Institute of Electron Technology
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Journal of Telecommunications and Information Technology, 2018, nr 1
Get PDFWe consider a two-link system that accommodates Poisson arriving calls from different service-classes and propose a multirate teletraffic loss model for its analysis. Each link has two thresholds, which refer to the number of in-service calls in the link. The lowest threshold, named support threshold, defines up to which point the link can support calls offloaded from the other link. The highest threshold, named offloading threshold, defines the point where the link starts offloading calls to the other link. The adopted bandwidth sharing policy is the complete sharing policy, in which a call can be accepted in a link if there exist enough available bandwidth units. The model does not have a product form solution for the steady state probabilities. However, we propose approximate formulas, based on a convolution algorithm, for the calculation of call blocking probabilities. The accuracy of the formulas is verified through simulation and found to be quite satisfactory
Non-crossing Rectilinear Shortest Minimum Bend Paths in the Presence of Rectilinear Obstacles, Journal of Telecommunications and Information Technology, 2018, nr 3
Get PDFThe paper presents a new algorithm to determine the shortest, non-crossing, rectilinear paths in a twodimensional grid graph. The shortest paths are determined in a manner ensuring that they do not cross each other and bypass any obstacles present. Such shortest paths are applied in robotic chip design, suburban railway track layouts, routing traffic in wireless sensor networks, printed circuit board design routing, etc. When more than one equal length noncrossing path is present between the source and the destination, the proposed algorithm selects the path which has the least number of corners (bends) along the path. This feature makes the path more suitable for moving objects, such as unmanned vehicles. In the author’s scheme presented herein, the grid points are the vertices of the graph and the lines joining the grid points are the edges of the graph. The obstacles are represented by their boundary grid points. Once the graph is ready, an adjacency matrix is generated and the Floyd-Warshall all-pairs shortest path algorithm is used iteratively to identify the non-crossing shortest paths. To get the minimum number of bends in a path, we make a modification to the Floyd-Warshall algorithm, which is constitutes the main contribution of the author presented herein
Optimization of Direct Direction Finding Method with Two-Dimensional Correlative Processing of Spatial Signal, Journal of Telecommunications and Information Technology, 2018, nr 4
Get PDFIn this article, the main parameter of the correlative-interferometric direction finding method with twodimensional correlative processing of spatial signal in the aperture of a linear antenna array (AA) is determined as the value of spatial shift within the AA aperture. The corresponding objective function is also formed. Analytical optimization of this parameter is presented and a comparative analysis of analytical calculations based on simulation results is conducted. In the simulation, a range of dependencies of the middle square deviation of estimation of direction on the value of the spatial shift for a signal-to-noise ratio of 0 dB, for minimum 3-sample and 4-sample Blackman-Harris windows of the spectral analysis, is received. The value of the middle square deviation of estimation of direction will be minimal and will equal 0.02 degrees using a minimum 3-sample Blackman-Harris window with the −67 dB level of side lobes. It offers high noise immunity and high accuracy of direction finding
Optimal Spectrum Sensor Assignment in Multi-channel Multi-user Cognitive Radio Networks, Journal of Telecommunications and Information Technology, 2018, nr 4
Get PDFAccurate detection of spectrum holes is the most important and critical task in any cognitive radio (CR) communication system. When a single spectrum sensor is assigned to detect a specific primary channel, then the detection may be unreliable because of noise, random multipath fading and shadowing. Also, even when the primary channel is invisible at the CR transmitter, it may be visible at the CR receiver (the hidden primary channel problem). With a single sensor per channel, a high and consistently uniform level of sensitivity is required for reliable detection. These problems are solved by deploying multiple heterogeneous sensors at distributed locations. The proposed spectrum hole detection method uses cooperative sensing, where the challenge is to properly assign sensors to different primary channels in order to achieve the best reliability, a minimum error rate and high efficiency. Existing methods use particle swarm optimization, the ant colony system, the binary firefly algorithm, genetic algorithms and non-linear mixed integer programming. These methods are complex and require substantial pre-processing. The aim of this paper is to provide a simpler solution by using simpler binary integer programming for optimal assignment. Optimal assignment minimizes the probability of interference which is a non-linear function of decision variables. We present an approach used to linearize the objective function. Since multiple spectrum sensors are used, the optimal constrained assignment minimizes the maximum of interferences. While performing the optimization, the proposed method also takes care of the topological layout concerned with channel accessibility. The proposed algorithm is easily scalable and flexible enough to adapt to different practical scenarios
Comparative Analysis of QoS Management and Technical Requirements in 3GPP Standards for Cellular IoT Technologies, Journal of Telecommunications and Information Technology, 2018, nr 2
Get PDFOptimization of 3GPP standards that apply to cellular technologies and their adaptation to LPWAN has not led to positive results only enabling to compete on the market with the growing number non-cellular greenfield LPWAN technologies – LoRa, Sigfox and others. The need to take into consideration, during the 3GPP standard optimization phase, the low-cost segment of narrow-band IoT devices relying on such new technologies as LTE-M, NB-IoT and EC-GSM, has also led to a loss of a number of technical characteristics and functions that offered low latency and guaranteed the quality of service. The aim of this article is therefore to review some of the most technical limitations and restrictions of the new 3GPP IoT technologies, as well as to indicate the direction for development of future standards applicable to cellular IoT technologies
Throughput Performance Comparison of MPT-GRE and MPTCP in the Fast Ethernet IPv4/IPv6 Environment, Journal of Telecommunications and Information Technology, 2018, nr 2
Get PDFThis paper presents the MPT-GRE software, a novel multipath communication technology founded on the Generic Routing Encapsulation (GRE) protocol in UDP tunneling RFC specification. It enables the creation of a GRE protocolbased UDP tunnel built on several communication channels. On the other hand, MPTCP is one of the most typical representatives among multipath communication technologies, basing its operation on the utilization of TCP subflows. The authors compare the path-aggregation capabilities of these two technologies using four Fast Ethernet channels. The tests were carried out with the iperf3 network bandwidth measurement tool, and while transferring data using the FTP protocol over both IPv4 and IPv6
Journal of Telecommunications and Information Technology, 2018, nr 1
Get PDFThis paper proposes a fuzzy Manhattan distance-based similarity for gang formation of resources (FMDSGR) method with priority task scheduling in cloud computing. The proposed work decides which processor is to execute the current task in order to achieve efficient resource utilization and effective task scheduling. FMDSGR groups the resources into gangs which rely upon the similarity of resource characteristics in order to use the resources effectively. Then, the tasks are scheduled based on the priority in the gang of processors using gang-based priority scheduling (GPS). This reduces mainly the cost of deciding which processor is to execute the current task. Performance has been evaluated in terms of makespan, scheduling length ratio, speedup, efficiency and load balancing. CloudSim simulator is the toolkit used for simulation and for demonstrating experimental results in cloud computing environments
Performance of Hybrid Sensing Method in Environment with Noise Uncertainty, Journal of Telecommunications and Information Technology, 2018, nr 1
Get PDFThe paper presents a novel hybrid spectrum sensing method used in cognitive radio and presents a hybrid detector (HD) which improves the sensing performance. The proposed HD takes advantage of the energy detection (ED) principle and a method based on Covariance Absolute Value (CAV), as well as on Cyclic Autocorrelation Function (CAF). The paper shows the limitations of using ED, resulting from the uncertainty of spectral density of noise power estimation, known as the SNR wall. The paper describes a system model and presents simulation results for the OFDM signal of a WiMAX-based communications system. The simulation results refer to an ideal environment with well-known parameters, and to an environment with uncertain spectral density of noise power estimation
Model-Based Method for Acoustic Echo Cancelation and Near-End Speaker Extraction: Non-negative Matrix Factorization, Journal of Telecommunications and Information Technology, 2018, nr 2
Get PDFRapid escalation of wireless communication and hands-free telephony creates a problem with acoustic echo in full-duplex communication applications. In this paper a simulation of model-based acoustic echo cancelation and near-end speaker extraction using statistical methods relying on nonnegative matrix factorization (NMF) is proposed. Acoustic echo cancelation using the NMF algorithm is developed and its implementation is presented, along with all positive, real time elements and factorization techniques. Experimental results are compared against the widely used existing adaptive algorithms which have a disadvantage in terms of long impulse response, increased computational load and wrong convergence due to change in near-end enclosure. All these shortcomings have been eliminated in the statistical method of NMF that reduces echo and enhances audio signal processing