Channel Estimation for RIS Assisted Wireless Communications—Part I: Fundamentals, Solutions, and Future Opportunities

Wei, Xiuhong; Shen, Decai; Dai, Linglong

doi:10.1109/lcomm.2021.3052822

Cited by 131 publications

(65 citation statements)

References 11 publications

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“…Therefore, high-dimensional quasistatic BS-RIS can be estimated in a larger time scale, and low-dimensional mobile RIS-UE and BS-UE channels can be estimated in a smaller time scale. This two-time scale channel estimation framework can significantly reduce pilot overhead [11]. Correspondingly, in the window RIS and wall RIS scenarios, the two-time scale channel estimation framework can also be used.…”

Section: A Channel Estimationmentioning

confidence: 99%

RIS-Aided Next-Generation High-Speed Train Communications: Challenges, Solutions, and Future Directions

Liu¹,

Zhang²,

Wu³

et al. 2021

Preprint

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High-speed train (HST) communication is a very challenging scenario in wireless communication systems due to its fast time-varying channels and significant penetration loss. Thanks to the low cost and smart channel reconfiguration ability, reconfigurable intelligent surface (RIS) has been proposed as a promising technology to solve the aforementioned challenges costeffectively and to achieve high spectral and energy-efficiency in the next-generation HST communication systems. In this article, we first provide a novel RIS-aided HST wireless communication paradigm, including its main challenges and application scenarios. Then, we propose practical solutions are provided to realize efficient signal processing and resource management in the considered system. Finally, future directions of RIS-aided HST communication systems are pointed out to inspire further investigation in future work.

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Section: A Channel Estimationmentioning

confidence: 99%

RIS-Aided Next-Generation High-Speed Train Communications: Challenges, Solutions, and Future Directions

Liu¹,

Zhang²,

Wu³

et al. 2021

Preprint

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“…The time, energy and resource utilization for channel estimation can quickly erase much of the benefits offered by the IRS. One approach to mitigate this loss is to exploit structure in the channel model to estimate the channel with lower overhead [20]- [22], but these approaches trade-off the reduction in overhead with more complex channel estimation algorithms, thereby substantially increasing the computational costs. In addition, the complexity of overall algorithm increases with the resolution with which phase shifts are configured [23].…”

Section: Introductionmentioning

confidence: 99%

“…One approach to accomplish this is illustrated in[20]. In this work, the authors rely on an active receiver near the IRS, whose direct channel to the BS is similar to that of the BS-IRS channel.…”

mentioning

confidence: 99%

Performance Analysis of Intelligent Reflecting Surface Assisted Opportunistic Communications

Yashvanth¹,

Murthy²

2022

Preprint

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Intelligent reflecting surfaces (IRSs) are a promising technology for enhancing coverage and spectral efficiency, especially in the millimeter wave (mmWave) bands. Existing approaches to leverage the benefits of IRS involve a resourceintensive channel estimation step followed by a computationally expensive algorithm to optimize the reflection coefficients at the IRS. In this work, we present and analyze several alternative schemes, where the phase configuration of the IRS is randomized and multi-user diversity is exploited to opportunistically select the best user at each point in time for data transmission. We show that the throughput of an IRS assisted opportunistic system asymptotically converges to the optimal beamformingbased throughput under fair allocation of resources, as the number of users gets large. Further, for all the proposed schemes, we derive the scaling law of the throughput in terms of the number of users and IRS elements, as the number of users gets large. We also introduce schemes that enhance the rate of convergence of the opportunistic rate to the beamforming rate as the number of users is increased. Following this, we extend the setup to wideband channels via an orthogonal frequency division multiplexing (OFDM) system and discuss two opportunistic schemes in an IRS assisted setting that elucidate the superior performance that IRS aided systems can offer over conventional systems at very low implementation cost and complexity.

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“…Specifically, an RIS is a large-scale array composed of passive elements, which can achieve significant beamforming gain by appropriately imposing phase shifts on the incident electromagnetic waves [4]. To achieve this beamforming gain, accurate channel state information (CSI) should be acquired beforehand, which makes channel estimation an essential problem for RIS-assisted communications [5].…”

Section: Introductionmentioning

confidence: 99%

Sensing RISs: Enabling Dimension-Independent CSI Acquisition for Beamforming

Zhu¹,

Liu²,

Wan³

et al. 2022

Preprint

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Reconfigurable intelligent surfaces (RISs) are envisioned as a potentially transformative technology for future wireless communications. However, RIS's inability to process signals and their attendant increased channel dimension have brought new challenges to RIS-assisted systems, which greatly increases the pilot overhead required for channel estimation. To address these problems, several prior contributions that enhance the hardware architecture of RISs or develop algorithms to exploit the channels' mathematical properties have been made, where the required pilot overhead is reduced to be proportional to the number of RIS elements. In this paper, we propose a dimension-independent channel state information (CSI) acquisition approach in which the required pilot overhead is independent of the number of RIS elements. Specifically, in contrast to traditional signal transmission methods, where signals from the base station (BS) and the users are transmitted in different time slots, we propose a novel method in which signals are transmitted from the BS and the user simultaneously during CSI acquisition. Under this method, an electromagnetic interference random field (IRF) will be induced on the RIS, and we employ a sensing RIS to capture its features. Moreover, we develop three algorithms for parameter estimation in this system, and also derive the Cramér-Rao lower bound (CRLB) and an asymptotic expression for it. Simulation results verify that our proposed signal transmission method and the corresponding algorithms can achieve dimension-independent CSI acquisition for beamforming.

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Channel Estimation for RIS Assisted Wireless Communications—Part I: Fundamentals, Solutions, and Future Opportunities

Cited by 131 publications

References 11 publications

RIS-Aided Next-Generation High-Speed Train Communications: Challenges, Solutions, and Future Directions

RIS-Aided Next-Generation High-Speed Train Communications: Challenges, Solutions, and Future Directions

Performance Analysis of Intelligent Reflecting Surface Assisted Opportunistic Communications

Sensing RISs: Enabling Dimension-Independent CSI Acquisition for Beamforming

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