antenna, we design RIS coefficient to convert planar waves into spherical waves. Simulation results demonstrate that the proposed scheme can reduce energy leakage at the receiver and thus enhance the channel capacity compared to the conventional scheme. More interestingly, with cylindrical or spherical wave radiation, the power received by the receiver is a function of its location and attitude, which could be utilized to sense the location and the attitude of the receiver with communication signaling.

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Cascaded Channel Estimation for RIS Assisted mmWave MIMO Transmissions

Cited by 58 publications

References 8 publications

Two-Stage Multiarmed Bandit for Reconfigurable Intelligent Surface Aided Millimeter Wave Communications

Two-Stage Multiarmed Bandit for Reconfigurable Intelligent Surface Aided Millimeter Wave Communications

Cost-Effective MAB Approaches for Reconfigurable Intelligent Surface Aided Millimeter Wave Relaying

Reconfigurable Intelligent Surface for Near Field Communications: Beamforming and Sensing

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