Millimeter-wave MIMO Research Articles

3-D High-Resolution Imaging and Array Calibration of Ground-Based Millimeter-Wave MIMO Radar

3-D High-Resolution Imaging and Array Calibration of Ground-Based Millimeter-Wave MIMO Radar

Dual-Band Millimeter-Wave MIMO Antennas For 5G Wireless Implementation

For 5G wireless applications, this exploration proposes a dual-band 28/38 GHz 4-component MIMO array depending on duplex-mode planar monopole antennas. Four planar monopole antennas are part of the layout framework, situated at the districts of a Rogers RO4003 substrate measuring 20 by 20 mm2 and with a dielectric constant of 3.55. The form of the suggested placoid monopole antenna is crescent-shaped. We created a notch at the bottom and inscribed two rectangular holes on each side to get the required behaviour and execution. For enhancement of isolation, we also employed a limited ground plane. Antenna elements can achieve significant isolation (> − 23 dB) using spatial and scattering behaviour approaches. A illustration of the four-element MIMO array is created, manufactured, and measured to multifariousness the outline idea. The investigational outcomes demonstrate that the suggested antenna has strong isolation and high efficiency while covering the 27.25–29 GHz and 34.5–41 GHz bands. Additionally, studies are done on the channel capacity, realized gain, and radiation pattern. The obtained findings suggest that, for millimeter-wave 5G MIMO implementation, the proposed MIMO antenna might be an excellent application-oriented design.

Energy Efficiency Analysis and Optimization for Millimeter-Wave MIMO With Variable-Resolution ADCs

Energy Efficiency Analysis and Optimization for Millimeter-Wave MIMO With Variable-Resolution ADCs

Bayesian Bilinear Inference for Joint Channel Tracking and Data Detection in Millimeter-Wave MIMO Systems

Bayesian Bilinear Inference for Joint Channel Tracking and Data Detection in Millimeter-Wave MIMO Systems

PRINCE: A Pruned AMP Integrated Deep CNN Method for Efficient Channel Estimation of Millimeter-Wave and Terahertz Ultra-Massive MIMO Systems

Millimeter-wave (mmWave) and Terahertz (THz)-band communications exploit the abundant bandwidth to fulfill the increasing data rate demands of 6G wireless communications. To compensate for the high propagation loss with reduced hardware costs, ultra-massive multiple-input multiple-output (UM-MIMO) with a hybrid beamforming structure is a promising technology in the mmWave and THz bands. However, channel estimation (CE) is challenging for hybrid UM-MIMO systems, which requires recovering the high-dimensional channels from severely few channel observations. In this paper, a Pruned Approximate Message Passing (AMP) Integrated Deep Convolutional-neural-network (DCNN) CE (PRINCE) method is firstly proposed, which enhances the estimation accuracy of the AMP method by appending a DCNN network. Moreover, by truncating the insignificant feature maps in the convolutional layers of the DCNN network, a pruning method including training with regularization, pruning and refining procedures is developed to reduce the network scale. Simulation results show that the PRINCE achieves a good trade-off between the CE accuracy and significantly low complexity, with normalized-mean-square-error (NMSE) of -10 dB at signal-to-noise-ratio (SNR) as 10 dB after eliminating 80% feature maps.

Wideband Millimeter-Wave MIMO Antenna with a Loaded Dielectric Cover for High-Gain Broadside Radiation

In a millimeter-wave terminal device, the use of a radome degrades the radiating performance of the broadside antenna, especially for the MIMO antenna system. In this study, a dielectric cover is de-signed and investigated to enhance the broadside gain of a millimeter-wave MIMO antenna, while keeping its wideband and high isolation performance. Firstly, a compact wideband ladder-shaped slot antenna is proposed with 21.9% bandwidth. The effectiveness of the dielectric cover design criteria over the wideband antenna is investigated. Then, this wideband antenna element is expanded to a 2 × 2 MIMO antenna by forming a center-symmetric structure and isolating it via the inserted metal vias. By loading the dielectric cover, this millimeter-wave MIMO antenna is verified with enhanced broadside gain for more than 2.1 dB. With the measured impedance bandwidth of 21.9% (57.0–71.0 GHz), peak broadside gain of 12.3 dBi, and high isolation over 15 dB, the proposed MIMO antenna is suitable for wireless gigabit terminal devices.

A Novel 3D ArcSAR Sensing System Applied to Unmanned Ground Vehicles

Microwave radar has advantages in detection accuracy and robustness, and it is an area of active research in unmanned ground vehicles. However, the existing conventional automotive corner radar, which employs real-aperture antenna arrays, has limitations in terms of observable angle and azimuthal resolution. This paper proposes a novel 3D ArcSAR method to address this issue, which combines rotational synthetic aperture radar (SAR) and direction estimation algorithms. The method aims to reconstruct 3D images of 360° scenes and offers distinctive advantages in both azimuthal and altitudinal sensing. Nevertheless, due to the unique structural characteristics of vehicle SAR, it is limited to receiving only a single snapshot signal for 3D sensing. We propose a resolution algorithm based on ArcSAR and the iterative adaptive approach (IAA) to resolve the limitation. Furthermore, the errors in altitude angle estimation of the proposed algorithm and conventional algorithms are analyzed under various conditions, including different target spacing and signal-to-noise ratio (SNR). Finally, we design and implement a prototype of the 3D ArcSAR sensing system, which utilizes a millimeter-wave MIMO radar system and a rotating scanning mechanical system. The experimental results obtained from this prototype effectively validate the effectiveness of the proposed method.

Low-Profile Polarization-Twisting Cassegrain Antenna for Generating Dual Circularly Polarized Multibeam Radiation in Ku-Band

In this paper, a low-profile polarization-twisting Cassegrain antenna (LPPTCA) is proposed to generate dual circularly polarized (CP) multi-beam radiation by integrating multifunctional metasurface (MM), polarization conversion metasurface (PCM), and multiple microstrip feeds. Considering that the LPPTCA removes the occlusion effect from the traditional Cassegrain antenna, the profile height of LPPTCA will be chosen as 1/3 focal length of PCM and can also be freely adjusted when employing corresponding phase gradient over the MM to mimic the hyperbolic reflector of the traditional Cassegrain antenna. The MM is capable of achieving the functionality of reflecting co-LP waves with performing diverged wave-fronts and transmitting cross-LP waves with linear-to-dual-circular polarization conversion. Based on the MM and PCM, the LPPTCA is designed and fabricated, then measurement results illustrate that the LPPTCA is capable of realizing dual CP multi-beam radiation in the range of 13.7 - 14.7 GHz when employing multiple microstrip antennas as feeds. In the meanwhile, the scanning range of multi-beams is ±20° with the minimum feed isolation of 15 dB. The proposed dual CP multi-beam LPPTCA integrating the MM and PCM should thus pave the way for building up current and future wireless communication systems with millimeter-wave MIMO applications in Ku-band.

Research on Joint Beamforming of High-Speed Railway Millimeter-wave MIMO Communication with Reconfigurable Intelligent Surface

The advantage of a reconfigurable intelligent surface (RIS) is that it optimizes the wireless signal transmission environment. It can ameliorate the high loss of high-speed railway (HSR) millimeter-wave (mmWave) communications and increase signal strength by coherently superimposing signals at the receiving end through an appropriate beamforming design. In this paper, an mmWave multiple-input multiple-output communication system for HSR is discussed. The channel modeling takes into account the Doppler effect and the properties of mmWave channels. Aiming at the problem of high coupling of optimization variables, the singular value decomposition method is utilized to decouple them and to achieve the optimal active beamforming design. The original optimization problem is then rewritten into a more manageable form through a sequence of transformations. In order to overcome the restrictions imposed by non-convex constraints, the optimal RIS phase shift is directly calculated using the Riemann gradient descent (RGD) method. In this paper, spectral efficiency (SE) is taken as the optimization objective. Considering the fast time-varying environment of HSR, a step size selection scheme with easier convergence is adopted in the RGD method to complete the joint beamforming design. The numerical simulations demonstrate that the proposed solution outperforms the semi-definite relaxation scheme and the RIS-free auxiliary scheme in terms of SE performance and computational complexity.

Simultaneous Beam and User Selection for the Beamspace mmWave/THz Massive MIMO Downlink

Beamspace millimeter-wave (mmWave) and terahertz (THz) massive MIMO constitute attractive schemes for next-generation communications, given their abundant bandwidth and high throughput. However, their user and beam selection problem has not been efficiently addressed yet. Inspired by this challenge, we develop low-complexity solutions explicitly. In contrast to the zero forcing in the prior art, we introduce the dirty paper coding (DPC) into the joint user and beam selection problem. We unveil the compelling properties of the DPC sum rate in beamspace massive MIMO, showing its monotonic evolution against the number of users and beams selected. We then exploit its beneficial properties for substantially simplifying the joint user and beam selection problem. Furthermore, we develop a set of algorithms striking unique trade-offs for solving the simplified problem, facilitating simultaneous user and beam selection based on partial beamspace channels for the first time. Additionally, we derive the sum rate bound of the algorithms and analyze their complexity. Our simulation results validate the effectiveness of the proposed design and analysis, confirming their superiority over prior solutions.

Ergodic Achievable Rate Analysis and Optimization of RIS-Assisted Millimeter-Wave MIMO Communication Systems

Reconfigurable intelligent surfaces (RISs) have emerged as a prospective technology for next-generation wireless networks due to their potential in coverage and capacity enhancement. Previous works on achievable rate analysis of RIS-assisted communication systems have mainly focused on the rich-scattering environment where Rayleigh and Rician channel models can be applied. This work studies the ergodic achievable rate of RIS-assisted multiple-input multiple-output communication systems in millimeter-wave band with limited scattering under the Saleh-Valenzuela channel model. Firstly, we derive an upper bound of the ergodic achievable rate by means of majorization theory and Jensen's inequality. The upper bound shows that the ergodic achievable rate increases logarithmically with the number of antennas at the base station (BS) and user, the number of the reflection units at the RIS, and the eigenvalues of the steering matrices associated with the BS, user and RIS. Then, we aim to maximize the ergodic achievable rate by jointly optimizing the transmit covariance matrix at the BS and the reflection coefficients at the RIS. Specifically, the transmit covariance matrix is optimized by the water-filling algorithm and the reflection coefficients are optimized using the Riemannian conjugate gradient algorithm. Simulation results validate the effectiveness of the proposed optimization algorithms.

2-Port High Gain Millimeter-wave MIMO Antenna for 5G Applications

2-Port High Gain Millimeter-wave MIMO Antenna for 5G Applications

Wideband mmWave MIMO: One Prior-Aided LAMP-Based Network Combining with Residual Learning for Beamspace Channel Estimation

Existing channel estimation schemes for wideband systems generally estimate the channel matrix by pre-estimating the common support, which has a limited validity owing to the effect of beam squint. It is worth noting that the learned approximate message passing (LAMP) network need not pre-estimate the support and has obtained a relatively reliable estimation quality in the narrowband systems. In order to degrade the performance penalty caused by inaccurate estimation of the support in the wideband millimeter-wave MIMO systems, a prior-aided Gaussian mixture LAMP (GM-LAMP) network combining with residual learning is presented. Specifically, the multicarrier Gaussian mixture threshold shrinkage function is constructed for the GM-LAMP network, which can directly estimate the wideband beamspace channel while avoiding pre-estimating the support; then, considering the impact of channel noise and the coarse estimation error by the GM-LAMP, a residual network (ResNet) is designed to improve the estimation performance. Simulation results validate the efficiency of the proposed network (referred to as GLAMP-ResNet) with the lower computational complexity compared with the existing schemes.

Analysis of OSTBC-OFDM Combined with Dual-Polarization and Time-Diversity in Millimeter-Wave MIMO Channels with Rain Distortions.

Various destructive weather and physical phenomena affect many parameters in the radio layer (i.e., affecting the wireless paths Over-The-Air (OTA)) of many outdoor-to-outdoor wireless systems. These destructive effects create polarization torsion and rotation of the signals propagating in space and cause the scattering of wireless spatial paths. The direct meaning is a significant degradation in system performance, especially in the Quality-of-Service (QoS). Under these challenging scenarios, intelligent utilization of advanced Multiple-Input-Multiple-Output (MIMO) techniques such as polarization-diversity and time-diversity at the transmitter, as well as at the receiver, and intelligent use of the Cross-Polarization-Isolation (XPI) mechanism, are essential. We prove that combining these techniques with the tuning of the XPI of the antennas creates optimal conditions in the wireless MIMO channels. This combination does not only improve the system’s performance, but also turns the destructive physical phenomena in the spatial-domain, into an advantage. In this article, we focus on formulating a wireless communication MIMO model in millimeter-Wave (mmWave) channels under rain distortions. We demonstrate the optimal use of combining Orthogonal-Space-Time-Coding (OSTBC) and Maximal-Ratio-Receive-Combiner (MRRC) with cross-polarization diversity techniques, that utilize the tuning of the XPI. An analytical exact optimal solution is proposed, that allows the tuning of the leading parameters to achieve global optimal performance, in terms of channel-capacity and Bit-Error-Rate (BER). In addition, we propose a process of approximation of feedback-closed-loop-MIMO. The feedback is employed between the transmitter and the receiver, in the scenario of changes in the channel-response-matrix in-between successive symbol-times. The feedback was designed to acheive global-maximum channel-capacity, while preserving the channel-path orthogonality in order to minimize the BER.

Estimation of Channel for Millimeter-Wave Hybrid Massive MIMO Systems using Orthogonal Matching Pursuit (OMP)

In a millimeter-wave (mm-Wave) large MIMO system, hybrid precoding is a critical component for lowering radio-frequency hardware costs as compared to the traditional full-digital precoding strategy. Knowledge of channels is required for hybrid precoding. Though, estimation of the channel is problematic for the mm-Wave system because of the usage of a massive array of antenna and hybrid architecture with analog precoding. Due to the extremely directed nature of wireless propagation, wireless channels have spatial sparsity. In this paper, we exploit this spatial sparsity nature of wireless channels to develop orthogonal matching pursuit technique-based estimation of channels for hybrid millimeter-wave (mm-Wave) wireless systems. Genie (Ideal) channel estimation is also performed in which we presume that actual angle of departures (AoD) and angle of arrivals (AoA) are known to us. Finally, the simulation results reveal that suggested OMP algorithm-based channel estimation has a significant advantage over conventional approaches like least-squares channel estimation.

Joint User Grouping and Beam Selection for Beamspace mmWave Multi-User MIMO System

Lens antenna arrays based beamspace millimeter-wave multi-user massive MIMO (B-MIMO) can significantly improve energy efficiency without significant loss of spectral efficiency (SE), which is considered as a highly expected technology for future wireless communication networks. Motivated by the requirement of reducing SE loss by efficient user grouping (UG) and beam selection (BS), a joint user grouping and beam selection algorithm is studied. Specifically, a local search based BS algorithm is proposed by proving the convexity of the BS problem after relaxing the constraints. Moreover, a deep learning based UG algorithm is proposed by equivalently transforming the UG problem into a classification problem. The results of theoretical analysis and numerical simulation show that the proposed algorithms can be more closely with the performance of the exhaustive search algorithm and the complexity is lower than that of the traditional algorithms.

Design and Development of Novel Hybrid Precoder for Millimeter-Wave MIMO System

Power consumption and hardware cost reduction with the use of hybrid beamforming in large-scale millimeter wave MIMO systems. The large dimensional analog precoding integrates with the hybrid beamforming based on the phase shifters including digital precoding with lower dimensionality. The reduction of Euclidean distance between the hybrid precoder and fully digital is the major problem to overcome the minimization of resultant spectral efficiency. The issue formulates as a fully digital precoder’s matrix factorization problem based on the analog RF precoder matrix and the digital baseband precoder matrix. An additional element-wise unit modulus constraint is imposed by the phase shifters on the analog RF precoder matrix. The traditional methods have a problem of performance loss in spectral efficiency. In the processing time and iteration, high complexities result in optimization algorithms. In this paper, a novel low complexity algorithm proposes which maximizes the spectral efficiency and reduces the computational processing time.

1-Bit Polarization Rotating and Beam-Switching Transmitarray for Millimeter Wave MIMO Applications

This paper presents a low profile, 1-bit phase quantized, polarization rotating (PR), and switchable beam transmitarray for millimeter-wave (29.7–30.7GHz) MIMO applications. The transmitarray is based on polarization rotating elements, designed on two substrate layers and have a volume of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$0.21\lambda _{0} \times 0.21\lambda _{0} \times 0.304\lambda _{0}$ </tex-math></inline-formula> ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{0}$ </tex-math></inline-formula> is corresponding to frequency at 30GHz). The polarization rotating elements have low insertion loss of 2.5dB in the frequency band of 29.5 GHz −39.5GHz with a phase difference of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\pi $ </tex-math></inline-formula> between two phase quantized bits and thus exhibit a wideband nature. The transmit panel is designed using 29 x 29 phase quantized unit cells and a 3-port patch MIMO antenna operating around 30GHz is used as a feed element to achieve one dimensional beam-switching (BS) of ±13° with respect to the broadside direction.The focal distance between the center feed element and the transmitarray panel is 30 mm with the maximum dimension of the panel as 60.9 mm giving an f/d ratio of 0.49. The MIMO antenna system has a port to port isolation greater than 30dB in the operating frequency band which is obtained by keeping the inter-element spacing as <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\lambda _{0}$ </tex-math></inline-formula> . The transmitarray prototype is fabricated and measured. The simulated and measured results are found to be in close agreement. A peak gain of 19.3dBi with a switching loss of 1dB, 3dB beamwidth of 10.1° and aperture efficiency of 21% are obtained in measurement. The wideband nature of the transmitarray is validated by feeding the surface with a wideband (26.5GHz−40 GHz) horn antenna. The switchable beam transmitarray can be used for beam-forming in base stations for future 5G millimeter wave communications.

A High Isolation, Low-Profile, Triple-Port SIW Based Annular Slot Antenna for Millimeter-Wave 5G MIMO Applications

This paper presents a compact, triple-port, millimeter-wave (mm-wave) substrate-integrated waveguide (SIW) based annular slot antenna. The presented antenna was fabricated on a single dielectric layer, 30 mil TLY-5 substrate with a standard PCB process. Measurement results show that, the proposed antenna can achieve better than 30 dB isolation between the ports at 28 GHz, thanks to carefully tuned distances between the ports and &#x007E;90% radiation efficiency. Furthermore, it has 4.7 dBi and 8 dBi radiation gain at 28 GHz for single-port and double-port excitation cases respectively. Because of its easy integration and the high isolation between the ports, the presented antenna can be a promising candidate to be used as a monostatic simultaneous transmit and receive (STAR) antenna. In addition, depending on application, it can also be directly adopted to a 5G phased array system in either transmitter or receiver, without requiring physical modification.

Design and Development of Novel Hybrid Precoder for Millimeter-Wave MIMO System

Power consumption and hardware cost reduction with the use of hybrid beamforming in large-scale millimeter wave MIMO systems. The large dimensional analog precoding integrates with the hybrid beamforming based on the phase shifters including digital precoding with lower dimensionality. The reduction of Euclidean distance between the hybrid precoder and fully digital is the major problem to overcome the minimization of resultant spectral efficiency. The issue formulates as a fully digital precoder’s matrix factorization problem based on the analog RF precoder matrix and the digital baseband precoder matrix. An additional element-wise unit modulus constraint is imposed by the phase shifters on the analog RF precoder matrix. The traditional methods have a problem of performance loss in spectral efficiency. In the processing time and iteration, high complexities result in optimization algorithms. In this paper, a novel low complexity algorithm proposes which maximizes the spectral efficiency and reduces the computational processing time.