UAV Users Research Articles

Line‐of‐sight probability for UAV communications in 3D grid urban streets

AbstractIn this letter, the authors present a novel expression for the probability of line‐of‐sight (LoS) between a UAV and ground users situated on a gridded street within urban and dense urban environments. Firstly, this study conducts extensive ray‐tracing simulations, encompassing over 50,000 receivers positioned along streets in Brooklyn and Manhattan, respectively. Moreover, the impact of street width on the probability of LoS is investigated, considering three different average widths. By fitting the LoS probability data corresponding to the UAV's elevation angle in two urban environments obtained by simulations, a unified expression representing the relationship between the LoS probability and the UAV's elevation angle is obtained. This obtained LoS probability expression is compared with three existing expressions. The findings presented in this letter can provide some valuable insights for analytical studies on channel modelling between UAVs and ground‐based street users including vehicles.

A Multi-Criteria Solution Approach for UAV Engine Selection in Terms of Technical Specification

Unmanned Aerial Vehicles are electronic systems that are used extensively in every field today and that develop and change very quickly with technology. UAVs are used extensively in many areas, especially in logistics processes, search and rescue activities, military operations, fight to forest fires, photography, monitoring and inspection of agricultural processes. Furthermore, considering their hobby use, it is understood that UAVs have a large commercial market and a high economic value. UAV systems contain many electronic and mechanical systems and many performance criteria can be found for UAV systems. The main ones of these performances are stabilization and engine power. The most important system affecting these performance criteria is the engine. In this study, engine alternatives available in the market for UAVs with take-off weights of 750 to 800 grams were evaluated in terms of mechanical and physical criteria of engine systems, and as a result, the ideal engine model was determined by Analytical Hierarchy method for maximum stabilization and velocity purposes. The article is the first in the literature in terms of the problem obtained and the application of the AHP method to this problem. Thanks to the study, it is aimed to create a Decision Support System for both UAV manufacturers and UAV users so that they can choose the ideal models in engine selection processes.

Modeling and Coverage Analysis for Cellular-Connected UAVs With Up-Tilted Antenna

Existing cellular network is designed mainly for terrestrial users (TUs) with down-tilted antennas, which couldn’t provide efficient 3D coverage for UAV users. This letter proposes up-tilted antenna model to provide 3D seamless coverage for cellular-connected UAVs, and derives coverage probability for both aerial users (AUs) and TUs via stochastic geometry, where the mutual interference between up-tilted and down-tilted antennas is characterized. Specifically, practical antenna model with tunable half power beamwidth <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\theta _{k}$ </tex-math></inline-formula> is adopted and power constraint between up-tilted and down-tilted antenna is considered by modelling power allocation parameter <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha $ </tex-math></inline-formula> , where the interference Laplace transform is rederived considering the mutual interference. In addition, the theoretical analysis is based on semi-closed expression of coverage probability, which can be used to explore the impact of various system parameters. Numerical results show that when 10% of the power is allocated to up-tilted antenna ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$\alpha =0.9$ </tex-math></inline-formula> ), coverage probability of AUs can be significantly increased by 192%, while coverage probability of TUs reduced by less than 1%, compared with only down-tilted antenna.

Using UAV Photogrammetric Technique for Monitoring, Change Detection, and Analysis of Archeological Excavation Sites

The shrinkage of the sensors installed in unmanned aerial vehicles and the increase in data quality have provided great advantages to UAV users, especially in analysis and interpretation works. Archaeologists, in particular, can take full advantage of new opportunities to research and identify objects and artifacts, using remote sensing methods, by studying the past at excavation sites using modern technologies such as UAVs. These methods enable researchers to discover objects on the ground with the help of sensors. This study includes the UAV monitoring, documentation, and analyses of the excavation works that took place in 2014 (phase 1), 2017 (phase 2- phase 3), and 2020 (phase 4) at the Ancient Theatre of Uzuncaburç built in the Roman Empire. For this purpose, photos were taken with the UAV for each phase, and measurements were made from the excavation site's points with precision gauges (total-station and GNSS). 3D point cloud, orthophoto map, Digital Elevation Model (DEM) map, and 3D models of each phase were produced with the taken pictures. Since UAV photogrammetry was used in this study, each excavation phase was recorded precisely. This, unlike classical documentation techniques, enabled the deformations in the excavation areas to be revealed. The 3D position accuracy calculated for the control point (ChP) used in the four excavation phases ranges from 5.8 mm to 33.5 mm. The most important feature of this study is the sensitive examination of the changes in the excavation area for many years with the UAV photogrammetry technique. At the end of the study, the excavation phases and the determination of the deformation points in the excavation area were recorded digitally.

Joint Subchannel Allocation and Power Control in Licensed and Unlicensed Spectrum for Multi-Cell UAV-Cellular Network

In this paper, we investigate the resource and interference management problem in a novel scenario where multiple unmanned aerial vehicle base stations (UAV-BSs) provide cellular services to UAV users (UAV-UEs) by reusing both licensed and unlicensed spectrum. Considering the co-existence of terrestrial cellular, WiFi and UAV-BSs, a joint optimization problem is formulated for both subchannel allocation and power control of UAV-UEs over the licensed/unlicensed spectrum in order to maximize the uplink sum-rate of the multi-cell UAV-cellular network. Since the formulated problem is NP-hard, we decompose it into three sub-problems. Specifically, we first use the convex optimization and the Hungarian algorithm to obtain the global optimal of power and subchannel allocations in the licensed spectrum, respectively. Then, we propose a matching game with externalities and coalition game algorithms to obtain the Nash stable of the subchannel allocation in the unlicensed band. Local optimal power assignment in the unlicensed spectrum is obtained using the successive convex approximation (SCA) method. An iterative algorithm is thereby developed to solve the three sub-problems sequentially till reaching convergence. Simulation results show that the proposed algorithm can improve the network capacity by nearly two times than the Long Term Evolution-Advanced (LTE-A).

Conceptualising and prototyping a decision support system for safer urban unmanned aerial vehicle operations

ABSTRACT Currently, there is limited discourse surrounding the safe operational planning of UAVs within complex multi-stakeholder urban environments. This paper conceptualises a methodology for prototyping a decision support system for urban UAV flight operations planning. The proposition is based on integrating urban 3-dimensional data with the physical factors of UAV flight operations. A simulated, holistic understanding of UAV usage in urban space emerges, enabling better informed decisions by planners around safe flight operations. The feasibility, applicability and benefits of the decision support system and associated policy implications for urban planners and UAV users are discussed scoping further development of this approach.

The enhancement of the prescribed track for unmanned air vehicles

Purpose Unmanned aerial vehicles (UAVs) are more affected by adverse wind conditions in especially landing. Therefore, they need to change the runway in use. In case of this change, to eliminate the uncertain maneuvers, there is a need for a special prescribed track. The purpose of this study is the construction of a prescribed track at a single runway to provide a facility to change the runway in use. Design/methodology/approach Two forms of prescribed tracks, as standard and alternate, were constructed for UAVs by taking into consideration the key parameters to design flight procedures. Both tracks were assessed in a real-time simulation method. Moreover, unmanned vehicle simulation was used for a validation process. Findings According to the real-time simulation results, 8.14 NM and 6.64 NM of flight distance and 5.43 min and 4.43 min of flight time for the standard and alternate prescribed tracks were found, respectively. The obtained results were in favor of the alternate prescribed track. Furthermore, the prescribed track was assessed and validated in both air traffic control and UAV simulations. The feedback of pilots and controllers was very positive for a prescribed track, as it provided them with foresight and time to take care in any situations. Practical implications The prescribed track in this paper may be applied by airspace designers and UAV users to perform safe and efficient landing in adverse wind conditions. Originality/value In this study, a prescribed track was constructed for UAVs. Quantitative results were achieved using a real-time simulation method in terms of flight distance and flight time. Additionally, validation of the prescribed track was achieved by unmanned air vehicle simulation.

Collaboration of UAV and HetNet for better QoS: a comparative study

To boost network performance in terms of QoS, the main approach to be considered is Heterogeneous Networks (HetNet) deployment. One example of UAV-assisted network is the combination of UAV and Ground Users (GU), where GU is connected via random HetNet. This paper shows the comparative performance evaluation of random HetNet for a real communication scenario: with and without UAVs assisted. Here, work is presented into two parts: The first one explains the concept of random HetNet and Random Waypoint Mobility Model (RWPM) for better QoS. The second part investigates the comparison of QoS parameters for the GUs connected in a random HetNet assisted by UAVs versus without UAVs. After comparison, results purely describe the betterment in terms of higher throughput, lower end-to-end delay, and reduced jitter as justified with simulation results and evaluations. The paper concludes that the collaboration between UAV and random HetNet increases performance and supports better QoS.

Collaboration of UAV and HetNet for better QoS: a comparative study

To boost network performance in terms of QoS, the main approach to be considered is Heterogeneous Networks (HetNet) deployment. One example of UAV-assisted network is the combination of UAV and Ground Users (GU), where GU is connected via random HetNet. This paper shows the comparative performance evaluation of random HetNet for a real communication scenario: with and without UAVs assisted. Here, work is presented into two parts: The first one explains the concept of random HetNet and Random Waypoint Mobility Model (RWPM) for better QoS. The second part investigates the comparison of QoS parameters for the GUs connected in a random HetNet assisted by UAVs versus without UAVs. After comparison, results purely describe the betterment in terms of higher throughput, lower end-to-end delay, and reduced jitter as justified with simulation results and evaluations. The paper concludes that the collaboration between UAV and random HetNet increases performance and supports better QoS.

DEVELOPMENT OF GPS SATELLITE VISIBILITY SIMULATION METHOD UNDER URBAN CANYON ENVIRONMENT

Abstract. When the UAV is flying in a lower area than the buildings in the urban environment, the GPS positioning accuracy of the aircraft reduced due to the blocked or reflected signals. Therefore, when the UAVs fly in this area, it should be able to provide a criterion that can give warning message to the UAV users such as stop the auto-flight mode or not rely too much on the position of the UAV represented on the monitor of GCS. In this study, the Elevation Mask Profile (EMP) generation algorithm proposed which calculates azimuth and elevation angle ranges blocked by obstacles at certain grid points by using DSM. It is a core algorithm for a GPS simulator developed that predict the blocked satellite signal by matching the EMP calculated for each grid point with the GPS satellites' azimuth and elevation angle information at the grid point. According to the comparison of EMP and observed data, most of the results had correlation with obstacles nearby. We found some signal blocking areas were not determined as EMP due to the skyscrapers located out of the target area where DSM was constructed. To overcome this limitation, larger spatial data than the DSM that used in this study must be applied. Furthermore, additional studies about optimal search radius definition in EMP calculation procedure to acquire more accurate and standardized EMP are necessary.

Secure probabilistic caching in random multi-user multi-UAV relay networks

In this paper, we investigate the system model of random multi-user multi-UAV relay networks, where the transmission can be overheard by multiple eavesdroppers. We consider the random networks where the users, UAV relays and eavesdroppers arrive at the network subject to the homogeneous Poisson Point Process (PPP). Cache is equipped at UAV relays and users, and can pre-storage part of contents, which can help reduce the information leakage. Hence, it is of vital importance to design an effective secure probabilistic caching strategy to ensure the security of content transmission by combining the cache strategy and the physical-layer security in the presence of eavesdroppers. To this end, we first design the caching placement at users and UAV relays by taking into account four transmission schemes. We then analyze the secure performance of the caching placement by analyzing the expression of secure cache throughput. To maximize the secure cache throughput, we further optimize the probabilistic caching strategy by using the heuristic algorithm. Numerical results and discussion are provided to demonstrate that the proposed probabilistic caching strategy outperforms the conventional most popular content (MPC) and equal probability content (EPC) cache strategies, and the system secure performance can be improved by increasing the cache size and the intensity of UAV relays and users.

Pole Placement Technique Applied in Unmanned Aerial Vehicles Automatic Flight Control Systems Design

Abstract Unmanned aerial vehicles are widely spread and intensively used ones both in governmental and in private applications. The standard arrangements of the commercial-off-the-shelves unmanned aerial vehicles sometimes neglect application of the automatic flight control system onboard. However, there are many initiatives to ensure autonomous flights of the unmanned aerial vehicles via pre-programmed flight paths. Moreover, automatic flight control system can ensure necessary level of the flight safety both in VFR and IFR flights. The aim of this study is to guide UAV users in set up commercial onboard autopilots available on the market. On the contrary, fitness of the autopilot to a given type of the air robot is not guaranteed, and, an extra load on users can appear in controller settings. The proposed pole placement technique is one of the proper methods eliminating difficulties, and, computer aided gain selection using MATLAB will be presented.

ComProSe: Shaping Future Public Safety Communities with ProSe-Based UAVs

3GPP ProSe supports direct discovery and communications between UE localized in proximity to each other. However, the existing 3GPP ProSe has limited support for user-friendly rich media content exchange between different public safety groups. This article proposes ComProSe, an innovative ProSe-enhanced multimedia communication framework for public safety services. By employing UAV as relays, ComProSe provides direct discovery and QoS-aware communications between public safety UEs from different organizations. Additionally, user-friendly interaction between public safety UEs is offered. ComProSe is designed in alignment with the emerging 3GPP 5G technologies and is compatible with both operator networks and mobile consumer electronics. The article also presents real-life testing illustrating the cooperation between UAV and public safety users availing from a public safety service in the context of ComProSe.

BENCHMARKING THE OPTICAL RESOLVING POWER OF UAV BASED CAMERA SYSTEMS

Abstract. UAV based imaging and 3D object point generation is an established technology. Some of the UAV users try to address (very) highaccuracy applications, i.e. inspection or monitoring scenarios. In order to guarantee such level of detail and accuracy high resolving imaging systems are mandatory. Furthermore, image quality considerably impacts photogrammetric processing, as the tie point transfer, mandatory for forming the block geometry, fully relies on the radiometric quality of images. Thus, empirical testing of radiometric camera performance is an important issue, in addition to standard (geometric) calibration, which normally is covered primarily. Within this paper the resolving power of ten different camera/lens installations has been investigated. Selected systems represent different camera classes, like DSLRs, system cameras, larger format cameras and proprietary systems. As the systems have been tested in wellcontrolled laboratory conditions and objective quality measures have been derived, individual performance can be compared directly, thus representing a first benchmark on radiometric performance of UAV cameras. The results have shown, that not only the selection of appropriate lens and camera body has an impact, in addition the image pre-processing, i.e. the use of a specific debayering method, significantly influences the final resolving power.

Two Dimensional Numerical Study of Aerodynamic Characteristic for Rotating Cylinder at High Reynolds Number

Efforts in this century for Unmanned Aerial Vehicle, UAV aerodynamic technology led to a broad of applications. Currently, UAV users are demanding of small, unprepared field or even no field for the aircraft to take off and landing operation. Aligned for the needs, several studies revealed the feasibility of rotating cylinders produced lifting which will impact the improvement of on lift coefficient. Magnus effect on rotating cylinder has the potential as a good lift generator. The studies have discovered the limitation on implementation discovered caused by induced and parasite drag occurrences. Accordingly, rotational rate, α, and Reynold number, Re, are the highlight in this study. The previous experimental and numerical data were used as a basis to compare the results. The methodological approach used for this research in order to prove the presence of Magnus effect, Finite Element Numerical Analysis method in form of 2D numerical is chosen and the simulation done by using ANSYS FLUENT R15.0 to examine the coefficient of lift, drag and understand the aerodynamic characteristics of the rotating cylinder surfaced body. Previous experimental studies carried out by Elliott G. Reid simulated on-design in 2D numerical analysis for validation. The results obtained showed 90.6% accuracy for the validation where the cylinder size to be tested was smaller compared to on-design size. The cylinder size of 30mm as adapted to J. Seifert studies on Magnus effect is used to compare the original size of 114.3mm where the Reynold number tested at the range of 1.17×103 ≤ Re ≤ 1.69×105 with rotational rate ranging from 0 ≤ α ≤ 4.32 determined by air velocity range within 5 ms-1 ≤ U ≤ 15 ms-1. Lift coefficient, CL and drag coefficient, CD determined in every stage analysis were recorded. The results obtained showed that the lift coefficient is slightly lower compared to the original size of cylinder at U are 5ms-1, 7ms-1, 10 ms-1 and 15 ms-1. However, the drag coefficient showed higher value U of 15 ms-1 and 10 ms-1 but lower at U of 5 ms-1 and 7 ms-1.

Dear UAV Users who Play the “Future Rule”

Dear UAV Users who Play the “Future Rule”