Enabling Indoor Mobile Millimeter-wave Networks Based on Smart Reflect-arrays

Tan, Xin; Sun, Zhi; Koutsonikolas, Dimitrios; Jornet, Josep Miquel

doi:10.1109/infocom.2018.8485924

Cited by 316 publications

(236 citation statements)

References 17 publications

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“…which is equivalent to (5) if K = M . Based on our proposed grouping method, we further propose a practical transmission protocol to approach the the theoretical maximum achievable rate shown in (8) in the next section.…”

Section: System Model and Irs Elements Grouping Designmentioning

confidence: 99%

Intelligent Reflecting Surface Meets OFDM: Protocol Design and Rate Maximization

Yang

Zheng

Zhang

et al. 2020

IEEE Trans. Commun.

658

581

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Intelligent reflecting surface (IRS) is a promising new technology for achieving both spectrum and energy efficient wireless communication systems in the future. However, existing works on IRS mainly consider frequency-flat channels and assume perfect knowledge of channel state information (CSI) at the transmitter. Motivated by this, in this paper we study an IRS-enhanced orthogonal frequency division multiplexing (OFDM) system under frequency-selective channels and propose a practical transmission protocol with channel estimation. First, to reduce the overhead in channel training and estimation and to exploit the channel spatial correlation, we propose a novel IRS elements grouping method, where each group consists of a set of adjacent IRS elements that share a common reflection coefficient. Based on this grouping method, we propose a practical transmission protocol where only the combined channel of each group needs to be estimated, thus substantially reducing the training overhead. Next, with any given grouping and estimated CSI, we formulate the problem to maximize the achievable rate by jointly optimizing the transmit power allocation and the IRS passive array reflection coefficients. Although the formulated problem is non-convex and thus difficult to solve, we propose an efficient algorithm to obtain a high-quality suboptimal solution for it, by alternately optimizing the power allocation and the passive array coefficients in an iterative manner, along with a customized method for the initialization.Simulation results show that the proposed design significantly improves the OFDM link rate performance as compared to the case without using IRS. Moreover, it is shown that there exists an optimal size for IRS elements grouping which achieves the maximum achievable rate due to the trade-off between the training overhead and IRS passive beamforming flexibility. Part of this work has been submittedIntelligent reflecting surface (IRS), passive array optimization, power allocation, OFDM, channel estimation. I. INTRODUCTIONThe explosion of mobile data and the ever-increasing demand for higher data rates have continuously driven the advancement of wireless communication technologies in the past decade, such as polar code, massive multiple-input multiple-output (MIMO) and millimeter wave (mmWave) communications, among others. Moreover, a 1000-fold increment in network capacity with ubiquitous connectivity and low latency is envisioned for the forthcoming fifth-generation (5G) wireless network [2]. Meanwhile, the energy efficiency of future wireless networks is expected to be improved by several orders of magnitude so as to maintain the power consumption at increasingly higher data rates. Although massive MIMO and mmWave, seen as the key enablers for 5G, are expected to achieve dramatic spectral efficiency improvements, the deployment of large-scale antenna arrays usually results in high implementation cost and increased power consumption [3]. In addition, combining mmWave with massive MIMO for further performance impro...

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Section: System Model and Irs Elements Grouping Designmentioning

confidence: 99%

Intelligent Reflecting Surface Meets OFDM: Protocol Design and Rate Maximization

Yang

Zheng

Zhang

et al. 2020

IEEE Trans. Commun.

658

581

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show abstract

“…As compared to existing wireless technologies based on active elements/RF chains such as MIMO relay and massive MIMO, it has been shown in [6], [7] that IRS with only passive reflecting elements can potentially yield superior performance scaling with the increasing number of elements, but at substantially reduced hardware and energy costs. It is worth noting that there have been other terminologies similar to IRS proposed in the literature, such as intelligent wall [8], passive intelligent mirror [9], [10], smart reflect-array [11], and reconfigurable metasurface [12], among others. IRS-aided wireless communications have drawn significant research attention recently (see, e.g.…”

Section: Introductionmentioning

confidence: 99%

Beamforming Optimization for Wireless Network Aided by Intelligent Reflecting Surface With Discrete Phase Shifts

Zhang

2020

IEEE Trans. Commun.

1,054

661

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Intelligent reflecting surface (IRS) is a cost-effective solution for achieving high spectrum and energy efficiency in future wireless networks by leveraging massive low-cost passive elements that are able to reflect the signals with adjustable phase shifts. Prior works on IRS mainly consider continuous phase shifts at reflecting elements, which are practically difficult to implement due to the hardware limitation.In contrast, we study in this paper an IRS-aided wireless network, where an IRS with only a finite number of phase shifts at each element is deployed to assist in the communication from a multi-antenna access point (AP) to multiple single-antenna users. We aim to minimize the transmit power at the AP by jointly optimizing the continuous transmit precoding at the AP and the discrete reflect phase shifts at the IRS, subject to a given set of minimum signal-to-interference-plus-noise ratio (SINR) constraints at the user receivers. The considered problem is shown to be a mixed-integer non-linear program (MINLP) and thus is difficult to solve in general. To tackle this problem, we first study the single-user case with one user assisted by the IRS and propose both optimal and suboptimal algorithms for solving it. Besides, we analytically show that as compared to the ideal case with continuous phase shifts, the IRS with discrete phase shifts achieves the same squared power gain in terms of asymptotically large number of reflecting elements, while a constant proportional power loss is incurred that depends only on the number of phase-shift levels. The proposed designs for the single-user case are also extended to the general setup with multiple users among which some are aided by the IRS. Simulation results verify our performance analysis as well as the effectiveness of our proposed designs as compared to various benchmark schemes. Index TermsIntelligent reflecting surface, joint active and passive beamforming design, discrete phase shifts optimization.The authors are with the

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“…Intelligent reflecting surface (IRS), which consists of a large number of low-cost passive reflecting elements with adjustable phase shifts, has recently been advocated as a costeffective solution to significantly enhance the performance of wireless communications [1], [2]. Owing to the tunable phase shifts of all the reflecting elements, the functions of signal enhancement and interference suppression can be achieved by the IRS without the use of active transmitters.…”

Section: Introductionmentioning

confidence: 99%

Secrecy Rate Maximization for Intelligent Reflecting Surface Assisted Multi-Antenna Communications

et al. 2019

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We investigate transmission optimization for intelligent reflecting surface (IRS) assisted multi-antenna systems from the physical-layer security perspective. The design goal is to maximize the system secrecy rate subject to the source transmit power constraint and the unit modulus constraints imposed on phase shifts at the IRS. To solve this complicated non-convex problem, we develop an efficient alternating algorithm where the solutions to the transmit covariance of the source and the phase shift matrix of the IRS are achieved in closed form and semi-closed forms, respectively. The convergence of the proposed algorithm is guaranteed theoretically. Simulations results validate the performance advantage of the proposed optimized design.

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Enabling Indoor Mobile Millimeter-wave Networks Based on Smart Reflect-arrays

Cited by 316 publications

References 17 publications

Intelligent Reflecting Surface Meets OFDM: Protocol Design and Rate Maximization

Intelligent Reflecting Surface Meets OFDM: Protocol Design and Rate Maximization

Beamforming Optimization for Wireless Network Aided by Intelligent Reflecting Surface With Discrete Phase Shifts

Secrecy Rate Maximization for Intelligent Reflecting Surface Assisted Multi-Antenna Communications

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