Institute of Electron Technology
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Rectangular Dielectric Resonator Antenna with Single Band Rejection Characteristics, Journal of Telecommunications and Information Technology, 2019, nr 1
Get PDFIn this paper, a rectangular dielectric resonator antenna (DRA) suitable for wideband applications is presented and a band notch of WLAN (5.15–5.75) GHz is proposed. The DRA is mainly composed of a 20 × 20 mm rectangular dielectric resonator, coated with metal on the top surface, and a circular monopole excitation patch with an air gap insert. A coaxial line feed is used to excite the circular, planar monopole. An open-ended quarter wavelength C-shaped slot is embedded in the circular patch to create the notched band. The simulated results demonstrate that the proposed design produces an impedance bandwidth of more than 80%, ranging from 3.10 to 7.25 GHz for a reflection coefficient of less than −10 dB and with a band rejection at 5.50 GHz. Band notch characteristics, VSWR, and radiation patterns are studied using the HFSS high-frequency simulator and CST Studio software
Empirical Approach in Topology Control of Sensor Networks for Urban Environment, Journal of Telecommunications and Information Technology, 2019, nr 1
Get PDFResearch into the topology control of Wireless Sensor Networks (WSNs) is geared towards modeling and analysis of methods that may be potentially harnessed to optimize the structure of connections. However, in practice, the ideas and concepts provided by researchers have actually been rarely used by network designers, while sensor systems that have already been deployed and are under continued development in urban environments frequently differ from the patterns and research models available. Moreover, easy access to diversified wireless technologies enabling new solutions to be empirically developed and popularized has also been conducive to strengthening this particular trend
Product of Three Random Variables and its Application in Relay Telecommunication Systems in the Presence of Multipath Fading, Journal of Telecommunications and Information Technology, 2019, nr 1
Get PDFIn this paper, the product of three random variables (RVs) will be considered. Distribution of the product of independent random variables is very important in many applied problems, including wireless relay telecommunication systems. A few of such products of three random variables are observed in this work: the level crossing rate (LCR) of the product of a Nakagami-m random variable, a Rician random variable and a Rayleigh random variable, and of the products of two Rician RVs and one Nakagami-m RV is calculated in closed forms and presented graphically. The LCR formula may be later used for derivation of average fade duration (AFD) of a wireless relay communication radio system with three sections, working in the multipath fading channel. The impact of fading parameters and multipath fading power on the LCR is analyzed based on the graphs presented
Blob Extraction Algorithm in Detection of Convective Cells for Data Fusion, Journal of Telecommunications and Information Technology, 2019, nr 4
Get PDFEarth’s atmosphere is monitored by a multitude of sensors. It is the troposphere that is of crucial importance for human activity, as it is there that the weather phenomena take place. Weather observations are performed by surface sensors monitoring, inter alia, humidity, temperature and winds. In order to observe the developments taking place in the atmosphere, especially in the clouds, weather radars are commonly used. They monitor severe weather that is associated with storm clouds, cumulonimbuses, which create precipitation visible on radar screens. Therefore, radar images can be utilized to track storm clouds in a data fusion system. In this paper an algorithm is developed for the extraction of blobs (interesting areas in radar imagery) used within data fusion systems to track storm cells. The algorithm has been tested with the use of real data sourced from a weather radar network. 100% of convection cells were detected, with 90% of them being actual thunderstorm
Implementation of C-PolSK Modulation in FSO Network and Analysis of its Atmospheric Performance, Journal of Telecommunications and Information Technology, 2019, nr 4
Get PDFFree Space Optical (FSO) communication is a quickly developing technology that is designed to handle high data rates while maintaining a good quality factor (Q-factor). Many novel techniques have been implemented to cope with atmospheric attenuating factors, such as fog and rain. Here, we have introduced circular polarization shift keying (C-PolSK) modulation to produce a stable and uniform light beam. The plane of polarized light keeps rotating along with the propagation vector, which helps reduce phase variations and cross-channel effects. C-PolSK provides higher penetrating power and attenuation resistance over linear polarization shift keying (L-PolSK). Two different C-PolSK models have been proposed and graphical comparisons, relying on such parameters as Q-factor, transmission distance and inputoutput power, have been made. The cases of moderate fog and rain attenuation are taken to verify the model’s efficiency. Polarized light is split into two orthogonal components and then modulated using the Mach-Zehnder modulator. One of the models also employs the principle of orthogonal differential phase shifting. Eye diagrams have been provided to verify the bit error rate (BER). The orthogonal differential phase shifted C-PolSK model proves to be the most suitable implementation prototyp
New OSTBC for Blind Channel Estimation and Tracking in MIMO-OFDM Systems, Journal of Telecommunications and Information Technology, 2019, nr 3
Get PDFApplying orthogonal space time block coding (OSTBC) to multiple-input multiple-output (MIMO) systems helps reduce receiver complexity. However, this approach has been applied only to flat fading channels, as when the channel is a frequency selective fading MIMO channel, OSTBC cannot be used directly since its orthogonal propriety may be lost. Furthermore, the MIMO channel is not always known. To deal with this problem, many techniques were proposed to estimate the channel using a training sequence. Unfortunately, these techniques reduce the useful spectral bandwidth. This paper proposes OSTBC for blind channel estimation and data detection in the case of a MIMO frequency selective channel. The aim of this new OSTBC is twofold: to solve the ambiguity of channel estimation and to reduce the complexity of the detector. By exploiting the well-known technique of orthogonal frequency division multiplexing (OFDM), the frequency selective fading MIMO channel is split into a set of flat fading subchannels. Moreover, to accommodate the fact that a MIMO channel can be time varying, the steady state Kalman channel estimator (SS-KCE) is extended to track the channel’s fast variations. The performance of the proposed blind algorithm is related by the adequate choice of the number of subcarriers and it is compared with other existing approaches by means of Monte Carlo simulations
Implementation of Selected Spectrum Sensing Systems for Cognitive Radio Networks using FPGA Platform, Journal of Telecommunications and Information Technology, 2018, nr 4
Get PDFThe energy efficient spectrum sensing method is very important in cognitive radio (CR), since high power drain may limit its implementation in mobile applications. The spectrum sensing feature consumes more energy than other functional blocks, as it depends on continuous detection of the presence or absence of the primary user (PU). In this paper, we proposed two methods to reduce energy consumption of the spectrum sensing feature. The first is of a single stage variety with a reduced number of sensed samples. The other uses two stages. The first stage performs coarse sensing for many subchannels, and the best subchannel is forwarded for fine sensing in the second stage. The performance of the proposed methods is evaluated in AWGN channel and compared with the existing approach. The proposed methods are simulated using Matlab and ModelSim and are then hardware implemented using the Altera Cyclone II FPGA board. Simulation results show that the proposed methods offer an improvement in energy consumption with an acceptable reduction in the probability of detection. At Eb/N0 Eb/N0 Eb/N0 of 0 dB, the energy consumption is reduced by 50% and 72% in the first and second proposed method, respectively, compared to the traditional method (100% sensing)
Journal of Telecommunications and Information Technology, 2018, nr 1
Get PDFIn most cases defragmentation occurs, in elastic optical networks, in the links between the network’s nodes. In this article, defragmentation in an elastic optical network’s node is investigated. The W-S-W switching architecture has been used as a node. A short description of a purpose-built simulator is introduced. Several methods of defragmentation which are implemented in this simulator are described as well
Journal of Telecommunications and Information Technology, 2018, nr 1
Get PDFThis paper is devoted to evaluating the performance of Space-Memory-Memory (SMM) Clos-network switches under a packet dispatching scheme employing static connection patterns, referred to as Static Dispatching (SD). The control algorithm with static connection patterns can be easily implemented in the SMM fabric due to bufferless switches in the first stage. Stability is one of the very important performance factors of packet switching nodes. In general, a switch is stable for a particular arrival process if the expected length of the packet queues does not increase without limitation. To prove the stability of the SMM Clos-network switches considered under the SD packet dispatching scheme the discrete Markov chain model of the switch is used and Foster’s criteria to extend Lyapunov’s second (direct) method of stability investigation of discrete time stochastic systems are used. The results of simulation experiments, in terms of average cell delay and packet queue lengths, are shown as well
Protocols for Wireless Sensor Networks: A Survey, Journal of Telecommunications and Information Technology, 2018, nr 1
Get PDFThis paper presents a survey on the MAC and network layer of Wireless Sensor Networks. Performance requirements of the MAC layer are explored. MAC layer protocols for battery-powered networks and energy harvesting-based networks are discussed and compared. A detailed discussion on design constraints and classification of routing protocols is presented. Several routing protocols are compared in terms of such parameters as: energy consumption, scalability, network lifetime and mobility. Problems that require future research are presented. The cross-layer approach for WSNs is also surveyed