Stefan Panic

In this study, we present an innovative approach to modelling the propagation channels of land mobile satellite (LMS) systems by employing the η − μ distribution for a comprehensive narrowband channel model, which is crucial for the foundation of wideband models. This model is pivotal for accurately representing the complexities of satellite-to-mob...

This study introduces a neural network-based approach to estimate the level crossing rate (LCR) and average fade duration (AFD) for wireless fading channels characterized by a \(\kappa \)–\(\mu \) shadowed model. The feed-forward architecture of the neural network is optimized for modeling the complex dynamics inherent in wireless communications, h...

In this paper, we are observing a reparable system comprised of several components. The aim is to determine at which repair rate the system achieves the highest availability. To accomplish that, the procedure for the calculation of the repair rate in function of the desired level of availability for the system with a predetermined repair rate thres...

As reliance on wind energy intensifies globally, optimizing the efficiency and reliability of wind turbines is becoming vital. This paper explores sophisticated maintenance strategies, crucial for enhancing the operational sustainability of wind turbines. It introduces an innovative approach to maintenance scheduling that utilizes a mathematical mo...

The manuscript introduces a novel turbulence model for free space optics (FSO) communication, constructed through the amalgamation of two distinct statistical models, rooted in the scintillation theory. A closed-form expression for the probability density function (PDF) and cumulative distribution function (CDF) of the turbulence channel, specifica...

Within mobile communication systems, the inherent limitations of mobile devices necessitate a considerable portion of signal processing to occur at the base station. The technique of multiple access at the base station, entailing the amalgamation of diverse received signals, plays a pivotal role in the reconstruction of the original signal. This in...

In this paper, performance analysis of free space optical (FSO) system operating in conditions of strong atmospheric turbulence over Gamma–Chi-square turbulence model, has been carried out. We have observed reception over multi-pulse pulse-position (MPPM) modulation format for the case of strong atmospheric turbulence conditions modeled with Gamma–...

The paper investigates the higher order statistics of the ratio of two Fisher-Snedecor F (FS-F) random variables (RVs) and its application to wireless communications in the presence of co-channel interference. Namely, the work provides novel expressions for probability density function (PDF), cumulative density function (CDF), level crossing rate (...

Non-orthogonal multiple Access (NOMA) is an efficient 5G technology that enables network spectral efficiency increase and network access latency. In order to additionally improve the reliability of transmission and increase the achievable rate of NOMA system, combined utilization of NOMA and cooperative relay transmission (CRS) could appear as effe...

The paper considers level crossing rate (LCR) and average fade duration (AFD) of the product of independent and identically distributed (i.i.d) Nakagami-m (NM) and double NM squared (also known as gamma-gamma) random variables (RVs). The derived statistics are then directly applied to the radio-frequency (RF) - free space optical (FSO), dual-hop (D...

The repair rate is a very important parameter for system maintainability and can be defined as a frequency of successfully performed repair actions on a failed component per unit of time. This paper analyzes the integral characteristics of a stochastic repair rate for corresponding values of availability in a system operating under maintenance cont...

This paper considers a system of macro diversity (MD) that consists of a macro receiver of SC diversity (MD SC) and two micro MRC (mD MRC) receivers, which operate in a correlated Gamma-shadowed Rayleigh multipath fading environment. The combination of the maximum L-branch ratio (SNR signal-to-noise) is realized at the micro level, and the optional...

Unmanned aerial vehicles (UAV) assisted edge computing has risen as an assuring technique to accommodate ubiquitous edge computation for resource-limited devices. Thus, this paper proposes an approach to maximize the latency fairness in a UAV-assisted multi-access edge computing (MEC) system. To maximize latency fairness, the authors focus on minim...

This article investigates outage statistics of double gamma–gamma random variable (RV) modeled as the product of two independent and identically distributed gamma–gamma RVs. The outage closed‐form statistics in terms of the first‐order statistical measures (probability density function and cumulative distribution function) and the second‐order stat...

In this paper we will propose new analytically traceable probability density function (PDF) model for free space optics (FSO) turbulence, obtained as a generalization of double Ricean turbulence model, that encompasses both large-scale and small-scale turbulence eddy effects along by taking into account performance decreasing influence of misalignm...

In this paper, the Average Bit Error Rate of the signal in the Free Space Optical system modulated with On-Off keying scheme is calculated and analysed. The Average Bit Error Rate is determined in the case of an atmospheric channel modelled with Gamma-Gamma distribution, Log-Normal distribution, K distribution and I-K distribution. The results are...

Reliability, the number of spare parts and repair time have a great impact on system availability. In this paper, we observed a repairable system comprised of several components. The aim was to determine the repair rate by emphasizing its stochastic nature. A model for the statistical analysis of the component repair rate in function of the desired...

Repair rate is very important parameter in a system maintainability and it can be defined as frequency of the successfully performed repair actions on failed component per unit of time. This paper analyses the integral characteristics of a stochastic repair rate for corresponding values of availability in the system operating under maintenance cont...

Unmanned-aerial-vehicles (UAVs) are intended to be a vital part of beyond 5G (B5G) and 6G communication networks. UAV-to-ground communications in urban and populated areas are usually exposed to highly variable propagation conditions that can be often characterized by composite fading channels. This paper provides mathematical framework for the per...

In this paper, we derive an average symbol error rate (ASER) expression of rectangular quadrature amplitude modulation (RQAM) scheme for unmanned aerial vehicle-enabled communication systems operating over double-shadowing and double-scattering composite fading channel. A moment generating function for the receiver output signal-to-noise ratio is o...

The paper explores N-hop FSO communications assisted by amplify-and-forward relays (AFRs) over N-gamma-gamma (N-gg) turbulence induced (TI) fading channels. We model TI fading signal as the product of independent but not necessarily identically distributed (i.n.i.d) N number of gg random processes (RPs) in order to address N-hop AFR FSO communicati...

In order to provide a novel analytically traceable free space optics (FSO) channel model for describing turbulence based irradiance fluctuations, following basic scintillation theory principles, we have derived closed-form expression for probability density function (PDF) of a new statistical Gamma–Chi-square model. Further, capitalizing on provide...

This paper, by using Borjesson’s and Benitez’s approximation of Q-function, presents a novel and improved composite approximation of Q-function with wide applicability. The presented approach is very general and can be implemented on any observed interval. Based on the proposed approximation of Q-function, the average bit error rate is assessed by...

Covid-19 causes one of the most alarming global health and economic crises in modern times. Countries around the world establish different preventing measures to stop or control Covid-19 spread. The goal of this paper is to present methods for the evaluation of indoor air quality in public transport to assess the risk of contracting Covid-19. The f...

This chapter provides a unified framework for channel modelling and performance evaluation of the wireless systems envisioned for 5G and beyond 5G (B5G) communications in terms of the first and the second order statistical measures (probability density function - PDF, cumulative density function - CDF, level crossing rate - LCR, average fade durati...

Rapid emergence of wireless sensor networks (WSN) faces significant challenges due to limited battery life capacity of composing sensor nodes. It is substantial to construct efficient techniques to prolong the battery life of the connected sensors in order to derive their full potential in the future Internet of Things (IoT) paradigm. For that purp...

In this paper, the performance of cellular communication system operating over η-µ fading channel, is considered. Using a Decode-and-Forward (DF) multi-hop relay system transmission performances can be enhanced. The closedform expression for the outage probability (Pout) of the system has been derived. In the proposed system, the transmission time...

In this paper, we consider a macro diversity (MD) system consisting of a macro SC diversity (MD SC) receiver and two micro MRC (mD MRC) receivers operating over correlated Gamma-shadowed Rayleigh multipath fading environment. The combination of the maximum L-branch ratio (SNR signal-tonoise) is realized at the micro level, and the optional selectio...

In this paper, a stochastic problem of multicenter location on a graph was formulated through the modification of the existing p-center problem to determine the location of a given number of facilities, to maximize the reliability of supplying the system. The system is represented by a graph whose nodes are the locations of demand and the potential...

In this paper, a resource allocation and data gathering scenario of an unmanned aerial vehicle (UAV) assisted wireless powered sensor network is investigated, in which the sensor nodes (SNs) are remotely powered by power beacons (PBs) via radio-frequency wireless power transmission (RF-WPT). A time-block structure with two phases is proposed to acc...

Radio frequency energy harvesting (RF-EH) offers an unorthodox solution to the painstaking energy constraint drawback in wireless sensor networks (WSNs). In this paper, a data-gathering scenario from a UAV assisted WSN that consists of multiple sensor nodes (SNs) and power beacons (PBs) is considered. All the SNs are remotely powered by the PBs via...

Mobile networks have significant impact on many aspects of our everyday lives. The number of users and requirements increase continuously, which poses many challenges to service providers. Efficient resource planning and ability to adapt to current demands are crucial when it comes to deployment of large-scale and high-performance commercial mobile...

In this paper we consider a wireless receiver model that employs the macro diversity (MD) technique, consisting of a selection combining (SC) receiver fed by two micro diversity (mD) SC branches, which is used to simultaneously reduce the effects of Nakagami-m short term fading, Gamma long term fading, and co-channel interference on the system perf...

Efikasno planiranje resursa i razmatranje performansi su od ključnog zanačaja za realizaciju mobilnih mreža poslednje generacije velikih brzina i širokih razmera. Upotreba alata za modelovanje i simulaciju omogućava bržu i jeftiniju analizu potencijalnih realizacija. U ovom radu, prikazano je softversko rešenje za modelovanje i simulaciju pojedinih...

The paper investigates mobile-to-mobile (M2M) dual-hop amplify-and-forward relay (AFR) communications in composite fading environments. We model composite fading signal as the product of Nakagami-m (Nm) and Gamma (G) random processes (RPs) in order to address multipath-shadowing scenario and derive novel, fast computing, closed form mathematical fo...

Covid-19 causes one of the most alarming global health and economic crises in modern times. Countries around the world establish different preventing measures to stop or control Covid-19 spread. The goal of this paper is to present methods for the evaluation of indoor air quality in public transport to assess the risk of contracting Covid19. The fi...

This paper proposes a new approach to edge detection on the images over which the wavelet decomposition was done to the third level and consisting of different levels of detail (small, medium and high level of detail). Images from the BSD (Berkeley Segmentation Dataset) database with the corresponding ground truth were used. Daubechies wavelet was...

In this paper, we are observing scenario of unmanned aerial vehicle (UAV) data collection from sensor network, where each sensor harvests energy from the data-collecting UAV for its own information transmission. In first time instant, the wireless energy transfer (WET) to sensor nodes is performed, while in the second time instant UAV collects data...

The aim of this paper is to set framework for the repair rate in order to achieve required availability of a repairable system with alternating renewal process where the failure rate is Weibull distributed. In order to accomplish this goal, this paper proposes a novel model for a complete stochastic analysis of the repair rate. The resulting equati...

In this study, the authors investigate average capacity of free space optics communication over Málaga atmospheric turbulence channel with pointing errors and path loss, for intensity modulated/direct detection (IM/DD) and heterodyne detection. Various algorithms which use adaptive transmission with both types of detection are considered, such as:...

In this paper, we consider an unmanned aerial vehicle (UAV) assisted wireless sensor network (WSN), where each sensor nodes' transmission capability is powered by the UAV using wireless power transfer (WPT). Sensor nodes harvest energy from the signal broadcast by the UAV in the down-link (DL) and all the harvested energy will be used for informati...

In this paper, an approximation of the average bit error rate (ABER) probability expression, standard performance measure of wireless transmission over fading channels using linear spline functions with corresponding number of segments has been provided. Further, possible approximation improvement obtained by appliance of composite piecewise spli...

In this paper, we present a few novel simultaneous wireless information and power transfer (SWIPT) schemes that can be effectively used in various 5G wireless network implementations. First, we study the possibility of integrating distributed energy beamforming with the data rate fairness beamforming in a cooperative communication system with multi...

We present a gradient descent algorithm with a line search procedure for solving unconstrained optimization problems which is defined as a result of applying Picard-Mann hybrid iterative process on accelerated gradient descent SM method described in Stanimirović and Miladinović (Numer. Algor. 54, 503–520, 2010). Using merged features of both analyz...

In this paper macrodiversity system consisting of two microdiversity SC (Selection Combiner) receivers and one macrodiversity SC receiver are analyzed. Independent ?-? fading and correlated slow Gamma fading are present at the inputs to the microdiversity SC receivers. For this system model, analytical expression for the probability density of the...

We improve the convergence properties of the iterative scheme for solving unconstrained optimisation problems introduced in Petrovic et al. [‘Hybridization of accelerated gradient descent method’, Numer. Algorithms (2017), doi: 10.1007/s11075-017-0460-4 ] by optimising the value of the initial step length parameter in the backtracking line search p...

Today’s world depends largely on information and communication technologies. These technologies are in use in different areas of human life and work. Each day, more examples of possible application of information and communications technology are being discovered. In most cases, computer science is used to solve complex problems which have mathemat...

This paper presents a novel approach for estimation of repair rate in an observed system comprised of two or more components. The presented approach is based on calculation of probability density function of maximal and minimal system’s repair time by observing the repair rates of its components. Based on the obtained information it can be conclude...

Modelling of complex wireless transmission scenario over fading channels in the presence of multiple co-channel (CCI) interferers will be presented in this paper. Propagation environment will be modelled with general kappa-mu shadowed model, which can be reduced to other well-known model as its singularities. Probability density function (PDF) and...

We will provide statistical analysis of the square ratio of κ-μ and η-μ random processes and its application in the signal-to-interference ratio (SIR) based performance analysis of wireless transmission subjected to the influence of multipath fading, modelled by κ-μ fading model, and undesired occurrence of co-channel interference (CCI), distribute...

Performance Based Logistics (PBL) concept has an aim to improve the system availability and it has been extensively researched in the recent years. These researches showed that inventory level does not impact system availability as much as component reliability and repair time in repairable system operating under PBL contract. Based on that, in thi...

In this paper, an approximation of the optimal compressor function using the quadratic spline functions with 2L = 8 segments is described. Since the quadratic spline with 2L = 8 segments provides better approximation of the optimal compression function than quadratic spline with 2L = 4 segments, capitalizing on the benefits of the obtained spline a...

In this paper, we will analyze signal-to-interference ratio (SIR) based selection combining (SC) diversity system over dual correlated \(\kappa -\mu \) fading channels, in the presence of mutually \(\kappa -\mu \) correlated interferences. Infinite series expressions for probability density function (PDF), and cumulative distribution function (CDF)...

In this paper, capitalizing on novely introduced interval approximation of Q-function, we have presented simple and tight approximation for the evaluation of the average symbol error probability (ASEP) over fading channels. First, comparison to other known Q-function closed-form approximations has been performed, and it has been shown that accuracy...

Macrodiversity (MACD) system with MACD selection combining (SC) receiver and two microdiversity (MICD) selection receivers in the presence of Gamma long-term fading, Rayleigh short-term fading, and co-channel interference affected to Rician short-term fading is studied in this article. The closed-form expressions for probability density function (P...

In this paper we will observe wireless propagation in non-homogenous environment under non-deterministic line-of-sight (LOS) conditions, when the random nature of dominant/scattering components ratio has been considered and modeled as Gamma distribution. First closed-form expressions have been derived for the probability density function (PDF) and...

In this paper, the signal transmission in the Free -Space Optics (FSO) communication system using the software package OptiSystem 7.0 is analyzed. The influence of parameters FSO (Free -Space-Optics) channels (Range, Attenuation, Beam Divergence, Transmitter Loss, Receiver Loss, and Additional Losses) on the reception quality is considered. The rec...

In this paper the efficiency of accelerated gradient descent methods regarding the way of determination of accelerated factor is considered. Due to the previous researches we assert that the use of Taylor's series of posed gradient descent iteration in calculation of accelerated parameter gives better final results than some other choices. We give...

In this paper, capitalizing on Mils ratio for Qfunction approximation, we have presented novel improved composite Q-function approximation. Based on our improved approximation, we have further presented tight approximation for the average symbol error probability (ASEP) expressions of digital modulations over Nakagami-m fading channels. First, comp...

For the development of new 5G systems to operate in mm bands, there is a need for accurate radio propagation modelling at these bands. In this paper novel approach for NLOS channels parameter estimation will be presented. Estimation will be performed based on LCR performance measure, which will enable us to estimate propagation parameters in real t...

In this paper performance analysis of colour image Free Space Optics (FSO) transmission over Double Generalized Gamma (DGG) turbulence communication channel is carried out. At the reception side, we have used an average bit error rate (ABER) for reconstructed image performance measure, as the function of FSO link transmission parameters, such as pr...

In this paper, we consider wireless mobile radio communication system with macro diversity reception. Signal is subject to Weibull small scale fading and Gamma large scale fading resulting in system performance degradation. Receiver uses macro diversity selection combining (SC) technique in order to reduce the impact of long term fading effects, an...

In this paper, HK statistical model is considered. The application of HK distribution in modeling atmospheric turbulence channel under the influence of strong and weak turbulences and all irradiance fluctuations are discussed. Expression for atmospherics turbulence channel model, pointing error models and path loss are given. Probability density fu...

The example of how to create and organize the ETL process on isolated small scale database system which is the part of the larger information system is given in this paper. We have given short description of the database, ETL process and given directions on how to expand classic ETL process with intermediate steps in order to automatize complete pr...

In this paper, the effects of multipath fading and shadowing over the propagation channel are observed through the performance analysis of switch and stay selection combining (SSC) technique. The short term fading (multipath fading) in conjunction with the long term fading (shadowing) are both modeled by Generalized-\textit{K} (\textit{K${}_{G}$})...

Performance analysis of double watermarked image transmission over the Rician turbulence FSO channel was carried out in this paper. First, we have considered the importance of copyright, robustness of watermark in FSO transmission and presented some algorithms for watermarking. Then, simulation of FSO transmission of double watermarked image over R...

Macrodiversity system with macrodiversity selection combining (SC) receiver and three microdiversity SC receivers operating over Gamma shadowed Nakagami-m multipath fading environment is considered in this work. Level crossing arte of signals at outputs microdiversity SC receivers are calculated and by using these formulas, closed form expression f...

Wireless mobile communication system with selection combining (SC) diversity receiver is investigated in this paper. Received signal envelope experiences α-κ-µ short term fading resulting in system performance degradation. Level crossing rate (LCR) and average fade duration (AFD) of SC receiver output signal envelope are obtained as rapidly converg...

Macrodiversity system with macrodiversity selection combining (SC) receiver and three microdiversity EGC receivers operating over Gamma shadowed k-μ multipath fading environment is considered. Macrodiversity SC receiver reduces Gamma long term fading effects and microdiversity SC receiver mitigates k-μ short term fading effects on system performanc...

Mathematical characterization of various types of propaga- tion environments and accompanying transmission phenomenons has arisen as major task in the processes of computing and evaluation the performances of modern generation wireless communication systems ser- vices. In this paper we will analyze standard performance criterions of wireless transm...

In this paper wireless transmission over κ-µ shadowed fading channels in the presence of co-channel interference will be analyzed. First, closed-form expressions will be derived for the probability density function (PDF) and cumulative distribution function (CDF) of equivalent signal-to-interference ratio (SIR) process. Further, dual-branch SSC rec...

In recent times, spare parts inventory systems have been extensively researched, but most inventory models were not fully adequate due to the stochastic nature of inventory environment. This paper proposes an approach that supports decision making process in planning and controlling of spare parts in aircraft maintenance systems. Reliability charac...