Journal of Communication EngineeringJournal of Communication Engineering
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Sun, 23 Sep 2018 10:11:07 +0100FeedCreatorJournal of Communication Engineering
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Feed provided by Journal of Communication Engineering. Click to visit.Design and fabrication of a high-Q near-field probe for subsurface crack detection
http://jce.shahed.ac.ir/article_586_128.html
Non-destructive detection and evaluation of invisible cracks in metal structures is an important matter in several critical environments including ground transportation, air transportation and power plants. In this paper, a high-Q near-field Microwave probe is designed and fabricated using defected ground structures for surface and subsurface crack detection in metal structures. For this purpose, several near-field probes with different DGSs are designed and probe with the highest quality factor is selected for subsurface detection. Experimental results show that the proposed probe is able accurately detect invisible crack of a size 1mm with at least 20dB magnitude and more than 300 degrees phase contrast. It has also been demonstrated that the proposed device can efficiently used for detection and imaging of small failure and crack in dielectric and metallic structures. Also, it is noted that if the probe dimensions scale down, spatial resolution for crack detection of size in micro and nanometer is achieved at millimeter waves.Thu, 31 May 2018 19:30:00 +0100A Novel Circularly polarized dielectric resonator antenna with Branch-Line Coupler and ...
http://jce.shahed.ac.ir/article_587_128.html
A new shaped circularly polarized dielectric resonator antenna (CP DRA) is studied with branch-line coupler and log-periodic balun for the GPS application. Since the coupler and balun are located under the DRA, it does not increase the footprint of the antenna, as a result the system is very compact. Two configurations are considered in this paper. In the first configuration, an external 50Ω load is used for the matching port of the branch-line coupler. For the second one, a three-resonator log-periodic balun is used instead of branch-line coupler, thus, no lumped elements are required in this configuration. Moreover, two modes HEM11δ of the cylindrical DRA are utilized to design the wide band circular polarization. The reflection coefficient, axial ratio, antenna gain, and radiation pattern are studied for each configuration. These first and the second configurations offer an impedance bandwidth (S11Thu, 31 May 2018 19:30:00 +0100A Data Focusing method for Microwave Imaging of Extended Targets
http://jce.shahed.ac.ir/article_588_128.html
This paper presents a data focusing method (DFM) to image extended targets using the multiple signal classification (MUSIC) algorithm. The restriction on the number of transmitter-receiver antennas in a microwave imaging system deteriorates profiling an extended target that comprises many point scatterers. Under such situation, the subspace-based linear inverse scattering methods, like the MUSIC algorithm, fail to image the extended targets. In proposed method, the DFM divides imaging region into several sections and maps the scattered data to each section by applying a linear transformation. Being weakened clutters from other sections, the resultant focused data contains, mostly, the responses of scatterers inside the desired section. In this way, the number of scatterers is reduced comparing to the number of transmitter-receiver antennas and the requirement for the MUSIC is satisfied. Using experimental data, we show that the DFM in conjunction with the MUSIC is successful in microwave imaging of extended targets.Thu, 31 May 2018 19:30:00 +0100Power Control and Scheduling For Low SNR Region in the Uplink of Two Cell Networks
http://jce.shahed.ac.ir/article_589_128.html
In this paper we investigate the sub-channel assignment and power control to maximize the total sum rate in the uplink of two-cell network. It is assumed that there are some sub-channels in each cell which should be allocated among some users. Also, each user is subjected to a power constraint. The underlying problem is a non-convex mixed integer non-linear optimization problem which does not have a trivial solution. To solve the problem, having fixed the consumed power of each user, and assuming low co-channel interference region, the sub-channel allocation problem is reformulated into a more mathematically tractable problem which is shown it can be tackled through the so-called Hungarian algorithm. Then, the consumed power of each user is reformulated as a quadratic fractional problem which can be numerically derived. Numerical results demonstrate the superiority of the proposed method in low SNR region as compared to existing works addressed in the literature.Thu, 31 May 2018 19:30:00 +0100Wideband Dispersion Compensation in Square Lattice Photonic Crystal Fibe
http://jce.shahed.ac.ir/article_610_128.html
In this paper, a new structure is provided for the dispersion compensating photonic crystal fibers in order to broaden the chromatic dispersion and increase the dispersion compensating capability in a wide wavelength range. In the structure, putting a combination of circular holes and a star structure in the inner core clad causes the dispersion coefficient profile to be broadened, and additionally causes the fiber to have a negative dispersion coefficient in the whole S to U telecommunication bands. In this fiber, the minimal dispersion coefficient will be -653ps/(nm.km). Furthermore, with the diameter of the circular holes of the inner clad in this structure increased, a relatively flat dispersion profile will be obtained in the whole E to U telecommunication bands with a dispersion variation equal to 46ps/(nm.km). In the S to C telecommunication bands, the dispersion variation is 17ps/(nm.km). The simulations are all done using the finite difference time domain numerical (FDTD) method.Thu, 31 May 2018 19:30:00 +0100Groove Gap Waveguide (GGW) H-plane Horn Antenna and a Method for Its Back lobe Suppression
http://jce.shahed.ac.ir/article_619_128.html
recently a new structure called groove gap waveguide (GGW) is ‎introduced to implement low loss microwave component devices ‎especially for millimeter wave applications. This paper presents a ‎new type of H-plane horn antenna making use of this new technology ‎in which backward radiation is significantly suppressed by ‎introducing a high impedance surface at the antenna aperture. The ‎high impedance surface that we used as the back lobe suppressor is a ‎corrugated surface. The designed antenna is simulated by HFSS and ‎its radiation performance is compared with an ordinary GGW H-‎plane horn in which no back lobe suppression mechanism is used. ‎Results show a significant improvement in back lobe suppression and ‎gain enhancement by the proposed structure.‎Thu, 31 May 2018 19:30:00 +0100BLIND PARAMETER ESTIMATION OF A RATE k/n CONVOLUTIONAL CODE IN NOISELESS CASE
http://jce.shahed.ac.ir/article_636_128.html
This paper concerns to blind identification of a convolutional code with desired rate in a noiseless transmission scenario. To the best of our knowledge, blind estimation of convolutional code based on only the received bitstream doesn’t lead to a unique solution. Hence, without loss of generality, we will assume that the transmitter employs a non-catastrophic encoder. Moreover, we consider a complete synchronous scenario in which one can extract separate codewords from received sequence. This assumption is valid in many practical communication systems because, the frame preambles allow us to identify the beginning of each codewords.In this paper, we examine the blind identification problem for rate1/n and rate k/n convolutional codes, respectively. For rate 1/n, we propose an iterative method that uses three steps in each iteration to test the validity of a possible value of n. We show that this method can identify the parameters of a rate 1/n convolutional code from only two different noiseless received codewords. Afterwards, we generalize this method for a rate k/n convolutional code in which each iteration is composed of seven successive steps. We show that this method requires at least k+1 different codewords to identify all parameters of a rate k/n code.Thu, 31 May 2018 19:30:00 +0100Design and Implementation of a Compact Super-Wideband Printed Antipodal Antenna Using Fractal ...
http://jce.shahed.ac.ir/article_637_128.html
A compact printed fractal antipodal bow-tie antenna is designed and implemented to simultaneously cover the operations in the C, X, and Ku-bands. It is demonstrated that by addition of small fractal elements at the sides of hexagonal arms of the bow-tie, a wide operating frequency range of 3.3 to 19.1 GHz can be covered while antenna size is only 30×34×1.2 mm3. In order to match the antenna to the 50Ω SMA connector, a multi-section microstrip line of different widths is designed. The simulation results obtained from HFSS simulator package are verified by experimental measurements. Measured data are in good agreement with the simulated results. The frequency- and time-domain characteristics of the antenna including impedance matching, far-field patterns, radiation efficiency, gain, and fidelity factor are presented and discussed. The proposed antenna features 141% impedance bandwidth (defined by -10-dB reflection coefficient), small size, and desirable radiation patterns that make it excellent candidate for integration in broadband array systems.Thu, 31 May 2018 19:30:00 +0100Dual Polarization Synthesis and Optimization of Cylindrical Offset Reflector Antenna for ...
http://jce.shahed.ac.ir/article_640_128.html
This paper presents the shaping optimization of an S-band cylindrical offset reflector antenna with cosecant-squared radiation pattern in elevation plane. The cross section of the antenna is mathematically modeled by a polynomial function and optimized by the genetic algorithm to obtain the desired pattern for both TE and TM polarizations. The physical optics method together with the uniform theory of diffraction is used to efficiently calculate the radiation pattern during the optimization. Numerical results show that the cosecant-squared radiation pattern can be achieved with good accuracy for angular span of 50◦. The computed radiation pattern agrees well with method of moments as well as CST software and deviates less than about 0.7 dB, on average, from the ideal cosecant-squared pattern.Thu, 31 May 2018 19:30:00 +0100Achievable Secrecy Rate Regions of State Dependent Causal Cognitive Interference Channel
http://jce.shahed.ac.ir/article_675_128.html
In this paper, the secrecy problem in the state dependent causal cognitive interference channel is studied. The channel state is non-causally known at the cognitive encoder. The message of the cognitive encoder must be kept secret from the primary receiver. We use a coding scheme which is a combination of compress-and-forward strategy with Marton coding, Gel’fand-Pinsker coding and Wyner’s wiretap coding at the cognitive encoder. We use rate splitting for messages at both transmitters. Furthermore, the cognitive user compresses its channel observation using Wyner-Ziv coding and splits the index of its compressed signal. By using this scheme we derive an achievable secrecy rate region for this channel and extend the results to the Gaussian case and provide some numerical results.Thu, 31 May 2018 19:30:00 +0100Radiation Pattern Analysis of Inverted-F Antenna Mounted on the Side Wall of a Long Cylinder
http://jce.shahed.ac.ir/article_682_0.html
An analytical technique is proposed for estimation of the radiation pattern of inverted-F antenna (IFA) which is mounted on the side wall of a long cylinder. The method can be applied to describe the IFA radiation in a lot of practical cases. It is indicated that this radiation pattern is a combination of radiation patterns of a horizontal and a vertical small radiator, near the cylinder with a certain proportion. Some discussion is presented about this proportion and analytical results are compared with the simulations. Also the proportion is formulated in terms of antenna dimensions using a GA optimization. Finally a typical applicable IFA with smooth radiation pattern is fabricated and its radiation pattern is measured to verify the proposed method. The proposed method can help the designer to estimate the radiation pattern of IFA antenna that mounted on a big cylinder quickly before the simulation.Tue, 10 Jul 2018 19:30:00 +0100A Lightweight Intrusion Detection System Based on Specifications to Improve Security in ...
http://jce.shahed.ac.ir/article_692_0.html
Due to the prevalence of Wireless Sensor Networks (WSNs) in the many mission-critical applications such as military areas, security has been considered as one of the essential parameters in Quality of Service (QoS), and Intrusion Detection System (IDS) is considered as a fundamental requirement for security in these networks. This paper presents a lightweight Intrusion Detection System to protect the WSNs against the most important of routing attacks in network layer based on their extracted specifications. The proposed IDS, in contrast to related works that often focuses on a specific attack, covers almost all recognized important routing attacks in WSNs. With the full simulation of the routing attacks and the careful examination of their behavior, we extracted key specifications to identify them in the proposed system. Also, due to local operations provided to detect and significantly reduce communications, the proposed method is a lightweight approach. Another advantage of the proposed method is reducing false alarms rate by applying appropriate thresholds. We considered all performance criteria to evaluate and compare the proposed method. Simulation results show that the proposed system is an effective and lightweight IDS in WSNs due to high detection accuracy, low false alarms rate, and low power consumption.Sat, 08 Sep 2018 19:30:00 +0100Incremental adaptive networks implemented by free space optical (FSO) communication
http://jce.shahed.ac.ir/article_699_0.html
The aim of this paper is to fully analyze the effects of free space optical (FSO) communication links on the estimation performance of the adaptive incremental networks. The FSO links in this paper are described with two turbulence models namely the Log-normal and Gamma-Gamma distributions. In order to investigate the impact of these models we produced the link coefficients using these distributions and assumed that the network is exchanging data between the nodes that are contaminated with these coefficients. Firstly, by the FSO link assumption, we performed the theoretical analysis for the steady-state performance of the adaptive network and driven closed-form relations explaining the link impacts. Secondly, we performed simulation results for Log-normal and Gamma-Gamma link conditions and presented various results for different levels of turbulence. Finally, we compared the theoretical and analytical results showing a close agreement between these two findings. The results are presented by the means of mean square deviation (MSD) and excess mean square error (EMSE) values.Sat, 08 Sep 2018 19:30:00 +0100A Priority-based Routing Algorithm for Underwater Wireless Sensor Networks (UWSNs)
http://jce.shahed.ac.ir/article_704_0.html
Advances in low-power electronics design and wireless communication have enabled the development of low cost, low power micro-sensor nodes. These sensor nodes are capable of sensing, processing and forwarding which have many applications such as underwater networks. In underwater wireless sensor networks (UWSNs) applications, sensors which are placed in underwater environments and predicted enable applications in oceanographic data collection, mine reconnaissance, pollution, assisted navigation, distributed tactical surveillance, and ocean sampling. Each sensor uses acoustic signals as its physical medium for communications. This study focuses on a priority-based routing protocol in underwater wireless sensor networks. This routing method tries to improve the QOS requirements with considering high and low priority traffic classes. Through simulation study using the OPNET simulator, we proved that proposed algorithm achieves high performance as compared to GEDAR, in terms of packet loss, end to end delay of data transmission and energy consumption.Sun, 16 Sep 2018 19:30:00 +0100Target Tracking with Unknown Maneuvers Using Adaptive Parameter Estimation in Wireless Sensor ...
http://jce.shahed.ac.ir/article_705_0.html
Abstract- Tracking a target which is sensed by a collection of randomly deployed, limited-capacity, and short-ranged sensors is a tricky problem and, yet applicable to the empirical world. In this paper, this challenge has been addressed a by introducing a nested algorithm to track a maneuvering target entering the sensor field. In the proposed nested algorithm, different modules are to fulfill different functions, including sensor selection, adaptive maneuver parameter estimation, and target trajectory extraction. To that end, proposed algorithm combines the auxiliary particle filter with the Liu and West filter and applies them for the first time in the wireless sensor network. Its performance is compared to one of the most common approaches for this kind of problem and the results show the superiority of proposed method in terms of the estimation accuracy. The simulation study also involves evaluating the proposed algorithm based on the scalability criterion and the results are promising since the reduction by 40 percent in the number of active sensors leads to, respectively, 18.2 and 14.3 percent increments in the RMSE of position and velocity estimates.Sun, 16 Sep 2018 19:30:00 +0100