Dimitar I. Radev

University ot Telecommunications and Post, Sofia ,Bulgaria · Telecommunications

Advances in the cloud computing and streaming multimedia are steadily increasing the demand on network resources, and telecommunications providers must ensure that their networks are managed effectively in order to ensure that users of the network remain satisfied with their quality of service. The pedagogical value of problem-based and inquiry-bas...

Modelling of MPEG Video Traffic with time series: The paper presents results from a number of investigations into the behaviourur of Asynchronous Transfer Mode (ATM) networks and the problems of video traffic. An approach for describing of Moving Picture Experts Group (MPEG) with time series for Histogram model and Markov chain model is suggested....

Highly reliable aircraft equipment, spacecraft equipment, weapons and military equipment, NPP control systems, medical systems require FPGAs. However, in this direction today develop almost only once-programmable radiation-resistant FPGAs company Actel, which have a triple-bath triggers with a majoritarian scheme of failure suppression and are used...

The world in which we live requires ever more rapid introduction of new technologies. The Internet of things is everywhere, in each field of life and business. Technological time for validation of new systems is reduced, so simulation acceleration methods are increasingly needed. The method for defining significant parameters with the RESTART metho...

Development of social services in Bulgaria is predetermined by the policies of last decades of the last century and is characterized by a number of features arising from the difficult transition to a market economy and modern challenges of dynamic social and economic environment. Social services are activities targeted at supporting assisted person...

SOCIAL ENTREPRENEURSHIP DEVELOPMENT IN BULGARIA

The brain-computer interface (BCI) aim to use Electroencephalography (EEG) or other measures of brain functions can be implemented for communication with smart devices for disabled persons. For connection with different smart devices was used recorded with experimental setup electrophysiological signals for execution of five different mental tasks....

Симулационен алгоритъм за определяне на вероятностните параметри на качеството на обслужване в широколентов хендовър, реализиран със схема с общи приоритети Екатерина Оцетова-Дудин, Eлена Иванова, Димитър Радев A Training Model of a Microprogramming Unit for Operation Control: In this paper, a simulation algorithm with priority scheme for service o...

Advances in the cloud computing and streaming multimedia are steadily increasing the demand on network resources, and telecommunications providers must ensure that their networks are managed effectively in order to ensure that users of the network remain satisfied with their quality of service. The pedagogical value of problem-based and inquiry-bas...

In this paper, a simulation model with priority scheme for service of the process of changing the channel associated with the current connection while a call is in progress at cellular radio networks is proposed. At this model the heterogeneous traffic is served on the base of different handover queues for voice calls and data transfer. An handover...

The basic problem at building of low-rate sensor networks is solving the problem with access to the link for data transfer with the help of set of sensors and limited resources of data transfer environment. An algorithm for determination of time for access to low-rate sensor network is suggested. This algorithm leads to decreasing the number of rep...

Advances in the cloud computing and streaming multimedia are steadily increasing the demand on network resources, and telecommunications providers must ensure that their networks are managed effectively in order to ensure that users of the network remain satisfied with their quality of service. The pedagogical value of problem-based and inquiry-bas...

A simulation approach based on rare event simulation is suggested for a queuing model of multimedia traffic system with three level handover priority schemes. In this approach a rare event simulation is implemented with importance sampling for the estimation of such probabilistic parameters of Quality of Service (QoS) as blocking probability of dro...

The processes, connected with wireless cellular network modelling and simulation is under consideration. On the base of provided comparative analysis of standards IEEE 802.11, 802.16 and 802.21 is chosen the type of network. The influence of network structure - nodes, connections between them, number of handover channels and handover queues, on the...

The processes of changing the channel associated with the current connection while a call is in progress is under consideration. The estimation of dropped calls is received with simulation of handover at one dimensional traffic system with two level priority schemes. Blocking calls at base station channels and handover queue overflow is considered...

Modeling and simulation of handover priority scheme for broadband wireless network are under investigation. The aim of simulation is estimation of the probabilities of handover Quality of Service (QoS) parameters as blocking probabilities of handover channels and overflow probabilities of queues. A handover traffic scheme for broadband wireless net...

The paper examines self-similar properties of real telecommunications network traffic data over a wide range of time scales. These self-similar properties are very different from the properties of traditional models based on Poisson and Markov-modulated Poisson processes. Simulation with stochastic and long range dependent traffic source models is...

Priority handover schemes in wireless mobile network are under consideration. Models of single traffic system, multiple traffic system, multiple traffic system with total priority and traffic system with State Dependent Processor Sharing are considered. Different schemes for handover handling with non-preemptive priorities are compared. The possibi...

When looking at packet-switched networks, Quality of Service (QoS) is affected by various factors, which can be divided into "human" and "technical" factors. Human factors include: stability of service, availability of service, delays, user information. Technical factors include: reliability, scalability, effectiveness, maintainability, Grade of Se...

Advanced Models and Algorithms for Self-Similar IP Network Traffic Simulation and Performance Analysis The paper examines self-similar (or fractal) properties of real communication network traffic data over a wide range of time scales. These self-similar properties are very different from the properties of traditional models based on Poisson and Ma...

The queuing modelling of handover in 4G mobile networks is under consideration. Handover is the process of changing the channel (frequency, time slot, spreading code, or combination of them) associated with the current connection while a call is in progress. Call Admission Control and quality of service requirements are considered for determining o...

The article examines self-similar properties of real telecommunications network traffic data over a wide range of time scales. These self-similar properties are very different from the properties of traditional models based on Poisson and Markov-modulated Poisson processes. Simulation with stochastic and long range dependent traffic source models i...

In this paper, we consider turbo codes that are now introduced in various international standards, including the UMTS standard for third generation personal communications and the ETSI DVB-T standard for Terrestrial Digital Video Broadcasting, and review the method of extrinsic information transfer. The convergence properties of the iterative decod...

The article examines self-similar properties of real telecommunications network traffic data over a wide range of time scales. These self-similar properties are very different from the properties of traditional models based on Poisson and Markov-modulated Poisson processes. Simulation with stochastic and long range dependent traffic source models i...

Call Admission Control in 4G mobile networks: An Call Admission Control (CAC) model for 4G mobile networks with tree buffers and six levels of services is suggested. Differences between CAS in 3G and 4G mobile networks are discussed. Analytical model of CAC for voice, data and video data is developed, which will increase the Quality of Service in m...

Performance modelling and evaluation of multi-service UMTS networks has been major interest for mobile networks providers. The quality of service (QoS) of individual mobile users and the efficient system resource utilisation are two of the most important requirements for the cost-effective management of radio resources. It is essential to assess th...

In this paper we analyze a decoding algorithm, which corrects both erasures and errors for Reed-Solomon (RS) codes based on the Euclidean algorithm together with the Berlekamp-Massey (BM) algorithm. We present and discuss the implementation of RS codes in the DVB (digital video broadcasting) standards and give a brief review of the new DVB-H standa...

The paper is devoted to modeling and simulation of traffic with compression at media gateway nodes for the next generation networks based on Markov Reward Models (MRM). The bandwidth sharing policy with partial overlapped transmission link is considered. Calls arriving to the link that belong to VBR and ABR traffic classes, are presented as indepen...

Modelling and Optimizing time for service in call center. In the suggested paper the traffic processes in telephone call centers are under investigation, where are employed queuing theory also we consider a system with two types of traffic and two types of agents. The distribution of waiting times for serviced/rejected calls was studied. Interestin...

In contemporary telecommunication systems Markov processes are seldom observed, and the widely used Markovian models don't represent precisely the real system. In order to omit the need of modeling the system with a Markov chain we apply different clustering approaches for obtaining the steady state probabilities, which are represented by the data...

An approach to overflow probability estimation in the queuing systems based on rare event simulation with Markov chains is proposed in this paper. Rare event probability that content of the second buffer exceeds some high level L before it becomes empty starting from a given state is considered. The approach is based on Markov additive representati...

This paper is devoted to modeling and analysis of media gateway nodes for the next generation networks based on Markov reward models. The bandwidth sharing policy with partial overlapped transmission link is considered. Calls arriving to the link that belong to VBR and ABR traffic classes, are presented as independent Poisson processes and Markov p...

In this paper, we present a core network model of universal mobile telecommunication system with calls that belong to one of four service classes and arrive randomly. Arriving calls are granted service based on specific service class, required maximum and minimum bandwidth, and available network resources. Performance of priority-based dynamic capa...

This paper examines self-similar (or fractal) properties of real teletraffic data over a wide range of time scales. These self-similar properties are very different from the properties of traditional models based on Poisson and Markov-modulated Poisson processes. The algorithms for modelling fixed-length sequence generators that are used to simulat...

This paper is devoted to research and development of the computational procedures to obtain the steady-state probability vectors in the queueing networks. The numerical methods for the Markov chains performance evaluation and analysis, such as direct, iterative and aggregative methods, are considered and compared. The enhanced computational procedu...

An approach for simulation modelling of overflow probability in M/M/1/N queuing system based on the rare event simulation is suggested. Тhe developed algorithm for M/M/1/N queuing system help to speed-up the simulation for estimation of overflow probability, which in this case is a rare event. Numerical and simulation results are shown.

In this paper a new approach to the network local-balance estimation is presented on the base of clustering and neural modelling, in which the cluster centres can replace the steady states of the Markov chain. The equilibrium of queueing networks is a mean for performance evaluation of real communication systems presented as Markov chains. The new...

The problem of site dependent estimation of the seismic strong motion for Sofia region is discussed. Deterministic modelling for micro-zonation of Sofia region is implemented for receiving an estimation of local site conditions as result of displacements provoked by seismic events in Sofia region with stochastic and neural modelling. An approach fo...

A new approach to two-dimensional evaluation of the queueing network equilibrium, based on calculations of the steady-state probability vector with use of neural modeling and clustering, is considered in this paper. The equilibrium of queueing networks is a mean for performance evaluation of real communication systems presented as Markov chains. Th...

In this paper, we present the Universal Mobile Telecommunication System (UMTS) core network model with calls that belong to one of four service classes and arrive randomly. Arriving calls are granted service based on specific service class, required maximum and minimum bandwidth and available network resources. Performance of priority-based dynamic...

The paper deals with computer generation of pseudorandom numbers, random variables and stochastic processes. Inverse-transform method, composition method and acceptance-rejection method for generation of one-dimensional continuous variations are considered. Algorithms for simulation of the basic distributions (exponential, gamma, beta, normal binom...

The problem of forecasting in general and in real-time of the behavior of seismic wave is discussed. Seismic waves classification on the base of principle axis transformation and evolutionary power spectrum estimation is provided for it implementation in an intelligent hybrid model. A hybrid model for real-time forecasting of strong motion accelera...

Mobile communication networks with calls which belong to one of four service classes and arrive randomly, are considered in the paper. Arriving calls are granted service based on the definite service class, required maximum and minimum bandwidth, and available network resources. Clustering procedure for performance analysis of mobile communication...

One of important tasks in link allocation policies in multirate circuit switched loss models is sharing of link capacity between service classes. For quality of service guarantees the most interesting are sharing policies that maximize throughput and keep the per-class blocking probabilities under some GoS constraints. In this work is suggested a m...

In this paper is solving the problem of performance evaluation of discrete Markov chains in which the topology is unknown in advance. Two heuristic classification procedures for clustering of classes are presented. The first is realized with the help of self-organizing Kohonen neural network in which the target classes are describing with winner we...

An approach for presentation of distribution of homogeneous continuous Markov chains with the help of vector quantization is suggested. Rules for 2D transformation of complex queuing systems, described with discrete time Markov chains and Markov reward models are summarized. Numerical results for simple tandem Jackson network are presented

An approach for real-time analyses, estimation and prognoses of strong motion seismic waves with stochastic modeling and neural network is presented. As input information are given the parameters of recorded part of accelerogram, principle axis transform and spectral characteristics of the wave. With the help of stochastic long range dependence tim...

A stochastic method for optimal graph alignment at analysis of embedded discrete-time Markov chain is presented. The method works by generating paths through a graph according to a Markov chain. Each path is assigned a score, and these scores are used to modify the transition probabilities of the Markov chain. This procedure converges to a fixed pa...

The purpose of this investigation is determining the parameters of non-stationary models for different kind of non-stationary processes. With the help of neural network and vector quantization is suggested an approach for modelling one-dimensional and two-dimensional time series. The parameters of vector quantization are determined for describing p...

The paper presents results from a number of investigations into the problems of implementing intelligent methods in the prediction and simulation of ATM traffic, based on time series and state models. A prognosis method based on a neuro-fuzzy model and learning vector quantization (LVQ) is suggested The implementation for stochastic and long range...

In this research is applied simulation modeling of queuing systems with the help of vector quantization. A technique for adjusting the boundaries between classes with vector quantization is suggested. With this technique is determined the function of density distribution of the input flow. The implementation of suggested approach for simple Jackson...

In this study is presented using a neural networks and learning vector quantization (LVQ) for generating of histogram and a simple Markov chain models of GOP size sequence of MPEG video traffic. The implementation of both models is shown for frame-based analysis of the cell loss probability.

Earthquake excitation has evident randomness and also has strong fuzziness owing to the uncertainties in the definition of earthquake intensity and site soil classification. The proposed method for simulation of seismic ground motions includes simulation of the event as a stationary filtered white noise with fuzzy parameters. The analytical procedu...

Analysis of Markov reward models with stochastic Petri nets is presented. Generation methods and analysis of continuous-time Markov chains and Markov reward models is provided for modeling of reliability of very large systems and working out measures for their performance. Examples and numerical results for M/D/1/2/2 system are shown.

The problem of forecasting in general and in real-time of the behaviour of seismic wave is discussed. A hybrid model for real-time forecasting of strong motion acceleration on the bases of general, tectonic, seismic and site parameters is developed. On the base of this forecasting can be made right decision for activating different devices and syst...

The problem of estimation of seismic wave's behaviour for Sofia region is discussed. An approach for seismic waves classification on the base of principal axis transformation, long-range dependence time series analysis and neural modelling is suggested. With the help of principle axis transformation, stochastic long-range dependence time series ana...

The paper is devoted on methods and algorithms for steady-state analysis of Markov chains. Basic, direct and iterative methods for steady-state analysis of Markov chains are concerned, where Gaussian Elimination method and Grassman method, as well as Power, Jacobi's and Gauss-Seidel's methods are implemented. Algorithms for computation of steady-st...

Two main approximation methods for steady-state analysis of Markov chains are introduced: Courtois's decomposition method and Takahashi's iterative method. The Courtois's approach is based on decomposability properties of the models under consideration. While Courtois's method is non- iterative and is applied for the approximate computation of the...

The paper is devoted on the problem of strong motion waves classification and real-time prognoses with neural network. As input information for the neural network are given the parameters of recorded part of accelerogram, principle axis transform and spectral characteristics of the wave. With the help of stochastic long-range dependence time series...

Fuzzy models are used for oestrus detection with dairy cows. The influence of the number of terms of input and output linguistic parameters and the number of observed input parameters in oestrus detection are studied. The received models are estimated on the base of the target value and the maximal probability of oestrus detection. 1 Introduction T...

A study of the site effects and the microzonation of Sofia region, based on the modeling of seismic ground motion along three cross sections were carried out. Realistic synthetic strong motion waveforms have been computed for an earthquake scenario applying a hybrid modeling method, based on the modal summation technique, finite differences scheme...

The paper is devoted on computer simulation of rare event probability, which is a critical issue in areas such as reliabilities, telecommunications, aircraft management, etc. This means that it is necessary to evaluate probabilityties less than 10 -9 , which is unreasonable to be simulated with standard Monte Carlo approach. M/M/1/N queuing system...