ANALYTICAL MODELING AND SIMULATION OF RELIABILITY OF A CLOSED HOMOGENEOUS SYSTEM WITH AN ARBITRARY NUMBER OF DATA SOURCES AND LIMITED RESOURCES FOR THEIR PROCESSING

Continuous development of computer networks and data transmission systems underlines the growing need for adequate mathematical models and methods for analyzing the performance and reliability metrics of these systems, taking into account the performance of their redundant components. We consider a mathematical model of a repairable data transmission system as a model of a closed homogeneous cold standby system with a single repair facility and with exponentially distributed lifetimes and generally distributed repair times of the system's elements. We study the system-level reliability, defined as the stationary probability of failure-free operation of the considered system. The proposed analytical methodology made it possible to evaluate the reliability of the entire system in case of failures of its elements. Explicit analytical expressions were obtained for the stationary probability of the system's failure-free operation and stationary system state probabilities, which allow analyzing other operational characteristics of the system with respect to the performance of its redundant elements. Explicit analytical expressions for the stationary state probabilities of the considered system cannot always be obtained; therefore, to obtain results in the case of general distribution of elements' repair time, a discrete-event simulation model was constructed to approximate the analytical model of the system. The simulation algorithm was programmatically implemented in R. The comparison of numerical and graphical results obtained using both analytical and simulation approaches showed that they were in close agreement, so the proposed simulation model can be used in cases where the analytical solution cannot be obtained explicitly or as part of a more complex simulation model. We’ve also studied the problem of analyzing the sensitivity of the reliability characteristics of the system at hand to the shape of input distributions. The obtained formulas showed the presence of an explicit dependence of these characteristics on the types of distribution functions of the repair time of the system's elements. However, numerical studies and graphical analysis have shown that this dependence becomes vanishingly small with the “fast” restoration of the system's element

Internet of Drones (IoD): Threats, Vulnerability, and Security Perspectives

The development of the Internet of Drones (IoD) becomes vital because of a proliferation of drone-based civilian or military applications. The IoD based technological revolution upgrades the current Internet environment into a more pervasive and ubiquitous world. IoD is capable of enhancing the state-of-the-art for drones while leveraging services from the existing cellular networks. Irrespective to a vast domain and range of applications, IoD is vulnerable to malicious attacks over open-air radio space. Due to increasing threats and attacks, there has been a lot of attention on deploying security measures for IoD networks. In this paper, critical threats and vulnerabilities of IoD are presented. Moreover, taxonomy is created to classify attacks based on the threats and vulnerabilities associated with the networking of drone and their incorporation in the existing cellular setups. In addition, this article summarizes the challenges and research directions to be followed for the security of IoD.Comment: 13 pages, 3 Figures, 1 Table, The 3rd International Symposium on Mobile Internet Security (MobiSec'18), Auguest 29-September 1, 2018, Cebu, Philippines, Article No. 37, pp. 1-1

A distributed man-machine dispatching architecture for emergency operations based on 3GPP mission critical services

With the number of non-human devices expected to significantly overtake human users of LTE networks, it is no surprise that First Responders in Mission Critical operations will need to interact with an increasing number of unmanned devices, “bots” or drones. In the paper we propose the Mission Critical “bot” concept as an entity capable of gathering environmental/situational information and triggering certain automated actions without the need of human intervention. We prove that in certain circumstances these bots can help quickly resolve emergency situations and complement traditional centralized coordination from Dispatch Control Rooms. We explain how such “bots” relate and expand the 3GPP Mission Critical Communications architecture framework, considering different architectural approaches and complexity levels. Importantly, because First Responders must remain focused, hands-free and context-aware most of the time, we cover specifically the case where man-machine interaction is based on voice communication without having to use hands or look at a screen. It is hence of particular interest to convert “bot” interactions into audio information exchanged over push-to-talk communication services, be it through the cellular network or leveraging the 3GPP device-to-device capability. The paper is complemented with theoretical use cases as well as description and multimedia material of a prototype implementation of a concept emulator.Peer ReviewedPostprint (published version

Effects of 3D Deployments on Interference and SINR in 5G New Radio Systems

Lately, the extremely high frequency (EHF) band has become one of the factors enabling fifth-generation (5G) mobile cellular technologies. By offering large bandwidth, New Radio (NR) systems operating in the lower part of EHF band, called millimeter waves (mmWave), may satisfy the extreme requirements of future 5G networks in terms of both data transfer rate and latency at the air interface. The use of highly directional antennas in prospective mmWave-based NR communications systems raises an important question: are conventional two-dimensional (2D) cellular network modeling techniques suitable for 5G NR systems? To address this question, we introduced a novel, three-dimensional framework for evaluating the performance of emerging mmWave band wireless networks. The proposed framework explicitly takes into account the blockage effects of propagating mmWave radiation, the vertical and planar directivities at transceiver antennas, and the randomness of user equipment (UE), base station (BS), and blocker heights. The model allows for different levels of accuracy, encompassing a number of models with different levels of computational complexity as special cases. Although the main metric of interest in this thesis is the signal-to-interference-plus-noise ratio (SINR), the model can be extended to obtain the Shannon rate of the channel under investigation. The proposed model was numerically evaluated in different deployment cases and communication scenarios with a wide range of system parameters. We found that randomness of UE and BS heights and vertical directionality of the mmWave antennas are essential for accurate evaluation of system performance. We also showed that the results of traditional 2D models are too optimistic and greatly overestimate the actual SINR. In contrast, fixed-height models that ignore the impact of height on the probability of exposure to interference are too pessimistic. Furthermore, we evaluated the models that provide the best trade-off between computational complexity and accuracy in specific scenarios and provided recommendations regarding their use for practical assessment of mmWave-based NR systems

RF-based automated UAV orientation and landing system

The number of Unmanned Areal Vehicle (UAV) applications is growing tremendously. The most critical applications are operations in use cases like natural disasters and rescue activities. Many of these operations are performed on water scenarios. A standalone niche covering autonomous UAV operation is thus becoming increasingly important. One of the crucial parts of mentioned operations is a technology capable to land an autonomous UAV on a moving platform on top of a water surface. This approach could not be entirely possible without precise UAV positioning. However, conventional strategies that rely on satellite positioning may not always be reliable, due to the existence of accuracy errors given by surrounding environmental conditions, high interferences, or other factors, that could lead to the loss of the UAV. Therefore, the development of independent precise landing technology is essential. The main objective of this thesis is to develop precise landing framework by applying indoor positioning techniques based on RF-anchors to autonomous outdoor UAV operations for cases when a lower accuracy error than the provided by Global Navigation Satellite System (GNSS) is required. In order to analyze the landing technology, a simulation tool was developed. The developed positioning strategy is based on modifications of Gauss-Newton's method, which utilizes as an input parameter the number of anchors, the spacing between them, the initial UAV position, and the Friis-transmission formula to calculate the distance between the anchors and the UAV. As an output, a calculated position of the UAV with an accuracy in the range of tens of centimeters is reached. The simulation campaign shows the dependencies of the effects of the anchor's number and corresponding spacing on positioning accuracy. Also, the simulation campaign shows Gauss-Newton's method parameter value that maximizes the system performance. The results prove that this approach can be applied in a real-life scenario due to achievements of both high accuracy achieved and close to perfect estimated landing trajectory. Keywords: UAV, Positioning, Automatic Landing, Simulatio

Effects of Heterogeneous Mobility on D2D-and Drone-Assisted Mission-Critical MTC in 5G

mcMTC is starting to play a central role in the industrial Internet of Things ecosystem and have the potential to create high-revenue businesses, including intelligent transportation systems, energy/ smart grid control, public safety services, and high-end wearable applications. Consequently, in the 5G of wireless networks, mcMTC have imposed a wide range of requirements on the enabling technology, such as low power, high reliability, and low latency connectivity. Recognizing these challenges, the recent and ongoing releases of LTE systems incorporate support for lowcost and enhanced coverage, reduced latency, and high reliability for devices at varying levels of mobility. In this article, we examine the effects of heterogeneous user and device mobility-produced by a mixture of various mobility patterns-on the performance of mcMTC across three representative scenarios within a multi-connectivity 5G network. We establish that the availability of alternative connectivity options, such as D2D links and drone-Assisted access, helps meet the requirements of mcMTC applications in a wide range of scenarios, including industrial automation, vehicular connectivity, and urban communications. In particular, we confirm improvements of up to 40 percent in link availability and reliability with the use of proximate connections on top of the cellular-only baseline.acceptedVersionPeer reviewe