The Internet of Things (IoT) connects billions of heterogenous things via the Internet. Therefore, the IoT network requires many network control methods for dynamic and efficient management. The ...Software Defined Networking (SDN) paradigm decouples the control plane from the data plane enabling programmability and centralized control and management of the network. Thus, it provides efficient and reliable IoT network management. However, the dynamicity, variability, and scalability of the IoT network topology are still a challenge despite the proposal of the distributed SDN controller as a solution for scalability. More precisely, the distributed controller reveals the distributed states management problem and it is ineffective in the automatization of the highly dynamic and variable IoT network. In this paper, we propose an auto-scalable distributed SDN control plane to manage and control the IoT network. The proposed distributed controller is deployed using Kubernetes. The test results validate the feasibility of our new approach.
Taking into account quality of transmission (QoT) constraints, wavelength continuity constraint and wavelength integrity constraint when solving the Routing and Wavelength Assignment (RWA) problem in ...Wavelength-Division Multiplexing (WDM) transparent networks leads to inefficient utilization of network resources and results in higher rejection ratio. This is especially severe when dynamic traffic is considered. In this paper, we investigate the problem of improving network resources utilization efficiency by applying rerouting and set-up delay tolerance, a metric of Service Level Agreement (SLA) that has been exploited in literature for improvement in network performances, taking into account the aforementioned constraints. Moreover, we investigate further improvement in the duration of the service disruption period due to rerouting. As far as we know, this is the first study that exploits traffic rerouting for network with QoT constraints provisioned with set-up delay tolerance to get further improvement in network performances. The performances of the proposed algorithms are evaluated and discussed through extensive numerical experiments. Significant improvements are demonstrated, either in terms of rejection ratio or in terms of service disruption period, in comparison with previously proposed algorithms.
Because of the substantial development of electronics and telecommunication technologies, materials that exhibit good electromagnetic interference shielding performance are important for alleviating ...the impact of interference induced by a remarkable variety of devices. There is thus currently great research interest in enhancing simulation tools and developing new techniques to protect electronic installations against such electromagnetic coupling. However, various numerical methods that are used to treat such electromagnetic problems are rapidly reaching their limits in terms of central processing unit (CPU) time and memory storage requirements. We therefore propose herein use of the method of moments (MoM)–generalized equivalent circuit (GEC) approach based on the wave concept as a convenient simulation tool to study structures designed for such shielding applications, considering the cases of both perfect and lossy metallic shielding surfaces. The shielding efficiency is optimized for each case based on a parametric study of structural parameters. We then numerically study the effect of the type of material used to introduce losses for shielding, modeled based on the surface impedance
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. The numerical results are validated against other methods.
Over the last few years, the evolution of multimedia streaming services has resulted in growth and significant explorations of Quality of Experience (QoE) since the concept of QoE is gaining an ...enormous research effort, but it is still complex to estimate. This estimation can be influenced by a wide range of quality affecting factors. In this work, we provide standard definitions, we review and survey existing models to classify QoE Influence Factors (IFs). Moreover, we present a classification of the QoE IFs into four groups: system factors, context factors, human factors, and social-behavioral factors. Finally, regarding the QoE IFs, we highlight some relevant studies. We believe that our overview and findings can provide an understanding of the related quality affecting factors and QoE assessment approaches over video communications.
In this paper, we will present an integral method based on wave formulation to resolve the electromagnetic radiation problem of circular loop antenna in the presence of multilayer cylindrical body of ...revolution. The characteristics of this antenna structure is determined, especially the Scattering parameter and the radiation pattern evaluated in different plans (theta and phi plans). In order to obtain an ideal model as close as possible to the real antenna, a sensitivity study that depends on many parameters (The number of rings, the number of excitation sources, and the location of the sources) has been presented.
The 3D structure electromagnetic computation presents several difficulties related to the volume mesh. In fact, the entire volume space must be taken into account even the smallest details. In this ...article, we propose a formulation based on the reciprocity theorem combined with the generalized equivalent circuit method to model a planar 3D structure with both coaxial and planar excitation. The major advantage of this formulation is the fact to reduce the computational volume into 2D ones in the discontinuity plane. In addition, we focused on the calculation of the discontinuity between the excitation source and the planar structure to determine the exact behavior of the electric coaxial excitation model. The obtained current density, electric field distributions, and the input impedance are presented and discussed in the following sections. An approximately good agreement of input impedance with those obtained by the simulator and measurement is shown.
This study presents, for the first time, a novel design of ultra‐wideband (UWB), circularly polarized and highly directive log‐spiral THz photoconductive antenna. The proposed antenna is simulated in ...High Frequency Structure Simulator using gold as the antenna electrode material which is backed by a quartz substrate (εr = 3.78, tan δ = 0.0001) and hemispherical silicon‐based lens with a diameter of 140 μm. A comprehensive detailed parametric study of the antenna design parameters is performed in the frequency range of 1 to 6 THz for the optimal design of the developed antenna structure. The optimal antenna structure with integrated lens has UWB characteristics with −10 dB impedance bandwidth of 5 THz and 3 dB axial ratio bandwidth of around 4 THz. The observed directivity and half‐power beam width of the presented design varies in the range 5 to 12 dBi and 34° to 62°, respectively, for the frequency range of 1 to 4 THz. The wideband, high directivity as well as high‐efficiency (>50%) characteristics of the proposed design make it a favorable choice for the THz sensing and imaging applications.
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