Off-Grid Compressed Channel Estimation with Parallel Interference Cancellation for Millimeter Wave Massive MIMO

Millimeter wave(mmWave)massive multiple-input multiple-output(MIMO)plays an important role in the fifth-generation(5G)mobile communications and beyond wireless communication systems owing to its potential of high capacity.However,channel estimation has become very challenging due to the use of massive MIMO antenna array.Fortunately,the mmWave channel has strong sparsity in the spatial angle domain,and the compressed sensing technology can be used to convert the original channel matrix into the sparse matrix of discrete angle grid.Thus the high-dimensional channel matrix estimation is transformed into a sparse recovery problem with greatly reduced computational complexity.However,the path angle in the actual scene appears randomly and is unlikely to be completely located on the quantization angle grid,thus leading to the problem of power leakage.Moreover,multiple paths with the random distribution of angles will bring about serious interpath interference and further deteriorate the performance of channel estimation.To address these off-grid issues,we propose a parallel interference cancellation assisted multi-grid matching pursuit(PIC-MGMP)algorithm in this paper.The proposed algorithm consists of three stages,including coarse estimation,refined estimation,and inter-path cyclic iterative inter-ference cancellation.More specifically,the angular resolution can be improved by locally refining the grid to reduce power leakage,while the inter-path interference is eliminated by parallel interference cancellation(PIC),and the two together improve the estimation accuracy.Simulation results show that compared with the traditional orthogonal matching pursuit(OMP)algorithm,the normalized mean square error(NMSE)of the proposed algorithm decreases by over 14dB in the case of 2 paths.

An ISGW Filtering Antenna with Spurious Modes and Surface Wave Suppression for Millimeter Wave Communications

In this paper,an integrated substrate gap waveguide(ISGW)filtering antenna is proposed at millimeter wave band,whose surface wave and spurious modes are simultaneously suppressed.A secondorder filtering response is obtained through a coupling feeding scheme using one uniform impedance resonator(UIR)and two stepped-impedance resonators(SIRs).To increase the stopband width of the antenna,the spurious modes are suppressed by selecting the appropriate sizes of the ISGW unit cell.Furthermore,the ISGW is implemented to improve the radiation performance of the antenna by alleviating the propagation of surface wave.And an equivalent circuit is investigated to reveal the working principle of ISGW.To demonstrate this methodology,an ISGW filtering antenna operating at a center frequency of 25 GHz is designed,fabricated,and measured.The results show that the antenna achieves a stopband width of 1.6f0(center frequency),an out-of-band suppression level of 21 dB,and a peak realized gain of 8.5 dBi.

Cubature Kalman Filter Based Millimeter Wave Beam Tracking for OTFS Systems

In this paper,a Millimeter wave(mmWave)beam tracking problem is studied in orthogonal time frequency space(OTFS)systems.Considering the nonlinearity of beamforming and the constraints of existing Kalman-filtering based beam tracking schemes,we propose a novel Cubature Kalman Filter(CKF)framework tracking the channel state information(CSI)to manage the challenge of highspeed channel variation in single-user moving scene for OTFS systems.Aiming for low complexity for mobile settings,this paper trains only one beam pair to track a path to maintain the reliable communication link in the analog beamforming architecture.Simulation results show that our proposed method has better tracking performance to improve the accuracy of the estimated beam angle compared with prior work.

High-Accuracy NLOS Identification Based on Random Forest and High-Precision Positioning on 60 GHz Millimeter Wave

60 GHz millimeter wave(mmWave)system provides extremely high time resolution and multipath components(MPC)separation and has great potential to achieve high precision in the indoor positioning.However,the ranging data is often contaminated by non-line-of-sight(NLOS)transmission.First,six features of 60GHz mm Wave signal under LOS and NLOS conditions are evaluated.Next,a classifier constructed by random forest(RF)algorithm is used to identify line-of-sight(LOS)or NLOS channel.The identification mechanism has excellent generalization performance and the classification accuracy is over 97%.Finally,based on the identification results,a residual weighted least squares positioning method is proposed.All ranging information including that under NLOS channels is fully utilized,positioning failure caused by insufficient LOS links can be avoided.Compared with the conventional least squares approach,the positioning error of the proposed algorithm is reduced by 49%.

Compressive near-field millimeter wave imaging algorithm based on Gini index and total variation mixed regularization

A compressive near-field millimeter wave(MMW)imaging algorithm is proposed.From the compressed sensing(CS)theory,the compressive near-field MMW imaging process can be considered to reconstruct an image from the under-sampled sparse data.The Gini index(GI)has been founded that it is the only sparsity measure that has all sparsity attributes that are called Robin Hood,Scaling,Rising Tide,Cloning,Bill Gates,and Babies.By combining the total variation(TV)operator,the GI-TV mixed regularization introduced compressive near-field MMW imaging model is proposed.In addition,the corresponding algorithm based on a primal-dual framework is also proposed.Experimental results demonstrate that the proposed GI-TV mixed regularization algorithm has superior convergence and stability performance compared with the widely used l1-TV mixed regularization algorithm.

Non-intrusive soil carbon content quantification methods using machine learning algorithms:A comparison of microwave and millimeter wave radar sensors

Agricultural and forestry biomass can be converted to biochar through pyrolysis gasification,making it a significant carbon source for soil.Applying biochar to soil is a carbon-negative process that helps combat climate change,sustain soil biodiversity,and regulate water cycling.However,quantifying soil carbon content conventionally is time-consuming,labor-intensive,imprecise,and expensive,making it difficult to accurately measure in-field soil carbon’s effect on storage water and nutrients.To address this challenge,this paper for the first time,reports on extensive lab tests demonstrating non-intrusive methods for sensing soil carbon and related smart biochar applications,such as differentiating between biochar types from various biomass feedstock species,monitoring soil moisture,and biochar water retention capacity using portable microwave and millimeter wave sensors,and machine learning.These methods can be scaled up by deploying the sensor in-field on a mobility platform,either ground or aerial.The paper provides details on the materials,methods,machine learning workflow,and results of our investigations.The significance of this work lays the foundation for assessing carbon-negative technology applications,such as soil carbon content accounting.We validated our quantification method using supervised machine learning algorithms by collecting real soil mixed with known biochar contents in the field.The results show that the millimeter wave sensor achieves high sensing accuracy(up to 100%)with proper classifiers selected and outperforms the microwave sensor by approximately 10%–15%accuracy in sensing soil carbon content.

Submillimeter wave communication versus millimeter wave communication

This paper studies the performance of a submillimeter wave antenna operating between frequencies 0.1 THz and 10 THz with a 4-cyano-4-pentylbiphenyl[5CB]substrate.Since the size and shape of the antenna impact its gain/directivity,resonant frequency,bandwidth,and efficiency,the two antenna types considered in this paper are:(a)Rectangular Patch Antenna(RPA),and(b)Cylindrical Dielectric Resonator Antenna(CDRA).Here a submillimeter wave antenna is compared with a millimeter wave(a few GHz to 100 GHz)antenna.These popular mmwave antennas are chosen for the submillimeter wave antenna in order to understand changes in their performance as the result of changes in their geometrical shape.FEldberechnung bei Korpern mit beliebiger Oberflache(FEKO)software is used for the design and calculation of the Three-Dimensional(3D)ElectroMagnetic(EM)patterns.This paper also concentrates on the design and analysis of a massive submillimeter wave Multiple-Input Multiple-Output(MIMO)(8 by 8)RPA and CDRA.

Cell-type continuous electromagnetic radiation system generating millimeter waves for active denial system applications

The cell-type continuous electromagnetic radiation system is a demonstration device capable of generating high-power millimeter electromagnetic waves of a specific wavelength and observing their effects on living organisms.It irradiates a biological sample placed in a 30×30×50 cm^(3)cell with electromagnetic waves in the 3.15-mm-wavelength region(with an output of≥1 W)and analyzes the temperature change of the sample.A vacuum electronic device-based coupled-cavity backward-wave oscillator converts the electron energy of the electron beam into radiofrequency(RF)energy and radiates it to the target through an antenna,increasing the temperature through the absorption of RF energy in the skin.The system causes pain and ultimately reduces combat power.A cell-type continuous electromagnetic radiation system consisting of four parts—an electromagnetic-wave generator,a highvoltage power supply,a test cell,and a system controller—generates an RF signal of≥1 W in a continuous waveform at a 95-GHz center frequency,as well as a chemical solution with a dielectric constant similar to that of the skin of a living organism.An increase of 5°C lasting approximately 10 s was confirmed through an experiment.

Ultra-Wideband Annular Ring Fed Rectangular Dielectric Resonator Antenna for Millimeter Wave 5G Applications

In this article an ultra-wideband rectangular Dielectric Resonator Antenna is designed for millimeter wave 5G frequency band applications.Indoor 5G communications require antenna system with wide bandwidth and high efficiency to enhance the throughput in the channel.To fulfill such requirements a Dielectric Resonator Antenna(DRA)is designed here which has achieved an ultra-wide bandwidth of 20.15%(22.32–27.56 GHz)which is 5.24 GHz of bandwidth centered at 26 GHz as resonating frequency.This covers the complete band 30(24.3–27.5 GHz)of 5G spectrum.26 and 28 GHz are considered as most popular frequencies in millimeter wave 5G communications.The aperture fed DRA designed here has also achieved an efficiency of 96 percentage with maximum radiation in the broadside direction(Phi=0,Theta=0).The measured gain of the DRA is 6.3 dB.The DRA designed here has dimensions of 0.25λ0×0.22λ0×0.12λ0.under the characteristic’s mode.The DRA is placed over a substrate with dimensions 0.5λ0×0.5λ0×0.02λ0.A cross slot aperture has been made on the ground plane which is placed above to the substrate.Here a full ground plane is used to resonate the antenna and is of similar dimension to the substrate.A microstrip line with two concentric rings makes an annular feed structure is used to excite the DRA and is placed below the substrate.The DRA is excited here in characteristics mode TE1Y1 and is the only mode of excitation.The DRA is linearly polarized,and the characteristic mode of excitation is maintained with 50 Ohm input impedance of the antenna.The DRA also gives here a good difference between the co-pol and cross pol approximately 15 to 20 dB.This antenna is more suitable for 5G indoor applications in millimeter wave frequency band centered at 26 GHz.

A Method for Improving Ranging Accuracy of Short-range Millimeter Wave Radar

The range-velocity ambiguity caused by moving target influences on the ranging accuracy of a short-range millimeter wave radar greatly.A new method was presented in this paper to reduce the range-velocity ambiguity and improve the ranging accuracy by estimating parameters of the echo signal with fractional Fourier transform and self-correlation.And,a new quick searching algorithm was given also to increase the calculation speed.Compared to the Chinese remainder theorem method,the proposed method is excellent for its simplicity and reducing the computation complexity.The simulation results show its validity.

Multi-Hop Transmission Method of 5G Millimeter Wave Relay Based on Network Coding

With the rapid development of the Internet technology,millimeter wave(mmWave)will be used as a supplement to 5G low frequency bands to meet the extremely high system capacity requirements of 5G in hot spots.Although 5G mmWave communication can adapt to the needs of 5G network and carry a large amount of transmitted data,transmission stability has become one of the key technical issues of 5G network mmWave communication due to problems such as strong attenuation and poor penetration of mmWave.In order to improve the efficiency of the mmWave multi-hop transmission,we propose a 5G mmWave multi-hop transmission method based on network coding,which can adapt to the current wireless network environment,improve spectrum efficiency and increase network throughput.Based on MATLAB simulation experiments,it is verified that the proposed method can greatly improve the transmission efficiency and reduce the signal loss under the premise of ensuring the accurate signal transmission.

A robust beam tracking scheme for millimeter wave HetNets

Millimeter Wave(mmWave)communication has been widely acknowledged as an attractive solution to address high-speed transmission of massive data in 5G and beyond 5G systems due to the promising spectrum availability.However,mmWave signals are highly susceptible to blockage and may suffer from rapidly changing channels.Thus,directional/beam tracking becomes imperative yet essential for robust mmWave communications.To address this challenge,we propose a robust beam tracking scheme for mmWave Heterogeneous Networks(HetNets)with multi-connectivity.Different from most existing schemes,the proposed beam tracking scheme is effective for outage events.We first discuss theμWave-assisted beam tracking procedure with and without candidate beams,and then analyze the inherent correlation between mmWave link quality and the operating beamwidth and occlusion range to derive the optimal beamwidth.Theoretical and numerical results show that the proposed beam tracking scheme can improve the robustness of mmWave communications while guaranteeing the rate performance.

Linearly Polarized Millimeter Wave Reflectarray with Mutual Coupling Optimization

This work provides the design and analysis of a single layer,linearly polarized millimeter wave reflectarray antenna with mutual coupling optimization.Detailed analysis was carried out at 26GHz design frequency using the simulations of the reflectarray unit cells as well as the periodic reflectarray antenna.The simulated results were verified by the scattering parameter and far-fieldmeasurements of the unit cell and periodic arrays,respectively.Aclose agreement between the simulated and measured results was observed in all the cases.Apart from the unit cells and reflectarray,the waveguide and horn antenna were also fabricated to be used in the measurements.The measured scattering parameter results of the proposed circular ring unit cells provided a maximum reflection loss of 2.8 dB with phase errors below 10°.On the other hand,the measured far-field results of the 20×20 reflectarray antenna provided a maximum gain of 26.45 dB with a maximum 3 dB beam width of 12°and 1 dB gain drop bandwidth of 13.1%.The performance demonstrated by the proposed reflectarray antenna makes it a potential candidate to be used in modern-day applications such as 5th Generation(5G)and 6th Generation(6G)communication systems.

Status Quo and Prospect of Millimeter Wave RoF Communication Technology

The optical communication technology features low cost,wide band,low loss,and anti-electromagnetic interference performance.By combining the optical communication technology with the radio millimeter wave communication system,the Millimeter Wave Radio over Fiber (MM-RoF) system boasts a lot of advantages,including wide band,small size,light weight,low cost,low loss,and resistance of electromagnetic interference as well as high transmission quality.The MM-RoF technology solves the problems faced by traditional microwave transmission system at the millimeter wave band,namely,high loss and inability to resist interference efficiently.Meanwhile,it puts an end to the bottleneck of millimeter wave electronic devices and thus is deemed as with great potentials.The MM-ROF technology that supports multiple formats and services signifies one of the significant trends for future development of the MM-RoF system.

Plasma Simulation of Dielectric-lined Multiwave Cerenkov Generators Producing High Power Millimeter Waves

This paper presents the concept of a Dielectric-lined Multiwave Cerenkov Generator producing high power millimeter waves, which has been investigated with a two and onehalf dimensional electromagnetic relativistic Particle-in-Cell (PIC) plasma simulation code. Themodified device can operate in a lower diode-voltage regime with much higher radiation efficiencyand slight downshift of operation frequency. There exist the optima for the permittivity of thedielectric liner and for the magnitude of the guiding magnetic field. The required intensity of theguiding field is reduced by the introduction of the liner. The enhanced propagation of the electronbeam is studied in the presence of the liner.

Indoor Environment and Human Sensing via Millimeter Wave Radio:A Review

With the rapid development of 5G technology,more and more attention has been attracted to mmWave sensing.As an emerging sensing medium,mmWave has the advantages of both high sensitivity and precision.Different from its networking applications,the core method of mmWave sensing is to analyze the reflected signal changes containing the relevant information of different surrounding environments.In this paper,we conduct a systemic review for mmWave sensing.We first summarize the prior works on environmental sensing with different signal analysis methods.Then,we classify and discuss the work of sensing humans,including their behavior and gestures.Finally,we discuss and put forward more possibilities of mmWave human perception.

Millimeter Wave Reconfigurable Metasurface Intelligent Reflecting Surface Based on Piezoelectric Crystal for 5th and 6th Generation of Wireless Communication

The new requirements from the 5th and the 6th generation of wireless communication are ultra-high data rate, energy efficiency, wide coverage and connectivity, high reliability, and low latency. The current technologies cannot achieve all the mentioned requirements. New technologies and new approaches for deploying more active and passive nodes must be developed. Furthermore, the use of MMW band and THz band (30 - 300 GHz), in order to utilize their huge bandwidth, results in deploying more active node and more antennas due to high propagation losses and “LOS” behavior at this band. Development of innovative technologies is necessary to realize the above demand for growth of future wireless communication. The main task is to suggest solutions for the time varying characteristic of the wireless channel due to the user mobility and shadowing or blocking of communication channel. The current methods such as use of pilot channel to estimate the fading, various modulation or coding and beamforming, have overhead and limitations over random (large, unexpected changes) channels.

Minimum Energy Requirement for Inducing Withdrawal Reflex in Millimeter Wave Exposures

We consider the problem of inducing withdrawal reflex on a test subject via exposure to a millimeter wave beam. In our physical model, there are 10 physical parameters affecting the occurrence of withdrawal reflex. Our goal is to pinpoint the roles of these physical parameters in inducing withdrawal reflex. We first carry out non-dimensionalization to reduce the model to a non-dimensional system of only 3 composite parameters: non-dimensional beam power density, non-dimensional beam radius, and non-dimensional exposure time. If the beam power is kept on and steady, withdrawal reflex occurs eventually;the shortest exposure time for inducing withdrawal reflex corresponds to the smallest energy consumption at the given power density and beam radius. In the 2D space of power density and beam radius, the overall minimum energy occurs at the corner of very large power density and very small beam radius, which also produces a very large value of maximum skin temperature and a long time to withdrawal reflex. To reduce the burn injury risk, we introduce a cap on the maximum skin temperature. At each given total beam power, we carry out optimizations with respect to the beam radius, constrained by the prescribed temperature cap. The energy consumption varies negatively with the prescribed temperature cap: a lower temperature cap can be accommodated only with a higher energy consumption via the venue of a larger beam radius. The energy consumption is relatively flat with respect to the total beam power and attains a minimum at a moderately large total beam power. The time to withdrawal reflex is approximately inversely proportional to the total beam power. Our analysis demonstrates that a moderately large total beam power is a good compromise to achieve both low energy consumption and short time to withdrawal reflex.

Detective Method for Water Pollution Based on Millimeter Wave Radiant Characteristics

Aim at monitoring water pollution, especially the aquatic vegetation, the multilayer dielectric model based on incoherent method is established to analysis the brightness temperature of aquatic vegetation. A 3 mm radiometer is used to measure the radiant characteristics of water pollution. Compared to 3 layer dielectric model, the simulation result of multilayer dielectric model is in better accordance with the experimental data, which shows that the multilayer dielectric model can model aquatic vegetation’s radiant characteristics more precisely. This result shows that water has millimeter wave radiant characteristics of low brightness temperature, cold target compared to aquatic vegetation. Based on the study of water’s brightness temperatures and aquatic vegetation’s radiant characteristics, the radiant characteristics can be used to monitor aquatic vegetation.

Dual-band dynamic reconfigurable intelligent surface for signal enhancement in millimeter wave

Millimeter wave with large bandwidth,high transmission rate,and low delay is considered a reliable alternative to cope with the spectrum shortage.However,the fast attenuation and narrow beam characteristics make it difficult to achieve long-distance or wide-range applications.Here,a 1-bit dual-band reflective reconfigurable intelligent surface(RIS)for signal enhancement in millimeter wave with 16×16 elements is designed,fabricated,and measured.Different from most existent RIS,dynamic programming is realized at two separate frequency bands by integrating the PIN diodes and field-programmable gate array(FPGA).Particularly,the beam deflection,dual-beam,and multi-beam are created based on the coding theory and convolution operation,proving the effectiveness of wavefront manipulation.Moreover,the far-field patterns and signal power with different coding sequences are measured and compared.It is indicated that the received signal power is 6–7 dB stronger than that without coding,which shows good agreement with the desired expectations.The proposed reconfigurable metasurface exhibits great potential in beam forming,making it a promising candidate for progressive wireless communication applications.