Omnidirectional Antenna Research Articles

Coverage Analysis for Cellular-Connected Random 3D Mobile UAVs With Directional Antennas

This letter proposes an analytical framework to evaluate the coverage performance of a cellular-connected unmanned aerial vehicle (UAV) network in which UAV user equipments (UAV-UEs) are equipped with directional antennas and move according to a three-dimensional (3D) mobility model. The ground base stations (GBSs) equipped with practical down-tilted antennas are distributed according to a Poisson point process (PPP). With tools from stochastic geometry, we derive the handover probability and coverage probability of a random UAV-UE under the strongest average received signal strength (RSS) association strategy. The proposed analytical framework allows to investigate the effect of UAV-UE antenna beamwidth, mobility speed, cell association, and vertical motions on both the handover probability and coverage probability. We conclude that the optimal UAV-UE antenna beamwidth decreases with the GBS density, and the omnidirectional antenna model is preferred in the sparse network scenario. What's more, the superiority of the strongest average RSS association over the nearest association diminishes with the increment of GBS density.

A Directional TDMA Protocol for High Throughput URLLC in mmWave Vehicular Networks

Future vehicular wireless applications, such as autonomous and remote driving, will demand High Throughput Ultra-Reliable Low Latency Communication (HT-URLLC) unsupported by current wireless standards. Hybrid network designs that combine Millimeter-Wave (mmWave) and Sub-6GHz communications were recently proposed to establish HTURLLC in Vehicle-To-Everything (V2X) networks. To enable such integration, new Medium Access Control (MAC) protocols must be developed. As such, we consider a linear vehicular network, in which vehicles driving closely in the same lane utilize both front and rear directional mmWave antennas to form a Lane Cluster (LC). Data packets, then, propagate forwards and backwards along the LC towards its terminals in a multihop fashion. In turn, the LC terminals utilize omnidirectional antennas at Sub-6GHz frequencies to disseminate the cluster's packets to nearby LCs, Road Side Units (RSUs), and cellular base stations. To resolve the channel contention between subsequent LC members, we devised a two-timeslot MAC scheme with a schedule alignment mechanism. Additionally, we developed centralized and distributed schedule coordination protocols aligning the schedules of adjacent LCs to mitigate cross-lane interference due to antenna beam misalignment. The proposed protocols were evaluated using VEINS (extension of OMNET++ network simulator) and compared against the CSMA-CA scheme of IEEE 802.11p under different parameters and scenarios. The results show that the proposed linear topology along with the scheduling protocols can potentially achieve HT-URLLC while addressing the mmWave practicality issues.

Mapping spatial distribution of comm‐satellite's beam based on ground omni‐antennas

SummaryThe current satellite communications (SatComs) systems are composed of a large number of satellites, beams and terrestrial devices. Due to their multinode dynamic nature, the usage of frequency resources is variable, complex and difficult to characterize. In particular, with the development of satellite‐borne phased array antenna technology, SatCom beams carrying different frequencies are directionally and dynamically distributed in global scale. Mapping and locating the spatial beam distributions of communication satellite (comm‐satellite) are the bases of intersystem cofrequency interference mitigation and spatial frequency reuse. In this paper, we design a data selection–multiparameter fitting iteration (DS‐MFI) algorithm on the basis of ground‐based omnidirectional antennas. The proposed approach can effectively map the spatial distribution of comm‐satellite's beam, including satellite transmitter position, equal‐gain off‐axis angle, and beam pointing in azimuth and elevation. Simulation results verify the effectiveness of the proposed approach for satellites with fixed or steerable beams at different altitudes. Furthermore, the results become increasingly accurate as the dense of ground omni‐antenna increases.

Directional antennas modelling and coverage analysis for UAV networks with blockage effects in urban environment

AbstractIn recent years, the use of unmanned aerial vehicles (UAVs) as flying base stations (BSs) has attracted widespread attention in both academia and industry. Most of the existing research on UAV networks in dense urban environment focus on omnidirectional antenna patterns, which results in severe interference and overlapping between coverage area due to dominant line‐of‐sight (LOS) links. This paper proposed a directional antennas model with tunable beamwidth and blockage effects in urban UAV networks, and derive the coverage probability of UAV networks in dense urban environment by stochastic geometry tools, where UAVs and users are deployed according to independent Poisson point process (PPP). Specifically, a realistic and mathematically tractable directional antenna pattern is adopted and radiation gain is modelled by a continuous function of the elevation angle . In addition, the blockage effects of the buildings are considered by establishing a three‐dimensional blockage model where buildings are distributed according to PPP with heights followed by Rayleigh distribution. Numerical results match well with simulations and provide optimal deployment parameters for UAV deployments.

Pulse-driven self-reconfigurable meta-antennas

Wireless communications and sensing have notably advanced thanks to the recent developments in both software and hardware. Although various modulation schemes have been proposed to efficiently use the limited frequency resources by exploiting several degrees of freedom, antenna performance is essentially governed by frequency only. Here, we present an antenna design concept based on metasurfaces to manipulate antenna performances in response to the time width of electromagnetic pulses. We numerically and experimentally show that by using a proper set of spatially arranged metasurfaces loaded with lumped circuits, ordinary omnidirectional antennas can be reconfigured by the incident pulse width to exhibit directional characteristics varying over hundreds of milliseconds or billions of cycles, far beyond conventional performance. We demonstrate that the proposed concept can be applied for sensing, selective reception under simultaneous incidence and mutual communications as the first step to expand existing frequency resources based on pulse width.

159-GHz Propagation Measurement and Analysis in Urban Microcellular Environment for 6G

This letter presents our 159 GHz measurements collected in an urban microcellular (UMi) environment and provides synthesized beamwidth-related propagation characteristics. Our directional antenna measurements include line-of-sight (LoS) scenarios (distances up to 170 m) and non-LoS (NLoS) (distances up to 97 m). To validate the synthesized beamwidth characteristics, an omnidirectional antenna was also used. So far, to the best of our knowledge, two organizations (NYU and USC) have reported their measurement-based propagation characteristics for UMi, especially including NLoS, at frequencies above 100 GHz. We compare our data with the two organizations’ data as well as the frequency-extrapolated 3GPP model.

Omni-Directional Pathloss Measurement Based on Virtual Antenna Array With Directional Antennas

Omni-directional pathloss, which refers to the pathloss when omni-directional antennas are used at the link ends, are essential for system design and evaluation. In the millimeter-wave (mm-Wave) and beyond bands, high gain directional antennas are widely used for channel measurements due to the significant signal attenuation. Conventional methods for omni-directional pathloss estimation are based on directional scanning sounding (DSS) system, i.e., a single directional antenna placed at the center of a rotator capturing signals from different rotation angles. The omni-directional pathloss is obtained by either summing up all the powers above the noise level or just summing up the powers of detected propagation paths. However, both methods are problematic with relatively wide main beams and high side-lobes provided by the directional antennas. In this correspondence, directional antenna based virtual antenna array (VAA) system is implemented for omni-directional pathloss estimation. The VAA scheme uses the same measurement system as the DSS, yet it offers high angular resolution (i.e. narrow main beam) and low side-lobes, which is essential for achieving accurate multipath detection in the power angle delay profiles (PADPs) and thereby obtaining accurate omni-directional pathloss. A measurement campaign was designed and conducted in an indoor corridor at 28-30 GHz to verify the effectiveness of the proposed method.

Optomechatronics OMEGA design project of SSPS with MWPT and omnidirectional scanning antenna

<p indent="0mm">Owing to the difficulties and shortcomings of the OMEGA design of the space solar power station, this study proposes an optomechatronics OMEGA design project. First, a spherical crown (instead of the whole sphere) is utilized to collect the parallel sunlight, which is focused on the top-shaped line feed. The DC energy is sent to the transmission antenna. Thus, the problem of designing a special membrane, which is semi-transmitting and semi-reflecting for the sunlight and meanwhile transparent for the microwave, could be avoided. Then, the electric brush with ultra-large DC power is replaced with the traditional DC transfer method to overcome the critical problem of lower reliability. Next, using the omnidirectional scanning antenna, an electric propulsion technique is introduced to adjust the crown pose to replace the control system of the line-feed moving. Afterward, employing a bionic butterflying technology with topology optimization to radiate the massive heat to the cold space resulted in an innovative cooler, checking for both requirements of a bigger radiation size and an ultra-low selfweight, simultaneously.

Effects of Body Shadowing in LoRa Localization Systems

Applications where a person carries environmental sensors benefit from knowing the position of the individual. Researchers can locate the device by analyzing the radio signals used for sending information. However, it is necessary to know the impact of body obstruction on communication links and, therefore, on the localization system. The paper studies this impact by using field tests employing one LoRa node with an omnidirectional antenna in an outdoor parking lot with vegetation. The tests use four LoRa gateways located in the corners of the area to measure the signals with and without body obstruction. The node was located on the subject’s chest to maximize signal obstruction. Results show that signal strength decreases by an average of 3 dB on links with body shadowing. Additionally, the study uses these signals with machine learning and Kalman filter localization algorithms. Finally, the results show that body shadowing affects location accuracy in most methods. These results are useful for IoT researchers that need to locate people carrying LoRaWAN devices but cannot use GPS/GNSS due to energy constraints.

Multi-Slope Path Loss Model-Based Performance Assessment of Heterogeneous Cellular Network in 5G

The coverage and capacity required for fifth generation (5G) and beyond can be achieved using heterogeneous wireless networks. This exploration set up a limited number of user equipment (UEs) while taking into account the three-dimensional (3D) distance between UEs and base stations (BSs), multi-slope line of sight (LOS) and non-line of sight (n-LOS), idle mode capability (IMC), and third generation partnership projects (3GPP) path loss (PL) models. In the current work, we examine the relationship between the height and gain of the macro (M) and pico (P) base stations (BSs) antennas and the ratio of the density of the MBSs to the PBSs, indicated by the symbol β. Recent research demonstrates that the antenna height of PBSs should be kept to a minimum to get the best performance in terms of coverage and capacity for a 5G wireless network, whereas ASE smashes as β crosses a specific value in 5G. We aim to address these issues and increased the performance of the 5G network by installing directional antennas at MBSs and omnidirectional antennas at Pico BSs while taking into consideration traditional antenna heights. The authors of this work used the multi-tier 3GPP PL model to take into account real-world scenarios and calculated SINR using average power. This study demonstrates that, when the multi-slope 3GPP PL model is used and directional antennas are installed at MBSs, coverage can be improved 10% and area spectral efficiency (ASE) can be improved 2.5 times over the course of the previous analysis [1]. Similarly to this, the issue of an ASE crash after a base station density of 1000 has been resolved in this study.

Wideband High-Gain Omnidirectional Biconical Antenna for Millimeter-Wave Applications

A novel omnidirectional biconical antenna for millimeter-wave (mm-wave) wireless communications is investigated. It is loaded by an annular metal lens that consists of rotationally symmetric annular metal plates (MPs). A nearly uniform <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$E$ </tex-math></inline-formula> -field distribution can be obtained at the radiating aperture across a wide frequency range, giving a wideband high-gain omnidirectional antenna. The operating principle and design flowchart of the lens are given. To validate the idea, a Ka-band vertically polarized prototype was fabricated. Both its measured −10 dB impedance and 3 dB gain bandwidths are 43.9% (25.6–40.0 GHz), with the maximum measured gain given by 9.2 dBi. As compared with the conventional biconical antenna, our antenna can obtain a higher gain by ~4 dB across the entire impedance passband.

Device Free Indoor Localization in the 28 GHz band based on machine learning

By exploiting the received power change in a communication link produced by the presence of a human body in an otherwise empty room, this work evaluates indoor free device localization methods in the 28 GHz band using machine learning techniques. For this objective, a database is built using results from ray tracing simulations of a system comprised of 4 receivers and up to 2 transmitters, while a person is standing within the room. Transmitters are equipped with uniform linear arrays that switch their main beams sequentially at 21 angles, whereas the receivers operate with omnidirectional antennas. Statistical localization error reduction of at least 16% over a global-based classification technique can be obtained through the combination of two independent classifiers using one transmitter and a reduction of at least 19% for 2 transmitters. An additional improvement is achieved by combining each independent classifier with a regression algorithm. Results also suggest that the number of examples per class and size of the blocks (strips) in which the study area is partitioned play a role in the localization error.

5G Indoor Base Station Application: Low Profile Broadband Horizontally Polarized Omnidirectional Antenna

5G Indoor Base Station Application: Low Profile Broadband Horizontally Polarized Omnidirectional Antenna

Picosatellite identification and Doppler estimation using passive radar techniques

In this article a novel method for satellite identification is presented for picosatellites. Utilizing apriori knowledge of the transmitted signals the cross-correlation of the received signal and a known transmission is calculated, from the results the Doppler shift is estimated and the satellite’s Doppler curve can be matched against the measurements of NORAD. Using this method an omnidirectional antenna can be used instead of a high gain directional antenna, and the gain difference is compensated by the processing gain of the algorithm described. The practicality of the algorithm is demonstrated through the mission of MRC-100 PocketQube.

Multimedia Imaging System of Data Collection and Antenna Alignment for Unmanned Aerial Vehicles Based Internet of Things

Because network of sensors gives a more accurate representation of remotely sensed environments, a network of wirelessly connected sensors is essential. Data packets must be routed to the base station hop by hop, which causes conventional network data collecting to use a lot of power. Unmanned aerial vehicles (UAV) were employed for hovering over the detected environment and gather data to solve this issue. The paper also aims to provide an automatic alignment for UAV antennas for tracking by utilising computer vision technologies. A directional antenna with high gain is used by a ground station that can operate by a pan-tilt to point towards the low-gain omnidirectional antenna carried by the UAV. To center the UAV's antenna's image in the frame, the antenna is equipped with a camera, and a computer detects the video and controls the pan-tilt. The antennas are aligned if there are no more than a few pixels between the UAV image center and the image center. The proposed imaging system exhibits fast data collection, thus attaining a high packet delivery rate and the minimum use of energy. With the suggested antenna auto-alignment approach, the antennas can be accurately aligned with an angle error of under one. UAVs must take the smoothest and shortest pathways possible to accommodate their motion and time constraints. As a result, the Traveling Sales Problem (TSP) is utilized to determine the shortest route, and Bezier curves are then employed to turn paths into a flyable path.

Switch-Beam Antenna Techniques for Bridge Structural Health Monitoring With GaAs-Based Solar Energy Harvesting

<bold xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">The structural health monitoring (SHM) of bridges with wireless sensor networks (WSNs) is addressed by leveraging two distinct but interrelated aspects: GaAs-based solar energy harvesting and switched-beam antenna strategies in combination with asynchronous media access control (MAC) protocols. The joint optimization of solar energy harvesting and switched-beam directional antennas at the nodes is considered and compared with an equivalent omnidirectional antenna network. To address the limited energy budget in battery-based sensor nodes which is a serious limitation in long-lived applications such as bridge SHM, an efficient solar harvesting solution is put forth based on the good performance of GaAs cells even under low-light conditions. Given the current state of the art in GaAs cells, single-junction cells were selected due to the cost of double-or triple-junction versions. The simulation model includes the residual energy capacity with GaAs-based solar energy harvesting of actual selected components (microcontroller, radio interface chip). The model was implemented on top of the Omnet<inline-formula> <tex-math notation="LaTeX">$++$</tex-math> </inline-formula> and Silvaco Atlas simulator. The comparative study in this article provides insights into realistic bridge SHM sensor networks, leveraging solar energy harvesting and switched-beam antennas.</b>

A Miniaturized Dual-Band Modified Rectangular-Shaped Antenna for Wireless Applications

In this article, compact dual-band with rectangular-shaped monopole is presented for wireless applications. Presented antenna built of modified rectangular monopole and two C-shaped strips are attached on the radiating patch. An excellent matching to get the desired dual band operation is found from the back side of the substrate for possible feeding through microstrip. The suggested antenna has extremely small dimensions, measuring just 12 × 15 × 1.59 mm3 while operating at the lower frequency of 2.4 GHz, and it has a bandwidth of 400 MHz (2.1-2.5 GHz) and 6.7 GHz (3.4-10.1 GHz) accordingly with an S11 value that is less than -10 dB. An investigation of the performance capabilities of this dual-band omnidirectional antenna with a variety of geometric parameters has been carried out. The final design is constructed and measured, and the findings from simulation and measurement show a good level of agreement with one another. Across the entirety of the operating band, observable characteristics include a stable radiation pattern, strong impedance matching, and a radiation efficiency of more than 91%.

Zero Energy IoT Devices in Smart Cities Using RF Energy Harvesting

The invention of batteries made it possible to store electricity for many purposes. One of the purposes is to keep the operations of WSN running without any interruptions. The main drawback of sensor nodes is their limited energy sources. The researcher introduces the energy harvesting (EH) concept for IoT-based WSNs to overcome energy limitations and charge the IoT devices. Many energy harvesting techniques have been introduced, such as solar, thermal, and flow-based ones, but radio frequency (RF)-based EH techniques received great attention from researchers due to their easy availability (from TV, radio, and wireless frequencies). In this paper, we have conducted a real-world experiment on Powercast energy harvesting devices and examined the behavior of sensed data in different scenarios, such as indoor, distance (feet/meters), and directional antennas. In our experiments, we have observed that when a device is removed from the charger, the energy scavenging process degrades and reaches a dead state. To stop a device from entering a dead state, we introduce a mobile charger technique to charge the device and find the optimal place for chargers and sensor devices. During mobile charging, we have also observed that when the directional antennas change their angle, the energy scavenging process degrades. To tackle these problems, we introduced two algorithms for directional and omni-directional antennas that efficiently solve the problem. Furthermore, we have obtained results for these scenarios and show that this technique has a promising output.

Distributed coloring and the local structure of unit-disk graphs

Coloring unit-disk graphs efficiently is an important problem in the global and distributed setting, with applications in radio channel assignment problems when the communication relies on omni-directional antennas of the same power. In this context it is important to bound not only the complexity of the coloring algorithms, but also the number of colors used. In this paper, we consider two natural distributed settings. In the location-aware setting (when nodes know their coordinates in the plane), we give a constant time distributed algorithm coloring any unit-disk graph G with at most 4ω(G) colors, where ω(G) is the clique number of G. This improves upon a classical 3-approximation algorithm for this problem, for all unit-disk graphs whose chromatic number significantly exceeds their clique number. When nodes do not know their coordinates in the plane, we give a distributed algorithm in the LOCAL model that colors every unit-disk graph G with at most 5.68ω(G)+1 colors in O(log⁎⁡n) rounds. This algorithm is based on a study of the local structure of unit-disk graphs, which is of independent interest. We conjecture that every unit-disk graph G has average degree at most 4ω(G), which would imply the existence of a O(log⁡n) round algorithm coloring any unit-disk graph G with (approximately) 4ω(G) colors in the LOCAL model. We provide partial results towards this conjecture using Fourier-analytical tools.

A metal hybrid bistable composite tube for multifunctional and reconfigurable antenna

The bistable composite is a deformable lightweight structure with two stable states, which are widely used in aerospace and space fields as deployment mechanisms and deformable structures. In this paper, a new application is proposed as an omnidirectional and directional radiation reconfigurable antenna based on a bistable composite tube. The antenna is prepared based on carbon fiber composite (CFRP) and glass fiber composite (GFRP) as the substrate and metal as the antenna layer co-cured. Mechanical behavior and material micro-interface analyses of the bistable structures are performed. Antennas of different materials and different layups are fabricated and analyzed. The results indicate that the designed antenna structure can be stabilized in the unfolded or stowed state without external support, unfolded into an omnidirectional antenna, and stowed into a directional antenna. The electromagnetic analysis is simulated and experimented to verify its performance as a multifunctional and reconfigurable antenna. Meanwhile, this bistable antenna possesses many advantages, including its lightweight, high storage ratio, and rapid reconfiguration, which make it an excellent candidate for satellite and spacecraft antennas.