Shahed UniversityJournal of Communication Engineering2322-408812120230101Grating-Lobe Reduction for Non-Uniform Linear SubArray Using High order mode114491110.22070/jce.2025.20912.1289ENMohsenEtebarianDepartment of Electrical Engineering, Amirkabir University of Technology0009-0000-0551-7058AyazGhorbanisecondJournal Article20250907a sub-array is a group of smaller antennas arranged into an array. It is a collection of smaller elements in the structure of an array antenna. Not only does this structure have advantages for performance antennas, but also the sub-array has problems, such as the occurrence of grating lobes (GLs) in the radiation pattern. Some of the advantages of these structures are reduced complexity, cost efficiency, and system flexibility. GLs are unwanted patterns that occur when the spacing between antenna elements is large relative to the signal wavelength. These lobes can appear in undesirable directions, decreasing the antenna's performance, including its directivity and gain. There are several methods for GL reduction, including reducing element spacing, using non-uniform or random spacing to disrupt periodicity, applying beamforming weights to suppress sidelobes, and employing multi-subarray techniques for additional control. The main approach to reducing GLs is to introduce a null in the radiation pattern using the high-order mode technique. This means that when the element pattern is a multiple of the array pattern, the GL is omitted from the pattern at -40 degrees. It is possible to change the radiation direction of an antenna by combining two modes. In other words, the beam scan in the element depends on the current excitation mode. Thus, each mode is excited by a coaxial cable, and each antenna element has two power supplies. Simulation results show that the reduction of GL is -21.54 dB.https://jce.shahed.ac.ir/article_4911_68abef8ee1ac9b664a90b0bbaff4f770.pdfShahed UniversityJournal of Communication Engineering2322-408812120230101Adaptive Infrastructure based Geographical Routing for Vehicular Ad hoc Networks1534491010.22070/jce.2025.20233.1280ENOmidAbediKerman UniversityVahidSattari-NaeiniDepartment of Computer Engineering, Shahid Bahonar University of KermanSepidehSabbaghShahid Bahonar University of Kerman, Computer engineeringJournal Article20250315Creating a smart city requires intelligent infrastructures and components. Smart transportation is one of the essential structures of a smart city that, by utilizing vehicular networks and data communications between vehicles and infrastructure, enables citizens to request high-quality services. However, the increase in these communications can lead to a decrease in network service quality. In this paper, an adaptive geographic routing method is proposed to establish a connection between two vehicles in a way that maintains service quality by creating a stable route despite increasing network load and vehicle mobility. To achieve this, three types of connections are considered: a multi-hop connection that only utilizes vehicles along the route, a single-hop infrastructure connection that seeks to connect source and destination RSUs, and a hybrid connection that leverages both types. The type of connection is selected based on mobility parameters and network load. The proposed method is compared with the most widely-used geographic routing in VANETs, namely GPSR, as well as its improved version, MMGPSR. Evaluation results indicate that the proposed method reduces end-to-end delay and also improves data delivery rate.https://jce.shahed.ac.ir/article_4910_43975bc2dfc84641a2a8c4d3fe653176.pdfShahed UniversityJournal of Communication Engineering2322-408812120230101Accurate sensing with dual-band absorber based on graphene doped lattice for terahertz frequencies3546491610.22070/jce.2025.20085.1279ENMahdiehGhaderiElectrical and Computer Engineering Faculty, Semnan University, Semnan, IranPejmanRezaeiSemnan University0000-0002-1266-3229Journal Article20250129Dual-band absorbers using identical shaped graphene doped lattice, with high absorbance coefficients are investigated in this paper. A dynamically tunable dual-band terahertz metamaterial absorber is proposed based on a hybrid graphene-doped frequency selective surface (FSS) structure. The unit cell incorporates concentric square graphene ring resonators and a planar graphene sheet sandwiched between dielectric layers, supported by a metallic backing. These resonators are responsible for the resonance effect and enable dual-band operation. By adjusting the chemical potential of graphene through external gate voltage, the absorption peaks can be dynamically tuned, demonstrating strong spectral flexibility. Simulation results show a maximum absorption of 99.63% at 32.42 THz. Additionally, the impact of different dielectric substrates on the tunability and bandwidth separation is studied, revealing further structural reconfigurability. The proposed absorber also maintains high absorption efficiency under oblique incidence, indicating robust angular stability. These features make the structure a strong candidate for advanced THz sensing and stealth applications.https://jce.shahed.ac.ir/article_4916_f5e62af885293cf4d511ceef31e61c80.pdfShahed UniversityJournal of Communication Engineering2322-408812120230101Introducing a Method-of-Moments Solution for 2-Dimensional TM Electromagnetic Problems4766491910.22070/jce.2025.19053.1269ENMahdiPariziElectrical Engineering Dept., Yazd University, Yazd, Iran0000-0003-3369-7046MansorNakhkashDepartment of Electrical Engineering
Yazd University,Yazd,Iran0000-0001-5826-5667Journal Article20240424This paper introduces a new solution for 2-dimensional (2D) TM electromagnetic problems by the method of moments (MoM) in polar coordinates. The main idea is to reformulate a 2D problem according to addition theorem for the zeroth-order Hankel function of the second kind. Recursive formulas in spatial frequency domain are derived and the scattering field is rewritten into inward and outward components. In this way, a 2D TM problem can be solved using 1D FFT in the stabilized biconjugate-gradient fast Fourier transform (BCGS-FFT) algorithm. Because the emerging method obtains 1D FFT over a circle, there is no need to expand an object region by zero padding, whereas it is necessary for the conventional 2D FFT in cartesian coordinates. Therefore, the polar coordinate approach concludes in less computational burden. Other interesting advantage is that the field on a circle outside a scattering object can be calculated, efficiently, using an analytical formula. This is, particularly, attractive in electromagnetic inverse scattering problems and microwave imaging (MI). The numerical examples for 2D TM problems demonstrate merits of the proposed technique in terms of the accuracy and computational efficiency.https://jce.shahed.ac.ir/article_4919_76b7a3a5cf67f3c4fcde3a8b39dab7be.pdfShahed UniversityJournal of Communication Engineering2322-408812120230101Characteristic mode analysis of graphene plates6790496310.22070/jce.2026.21170.1291ENKhaterehMoradikermanshah university of technology0000-0001-5722-8493AliPourziadDepartment of Electrical and Computer Engineering, University of Tabriz, Tabriz, IranSaeidNikmehrDepartment of Electrical and Computer Engineering, University of Tabriz, Tabriz, IranJournal Article20251105In this paper, the resonance behavior of graphene plates with different shapes, rectangular, circular and triangular in the terahertz frequency range is analyzed with a new approach using the characteristic mode analysis. Studying the modal behavior of graphene plates leads to provide a systematic method for analyzing and designing graphene-based patch terahertz antennas, also, the parameters of graphene antennas can be obtained with simpler analyzes and better physical view. At first the effect of graphene parameters, such as chemical potential and relaxation time is studied especially on the first and second modes of the graphene plate with constant dimension. Then the effect of plate dimensions and the presence of a metal ground plane under the graphene plate on the behavior of characteristic modes is investigated. Finally, functions to calculate the resonance frequency of the plate in terms of effective parameters of the plate are presented. These functions can be used to calculate the resonance frequency in the analysis and design of graphene antennas.https://jce.shahed.ac.ir/article_4963_401704ef750f5f2e9fc84ed2c5db8292.pdfShahed UniversityJournal of Communication Engineering2322-408812120230101Statistical Analysis of Connectivity Enhancement for Cell-Edge Users in MIMO-Enabled Wireless Cellular Networks Using Cooperative Non-Orthogonal Multiple Access (CNOMA) with Power Allocation91108496410.22070/jce.2026.19475.1273ENAsmaBagheriDepartment of Electrical Engineering, Esfarayen University of Technology, Esfarayen, North Khorasan, Iran0000-0001-5780-2037Mohammad AminKarimiDepartment of Electrical Engineering, Esfarayen University of Technology, Esfarayen, North Khorasan, IranJournal Article20240813This paper investigates the integration of Cooperative Non-Orthogonal Multiple Access (CNOMA) with Multiple-Input Multiple-Output (MIMO) technology to enhance connectivity for cell-edge users in wireless cellular networks. In the proposed framework, intra-cell users act as relays to forward data to cell-edge users, improving signal reception through selection and spatial diversity provided by MIMO antennas. Connectivity analysis is essential to evaluate Quality of Service (QoS) and overall network performance, but it is complicated by channel fading, MIMO channel correlation, and the influence of successive interference cancellation (SIC) in relay users. To address these challenges, we develop a closed-form expression for the connectivity probability of cell-edge users in CNOMA-based MIMO networks. The model assumes Rayleigh fading channels, exponential channel gain distributions, and distinct power allocation for each sub-channel. By analytically modeling the Signal-to-Interference-plus-Noise Ratio (SINR) and applying a Gamma approximation, we derive a closed-form solution under imperfect SIC conditions, incorporating the probability of SIC success in relay users. Simulation results validate the analytical findings and provide insights into performance enhancement, offering a practical framework for designing robust CNOMA-MIMO systems for improved cell-edge connectivity.https://jce.shahed.ac.ir/article_4964_02052c0f4599c2aa6bead905338f1214.pdfShahed UniversityJournal of Communication Engineering2322-408812120260101A Key Management Scheme for Secure Communication in Underwater Wireless Sensor Networks501810.22070/jce.2026.20725.1286ENMohaddeseAnzaniDepartment of Computer Science, University of Science and Technology of Mazandaran, Behshahr,Iran,Journal Article20250721Underwater Wireless Sensor Networks (UWSNs) explore the aquatic environment to facilitate various underwater surveillance applications. Since UWSNs are deployed in hostile environments, ensuring secure communication between the sensor nodes is important. This underscores the need for an efficient and secure key distribution scheme to allow sensor nodes to establish secure communication channels. Existing secure key distribution schemes designed for hierarchical networks may be deployable in UWSNs, but they suffer from high computational and communication overheads and thus consume significant memory. In this paper, we propose a new hierarchical key pre-distribution scheme based on "Residual Design" for UWSNs. Our proposed approach is a highly scalable key management scheme which provides good secure connectivity. The proposed key distribution scheme is designed to minimize storage overhead while increasing the resistance of the network against node capture attacks. The performance and security properties of the proposed scheme demonstrate that in an equal-size network, our scheme reduces node storage overhead significantly and provides high connectivity and resilience.Shahed UniversityJournal of Communication Engineering2322-408812120260101Distributed Target Tracking Based on the One-bit RLS Algorithm over Mobile Satellite Networks506210.22070/jce.2026.21036.1290ENAfshinKolijiUrmia UniversityChangizGhobadiUrmia University0000-0002-2664-1805JavadNouriniaUrmia University0000-0002-0436-3883EhsanMostafapourUrmia UniversityJournal Article20251002diffusion networks for localization in satellite target tracking applications. It provides a comprehensive convergence analysis for the Mobile DQA-RLS (MDQA-RLS) algorithm, considering various quantization levels and the corresponding convergence conditions. The simulation results confirm the potential for convergence in the MDQA-RLS network and demonstrate that the power consumption of this method is highly suitable for satellite localization tasks. Additionally, the observed convergence degradation remains within reasonable limits when compared to the mobile DRLS (MDRLS) algorithm, which does not account for quantization. Comprehensive convergence analyses are conducted across various quantization levels, and the specific conditions under which the Mobile MDQA-RLS algorithm converges are thoroughly outlined. Simulation experiments confirm the convergence capability of the MDQA-RLS-based network and indicate that its power efficiency is well-suited for satellite target tracking scenarios. Additionally, the observed degradation in convergence performance is within acceptable limits when compared to the Mobile DRLS (MDRLS) algorithm, which lacks quantization awareness. The findings further illustrate that as signal quantization resolution decreases, the advantages of MDQA-RLS over MDRLS become significantly more pronounced.