Reconfigurable intelligent surface (RIS) is a promising technology that can reshape the electromagnetic environment in wireless networks, offering various possibilities for enhancing wireless channels. Motivated by th...
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Reconfigurable intelligent surface (RIS) is a promising technology that can reshape the electromagnetic environment in wireless networks, offering various possibilities for enhancing wireless channels. Motivated by this, we investigate the channel optimization for multiple-input multiple-output (MIMO) systems assisted by RIS. In this letter, an efficient RIS optimization method is proposed to enhance the effective rank of the MIMO channel for achievable rate improvement. Numerical results are presented to verify the effectiveness of RIS in improving MIMO channels. Additionally, we construct a 2 x 2 RIS-assisted MIMO prototype to perform experimental measurements and validate the performance of our proposed algorithm. The results reveal a significant increase in effective rank and achievable rate for the RIS-assisted MIMO channel compared to the MIMO channel without RIS.
Reconfigurable intelligent surfaces (RISs) have emerged as a promising technique to enhance the system spectral efficiency. This paper investigates the ergodic channel capacity (ECC) of an RIS-aided multiple-input mul...
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ISBN:
(纸本)9781665454681
Reconfigurable intelligent surfaces (RISs) have emerged as a promising technique to enhance the system spectral efficiency. This paper investigates the ergodic channel capacity (ECC) of an RIS-aided multiple-input multiple-output channel under the assumption that the transmitter-RIS, RIS-receiver, and transmitter-receiver channels contain deterministic line-of-sight paths. Novel expressions are derived to characterize the upper and lower bounds of the ECC. To unveil more system insights, asymptotic analyses are performed to the system ECC in the limit of large signal-to-noise ratio (SNR) and number of reflecting elements (REs). Theoretical analyses suggest that the RIS's deployment can shape the ECC curve by influencing its high-SNR power offset and the ECC can get improved by increasing the number of REs.
We analyze the potential of using reconfigurable intelligent surfaces (RISs) as an alternative to classical active beamforming to encounter the effects of non-ideal hardware components in the transmitter chain of a ba...
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ISBN:
(纸本)9781665473507
We analyze the potential of using reconfigurable intelligent surfaces (RISs) as an alternative to classical active beamforming to encounter the effects of non-ideal hardware components in the transmitter chain of a base station (BS). In particular, we consider a RIS-assisted multi-user multiple-input multiple-output (MIMO) downlink system, where the received signal-to-noise ratio is not only affected by inter-user interference but also hardware impairments due to amplifier nonlinearity, phase noise, and I/Q channel imbalance. Accordingly, we propose a hybrid beamforming strategy by minimizing the sum of mean-squared errors of all estimated symbols subject to the total transmit power and element-wise phase-shift constraint to obtain the optimal beamforming vectors at the BS and phase shift matrices at the RIS. We show that this problem can be cast as a second-order cone programming problem, and a joint design of the active beamforming vectors and phase-shift matrices can be obtained through an iterative algorithm. Through numerical results, we demonstrate that by using RISs in a cellular communication system, it is possible to effectively mitigate the impact of hardware impairments and achieve better sum-rate and power-efficiency.
Reconfigurable intelligent surfaces (RISs) are a promising technology for enhancing the communication performance of future wireless systems by controlling the wireless environment. In addition, dynamic metasurface an...
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ISBN:
(纸本)9781665406338
Reconfigurable intelligent surfaces (RISs) are a promising technology for enhancing the communication performance of future wireless systems by controlling the wireless environment. In addition, dynamic metasurface antennas (DMAs) are a promising technology for increasing the number of antenna elements of multiple-input multiple-output (MIMO) systems at a reduced cost and power consumption compared to conventional MIMO arrays. In this paper, we amalgamate these two technologies in order to realize massive MIMO communication networks with superior performance at a reduced complexity. We first introduce the considered RIS-assisted DMA-based MIMO system, and we then formulate an optimization problem to maximize the system rate. The problem is solved by using an alternating optimization algorithm, which iteratively optimizes the RIS elements, as well as the precoding matrices and the DMA elements at the transceivers. Simulation results demonstrate that jointly utilizing RISs for controlling the wireless environment and DMAs at the transceivers results in superior achieavble rates.
We study the performance of multiple-input multiple-output orthogonal space-time block coded systems over mixed Nakagami-m/Rice fading channels. Novel closed-form expression for the exact average bit error rate (ABER)...
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ISBN:
(纸本)9781538612248
We study the performance of multiple-input multiple-output orthogonal space-time block coded systems over mixed Nakagami-m/Rice fading channels. Novel closed-form expression for the exact average bit error rate (ABER) of Gray coded rectangular quadrature amplitude modulation is obtained. This expression include already published formulae for other fading channels as special cases. We further derive simple expression for the asymptotic ABER, the diversity order, and the coding gain, which give useful insights for the system performance at high signal-to-noise ratio values. Extensive numerical and computer simulation results are presented to validate the accuracy of the proposed analysis.
Noncooperative classification of the modulation type of communication signals finds application in both civilian and military contexts. Existing modulation classification methods for multiple-input multiple-output (MI...
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Noncooperative classification of the modulation type of communication signals finds application in both civilian and military contexts. Existing modulation classification methods for multiple-input multiple-output (MIMO) communication systems commonly require a priori information on the number of transmit antennas employed by the multiantenna transmitter, which, in most of the noncooperative scenarios involving modulation classification, is unknown and needs to be blindly extracted from the received signal. Since the problems of MIMO modulation classification and detection of the number of transmit antennas are highly coupled, we propose a decision theoretic approach for spatial multiplexing MIMO systems that considers these two tasks as a joint multiple hypothesis testing problem. The proposed method exhibits a high performance even in moderate to low SNR regimes while requiring no a priori knowledge of the channel state information and the noise variance.
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