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In the electronic warfare environment, the performance of ground-based radar target search is seriously degraded due to the existence of smeared spectrum (SMSP) jamming. SMSP jamming is generated by the self-defense jammer on the platform, playing an important role in electronic warfare, making traditional radars based on linear frequency modulation (LFM) waveforms face great challenges in searching for targets. To solve this problem, an SMSP mainlobe jamming suppression method based on a frequency diverse array (FDA) multiple-input multiple-output (MIMO) radar is proposed. The proposed method first uses the maximum entropy algorithm to estimate the target angle and eliminate the interference signals from the sidelobe. Then, the range-angle dependence of the FDA-MIMO radar signal is utilized, and the blind source separation (BSS) algorithm is used to separate the mainlobe interference signal and the target signal, avoiding the impact of mainlobe interference on target search. The simulation verifies that the target echo signal can be effectively separated, the similarity coefficient can reach more than 90% and the detection probability of the radar is significantly enhanced at a low signal-to-noise ratio. [ABSTRACT FROM AUTHOR]

Underwater wireless optical communication (UWOC) has been widely used in the construction of underwater communication network for the advantages of high data rates, small latency, high flexibility and scalability. However, due to the absorption and scattering effects of seawater, the spatial characteristics of UWOC links have not been studied extensively, especially in multiple-input multiple-output (MIMO) scenario. A linear array MIMO UWOC link geometry was considered and a weighted exponential function polynomial (WEFP) model was proposed to characterize the photon irradiance distribution at the receiving plane of general MIMO UWOC links with arbitrary numbers of light sources. Numerical results suggest that the proposed WEFP model fits well with the results of Monte Carlo simulations in turbid water environment. [ABSTRACT FROM AUTHOR]

In this paper, a compact super wideband annular ring antenna using 45° clock-wise square patch inclusions for super high frequency and polarization diversity applications is proposed. The inclusions consist of a combination of squares and circles into one another in the inner area of a main annular ring radiator. The antenna uses a partial ground plane having a stair-type defected ground structure, is designed on an FR-4 substrate, and has a total size of 25 × 26 × 1.6 mm3 (0.17λ × 0.18λ). The design was fabricated and experimental results fairly agreed with simulations and resulted in an antenna with an operating frequency from 2.07 to 30 GHz; that is, a large fractional bandwidth of 174.2 $\%$ with a bandwidth (BW) ratio of 14.5:1 and a high BW dimension ratio, BW per unit electrical length of 5693, and a measured peak gain of 8 dBi with an average gain of 5 dBi for the overall operating frequency. For the polarization diversity, a 4 × 4 multiple input-multiple output configuration is additionally presented, offering an effective isolation of ≥ 22.5 dB between ports and corroborated by measurements. [ABSTRACT FROM AUTHOR]

With the tremendous increase in wireless user traffic, investigation on the end-to-end reliability of wireless networks in practical conditions such as non-homogeneous fading channel conditions is becoming increasingly widespread. Because they fit well to the experimental data, generalized channel fading distributions like κ–μ are well suited for modeling diverse fading channels. This paper analyzes the symbol error rate (SER) and outage probability (OP) performance of multiple-input multiple-output (MIMO) space-time block-code (STBC) selective decode and forward (S-DF) network over κ–μ fading channel conditions considering the additive white Gaussian noise (AWGN). First, the closed-form (CF) analytical expressions for the probability density function (PDF) and the cumulative distribution function (CDF) of the received signal-to-noise ratio (SNR) as well as its moment generating function (MGF) are derived. Second, the OP performance is then investigated for various values of the channel fading parameter and SNR regimes. The simulation findings show an increase in SER performance with an improved line-of-sight (LOS) component. Furthermore, the results show that the S-DF relaying systems can function properly even when there is no fading or LOS component. The OP has been increasing with the increase in the value of μ and κ. In medium and high SNR regimes, simulation results exactly match with analytical results. [ABSTRACT FROM AUTHOR]

Ground-based multiple-input multiple-output synthetic aperture radar (MIMO-SAR) is a new type of deformation monitoring sensor that has the advantages of no mechanical motion and fast echo acquisition. Ground-based MIMO-SAR can significantly improve the data rate of deformation monitoring. In this paper, a fast imaging algorithm tailored for ground-based MIMO-SAR data is proposed, which can be applied in both far-field and near-field scenarios. First, the phase center approximation error of the non-collinear array in the near field is analyzed. Then, a fast imaging algorithm based on geometric transformation for the coherent synthesis of subimages is put forward. The algorithm uses the geometric transformation to convert the subaperture imaging results into the full aperture coordinate system, which avoids the point-by-point interpolation calculation and further reduces the computational cost of the subimage coherent synthesis algorithm. Simulations and experiments show that the algorithm can achieve high-precision focusing imaging, and its operation efficiency is significantly improved compared with the algorithm based on interpolation. [ABSTRACT FROM AUTHOR]

The demand for high-speed wireless communication systems has led to the development of ultrawide-band (UWB) antennas with a compact size and high performance. In this paper, we propose a novel four-port multiple-input multiple-output (MIMO) antenna with an asymptote-shaped structure that overcomes the limitations of existing designs for UWB applications. The antenna elements are placed orthogonally to each other for polarization diversity, and each element features a stepped rectangular patch with a tapered microstrip feedline. The unique structure of the antenna significantly reduces its dimensions to 42 × 42 mm2 ( 0.43 λ × 0.43 λ @   3.09 GHz ), making it highly desirable for use in small wireless devices. To further enhance the antenna's performance, we use two parasitic tapes on the ground plane at the back as decoupling structures between adjacent elements. The tapes are designed in a windmill shape and a rotating extended cross shape, respectively, to further improve the isolation. We fabricated and measured the proposed antenna design on a single-layer substrate (FR4) with a dielectric constant of 4.4 and a thickness of 1 mm. The measured results show that the impedance bandwidth of the antenna is 3.09–12 GHz, with an isolation of −16.4 dB, an envelope correlation coefficient (ECC) of 0.02, a diversity gain (DG) of 9.991 dB, an average total effective reflection coefficient (TARC) of −20 dB, an overall group delay value less than 1.4 ns, and a peak gain of 5.1 dBi. Although there may be some antennas that have better performance in one or two specific aspects, our proposed antenna has an excellent trade-off among all the antenna characteristics including bandwidth, size, and isolation. The proposed antenna also exhibits good quasi-omnidirectional radiation properties, making it well-suited for a range of emerging UWB-MIMO communication systems, particularly in small wireless devices. In summary, the compact size and ultrawide-band capabilities of the proposed MIMO antenna design, coupled with its improved performance compared to other recent UWB-MIMO designs, make it a promising candidate for 5G and next-generation wireless communication systems. [ABSTRACT FROM AUTHOR]

OFDM (ORTHOGONAL frequency-division multiplexing) is a well-known modulation scheme that has been widely employed in wireless broadband systems in the previous decade to combat frequency-selective type fading in wireless channels. In OFDM approaches, channel state information is critical for detecting and decoding coherent signals. Pilot tones are frequently included into the subcarriers of OFDM signals to perform channel estimation. The perceptron neural network (DNN) has shown to be an effective tool for channel estimation in wireless communication's suboptimal conditions. Prior to the demodulation of OFDM signals, a dynamic channel estimate is important. Depending on the channel types and circumstances, deep learning-based channel estimation outperforms classical channel estimation methods such as minimal mean-square error (MMSE) and least squares (LS). The simulation results validate the projected Perceptron model's validity and demonstrate the use of our proposed Perceptron-based channel estimation in both nonlinear and linear signal models. [ABSTRACT FROM AUTHOR]

At present, the study of ancient literature is gradually gaining attention but related knowledge still mostly exists offline without enough sharing online. In order to design an online sharing platform for ancient literature, an improved particle swarm optimization algorithm is used to form AAD-MOPSO based on cognitive radio architecture and multiple input multiple output and adaptive angular region partitioning. The improved algorithm is capable of adaptively and reasonably partitioning the channel in complex situations and avoiding the problem of local optimal solutions and over convergence, ensuring the balance of the number of particles in each region by angular partitioning, and balancing the population optimal solution and global optimal solution among each user target. In the simulation experiments, the sample targets are divided into two data sets equally and randomly, and each data set is divided into five groups and the test results and statistical averaging results of each group are recorded, and four other algorithms, namely PSO, MOPSO, logistics and K-means, are used for comparison. The experimental results show that the average accuracy rate of AAD-MOPSO algorithm is 88.05%, the average adaptation rate is 53.41%, and the average F1 value is 1.082, which are significantly higher than the other four algorithms, verifying the feasibility of the improved algorithm. [ABSTRACT FROM AUTHOR]

A novel wideband self-decoupled loop-coupled antenna element is proposed for the fifth-generation (5G) multiple-input multiple-output (MIMO) smartphones. The proposed loop-coupled antenna element generates two resonance modes of 0.75 and 1 λ. With the help of these two resonance modes, a wide bandwidth is achieved. The self-decoupled performance is realized by loading the loop antenna element with coupled lines. The common/differential mode theory is used to analyze and guide the antenna design to clarify the self-decoupling principle. At the same time, miniaturization of the proposed antenna element is also studied. The antenna element provides good isolation and diversity/multiplexing performances over N77/N78/N79 bands. An 8-port MIMO antenna is constructed using the proposed antenna element. The MIMO antenna is simulated, manufactured, and tested to verify and evaluate the performance metrics, such as isolation, envelope correlation coefficient, efficiency, and spatial multiplexing efficiency. The test results are in good agreement with the simulated ones. [ABSTRACT FROM AUTHOR]

Unmanned aerial vehicles (UAVs) and millimeter-wave frequencies play key roles in supporting 5G wireless communication systems. They expand the field of wireless communication by increasing the data capacities of communication systems and supporting high data rates. However, short wavelengths, owing to the high millimeter-wave frequencies can cause problems, such as signal attenuation and path loss. To address these limitations, research on high directional beamforming technologies continue to garner interest. Furthermore, owing to the mobility of the UAVs, it is essential to track the beam angle accurately to obtain full beamforming gain. This study presents a beam tracking method based on the unscented Kalman filter using hybrid beamforming. The simulation results reveal that the proposed beam tracking scheme improves the overall performance in terms of the mean-squared error and spectral efficiency. In addition, by expanding analog beamforming to hybrid beamforming, the proposed algorithm can be used even in multi-user and multi-stream environments to increase data capacity, thereby increasing utilization in new-radio multipleinput multiple-output orthogonal frequency-division multiplexing systems. [ABSTRACT FROM AUTHOR]

In order to verify the impact of transceiver hardware impairments on the performance of communication system, we explore the robust transmission design of an intelligent reflecting surface (IRS) aided simultaneous wireless information and power transfer (SWIPT) communication system in consideration of hardware impairments of transceiver. Under the constraints of maximum transmitting power of base station, the minimum receiving energy of the energy collector and IRS passive beamforming, the optimization objective is set to maximize the weighted sum rate of all information receivers. And the block coordinate descent (BCD) algorithm is used to decompose the optimization problem into multiple optimization subproblems for alternate optimization. The Lagrange dual method and maximization minimization (MM) algorithm are respectively adopted to solve the optimization problems of active beamforming and IRS passive beamforming. Simulation results validate the impact of transceiver hardware impairments on system performance, and also confirm that the hardware impairment at information receiver is more obvious than the hardware impairment at base station transmitter. [ABSTRACT FROM AUTHOR]

multiple-input multiple-output technology has emerged as a pivotal solution for addressing the capacity constraints of high-speed broadband wireless networks. By employing multiple antennas at both the transmitter and receiver, multiple-input multiple-output significantly enhances wireless communication efficiency. This paper presents a comprehensive review of multiple-input multiple-output antenna design strategies tailored for fifth-generation (5 G) networks and beyond. Specifically, it critically examines methodologies aimed at mitigating radar cross section in multiple-input multiple-output antennas, a crucial aspect of antenna engineering, especially in scenarios requiring reduced detectability. Various design and performance enhancement techniques proposed in the literature for RCS reduction in multiple-input multiple-output antennas are systematically analyzed, focusing on aspects such as antenna geometry and materials methods. Synthesizing these findings provides valuable insights into the current state of research, highlighting advancements, challenges, and future directions in developing efficient multiple-input multiple-output antennas with minimized radar cross section. This review contributes to antenna technology by aiding researchers and practitioners in informed decision-making regarding radar cross section reduction techniques for multiple-input multiple-output systems, and it identifies innovative approaches pertinent to multiple-input multiple-output applications. Finally, key considerations in multiple-input multiple-output antenna design are addressed, proposing potential directions for future research and development initiatives. [ABSTRACT FROM AUTHOR]

Energy harvesting (EH)-assisted non-orthogonal multiple access (NOMA) cognitive radio (CR) networks allow simultaneous transmission of multiple secondary user signals on primary frequency bands with harvested energy, enhancing spectral, spectrum utilization, and energy efficiencies. Although multiple antennas are used for efficient energy transfer and signal transceiving, multiple-input multiple-output (MIMO) communication in these networks is facing reliability/security performance degradation due to nonlinear EH, hardware impairment (HWi), and wire-tapping. The paper aims to numerically evaluate the security and reliability of MIMO communication in EH-assisted NOMA CR networks with jamming (MehNOwJ) under such effects. The results indicate that MehNOwJ prevents full outage and achieves optimum performance with proper parameter selection of preset spectral efficiency, power saturation threshold, EH duration, number of antennas of jammer. In addition, the performance improves with an accreting quantity of antennas but experiences saturation. Moreover, MehNOwJ drastically outperforms alternative approaches (MIMO communication in EH-assisted orthogonal multiple access CR network with jamming and MIMO communication in EH-assisted NOMA CR network without jamming), offering insights into the benefits of combining NOMA and jamming techniques. [ABSTRACT FROM AUTHOR]

Firstly, the key technologies in photonics-aided broadband terahertz communication systems were introduced, and then the research progress in large-capacity and long-distance terahertz communication technologies was introduced.Using these key technologies, wireless transmission of THz signals had been successively achieved exceeding 1 Tbit/s, wireless transmission of THz signals exceeding 100 Gb/s for 54.6 meters without a THz amplifier.The use of air-core optical fiber to transmit terahertz signals exceeding 100 Gbit/s was also introduced.

In this paper, in order to improve the reliability of Multi-User Multiple-Input Multiple-Output Visible Light Communication (MU-MIMO-VLC) system, we propose a precoding scheme that based on Singular Value Decomposition (SVD) and Geometric Mean Decomposition (GMD) assisted Orthogonal Transformation (OT). In this design, we use SVD to conduct the decomposition of the user’s complementary channel matrix. Then, the equivalent channel matrix is obtained by multiplying the user’s channel matrix and the decomposed component. After that, the GMD is carried out to decompose the equivalent channel matrix. Finally, the precoding matrix of the proposed scheme is obtained. We then derive the theoretical Symbol Error Rate (SER) of the proposed scheme. The simulation results are provided to validate the effectiveness of the proposed scheme, and to demonstrate that the reliability of the proposed design is superior to benchmark schemes.

In this paper, a novel two-dimensional (2D) generalized optical spatial modulation (GOSM) scheme is proposed for multiple-input multiple-output optical wireless communication (MIMO-OWC) systems. By grouping multiple successive time slots as one time block, 2D GOSM mapping can be performed not only in the space domain but also in the time domain. Specifically, two types of 2D GOSM mapping schemes are designed, including 2D-1 and 2D-2 GOSM mappings. Moreover, to address the high complexity issue of optimal joint maximum-likelihood (ML) detection and the noise amplification and error propagation issues of zero-forcing-based ML (ZF-ML) detection, a deep neural network (DNN)-aided detection scheme is further designed for 2D GOSM systems. Simulation results demonstrate the superiority of the proposed 2D GOSM scheme with deep learning-aided detection for high-speed and low-complexity MIMO-OWC systems. More specifically, a remarkable 3.4-dB signal-to-noise ratio (SNR) gain can be achieved by 2D GOSM in comparison to the conventional one-dimensional (1D) GOSM, when applying the DNN-aided detection.

Terahertz (THz) band is one of the most promising aspects of wireless communication systems because of its potential to meet the growing demands for the envisioned next-generation of cellular communications. THz band connectivity can alleviate bandwidth shortages and transmit power constraints using multiple-input multiple-output (MIMO) systems. To obtain better throughput and enhanced spectral efficiency, non-orthogonal multiple access (NOMA) configuration can be incorporated into MIMO systems, as NOMA uses non-orthogonal resource allocation by assigning the same carrier frequency to multiple devices in the power domain. In this paper, we focus on 2 × 1 MIMO-NOMA and cooperative 2 × 1 MIMO-NOMA systems for THz spectrum in the downlink transmission. In order to evaluate the effectiveness of the proposed system architecture, we derive accurate data rate, transmission latency, and reliability expressions for 2 × 1 MIMO-NOMA system consists of critical and non-critical devices by leveraging finite block length theory. Moreover, we derive the closed-form expressions for power splitting coefficients, data rate, transmission latency, and reliability for the considered cooperative 2 × 1 MIMO-NOMA system. Extensive numerical results are presented to validate the feasibility of the proposed 2 × 1 MIMO-NOMA as well as the cooperative 2 × 1 MIMO-NOMA systems in the THz band.

In visible light communication systems, the ability to suppress interference caused by other light sources is a major benefit towards performance improvements. Especially for large transmitter arrays or even multi-cell arrangements, the interference problem needs to be handled. In previous work, we have presented a liquid crystal display (LCD) used as an adaptive interference-suppression filter mounted in front of each photodetector. The display elements are switched on and off in such a way that light emitted by unwanted light sources ideally is blocked, but light emitted by desired light sources reaches the detector. The pattern generated by the LC display has strong impact on the system performance. In this paper, we propose combined precoding in conjunction with LCD-based interference suppression in order to increase the signal-to-interference-plus-noise ratio and to ensure user fairness in massive MIMO scenarios. The suggested precoding strategy uses a new heuristic optimization approach based on the Santa Claus problem on unrelated machines known from computer sciences, and employs only binary entries in the weighting matrix. Corresponding results are compared with a genetic evolutionary optimization strategy and with conventional zero-forcing precoding. Regarding performance evaluation, we perform numerical ray-tracing simulations and present a room-scale VLC testbed for experimental verification.

In this paper, we propose an orthogonal frequency division multiplexing (OFDM)-based generalized optical quadrature spatial modulation (GOQSM) technique for multiple-input multiple-output optical wireless communication (MIMO-OWC) systems. Considering the error propagation and noise amplification effects when applying maximum likelihood and maximum ratio combining (ML-MRC)-based detection, we further propose a deep neural network (DNN)-aided detection for OFDM-based GOQSM systems. The proposed DNN-aided detection scheme performs the GOQSM detection in a joint manner, which can efficiently eliminate the adverse effects of both error propagation and noise amplification. The obtained simulation results successfully verify the superiority of the deep learning-aided OFDM-based GOQSM technique for high-speed MIMO-OWC systems.

Optical channel decorrelation is a key aspect in designing a multi-user visible light communication system. As light-emitting diodes (LEDs) are commonly used for illumination and data transmission in such a system simultaneously, the interference between them is a major problem for suitable modulation schemes. We have proposed to position liquid-crystal (LC) matrix elements in front of the receivers in order to block unwanted light – so effectively acting as filter and reducing the interference. To do so, the appropriate pixels of the LC filter are switched either to a transmissive state or to an opaque state. The selection of the correct pixel patterns is a high-order optimization problem, which makes it challenging for classic algorithms. In this paper, we suggest applying a genetic optimization to find suitable pixel patterns. We combine this kind of receiver-side optimization with conventional convex precoding at the transmitter side in an iterative manner. The overall optimization goal is to maximize the sum rate over all users. To prove the effectiveness, we use a numeric ray-tracing simulation with different settings. Also we analyze the impact of the main parameters for the genetic algorithm.

High-order modulation formats with high symbol rates are promising candidates for meeting the growing traffic requirements of digital coherent transmission. In using these modulation formats, the impact of transceiver impairment on the signal quality becomes significant. In this paper, we propose an 8×2 widely linear (WL) multiple-input multiple-output (MIMO) equalizer with independent complex filtering on IQ signals to mitigate linear transceiver impairments. Furthermore, we extend the equalizer for digital subcarrier (SC) multiplexing. Accordingly, a 16×4 WL MIMO equalizer is also proposed to mitigate linear transceiver impairments, through application to a pair of SC inputs. Experimental results show that, for transmission of a 58-GBaud polarization-multiplexing 64 quadrature amplitude modulation (PM-64QAM) single-carrier signal, the proposed method effectively compensates for various receiver impairments and also mitigates transmitter (Tx) impairments. Q-penalties of 0.1 dB up to a 10-ps skew, 2.5-dB gain imbalance, 7.2-degree phase error, and –15-dB crosstalk in Tx were achieved for 100-km standard single-mode fiber transmission. Moreover, for a 29-GBaud PM-64QAM dual-SC signal, the proposed 16 × 4 WL MIMO equalizer shows transceiver impairment mitigation performance similar to that in the single-carrier case, even though dual-SC transmission is less tolerant of laser phase noise.

Millimeter-wave (mmWave) communications have been considered as a key technology for next-generation cellular systems and Wi-Fi networks because of its advances in providing orders-of-magnitude wider bandwidth than current wireless networks. Economical and energy-efficient analog/digital hybrid precoding and combining transceivers have been often proposed for mmWave massive multiple-input multiple-output (MIMO) systems to overcome the severe propagation loss of mmWave channels. One major shortcoming of existing solutions lies in the assumption of infinite or high-resolution phase shifters (PSs) to realize the analog beamformers. However, low-resolution PSs are typically adopted in practice to reduce the hardware cost and power consumption. Motivated by this fact, in this paper, we investigate the practical design of hybrid precoders and combiners with low-resolution PSs in mmWave MIMO systems. In particular, we propose an iterative algorithm which successively designs the low-resolution analog precoder and combiner pair, aiming at conditionally maximizing the spectral efficiency. Then, the digital precoder and combiner are computed based on the obtained effective baseband channel to further enhance the spectral efficiency. In an effort to achieve an even more hardware-efficient large antenna array, we also investigate the design of hybrid beamformers with one-bit resolution (binary) PSs, and present a novel binary analog precoder and combiner optimization algorithm. After analyzing the computational complexity, the proposed low-resolution hybrid beamforming design is further extended to multiuser MIMO communication systems. Simulation results demonstrate the performance advantages of the proposed algorithms compared to existing low-resolution hybrid beamforming designs, particularly for the one-bit resolution PSs scenario.

This paper proposes two flexible ultra‐wideband (UWB) multiple‐input multiple‐output (MIMO) slot antennas with connected ground and high isolation. Two MIMO antennas consist of two parallel slot antenna elements with coplanar waveguide feeds and ground. The antennas are etched on the liquid crystal polymer substrate and have the consistent sizes of 30 × 56 × 0.1 mm3. The first UWB‐MIMO antenna can cover 3–13 GHz. By adding a U‐shaped slot on the first antenna, a second UWB‐MIMO antenna with a notch‐band is designed, which can work in 3.2–13 GHz and filter the wireless fidelity frequency band (5–6 GHz). High isolation better than 20 dB is obtained by adding fence‐shaped branches. In addition, the performance of the flexible MIMO antenna is analyzed, including diversity performance parameters such as envelope correlation coefficient, diversity gain, gain, and total active reflection coefficient. The proposed UWB‐MIMO antenna can be applied in internet of things and wireless body area network frequency bands. [ABSTRACT FROM AUTHOR]

A highly efficient self‐isolated multiple‐input multiple‐output (MIMO) antenna system functioning in the n46 5G NR band (5.15–5.925 GHz) for smartphone implementation is discussed in this paper. The system is made up of two blocks of vertically printed antenna pairs, placed at the exact center of the side frames of the smartphone. Each block comprises of a self‐isolated antenna pair with two inverted L‐shaped radiators facing each other, a T‐shaped isolating element, and a U‐shaped structure placed at the back of the radiators, and is attached to the ground plane. A simple coaxial feeding structure is deployed to excite the L‐shaped radiators. The T‐shaped structure placed between the two radiators has a crucial role in minimizing the mutual coupling between the two radiators, and its arm serves as a radiator. The self‐isolated antenna pair functions from 5.10 to 5.98 GHz, covering the entire n46 band (5.15–5.925 GHz) with over −16.8 dB isolation in the complete operating bandwidth. The parametric investigation of some ideal parameters and the antenna pair evolution stages to obtain the final structure is examined for a superior understanding of the functioning of the proposed MIMO smartphone system. The proposed self‐decoupled antenna pair MIMO system operates with a very high radiation efficiency and gain in the complete operating bandwidth, with radiating efficiency, total efficiency, and peak gain greater than 92%, 85%, and 6 dB respectively. The lowest obtained envelope correlation coefficient (ECC) value is 0.025 between the two elements in the antenna pair, which is very low when compared with the ideal value of 0.5. Various other parameters like channel capacity loss (CCL), mean effective gain (MEG), total active reflection coefficient (TARC), and diversity gain (DG) of the proposed system are also calculated and examined with the experimental results to study the diversity performance of the proposed MIMO smartphone system. A prototype of the proposed 4‐port MIMO smartphone system is fabricated and various parameters are examined. The coherence between the measured and the experimental outcomes stipulates that the proposed system is a capable contender for application in the upcoming 5G handheld devices. [ABSTRACT FROM AUTHOR]

ABSTARCT: In this paper, a high‐isolation eight‐unit multiple‐input multiple‐output (MIMO) array is proposed, which applies to future smartphones with unbroken metal frames. Two types of elements (inverted H‐shaped slot antenna [IHSA] and modified top‐loaded monopole [MTLM]) are adopted to realize low mutual coupling, and the detailed decoupling mechanism is also presented. The IHSA with a better‐reduced ground effect is utilized, which contributes to suppressing mutual coupling. To further enhance isolation, the MTLM without ground clearance is exploited, which cannot excite the radiated mode of the IHSA. To mitigate the effects of an unbroken metal frame, a shorting strip is introduced, which not only improves the impedance matching but also reduces the profile of the MTLM. Ultimately, the proposed MIMO system integrated with an unbroken metal frame is constituted by four IHSAs and four MTLMs, which offers a measured isolation of more than 20 dB. What's more, the calculated envelop correlation coefficients (ECCs) are less than 0.013. [ABSTRACT FROM AUTHOR]

Generalized optical multiple-input multiple-output (GOMIMO) techniques have been recently shown to be promising for high-speed optical wireless communication (OWC) systems. In this paper, we propose a novel deep learning-aided GOMIMO (DeepGOMIMO) framework for GOMIMO systems, wherein channel state information (CSI)-free detection can be enabled by employing a specially designed deep neural network (DNN)-based MIMO detector. The CSI-free DNN detector mainly consists of two modules: one is the preprocessing module, which is designed to address both the path loss and channel crosstalk issues caused by MIMO transmission, and the other is the feedforward DNN module, which is used for joint detection of spatial and constellation information by learning the statistics of both the input signal and the additive noise. Our simulation results clearly verify that, in a typical indoor 4 × 4 MIMO-OWC system using both generalized optical spatial modulation (GOSM) and generalized optical spatial multiplexing (GOSMP) with unipolar nonzero 4-level pulse-amplitude modulation (4-PAM) modulation, the proposed CSI-free DNN detector achieves near the same bit error rate (BER) performance as the optimal joint maximum-likelihood (ML) detector, but with much-reduced computational complexity. Moreover, because the CSI-free DNN detector does not require instantaneous channel estimation to obtain accurate CSI, it enjoys the unique advantages of improved achievable data rate and reduced communication time delay in comparison to the CSI-based zero-forcing DNN (ZF-DNN) detector. [ABSTRACT FROM AUTHOR]

This paper proposes a multiple-input multiple-output (MIMO) terrestrial-satellite laser communication uplink system based on optical spatial modulation with medium-based modulation (OSM-MBM) joint modulation. The Málaga(M) distribution is used to describe the combined effects of near-ground turbulent light intensity scintillation, beam wander and angle of arrival fluctuation. The closed expression of the bit error rate (BER) of the OSM-MBM joint modulation MIMO terrestrial-satellite laser communication uplink is derived. The simulation analyzes the influence of transmitting radius, receiving aperture, beam divergence, zenith angle and signal-to-noise ratio on the system error performance, and compares it with traditional modulation, media-based modulation and optical space modulation. Finally, the experiment is verified by Monte Carlo. This research provides a theoretical reference for the engineering realization of the modulation technology for the MIMO terrestrial-satellite laser communication uplink system. [ABSTRACT FROM AUTHOR]

A 1 × 2 multiple‐input multiple‐output (MIMO) antenna with super‐ultra wideband (super‐UWB) operation and high isolation is proposed. The antenna element has an eye‐shape radiator fed by a tapered shape feedline on the top side and a defected ground structure etched on the bottom ground plane. A high isolation between two radiators is achieved by introducing a T‐shape and two small arm shape stubs at the center of the ground plane. The proposed design was verified by a fabricated prototype and measurement. The measured results show that the MIMO antenna achieves impedance bandwidth of 3 ~ 45 GHz, isolation of 21 dB, and a peak gain of 10.1 dBi. The envelope correlation coefficient is less than 0.02. The overall size of the design is only 0.26λ0L × 0.3λ0L (λ0L is the free space wavelength at 3 GHz). [ABSTRACT FROM AUTHOR]

In this article, a novel self‐decoupling method for closely arranged multi‐unit antenna array design is proposed. The orthogonal mode and the pattern diversity are adopted to weaken the electromagnetic coupling between the multi‐antenna elements. To verify the proposed self‐decoupling concept, a closely arranged 4‐port antenna group consisting of dual antenna pairs is designed. One of the antenna pairs is composed of overlapping loop antenna and monopole, and the other antenna pair shares a radiator, which are arranged on the upper and lower sides of the metal ground respectively. The proposed 4‐port antenna group exhibits good isolation and complementary patterns without adding any extra decoupling structures. Based on the proposed self‐decoupled 4‐port antenna group, a 16 × 16 multiple‐input multiple‐output (MIMO) antenna array is constructed. The simulated and measured results show that the proposed 16 × 16 MIMO array has good antenna performance, such as isolation better than 15 dB, efficiency higher than 51% and channel capacity about 73 bps/Hz with 20 dB SNR. The proposed design concept is a great choice for highly integrated multi‐antenna array and 5G mobile terminal. [ABSTRACT FROM AUTHOR]

With the high availability of low-cost and energy-efficient LEDs and cameras, there is increased interest in optical camera communication (OCC) to provide nonradio-frequency-based communication solutions in the domains of advertisement, vehicular communication, and the Internet of Things (IoT). As per the IEEE 802.15.7-2018 standard, new physical-layer clauses support low-frame-rate camera communication with allowable flickering. This paper proposes an OCC system that can provide user-centric multiple-input multiple-output (MIMO) loosely based on quantum-chromodynamics (QCD) concepts. A QCD–OCC simulator and prototype are proposed, implemented, and evaluated on the basis of the pixel intensity profile, peak signal-to-noise ratio (PSNR), the success of reception (%), bit-error rate (BER), and throughput under different ambient lighting conditions and distances. We observed 100% and 84% success of reception using the proposed prototype and simulator, respectively, for the data rate of 720 bps. The maximal tolerable BER of 1.13 × 10 − 2 for IoT applications was observed at a maximal distance of 200 cm and a maximal data rate of 3600 bps. The proposed system was also compared with other existing OCC systems with similar hardware and implementation requirements. The proposed QCD–OCC system provided rotation support up to 90 degrees and throughput of 4.32 kbps for a 30 fps camera. [ABSTRACT FROM AUTHOR]

A low profile printed dipole antenna (PDA) backed by broadband Giuseppe Peano fractal artificial magnetic conductor (AMC) is introduced for wireless communications. First, a suggested PDA with a pair of microstrip dipoles excited by an E‐shaped microstrip feedline is used to expand the bandwidth in the range of 5.96–7.04 GHz (S11 ≤ −10 dB). Then, the suggested Giuseppe Peano fractal AMC surface as a reflector of the antenna is inserted into the PDA to gain improved radiation efficiency. The PDA with the 6 × 6 Giuseppe Peano AMC array exhibits −10 dB measured impedance bandwidth of 4.95–7.05 GHz (35%) for wireless local area network (WLAN) and worldwide interoperability for microwave access (WiMAX) applications. The suggested PDA with AMC compared to the PDA without AMC exhibits a size reduction of 38%, enhanced gain up to 8.2 dBi, and excellent impedance matching (at least −20 dB) with directional radiation patterns. The novel AMC unit cell is realized based on the Giuseppe Peano fractal patch to operate at 6.10 GHz with an AMC bandwidth of 5.15–7.10 GHz (32%). Besides, by loading 12 × 12 AMC reflector into the four‐element array of PDA, low profile wideband structure with enhanced radiation properties are achieved. The measured results show the broad bandwidths of 5–7 GHz for all elements with enhanced gains and good isolations between the elements (more than 24 dB) for multiple‐input multiple‐output (MIMO) systems. [ABSTRACT FROM AUTHOR]

In modern wireless communication scenarios, non-orthogonal multiple access (NOMA) provides high throughput and spectral efficiency for fifth generation (5G) and beyond 5G systems. Traditional NOMA detectors are based on successive interference cancellation (SIC) techniques at both uplink and downlink NOMA transmissions. However, due to imperfect SIC, these detectors are not suitable for defense applications. In this paper, we investigate the 5G multiple-input multiple-output NOMA deep learning technique for defense applications and proposed a learning approach that investigates the communication system's channel state information automatically and identifies the initial transmission sequences. With the use of the proposed deep neural network, the optimal solution is provided, and performance is much better than the traditional SIC-based NOMA detectors. Through simulations, the analytical outcomes are verified. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Signal Processing is the property of Journal of Signal Processing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

In visible light communication systems, the ability to suppress interference caused by other light sources is a major benefit towards performance improvements. Especially for large transmitter arrays or even multi-cell arrangements, the interference problem needs to be handled. In previous work, we have presented a liquid crystal display (LCD) used as an adaptive interference-suppression filter mounted in front of each photodetector. The display elements are switched on and off in such a way that light emitted by unwanted light sources ideally is blocked, but light emitted by desired light sources reaches the detector. The pattern generated by the LC display has strong impact on the system performance. In this paper, we propose combined precoding in conjunction with LCD-based interference suppression in order to increase the signal-to-interference-plus-noise ratio and to ensure user fairness in massive MIMO scenarios. The suggested precoding strategy uses a new heuristic optimization approach based on the Santa Claus problem on unrelated machines known from computer sciences, and employs only binary entries in the weighting matrix. Corresponding results are compared with a genetic evolutionary optimization strategy and with conventional zero-forcing precoding. Regarding performance evaluation, we perform numerical ray-tracing simulations and present a room-scale VLC testbed for experimental verification. [ABSTRACT FROM AUTHOR]

In this paper, a multiple-input multiple-output (MIMO) communication system with frequency hopping (FH) aided orthogonal frequency division multiplexing differential chaotic shift keying (OFDM-DCSK) modulation is proposed. Our objective is to improve the security of MIMO communication system which is encoded by space time block coding (STBC). In order to combat the eavesdropping or malicious attacks due to the broadcast characteristics of wireless communication system, we propose to use DCSK and FH modules to encrypt the information, and hide the user data in the chaotic sequences, where the initial value of chaotic sequences and the method of generating FH module are only shared among legitimate users. Moreover, we derive the bit error rate (BER) and the secrecy capacity of the scheme in additive white Gaussian noise (AWGN) channel and Rayleigh fading channel. Simulation results show that the proposed scheme can effectively improve the security of MIMO communication system, which can be seen from the BER of eavesdroppers and legitimate users, and the secrecy capacity of the proposed scheme and the benchmark schemes. [ABSTRACT FROM AUTHOR]

Exploitation of massive Multiple-Input Multiple-Output gains for downlink transmission in Millimetre Wave Systems comes at the expense of obtaining accurate channel estimation and computing complexity. Moreover, the fundamental task of massive Multiple-Input Multiple-Output channel estimation is to exploit the characteristics of the channel and sparsity of these multi-antennas systems to simplify complicated spatial structures. We tackle the channel estimation problem in constructing angle domain channel model with multivariate optimization. In the proposed global particle swarm optimization for angle domain aided scheme, the channel estimation design is decoupled into two parts The simulation results are provided to demonstrate the superior performance of the proposed algorithm over the traditional CS-based channel estimation methods. [ABSTRACT FROM AUTHOR]

The THz wireless transmission system based on photonics has been a promising candidate for further 6G communication, which can provide hundreds of Gbps or even Tbps data capacity. In this paper, 144-Gbps dual polarization quadrature-phase-shift-keying (DP-QPSK) signal generation and transmission over a 20-km SSMF and 3-m wireless 2 × 2 multiple-input multiple-output (MIMO) link at 500 GHz have been demonstrated. To further compensate for the linear and nonlinear distortions during the fiber–wireless transmission, a novel joint Deep Belief Network (J-DBN) equalizer is proposed. Our proposed J-DBN-based schemes are mainly optimized based upon the constant modulus algorithm (CMA) and direct-detection least mean square (DD-LMS) equalization. The results indicate that the J-DBN equalizer has better bit error rate (BER) performance in receiver sensitivity. In addition, the computational complexity of the J-DBN-based equalizer can be approximately 46% lower than that of conventional equalizers with similar performance. To our knowledge, this is the first time that a novel joint DBN equalizer has been proposed based on classical algorithms. It is a promising scheme to meet the demands of future fiber–wireless integration communication for low power consumption, low cost, and high capacity. [ABSTRACT FROM AUTHOR]

Reusing the widely deployed multimode fibers (MMFs) in buildings to transmit multiple-input multiple-output (MIMO) signals via mode-division multiplexing (MDM) is an attractive solution to provide low-cost indoor wireless coverage. However, due to the random mode coupling, MMF channel varies over time. In this letter, the MDM-based MMF MIMO channel condition for different fiber lengths is studied. Next, the influence of the fluctuation of channel condition on the outage performance of the MIMO system with zero-forcing receiver is analyzed, in terms of information-theoretic capacity and practical error probability. Finally, by using adaptive coded modulation (according to channel condition), the MDM-based $3 \times 3$ MIMO channel achieves up to 8.62 bit/s/Hz spectral efficiency with 10% outage probability. [ABSTRACT FROM AUTHOR]

In this letter a novel notched multi‐input‐multi‐output (MIMO) flexible slot antenna with a C‐slot is proposed and designed for wireless body area network (WBAN) and Internet of Things (IoT) applications. The proposed antenna is comprised of four similar elements with the feed line of coplanar waveguide (CPW). Antenna is printed on flexible liquid crystal polymer (LCP) substrate with compact dimensions. The proposed UWB‐MIMO slot antenna can operate in range of 2.85–10.85 GHz with notched band from 4.9–6.425 GHz. The achieved notched band can filter the interference of WLAN (5.15–5.825 GHz), by adding an inverted orthogonal branch, great isolation is achieved, which is better than 24 dB over working bands. What's more, the parameters of diversity performance like gain, envelope correlation coefficient (ECC) and diversity gain (DG) are also analyzed. The actual measurement of bending test and the effect of human body indicates that the presented antenna is suitable for WBAN and IoT applications. [ABSTRACT FROM AUTHOR]

An antenna decoupling method based on modal control is proposed in this paper. Different from the previous characteristic mode decoupling methods, which excite one of the characteristic modes from each port, a pair of decoupling modes is excited simultaneously at each port. To validate our method, a head‐to‐head antenna pair is analyzed and designed. According to the characteristic mode analysis, an inductor‐loaded coupled sheet is introduced for the head‐to‐head antenna pair. Thus, the resonant frequencies of decoupling modes can be tuned individually. To further demonstrate the flexibility of our design, an eight‐element multiple‐input multiple‐output (MIMO) antenna composed of two integrated four‐element blocks is designed, fabricated, and measured. The proposed antennas show good impedance matching, isolation, and diversity performance varying from 3.35 to 3.71 GHz. Both simulated and measured results show the 8 × 8 MIMO system can achieve isolations of better than 11.5 dB and envelope correlation coefficients of less than 0.2 of each port. [ABSTRACT FROM AUTHOR]

Vehicular Visible Light Communication (VLC) has recently attracted much interest from researchers and scientists. This technology enables the connectivity between the vehicles and the infrastructures along the road utilizing the Lighting-Emitting-Diodes based vehicle HeadLights (HLs) and TailLights (TLs) as wireless transmitters. This paper investigates the performance of a Vehicle-to-Vehicle VLC system using a Multiple-Input Multiple-Output (MIMO) scheme. Specifically, we establish the MIMO transmission system by using the two HLs of the source vehicle as wireless transmitters and multiple receivers (RXs) installed at the rear of the destination vehicle as wireless receivers. We consider different numbers of RXs, which result in various MIMO configurations, i.e., 2 × 2 , 2 × 3 , and 2 × 4 . We conduct a channel modeling study based on the non-sequential ray-tracing capabilities of the OpticStudio software to obtain the optical channel gain, considering the possibility of both horizontal and vertical displacement between vehicles. We then explore the contribution of each RX in the total received power. In addition, we investigate the effect of weather conditions, modulation orders, and artificial light sources on the bit error rate (BER) performance of the considered MIMO configurations. The obtained results demonstrate that deploying the MIMO with higher orders can significantly enhance the system performance, particularly when there is a lateral shift between the two cars. It has been drawn from our results that the required SNR to achieve a BER of 10 - 4 reduces by 6 dB when 2 × 4 MIMO configuration is deployed compared to the 2 × 2 MIMO configuration. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Signal Processing is the property of Journal of Signal Processing and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

This paper proposes, a 2x2 circularly polarized multiple-input multiple-output antenna with improved impedance bandwidth, axial ratio bandwidth, larger gain, and high isolation. The proposed antenna is used in the design of a compact multi-port multi-element antenna array for Massive MIMO Base Station applications at 5.5GHz. The proposed antenna has four ports and plays an important role in implementing 5G. The proposed hexagonal patch antenna is designed using a suspended substrate technique in which an air gap between ground and substrate is varied to achieve the different bands of 10 dB bandwidth, 3 dB BW, and gain as compared to the previously published methods in the literature. The impedance bandwidth (S11 < -10 dB) over a useful frequency spectrum of 5.18 to 5.86 GHz which covers (5.15-5.35 and 5.72-5.87 ) GHz and (5.48- 5.72) GHz frequency band for WLAN and Wi- MAX application respectively. The proposed antenna has an impedance bandwidth of 680 MHz (12.36%), axial ratio BW of 470 MHz (8.54%), and a gain of more than 7.67 dBi per port. Envelope correlation coefficient < 0.2, diversity gain > 9.8 dBi, and radiation efficiency of 93% are achieved over the working frequency range. The mutual coupling between antenna elements is less than - 22(S21) to -31 dB(S41) for the center-to-center spacing of 0.65λ, where λ is the signal’s wavelength. The CP MIMO antenna is the ultimate candidate for massive MIMO base station application. [ABSTRACT FROM AUTHOR]

In a reconfigurable intelligent surface (RIS) assisted millimeter Wave (mmWave) communication system, the channel coefficient increases exponentially with the number of RIS elements which results in expensive pilot overhead. Most previous works have proposed some channel estimation algorithms for the estimation accuracy of cascaded channels, which have improved the estimation accuracy, but the pilot overhead is discouraging in the estimation process. To improve the channel estimation accuracy with reduced pilot overhead, we propose a two-stage channel estimation protocol by exploiting semi-passive elements and the coherent time difference of the channel, where the quasi-static channel between the base stations (BS) and RIS is estimated at the RIS, and the user (UE)-RIS time-varying channel is estimated at the BS. In the first stage, we formulate the BS-RIS channel estimation as a mathematical optimization problem by an iterative weighting method and then propose a gradient descent (GD)-based algorithm to solve it. In the second stage, we first transform the received the UE-RIS signal model into an equivalent parallel factor (PARAFAC) tensor model and estimate the UE-RIS channel by the least-squares (LS) algorithm. The simulation results show that the proposed method has better estimation accuracy than the LS, compression sensing (CS) and minimum mean square error (MMSE) methods with less pilot overhead, and the spectral efficiency is improved by at least 10.5% compared to the other three methods. [ABSTRACT FROM AUTHOR]