Wave Frequency Band Research Articles

Tropospheric attenuation prediction for future millimeter wave terrestrial systems: Estimating statistics and extremes.

SummaryTropospheric attenuations can be significant in the millimeter wave (mmWave) frequency bands; hence, accurate prediction modeling of tropospheric attenuation is important for reliable mmWave communication. Several models have been established by the International Telecommunication Union (ITU), yet estimation accuracy is limited due to the large spatial scales used for model input parameters. In this paper, we address this and apply local precipitation data to analyze tropospheric attenuation statistics and compare to results when using ITU regional input rain data. Specifically, tropospheric attenuation is predicted via simulations using the ITU method at 30, 60, and 90 GHz in four distinct geographic locations with different climate types. From our simulations, we gather statistics for annual average rain attenuation, worst month rain attenuation, and rain attenuation per decade. Our results indicate that when using local measured rain data, for 1 km link distance, mean rain event attenuation increases from 0.5 to 2 dB. Local rain data yield larger attenuations at essentially all percentages of time not exceeded (essentially corresponding to all probability values): for example, for 0.1% of time not exceeded, in Columbia, SC, rain attenuation for 30 GHz frequency increases to 9 dB with local rain data, compared to 5 dB with ITU's regional data, corresponding to rain rates of 38.2 and 17.5 mm/h, respectively; at the same probability and location, the 90 GHz attenuation increases by 10 dB, from 10 to 20 dB when local rain data are used. Fog attenuations are also appreciable, reaching 8 dB for the 90 GHz frequency. Moreover, for the example locations, peak rain attenuations have increased at a rate of approximately 2 dB/decade over the past 50 years. Our results indicate that actual tropospheric attenuations may be substantially larger than that predicted by the ITU model when using regional rain rate data.

Design of Microstrip Tchebyscheff Phased Array Antennas for Inter-Vehicular Communication

To enhance the safety and comfort of a driver, the wireless technology is used for inter-vehicular communication (IVC). During the lane change in highways, the driver of a high speed vehicle can exploit the antenna technology using a microcontroller. Here, a 4-element Tchebyscheff phased array of microstrip antennas for IVC application is designed at millimeter wave frequency band of 60GHz. The details of this array design with feed network, its design layout and fabricated prototype are presented. Another 4-element microstrip Tchebyscheff phased array for 6GHz IVC application is designed and the measured result is compared with the simulated result.

Joint Beam Training and Data Transmission Control for mmWave Delay-Sensitive Communications: A Parallel Reinforcement Learning Approach

Future communication networks call for new solutions to support their capacity and delay demands by leveraging potentials of the millimeter wave (mmWave) frequency band. However, the beam training procedure in mmWave systems incurs significant overhead as well as huge energy consumption. As such, deriving an adaptive control policy is beneficial to both delay-sensitive and energy-efficient data transmission over mmWave networks. To this end, we investigate the problem of joint beam training and data transmission control for mmWave delay-sensitive communications in this paper. Specifically, the considered problem is firstly formulated as a constrained Markov Decision Process (MDP), which aims to minimize the cumulative energy consumption over the whole considered period of time under delay constraint. By introducing a Lagrange multiplier, we transform the constrained MDP into an unconstrained one, which is then solved via a parallel-rollout-based reinforcement learning method in a data-driven manner. Our numerical results demonstrate that the optimized policy via parallel-rollout significantly outperforms other baseline policies in both energy consumption and delay performance.

Advanced NOMA-Based RRM Schemes for Broadcasting in 5G mmWave Frequency Bands

A relevant solution for the high demand for new multimedia applications and services is millimeter wave (mmWave) frequency band in 5G. However, in order to face the technological challenges of the present and those that will appear in the short-term future, it is necessary to improve the spectral efficiency of 5G systems. In particular, the Radio Resource Management (RRM) module is considered an essential component. Nevertheless, resource allocation techniques that combine orthogonal multiplexing (OMA) schemes, such as Time Division Multiple Access (TDMA), with Non-Orthogonal Multiple Access (NOMA) techniques have not been studied in-depth. Therefore, this article designs and evaluates different RRM models that combine TDMA with NOMA for innovative applications in the 5G mmWave frequency bands. To this end, the advantages and challenges associated with mmWave frequency bands and potential future applications are introduced. An innovative use case has been designed to test the RRM models. The use case is based on the on-demand distribution of multimedia content in high-density environments, such as museum halls. The on-demand content aims at offering Augmented Reality (AR) services to unicast users in order to provide personalized services. The models have been evaluated in terms of throughput, capacity, and availability. According to the results, the combined RRM techniques offer up to 50% more capacity than the single multiplexing technology models and can provide video-on-demand service to practically the entire cell.

Effect of electron density gradient on power absorption during gigahertz electromagnetic wave propagating in cold plasma

Considering the effect of electron density gradient, an analytical, parameter adjustable density distribution function is presented, and a multislab plasma model is used to investigate power absorption of gigahertz electromagnetic waves between 0.20 and 30 GHz in a partially ionized cold plasma layer. The effects of plasma parameters on the absorbed power during electromagnetic wave propagation are investigated and compared with corresponding uniform cases. An optimized asymmetric electron density gradient profile is designed by calculating the corresponding absorption spectrum with selected parameters to enhance the absorption rate near original peak frequencies. The possibility of theoretically designing electron density gradient profiles is important to understand how to enhance the plasma cloaking in some specific electromagnetic wave frequency bands.

Dopaminergic medication reduces interhemispheric hyper-synchronization in Parkinson's disease

IntroductionWe previously reported on interhemispheric cortical hyper synchronization in PD. The aim of the present study was to address the hypothesis that increased interhemispheric cortical synchronization in PD is related to dopamine deficiency and is correlated with motor function. MethodsWe studied participants with PD and characterized cortical synchronization with reference to brain regions. Electroencephalography (EEG) was recorded from 20 participants with PD while OFF and ON their dopaminergic medications (two separate visits), during quiet standing and straight-line walking. Cortical interactions in the theta, alpha, beta, and gamma brain wave frequency bands were evaluated using interhemispheric phase synchronization (inter-PS). ResultsInter-PS values were found to be significantly higher during the OFF state as compared to the ON state in standing and walking trials for theta, alpha and beta bands.In addition, inter-PS reduction from OFF to ON was associated with mobility improvement evaluated by the Timed Up and Go test, and with daily levodopa equivalent dose across individuals. Higher differences in inter-PS values between OFF and ON states were evident mainly in the occipital-parietal cortex. ConclusionsPersons with PD have increased inter-PS during the OFF state compared to their ON state, and this increase in inter-PS is associated with the clinical improvement between OFF and ON. We speculate that these findings, together with previous evidence of higher inter-PS in PD as compared to healthy older adults, reflect neuronal processes consequential to asymmetric subcortical dopamine deficiency.

SLNR-Based Beamspace Precoding and Beam Selection for Wideband mmWave Massive MIMO

Beamspace multiple-input multiple-output (MIMO) systems leverage the lens antenna array to reduce their hardware cost, which is a promising technology in millimeter wave (mmWave) frequency bands. This letter proposes a novel signal-to-leakage-plus-noise ratio (SLNR)-based beamspace precoding and beam selection scheme to improve the downlink sum rate (SR) of the beamspace mmWave massive MIMO channels. First, for a given beam subset, a SLNR maximization-based beamspace precoder is designed to mitigate the inter-user interference caused by leakage power, thus enhancing the SR. Then, an approximated expression of the SR is formulated, based on which an iterative radio frequency (RF) precoding and beam selection method is designed to further improve the system SR. Numerical results demonstrate a superior SR performance of the proposed scheme over state-of-the-art methods.

Optical Interconnects for Future Advanced Antenna Systems: Architectures, Requirements and Technologies

This paper aims to give an outlook of future advanced antenna systems for 5G and 6G wireless networks. The trend to increase the peak data rate and to reduce latency and power consumption will continue in the future. This will be made possible by the exploitation of millimeter wave frequency bands and by the introduction of massive multiple-input multiple-output antenna technology which requires a transformation of the antenna hardware architectures and technologies. Advanced antenna systems based on arrays of several hundreds of antenna elements are under development and to keep the fronthaul throughput manageable, some digital signal processing functions have been moved inside the antenna, creating the need to distribute very big volumes of data at high bit rate across the antenna. The characteristics and hardware architecture of future advanced antenna systems are discussed and the relevant interconnect requirements are presented. A new type of monolithically integrated optical transceiver is presented, integrating electronic and photonic circuits on the same chip with high bandwidth density, high energy efficiency and low latency. The transceiver technology is discussed and results of experimental demonstrations are given.

Reconfigurable multifunctional polarization converter based on asymmetric hybridized metasurfaces

In the terahertz (THz) band, it is a challenge to integrate multiple functions into a very small unit cell structure of metasurface. However, the hybrid metasurfaces composed of several controllable materials provide a solution to this problem. In this paper, two multifunctional polarization converters based on asymmetric hybrid metasurface operating in the THz band are designed. The both polarization converters are designed with double-layer resonators that embedded by photosensitive silicon (Si) and vanadium dioxide (VO2) at the appropriate positions. By controlling the optical pump intensity and the temperature of the VO2, the designed metasurface polarization converter (MPC) I can realize the identical linear polarization conversion for both forward and backward reflection modes. When the external excitation conditions are changed, the polarization conversion frequency bands of forward and backward incident waves can be switched. Moreover, the MPC II can operate in both reflection and transmission modes and realize multifunctional polarization conversion. For the forward incident THz wave, the MPC II can perform two different functions under different excitation conditions: the conversion from co-polarization to cross-polarization in the reflection mode and the conversion from linear polarization to right-handed circular polarization (RHCP) or left-handed circular polarization (LHCP) in the transmission mode. While for the backward incident THz wave, the MPC II operates in the transmission mode and converts the electromagnetic (EM) wave from co-polarization to cross-polarization one. Our designs may provide a scheme for multifunctional integrated devices operating in THz band.

The Proximity Radio Access Network for 5G and 6G

One popular subject of 6G research is the millimeter wave and Tera Hertz frequency bands for which there is both enthusiasm and pessimism. The expected adoption of high bands in 6G has been known to cause two major problems for deployment: a reduced coverage radius and a drastic increase of small coverage holes within the radius. This article examines practical constraints that may hinder the commercial success of high band deployment and proposes an approach that addresses many of the concerns from operators. The proposal is particularly effective in minimizing small coverage holes in addition to improving the system capacity, thus improving the chance for the adoption of high bands for cellular networks of future generations.

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 0.25 λ0×0.22 λ0×0.12 λ0. under the characteristic's mode. The DRA is placed over a substrate with dimensions 0.5 λ0×0.5 λ0×0.02 λ0. 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.

Design and Analysis of Novel Antenna for Millimeter-Wave Communication

At present, the microwave frequency band bandwidth used for mobile communication is only 600 MHz. In 2020, the 5G mobile Communication required about 1 GHz of bandwidth, so people need to tap new spectrum resources to meet the development needs of mobile Internet traffic that will increase by 1,000 times in the next 10 years. Utilize the potentially large bandwidth (30∼300 GHz) of the millimeter wave frequency band to provide higher data rates is regarded as the potential development trend of the future wireless communication technology. A microstrip patch implementation approach based on electromagnetic coupling feeding is presented to increase the bandwidth of a dual-polarized millimeter-wave antenna. To extend the antenna unit's impedance bandwidth, coplanar parasitic patches and spatial parallel parasitic patches are used, and a 22 sub-array antenna is developed using paired inverse feed technology. The standing wave at the centre frequency of 37.5 GHz is less than 2 GHz. The antenna array's relative bandwidth is 6.13 percent, the isolation is >30 dB, the cross-polarization is −23.6 dB, and the gain is 11.5 dBi, according to the norm. The proposed dual-polarized microstrip antenna has the characteristics of wide frequency bandwidth, large port isolation, low cross-polarization, and high gain. The antenna performance meets the general engineering requirements of millimeter-wave dual-polarized antennas.

ABSORPTION OF ELECTROMAGNETIC WAVES WITH VARIOUS WAVELENGTH BY NANOPARTICLES

An aim of the article is to review the potential of nanotechnology in military for the development of stealth technologies. Methods. Analysis of information, synthesis, generalization and comparison. Results. An overview of nanoparticles use in the development of stealth technologies has been made. Foreign and Ukrainian publications were analyzed. The possibility of using nanoparticles of metals like iron, cobalt, nickel, zinc, manganese and other metals and composite nanomaterials for absorption, refraction and scattering of waves of different lengths and frequencies, which can be used in the development of coatings for military equipment to reduce visibility and counter targeting systems has been shown.
 The possibility of using nanoparticles of nonmetals to absorb infrared radiation, which is important for masking equipment, military facilities and personnel, has been highlighted.
 High-tech weapons, technical means of detection and guidance are constantly being modernized and improved. One of the most important conditions for tactical superiority over the enemy is camouflage and counteraction to these systems. One of the ways to increase the resistance to detection and guidance systems is the development of stealth technologies based on nanoparticles of metals and non-metals.
 In the long run, nanotechnology and stealth coating should ensure the invisibility of objects in a wide frequency band of electromagnetic waves, which can reach two to three orders of magnitude. These are ambitious tasks, however, they are real.
 Foreign and domestic scientists have proven the possibility of using nanoparticles of metals and composite materials to develop coatings with the ability to absorb electromagnetic waves in a wide range, which can be used in the development of coatings to counter radar stations and other detection systems.
 Given the significant scientific potential of Ukrainian scientists, presence of technologies needed for the synthesis of nanoparticles of metals and nonmetals of various shapes and sizes, based on previous research on the ability of nanoparticles to absorb waves of different lengths and frequencies, we see high prospects for stealth technologies for the Military Forces of Ukraine.

Experimental validation on the dynamic response of a novel floater uniting a vertical-axis wind turbine with a steel fishing cage

A floating vertical-axis wind turbine (VAWT) concept that combines a VAWT with a steel fishing cage has been proposed by lead authors. To probe kinetic characteristics of this floater, this study performs a series of model tests at a 1/40 scale. The comprehensive calibration tests, including wind/wave field quality validation tests, hammer tests, quasi-static mooring tests, and decay tests, are performed for various identification purposes. After that a series of basin tests for the floater under regular waves, irregular waves, and irregular waves with steady/turbulent wind are performed. The experimental data of motions and loads are compared with numerical predictions from an in-house fully coupled simulation tool. Good agreements are observed, affirming the accuracy of the developed simulation tool. Because the main dimension of cage coincides with wavelength and , multi-peaks appear in surge and pitch spectra in the wave frequency band (0.3–1.3 rad/s). The second-order wave effects are clearly observed in tests, but they induce a much smaller low-frequency motion response (<0.3 rad/s) than that by aerodynamic effects. The mooring tension response is influenced by surge motions more than by first-order wave actions. Third-per-revolution (3P) effects are dominant in tower-top shear forces but insignificant to the platform motions.

Analysis of Propagation Characteristics for Various Subway Tunnel Scenarios at 28 GHz

In order to meet the higher data transmission rate requirements of subway communication services, the millimeter wave (mmWave) broadband communication is considered as a potential solution in 5G technology. Based on the channel measurement data in subway tunnels, this paper uses ray-tracing (RT) simulation to predict the propagation characteristics of the 28 GHz millimeter wave frequency band in different tunnel scenarios. A large number of simulations based on ray-tracing software have been carried out for tunnel models with different bending radiuses and different slopes, and we further compared the simulation results with the real time measurement data of various subway tunnels. The large-scale and small-scale propagation characteristics of the channel, such as path loss (PL), root mean square delay spread (RMS-DS), and angle spread (AS), for different tunnel scenarios are analyzed, and it was found that the tunnel with a greater slope causes larger path loss and root mean square delay spread. Furthermore, in the curved tunnel, the angle spread of the azimuth angle is larger than that in a straight tunnel. The proposed results can provide a reference for the design of future 5G communication systems in subway tunnels.

HYDRODYNAMICS OF A DUAL-CHAMBER OWC WAVE ENERGY CONVERTER IN HEAVING MOTION

The oscillating water column (OWC) wave energy conversion device have been recognized as the most promising wave energy conversion technology due to the advantages of its simple structure, convenient assembly and easy maintenance. A heave-only dual-chamber OWC device was numerically investigated by a well-developed open source software OpenFOAM coupled with a wave generation and absorption toolbox Waves2Foam. The volume of fluid (VOF) method tracking the water-air interface and the six-degree-freedom (6DOF) Dynamic Mesh solver duplicating the heave motion of the OWC device were employed to examine the influences of the relative width of the front and rear chambers and the spring elastic coefficient on the energy capture width ratio and hydrodynamic characteristics of the device under the actions of different incident regular waves. Through comparing the present results with the existing ones of a fixed dual-chamber OWC wave energy converter, and examining the free-decay motion of a cylinder, the rationality and effectiveness of the present numerical model has been revealed. The results show that the wider rear chamber can make for the extraction of wave energy of the dual-chamber OWC in heave motion. The heave-only dual-chamber OWC device can improve the device performance as the relative width ratio of the front and rear chambers is 1/2, and the rear chamber has larger capture width ratio in the middle and high frequency wave bands, compared with that of the fixed one. Multiple-peak values of the relative water surface elevation and the relative pressure occur in the whole test wave frequency bands due to the phase gap between the dual-chamber OWC device and the water columns in the front and rear chambers. In addition, it is found that by adjusting the spring stiffness coefficient, the wave-frequency bandwidth of high-efficiency can be significantly broadened and larger energy capture width ratio can be achieved.

A review on mmWave based energy efficient RoF system for next generation mobile communication and broadband systems

Abstract In today’s scenario, wireless communication is turning into a decisive and leading backbone to access the worldwide network. Therefore, the usage of mobile phones and broadband is rising staggeringly. To satisfy their expulsive needs, it demands increment in data rates while providing higher bandwidth and utilizing optical fiber in wireless communication, and this becomes a worldwide analysis area. Radio over fiber (RoF) system is taken into account as best solution to fulfill these needs. In RoF system, the radio frequency signal operated at millimeter wave (30–300 GHz) is centralized and processed at control station (CS) and also, the CS upconverts this electrical signal to optical domain. By employing optical fiber link, this signal reaches to base station (BS). Then, the received optical signal converts back to electrical domain at the respective BS. Now BS radiates the electrical signal to corresponding mobile station (MS) in commission with the millimeter wave frequency bands. This RoF system is providing massive bandwidth, facilitating large mobility for RF frequency signals, small loss, fast and cost effective setup, wonderful security, and unlicensed spectrum etc. The RoF system introduces microcells structure for BS cells to boost the frequency reuse and needed capacity. It has benefits in terms of ability to fulfill increasing bandwidth demands to cut back the power consumption and the dimensions of the handset devices. This paper firstly explains the overview of existing wireless mobile communication and broadband systems and then, targets the review of RoF system which will become energy efficient system for next generation mobile communication and future broadband systems. This paper also includes the performance degradation and evaluation parameters. Finally, this paper presents the various research opportunities for its implementation zone.

Experimental comparison of DSB and CS-DSB mmW formats over a hybrid fiber and FSO fronthaul network for 5G.

The telecommunication world is experiencing the 5th generation (5G) networks deployment including the use of millimeter wave (mmW) frequency bands to satisfy capacity demands. This leads to the extensive use of optical communications, especially the optical fiber connectivity at the last mile access and the edge networks. In this paper we outline fiber and free space optics (FSO) technologies for use as part of the 5G optical fronthaul network. We investigate two different mmW transmission schemes based on (i) the conventional analog radio over fiber transmission using one Mach-Zehnder modulator (MZM) with double sideband (DSB) optical modulation, and (ii) an optical-based frequency doubling with one MZM biased at the null point to introduce carrier suppression DSB (CS DSB) transmission and second MZM used for data modulation. Both systems are assessed in terms of the error vector magnitude, signal-to-noise ratio, dynamic range and phase noise. We consider a configuration for the fronthaul network in the frequency range 2 (FR2) at 27 and 39 GHz with the scale of bandwidth up to 400 MHz with M-quadrature amplitude modulation and quadrature phase shift keying. Results are also shown for FR1 at 3.5 GHz. Moreover, we investigate for the first time the 5G new radio signal transmission under strong turbulence conditions and show the turbulence-induced FSO link impairment. We finally demonstrate the CS DSB scheme performs well under chromatic dispersion-induced fading for the frequency up to 40 GHz and single mode fiber length of 30 km, whereas the DSB format seems more appropriate for an antenna seamless transmission.

Quantifying the Density of mmWave NR Deployments for Provisioning Multi-Layer VR Services

The 5G New Radio (NR) technology operating in millimeter wave (mmWave) frequency band is designed for support bandwidth-greedy applications requiring extraordinary rates at the access interface. However, the use of directional antenna radiation patterns, as well as extremely large path losses and blockage phenomenon, requires efficient algorithms to support these services. In this study, we consider the multi-layer virtual reality (VR) service that utilizes multicast capabilities for baseline layer and unicast transmissions for delivering an enhanced experience. By utilizing the tools of stochastic geometry and queuing theory we develop a simple algorithm allowing to estimate the deployment density of mmWave NR base stations (BS) supporting prescribed delivery guarantees. Our numerical results show that the highest gains of utilizing multicast service for distributing base layer is observed for high UE densities. Despite of its simplicity, the proposed multicast group formation scheme operates close to the state-of-the-art algorithms utilizing the widest beams with longest coverage distance in approximately 50–70% of cases when UE density is λ≥0.3. Among other parameters, QoS profile and UE density have a profound impact on the required density of NR BSs while the effect of blockers density is non-linear having the greatest impact on strict QoS profiles. Depending on the system and service parameters the required density of NR BSs may vary in the range of 20–250 BS/km2.

Numerical investigation of scaling effect in two-dimensional oscillating water column wave energy devices for harvesting wave energy

Oscillating water column (OWC) devices utilise wave-induced oscillation of water column in partially submerged chambers to extract energy of waves in ocean. The principal aim of this paper is to investigate scaling effects of two-dimensional OWC through numerical simulations. The fluid motion under waves is simulated by solving the two-dimensional incompressible Reynolds-Averaged Navier-Stokes equations using finite element method under Arbitrary Lagrangian-Eulerian scheme. To investigate scaling effects, the waves and the OWC are scaled up or down according to Froude number similarity. The turbine is scaled up or down using three different scaling methods: (1) Turbine coefficient remains unchanged, i.e. not scaling the turbine at all; (2) Equivalent pneumatic damping coefficient of the turbine is constant and (3) the two-dimensional turbine coefficient is constant. The numerical results show that method (2) has the smallest effects on the best hydraulic efficiency and method (3) has the smallest effects on the best performance wave number, i.e. the wave number where the OWC receives the largest percentage of the wave energy. The worst scaling method is not scaling the turbine. Because the best performance wave number varies with the model scale in method (1) and (2), it is very likely the scaling effects of the model scale on the hydrodynamic performance at different wave numbers are different from each other. In addition, the effects of the wave height and the chamber volume are studied. Increasing chamber volume causes a reduction of the best performance, however it may improve general performance of OWC because it increases the frequency band of waves with high hydraulic efficiency. Increasing wave height causes a reduction of the hydraulic efficiency.