Journal of Communication Engineering
Volume:10 Issue: 2, Summer-Autumn 2021

In recent years, the problem of online data and information security has been increasingly serious and prevalent. Security issues are resolved via cryptography. Access control over the encrypted messages is necessary for some applications, therefore message encryption cannot simply achieve the stated aims. To achieve these requirements, attribute-based encryption (ABE) is used. This type of encryption provides both security and access structure for the network users simultaneously. Fuzzy Identity-Based Encryption (FIBE) is a special mode of ABE that provides a threshold access structure for the users. This threshold value is set by the authority for users, which is always fixed and cannot be changed. So, the sender (encryptor) will not play a role in determining the threshold value. The mentioned issue exists also in Key Policy Attribute Based Encryption (KP-ABE) schemes. In this paper, we present a FIBE scheme in addition to the authority, the sender also plays a role in determining the threshold value. Thus, the policy will be more flexible than previous FIBE schemes in that the threshold value is selected only by the authority. We can call the proposed scheme a dual-policy ABE. The proposed technique for flexibility of threshold value can be applied in most of exist KP-ABE schemes. We use the (indistinguishable) selective security model for a security proof. The hardness assumption that we use is the modified bilinear decision Diffie-Hellman problem.

This paper presents a novel microstrip bandpass filter (BPF), whose one of the most important feature of the filter is that the bandwidth remains fix as the center frequency changes. Therefore, the structure is suitable for reconfigurable communication systems. The BPF is consist of coupled-lines and a modify three section stepped impedance resonator (SIR) and a LPF that consists of one open-ended stub to suppress spurious harmonics at high frequencies. Even and odd mode analysis has been used for designing process of the BPF. Finally, the proposed filter has a fractional bandwidth of 20% at 3.15 GHz with the insertion loss less than 0.1 dB in the pass-band, compact size, low insertion loss, right out of band rejection, high-frequency selectivity. The BPF is fabricated and measured. The excellent agreement between the measured and simulated results demonstrates the validity of the proposed filter and method.

Today, wireless sensor networks are widely employed in various applications, including monitoring environments and tracking objects for military surveillance, industrial applications, and healthcare. Thus, the establishment of security in such networks is of great importance. One of the dangerous attacks against these networks is the Sybil attack. In this attack, a malicious node propagates multiple fake identities simultaneously, which affects routing protocols and many other operations like voting, reputation evaluation, and data aggregation. In this paper, we study the sensor node rate trust decision to defend against Sybil attacks in WSNs and its dynamics that play a key role in stabilizing the whole WSN using evolutionary game theory. We then propose and prove the theorems indicating that evolutionarily stable strategies can be attained under different parameter values, which supply the theoretical foundations to devise defiance against Sybil attacks in WSNs. Moreover, we can find out the conditions that will lead SNs to choose the strategy Healthy as their final behavior. In this manner, we can assure WSNs’ security and stability by introducing a rate-trust mechanism to satisfy these conditions. And furthermore, the efficiency of algorithms in terms of true detection rate and false detection rate is evaluated through a series of experiments. Experiment results show that the proposed algorithm is able to detect 99.9% of Sybil nodes with a 0.005% false detection rate. Additionally, the proposed algorithm is compared with other algorithms in terms of true detection rate and false detection rate, which shows that the proposed algorithm performs satisfactorily.

In this paper, we report the sensitivity of superconducting detector resonators and shows which kind of detector is appropriate for detecting cosmic microwave background (CMB). Photons absorbed from galaxies have information about dark matter and dark energy and we need advanced technology to observe cosmic rays. Microwave kinetic inductance detectors (MKIDs) can be used to enjoy an array of thousands of pixels, and a small size design. Sensitive MKIDs with little quantity of noise equivalent power (NEP) could detect photons that have very low energy but intrinsic noise particularly TLS noise. How to design an MKID based on decreasing TLS noise is discussed here. This transmission line resonator was designed with an open circuit lambda second waveguide. This MKID has a reliable quality factor in 6 GHz frequency. An array that includes 8 MKIDs has been designed. The responses which were taken prove that the sensitivity of these MKIDs compare to former MKIDs is slightly more valid.

In this paper, in order to simplify calculation of the distributed target response, a new model of distributed targets is presented using monostatic SAR (Synthetic Aperture Radar) imagery. Distributed targets are strategic, because they are important in various fields, especially in military. Calculating the response of these targets is difficult due to the complexity of modelling and scattering data calculation. We solve this problem with replacing the scattered pixels with canonical shapes. Besides the simplicity, this model gives the response close to the real model. This model facilitates the target detection, target design, scattering data analysis, and distributed targets interpretation of radar viewing. In fact, one of the goals of this paper is to predict the scattering data of a scene. For this purpose, the scattering field of a real model is calculated and compared with the proposed model.

The Internet of Things (IoT) has a significant demand in society due to its features, and it is constantly improving. In the context of wireless technology, Ultra-reliable and low-latency communication (URLLC) is one of the essential and challenging services in fifth-generation (5G) networks and beyond. The research on URLLC is still in its early stages due to its conflicting requirements, regarding high reliability and low latency. In this paper, we study the performance of secure short-packet communications and resource allocation in IoT systems. To this end, we investigate a health center automation, where the goal of the access point is to send critical messages to devices without eavesdropping. In this context, our goal is to maximize the weighted sum throughput and minimize the total transmit power, respectively. The problems of maximizing the weighted sum throughput, and minimizing the total transmit power are non-convex and hard to solve. To overcome this challenge, we use efficient mathematical techniques, such as the block coordinate descent (BCD) method and gradient ascent algorithm; we also use estimation methods such as Ralston, Heun, and forward-backward, in the derivative part of the gradient ascent algorithm. The simulation results show the performance advantages of the BCD algorithm and the gradient ascent in the short packet transmission scheme, also the simulation results show the superiority of the proposed methods in most cases.

In this paper a simple ultra-wide band (UWB) microstrip band pass filter (BPF) with an ultra-wide stopband using novel dual hairpin resonators and parallel-coupled lines is proposed. The proposed filter has a wide pass band of 3.1 to 10.2 GHz with only 0.1 dB insertion loss. This wide pass band of 7.1 GHz, shows 106.7% fractional band width (FBW). The proposed BPF not only correctly operates at the ultra-wide pass band, but also provides an ultra-wide stopband from 12.8 to 28.2 GHz with more than 20 dB attenuation level. The proposed BPF has a very simple structure, which consists of four novel hairpin resonators and simple parallel-coupled lines. The proposed BPF has a compact size, which the overall circuit size of the device is only 11.7 mm × 7.2 mm (0.35 λ × 0.22 λ), where λ, is calculated at the center frequency of 6.65 GHz. The proposed device is simulated, fabricated and tested. The measured results confirm the correct performance of the proposed BPF.

Abstract- The rapid proliferation of fifth-generation (5G) technology has resulted in a wide range of applications, posing challenges in managing network resources effectively and efficiently. To address these challenges, network slicing (NS) and Fog-Radio Access Networks (F-RAN) have emerged as key technologies, enabling the creation of isolated virtual networks on shared physical infrastructure to support high-bandwidth and low-latency communication. However, allocating network resources to latency-sensitive applications like self-driving cars and remote surgery, while ensuring a quality experience, is complex due to stringent latency requirements and limited availability. In this paper, we propose a novel approach, leveraging the Q-learning algorithm, specifically the Approximate Reinforcement Learning for dynamic resource allocation (RA-ARL), in the context of 5G environments. Our modified algorithm takes into account crucial network attributes, introduces innovations such as service type classification based on latency sensitivity, and considers time-varying resource conditions and service demands. We propose an RL model to optimize network utility, focusing on the F-RAN model. Our experimental results demonstrate the effectiveness of ARL-RA in terms of convergence, resource utilization, and the ability to handle user request rejections. This work contributes to the advancement of efficient and effective resource allocation in dynamic 5G networks, particularly for latency-sensitive applications with stringent quality requirements.

In this paper, the calculation of the dimensions of the area illuminated by the antenna (antenna footprint) of an Airborne Ground Penetrating Radar (airborne GPR) has been investigated on the ground's surface and subsurface. In the topic of detecting buried targets by airborne GPR radars, knowing the area illuminated by the radar antenna is very important. By having the dimensions of the illuminated area, we can cell the search area according to it and excite these cells with appropriate power and at a certain time. The advantages of celling according to the antenna footprint are managing the transmitted power and reducing the search time. In this paper, two methods are provided to simulate the detection of buried targets in CST software. In the first method, a horn antenna is used as a radiation element in the structure itself, but in the second method, the antenna is simulated separately and its parameters are used to calculate the antenna footprint. In the first method, the meshing is very large due to the distance between the antenna and the ground's surface, which increases the simulation time, but in the second method, due to the removal of this distance and the use of the antenna footprint as a radiation element, the meshing And the simulation time is greatly reduced.

A low profile fractal defected ground structure (DGS) antenna is presented for super-wideband (SWB) wireless communication applications. The designed antenna covers a very wide frequency range from 1 to 27.4 GHz (impedance bandwidth of 186%) with |S11|<-10 dB. Moreover, In spite of small electrical dimension of the proposed antenna (0.11 λ× 0.11 λ), a large bandwidth dimension ratio of 15372 is resulted. The SWB operation is achieved by using fractal DGS on the ground plane to improve the impedance characteristics between adjacent resonant frequencies. The antenna consists of a 34×34×1.6 mm3 FR4 substrate with a dielectric constant of 4.4 and a narrow rectangular radiator. A multi-frequency resonance characteristic is obtained by increasing the fractal slot iterations on the ground plane. The simulation results 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, gain, radiation efficiency, group delay, and fidelity factor are presented and discussed. The results indicate that the antenna has good performance over the entire operating bandwidth which make it very potential candidate for integration in SWB wireless communication systems.

A miniaturized ultra-wideband (UWB) microstrip bandpass filter (BPF) with triple notched Bands using a new multimode resonator (MMR) is designed in this letter. The MMR is accompanied by folded high-impedance interdigital coupled-line structures to achieve a UWB characteristic with triple notched bands. All of the introduced bands are independently controllable to avoid interfering with the other existing operating systems. Besides, with using folded interdigital coupled-line structures, the overall dimensions are significantly reduced, as compared with the UWB BPF using common interdigital coupled-line structures. LC equivalent circuits and the transfer function of the proposed MMR are extracted to analyze the filter. Finally, triple notched bands have been located at 5.4, 8.1, and 10.1 GHz with attenuations of more than -22 dB. The measured results adequately illustrated that the designed filter prepares a passband from 4.2 to 12 GHz plus a wide rejection bandwidth up to 20 GHz.

Automatic modulation classification is used in various applications, including satellite communication systems, military communication, and submarine communications. In this paper, the automatic classification of modulation types is done using a two-stage method that combines a short-time Fourier transform (STFT) and a hybrid deep neural network (HDNN). At the first stage, using the STFT as a data source, the time-frequency information is retrieved from the modulated signals. A hybrid deep neural network feed two-dimensional (2D) images as inputs. In the second stage, the HDNN feeds the 2D time-frequency data to classify the various modulation types. Six various types of modulation schemes, including amplitude-shift keying, frequency-shift keying, phase-shift keying, quadrature amplitude-shift keying, quadrature frequency-shift keying, and quadrature phase-shift keying, are recognized automatically in the SNR range of 0 to 25 dB. An exhaustive computer simulation has been performed to evaluate the performance of the proposed digital modulation classification method. The simulation results show that, in comparison with the existing methods, our proposed method performs well and significantly reduces the processing time.