فهرست مطالب

  • Volume:8 Issue:1, 2019
  • تاریخ انتشار: 1398/03/11
  • تعداد عناوین: 11
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  • Mahdi Sadeghizadeh *, Omid Reza Marouzi Pages 1-19
    Cluster-based Wireless Sensor Network (CWSN) is a kind of WSNs that because of avoiding long distance communications, preserve the energy of nodes and so is attractive for related applications. The criticality of most applications of WSNs and also their unattended nature, makes sensor nodes often susceptible to many types of attacks. Based on this fact, it is clear that cluster heads (CHs) are the most attacked targets by attackers, And also according to their critical operations in CWSNs, their compromise and control by an attacker will disrupt the entire cluster and sometimes the entire network, so their security needs more attentiveness and must be ensured. In this paper, we introduce a hybrid Intrusion Detection System (HIDS) for securing CHs, to take advantages of both anomaly-based and misuse-based detection methods, that is high detection and low false alarm rate. Also by using a novel preprocessing model, significantly reduces the computational and memory complexities of the proposed IDS, and finally allows the use of the clustering algorithms for it. The simulation results show that the proposed IDS in comparison to existing works, which often have high computational and memory complexities, can be as an effective and lightweight IDS for securing CHs.
    Keywords: Wireless Sensor Networks (WSNs), Intrusion Detection Systems (IDSs), Cluster-heads (CHs), data preprocessing model, clustering algorithms
  • Aliakbar Dastranj *, Mosayeb Bornapour Pages 20-34
    An ultra-wideband (UWB) self-complementary planar bow-tie antenna (SCPBTA) is proposed. The antenna consists of a printed conical horn-shaped (CHS) radiator and a counterpart CHS slot etched on a rectangular ground plane. The printed CHS radiator is connected directly to the 50Ω microstrip line by bending the end portion of the feed line. As a result, the antenna has a simple structure which does not require impedance matching networks. The antenna with a compact size of 32×38×1.2 mm3 can cover UWB spectrum from 3.1 to 10.6 GHz. The simulation time- and frequency-domain results obtained from HFSS simulator package are verified by experimental measurements. Measured results for the reflection coefficient, far-field radiation patterns, radiation efficiency, gain, and group delay of the designed antenna over the UWB spectrum are presented and discussed. Measured data show good concordance with the numerical results. Also, the fidelity factor is calculated in both E- and H-plane by using CST Microwave Studio. The obtained results in both time- and frequency-domain indicate that the proposed SCPBTA is a good option for most practical UWB applications.
    Keywords: Bow-tie antenna, conical horn-shaped (CHS), impedance matching, UWB, SCPBTA, self-complementary
  • Siavash Khorsandi *, Vahid Haghighatdoost Pages 35-56
    With the rapid growth of wireless access networks, various providers offer their services using different technologies such as Wi-Fi, Wimax, 3G, 4G and so on. These networks compete for the scarce wireless spectrum. The spectrum is considered to be a scarce resource moderated by the spectrum allocation regulatory (“regulatory” for short) which is the governance body aiming to maximize the social welfare through moderation of the spectrum allocation table (SAT). In this paper, we present a three stage dynamic game model directed by the regulatory to maximize the clients' welfare. The regulatory controls the proposed prices announced by networks and it determines the tax in proportion to the price and load of each network. The model simulates the behavior of end users, network providers and the regulatory agent through which spectrum allocation strategy is deducted, the rules and parameters are defined, and the system equilibrium in terms of resource allocation and pricing is analyzed. The experimental results show that the proposed spectrum allocation schema results in a situation with the highest clients' welfare and network providers have enough advantages to stay in the market.
    Keywords: Heterogeneous wireless networks, Micro Economic, Social welfare
  • Payman Mohamadi Khalil Abad, Gholamreza Dadashzadeh *, Mohammad Naser, Moghadasi Pages 57-70
    Abstract- In this article, the design of conformal antennas has been discussed using the characteristic modes (CM) method. For this purpose, the vector wave function(VWF) has been utilized to achieve a two-dimensional mapping of the conformal antenna. In designing and analyzing of cone-shaped antennas applicable for multi-input multi-output (MIMO) systems, the most important goal is to achieve a structure with the least correlation coefficient. In order to achieve this goal in these types of antennas, first an appropriate two-dimensional mapping has been selected using the vector wave functions and then its orthogonal characteristic modes have been obtained by the CPM method. In this way, a 4-port conical antenna, whose analysis had many computational problems, was designed; the results obtained from the simulation and the prototype as well as the measurement of this antenna also confirmed the low correlation coefficient (< 0.001), the gain of about 4.2 dB in a frequency of 5.5 GHz, and SWR < 1.22 in the frequency range of 4.6 to 6.6 GHz, indicating a broad bandwidth of around 32%.
    Keywords: Multiple Input Multiple Output (MIMO) Systems, Characteristic Port Modes (CPM), Correlation Coefficient, Characteristic Modes methods (CMs), Vector Wave Functions(VWF)
  • Tahereh Shojaeezand, Gholamreza Mohamadkhani *, Paeiz Azmi, Shervin Amiri Pages 71-82
    In high dynamic conditions, using vector tracking loops instead of scalar tracking loops in GPS receivers is proved as an efficient method to compensate the performance. The Minimum Mean Squared Error detector as a multiuser detector is applied in the vector tracking loop for more reliability and efficiency. The Kalman filter does the two tasks of tracking and extracting the navigation data after applying the multiuser detection on the correlator outputs. The covariance analysis is performed to study the effect of applying a multiuser detector along with a vector tracking loop against the conventional one. The covariance analysis is performed and the variance in the pseudorange-rate estimates produced by the two architectures of conventional vector tracking and the one with multiuser detector are used as the performance criteria. The steady state, state covariance of the Kalman filter of vector tracking loop is calculated. Comparing the psuedorange rate variances obtained from covariance analysis of each method shows improved performance of the new joint receiver of vector and multiuser detector.
    Keywords: Covariance Analysis, GPS, MMSE, Vector Tracking
  • Abbas Ali Sharifi * Pages 82-97
    Cognitive radio (CR) network is an excellent solution to the spectrum scarcity problem. Cooperative spectrum sensing (CSS) has been widely used to precisely detect of primary user (PU) signals. The trustworthiness of the CSS is vulnerable to spectrum sensing data falsification (SSDF) attack. In an SSDF attack, some malicious users intentionally report wrong sensing results to cheat the fusion center (FC) and disturb the FC’s global decision on the PU activity. In this paper, we introduce an effective data fusion rule called attack-aware optimal voting rule (AOVR) to confront the SSDF attack in the CSS procedure. In the beginning stages of the cooperative sensing, two important SSDF attack parameters are estimated and then applied in a conventional voting rule to acquire an optimal number of CR users to minimize the global error probability. Two estimated attack parameters include the probabilities of attack in both occupied and empty frequency bands. Simulation results confirm that the proposed attack-aware approach achieves very good performance over the existing conventional cooperative sensing methods.
    Keywords: Attack-aware, optimal voting rule, spectrum sensing data falsification attack, cognitive radio
  • Ashkan Ghanbari, Alireza Kashani Nia *, Ali Sadr, Hamed Saghaei Pages 98-109
    In this paper, we present a solid-core Silica-based photonic crystal fiber (PCF) composed of hexagonal lattice of air-holes and calculate the effective index and chromatic dispersion of PCF for different physical parameters using the empirical relations method (ERM). These results are compared with the data obtained from the conventional multipole method (MPM). Our simulation results reveal that the ERM is an accurate and fast method for dispersion analysis of PCFs with large pitch sizes. However, for small pitch sizes of PCFs, it is not as accurate as the MPM method. Therefore, ERM is a fast, simple and accurate method for modelling and analysis of Silica-based PCFs with large pitch sizes.
    Keywords: Dispersion, empirical relations method, multipole method, photonic crystal fiber, Silica
  • Meisam Shafaee, Seyyed Mohamad Javad Razavi *, Emad Hamidi Pages 110-122
    In this paper, a new X band Metamaterial (MTM) based ferrite phase shifter is presented. The phase shifter is excited by circular polarized wave base on combination of TE10 and TE01 modes in a square waveguide. In order to synthesize negative refractive index metamaterial (NIM), negative permeability of ferrite slabs in extraordinary mode is mixed with the negative permitivity of printed periodic metallic wires on substrate, in the same frequency band. By using the introduced new circular polarized MTM based layout, the proposed phase shifter loss is less than 3 dB, which treated the main disadvantage of MTM waveguide phase shifters with about 10 dB loss. Also, the proposed phase shifter profits the miniaturization property of MTM design usage. The total length of the phase shifter is 2 cm with 360° differential phase shift, compared to common dual mode phase shifter with 6 cm length in X band.
    Keywords: phase shifter, metamaterial, circular polarization, insertion loss, and miniaturization
  • Mohammad Hasan Ghiasi, Emad Hamidi *, Farokh Hodjatkashani Pages 123-132
    Traveling Wave Tubes (TWTs) consist of different elements. The most important element of TWT is the RF circuit. RF circuits in helix TWTs need a dielectric support to hold the helix; this support also has an effect in electromagnetic properties of RF circuits. A novel dielectric support is proposed to reduce the second harmonic of helix TWTs. The dielectric support in this structure consists of two sections. The first section consists of dielectric material as used in all TWT(s) supports, and the second one is a ferrite rod replaced in a portion of dielectric support. This configuration can act as a tunable band stop filter. The center frequency of the filter can be adjusted based on the second harmonic of the input frequency to reduce the second harmonic of TWT without any loss on fundamental amplified signal.
    Keywords: Traveling wave tubes, bandstop filter, tunable filter, ferrite, second harmonic
  • Hossein Ghani *, Mahmood Mohammadtaheri Pages 133-146
    In this paper a new method for the design of a linear phase distributed amplifier in 180nm CMOS technology is presented. The method is based on analogy between transversal filters and distributed amplifiers topologies. In the proposed method the linearity of the phase at frequency range of 0-50 GHz is obtained by using proper weighting factors for each gain stage in cascaded amplifier topology. These weighting factors have been extracted using MATLAB software. Finally, by plotting the frequency response of the amplifier resulted from MATLAB code and also simulation from ADS, the phase linearity of the designed amplifier is shown.
    Keywords: Distributed Amplifier, Group delay, Transversal Filter, Linear phase, Weighting
  • Behnoush Ghafari Tirabadi *, Majid Afsahi Pages 147-155
    In this paper, two compact quad-channel and six-channel diplexer are designed and fabricated using defected microstrip structure (DMS). This structure is designed for the desired frequency based on the literature reviews. The proposed configuration is composed of a conventional T-junction divider with two pairs of open bended stubs and dual/tri-band filters. In designing dual band filters, a loop resonator loaded with two stepped-impedance resonator and defected microstrip structure. In addition, by adding a pair of open stubs, tri-band responses easily achieved without increasing the circuit size. The operating mechanism in resonance frequencies by surface current density is obtained. As a result, the multi-channel diplexer occupies a compact size of 0.13λg by 0.13λg. The measured results are fully in agreement with the simulated predictions indicating that an isolation between channels is more than 29 dB.
    Keywords: Index Terms- Compact Diplexer, Defected Microstrip Structure, Multi-Channel Diplexer