Communication Links Research Articles

Experimental study on designing smart antenna sensor networks and modelling management energy consumption for intelligent systems of internet of medical things

ABSTRACT The Internet of Medical Things (IoMT) is revolutionizing healthcare through technologies like artificial intelligence, data analysis, and remote monitoring. However, designing energy-efficient Wireless Body Area Networks (WBANs) remains challenging due to the complex propagation characteristics of on-body communication links, which vary with human body posture and size. This study aims to develop smart wearable antenna sensors and model energy consumption in on-body communication links. We have conducted experimental studies on monopole and patch antennas at 2.4 GHz, focusing on body morphological factors and channel characteristics. Our findings reveal that the path loss exponent of on-body links significantly varies with body posture and size, and the proposed energy consumption model effectively enhances energy efficiency during signal transmission. This research contributes to optimizing WBANs for improved healthcare applications.

Model-Free Resilient Grid-Forming and Grid-Following Inverter Control Against Cyberattacks Using Reinforcement Learning

The U.S. movement toward clean energy generation has increased the number of installed inverter-based resources (IBR) in the grid, introducing new challenges in IBR control and cybersecurity. IBRs receive their set point through the communication link, which may expose them to cyber threats. Previous work has developed various techniques to detect and mitigate cyberattacks on IBRs, developing schemes for new inverters being installed in the grid. This work focuses on developing model-free control techniques for already installed IBR in the grid without the need to access IBR internal control parameters. The proposed method is tested for both the grid-forming and grid-following inverter control. Different detection and mitigation algorithms are used to enhance the accuracy of the proposed method. The proposed method is tested using the modified CIGRE 14-bus North American grid with seven IBRs in PSCAD/EMTDC. Finally, the performance of the detection algorithm is tested under grid normal transients, such as set point change, load change, and short-circuit fault, to make sure the proposed detection method does not provide false positives.

Secrecy Analysis of LEO Satellite-to-Ground Station Communication System Influenced by Gamma-Shadowed Ricean Fading

The Low Earth Orbit (LEO) small satellites are extensively used for global connectivity to enable services in underpopulated, remote or underdeveloped areas. Their inherent broadcast nature exposes LEO–terrestrial communication links to severe security threats, which always reveal new challenges. The secrecy performance of the satellite-to-ground user link in the presence of a ground eavesdropper is studied in this paper. We observe both scenarios of the eavesdropper’s channel state information (CSI) being known or unknown to the satellite. Throughout the analysis, we consider that locations of the intended and unauthorized user are both arbitrary in the satellite’s footprint. On the other hand, we analyze the case when the user is in the center of the satellite’s central beam. In order to achieve realistic physical layer security features of the system, the satellite channels are assumed to undergo Gamma-shadowed Ricean fading, where both line-of-site and scattering components are influenced by shadowing effect. In addition, some practical effects, such as satellite multi-beam pattern and free space loss, are considered in the analysis. Capitalizing on the aforementioned scenarios, we derive the novel analytical expressions for the average secrecy capacity, secrecy outage probability, probability of non-zero secrecy capacity, and probability of intercept events in the form of Meijer’s G functions. In addition, novel asymptotic expressions are derived from previously mentioned metrics. Numerical results are presented to illustrate the effects of beam radius, satellite altitude, receivers’ position, as well as the interplay of the fading or/and shadowing impacts over main and wiretap channels on the system security. Analytical results are confirmed by Monte Carlo simulations.

Impact of Rain Weather Conditions over Hybrid FSO/58GHz Communication Link in Tropical Region

Impact of Rain Weather Conditions over Hybrid FSO/58GHz Communication Link in Tropical Region

Distributed observers for linear systems with communication noises over Markovian switching topologies

This paper studies the distributed state estimation problem for a linear system that is jointly observable with the consideration of communication noises and Markovian switching topologies. To address this issue, a network of observers is proposed, where each observer only measures partial system output, which may not be sufficient to observe the complete state of the system. Subsequently, all observers within the network collaborate by sharing their estimated states with their neighbours through the network, facilitating a cooperative reconstruction of the entire state at each local observer. To better reflect the communication environment, we consider a situation in which communication links may fail and rebuild over time, and communication noises may occur when observers exchange information through Markovian switching topologies. Parameters of observers are designed properly, under which each observer fulfills the estimation task in the mean square sense. Illustrative examples to demonstrate the effectiveness of the distributed observers are also provided.

Enhancing smart grid reliability through cross-domain optimization of IoT sensor placement and communication links

Enhancing smart grid reliability through cross-domain optimization of IoT sensor placement and communication links

Asymmetrical vulnerability of heterogeneous multi-agent systems under false-data injection attacks

This paper investigates the vulnerability of heterogeneous multi-agent systems (MASs) in face of perfect false-data injection (FDI) attacks that stealthily destabilize the synchronization processes of agents. In contrast to homogeneous dynamics, heterogeneous dynamics can be asymmetrically worsened by attackers, which is a greater challenge for MAS security. First of all, the existence conditions of perfect FDI attacks in different agents are established based on the spectral radius of heterogeneous system matrices. Then, it is proven that the attack targets against communication links are determined by the characteristic space of different agents. Since the attack properties including the attack existence and targets are different in each agent, heterogeneous MASs have the asymmetrical vulnerability under perfect FDI attacks. Finally, a sufficient condition and a necessary condition are obtained to achieve perfect FDI attacks with minimum attack targets. A numerical simulation of heterogeneous MASs is presented to demonstrate the effectiveness of perfect FDI attacks.

Hierarchical control of inverter-based microgrid with droop approach and proportional-integral controller

By increasing the penetration of renewable resources in power systems, which are mostly inverter-based, voltage and frequency control has faced many challenges. Unlike the synchronous generators in large power systems, these sources have no resistance against load changes due to their low inertia, therefore, controlling the voltage and frequency of inverter-based microgrids requires new approaches. In this article, by taking feedback from the output voltage and current of the inverter and using the Proportional Integral controller, the desired control signal to be applied to the inverter is obtained in a way that initially creates a phase and voltage difference between the DGs in the microgrid, the power flow is established in a way that without the need for any communication link, the balance of energy production and consumption is established in an island mode, and at the end, the voltage and frequency of Distributed Generations are restored to their nominal values. The presented control logic is also implemented in Simulink MATLAB software and its results are measured and evaluated.

Distributed coordinated motion control of multiple UAVs oriented to optimization of air-ground relay network

A novel adaptive model-based motion control method for multi-UAV communication relay is proposed, which aims at improving the networks connectivity and the communications performance among a fleet of ground unmanned vehicles. The method addresses the challenge of relay UAVs motion control through joint consideration with unknown multi-user mobility, environmental effects on channel characteristics, unavailable angle-of-arrival data of received signals, and coordination among multiple UAVs. The method consists of two parts: (1) Network connectivity is constructed and communication performance index is defined using the minimum spanning tree in graph theory, which considers both the communication link between ground node and UAV, and the communication link between ground nodes. (2) A multi-UAV motion control strategy is proposed that combines Improved Particle Swarm Optimization (IPSO) and Distributed Nonlinear Model Predictive Control (DNMPC), where the Kalman filter is utilised to estimate future positions of the mobile nodes. Simulation results in both single and complex environments show that the presented method can drive the UAVs to reach or track the optimal relay positions and improve network performance, while demonstrating the benefits of considering the impact of environments on channel characteristics.

INTEGRATED STUDY OF INVESTMENT PROCESSES IN THE TURKESTAN REGION

The article presents key indicators that allow ranking regions by the level of their investment attractiveness and activity. An effective regional investment policy is possible only with the development of a specialized mechanism that combines methods, tools, techniques, rules and technologies, as well as communication and organizational links. Such a mechanism allows regional authorities to purposefully regulate investment processes in accordance with set strategic priorities and development goals, ensuring sustainable economic improvement and capital attraction.

Dynamic Hierarchical Optimization for Train-to-Train Communication System

To enhance the operational efficiency of high-speed trains (HSTs), Train-to-Train (T2T) communication has received considerable attention. This paper introduces a T2T cooperative communication model that allows direct information exchange between HSTs, enhancing communication efficiency and system performance. The model incorporates a mix of dynamic and static nodes, and within this framework, we have developed a novel Dynamic Hierarchical Algorithm (DHA) to optimize communication paths. The DHA combines the stability of traditional algorithms with the flexibility of machine learning to adapt to changing network topologies. Furthermore, a communication link quality assessment function is proposed based on stochastic network calculus, which accounts for channel randomness, allowing for a more precise adaptation to the actual channel environment. Simulation results demonstrate that DHA has superior performance in terms of optimization time and effect, particularly in large-scale and highly dynamic network environments. The algorithm’s effectiveness is validated through comparative analysis with traditional and machine learning-based approaches, showing significant improvements in optimization efficiency as the network size and dynamics increase.

Design of TMLAA for the Utilization of Radiated Harmonic Beam Over Digital Modulation Schemes

ABSTRACTThis work presents the effective steering of multi‐harmonic beams of a time‐modulated linear antenna array (TMLAA) for multi‐channel communication. A classroom learning‐inspired Teaching Learning Based Optimization (TLBO) is utilized for active duration optimization of the 16‐element TMLAA for harmonic steering. The simulation study employing the optimization technique effectively steered the first two harmonic beams with enhanced radiated power and considerable Sidelobe level (SLL) below . Further, for practical validation, the measurement of the fabricated prototype is presented for one scenario. Finally, the use of harmonic beams for the communication links is validated by measuring the bit error rate (BER) of the considered digitally modulated scheme.

Communication Link Analysis of a Low-Earth Orbit Satellites Considering Interference Sources Moving Along Various Parabola-Curved Paths.

We analyze the communication link of an LEO satellite considering interference sources moving along various parabola-curved paths. In this situation, the location of the ground station, airborne interference source paths, and the satellite's trajectory were expressed in the East-North-Up (ENU) coordinate system. The airborne interference source path is designed using a parabola equation with a directrix parallel to the satellite's trajectory to analyze the interference situation for more diverse interference source paths, rather than using a straight path. To investigate critical interference situations where the J/S ratio is maintained above -20 dB with a small deviation during the communication time, we investigate interference situations by changing the parameters of the interference source path. The genetic algorithm (GA) is used to easily find an airborne interference source path that maintains the J/S ratio above -20 dB with a small deviation. A cost function for the GA is then defined as the average difference between the J/S ratio and the reference value (-10 dB and -20 dB) during the communication time. The optimum parameters of the interference source path are determined at a minimum cost in the GA. These results demonstrate that more significant interference situations for the communication link can be easily found by using parabola-curved paths and the GA. As a result, previous studies investigated the basic tendency of the J/S ratio using straight paths. However, this study provides a database for operating an anti-jamming system based on the obtained optimized path.

Linear Detection and Circuit Structure Based on ZF, MMSE Matrix Iteration and Operations

The Multiple-Input Multiple-Output (MIMO) technology substantially boosts the reliability and data transfer rates of communication links by enabling the parallel transmission of multiple data signals over the same frequency bandwidth, utilizing multiple transmit and receive antennas.Despite these enhancements, traditional MIMO systems are approaching their theoretical throughput limits, which underscores the need for developing new algorithms to tackle computational complexity.This paper categorizes the primary technical approaches into three types: iterative approximation methods, matrix operation-based methods, and the emerging Joint channel Estimation and Data detection (JED) algorithms.It delves into the Neumann series approximation for efficient matrix inversion in large-scale MIMO systems, the Gauss-Seidel iterative approach for soft-output detection, and LDLT decomposition-based algorithms for matrix inversion efficiency. Additionally, the paper emphasizes the JED algorithm, such as PROX, which presents a low-complexity solution for large Single-Input Multiple-Output (SIMO) wireless systems.

Measurement of Atmospheric Coherence Length from a Shack–Hartmann Wavefront Sensor with Extended Sources

Free Space Optical Communication (FSOC) is a wireless communication method that utilizes laser beams for high speed and secure data transmission. Its performance is affected by various factors, among which atmospheric turbulence causes random fluctuations in the atmospheric refractive index, significantly impacting the reliability of communication links. The atmospheric coherence length is a key parameter describing the coherence properties of a laser signal as it propagates through the atmosphere, and accurately measuring it is crucial for assessing the quality of FSOC links. This paper proposes a novel strategy that utilizes extended sources directly as the information sources, combining the wavefront phase variance method with the extended source offset algorithm based on Shack–Hartmann wavefront sensors to directly measure atmospheric coherence length. Existing methods in extended scenarios typically rely on deploying laser beacons to aid in the calibration of atmospheric coherence length but setting up suitable beacons on horizontal communication links is challenging. Additionally, these approaches can be costly in terms of equipment and measurement expenses. Compared to traditional measurement methods, the algorithm proposed in this paper can measure directly based on extended scenarios in horizontal links, thereby effectively reducing system complexity and equipment costs. To verify the feasibility and effectiveness of this method, targeted simulations and experiments were conducted, and the results show that the coherence length measured by the algorithm is highly consistent with that measured by the Differential Image Motion Monitor (DIMM), with a deviation of less than 2% from actual values, effectively demonstrating the algorithm’s feasibility in coherence length assessment.

A Resilient Event‐Triggered Control Scheme for Nonlinear Multi‐Agent Systems Under Communication Delays and Denial‐Of‐Service Attacks

ABSTRACTThis paper investigates the resilient event‐triggered control (ETC) for nonlinear multi‐agent systems in the presence of communication delays and denial‐of‐service (DoS) attacks. The communication delays and asynchronous DoS attack are considered for each communication link. Based on sampling‐receiving events and DoS attack events, flow and jump sets are formulated to describe the system's transmission time status. An independent event‐triggering mechanism (ETM) is designed for each communication link. Furthermore, a resilient control scheme is constructed in which sufficient conditions for achieving system input‐output stability are provided, including the constraints of frequency and DoS attack duration, the conditions of Lyapunov functions, and the maximally allowable transmission interval. Finally, the attitude cooperative control problem of multiple unmanned aerial vehicles (multi‐UAVs) is adopted as a simulation example. The simulation results show the effectiveness of the proposed scheme.

CCOA‐AdaLS: Hybrid Beamforming Using Chaotic Chebyshev Aquila Optimization for mmWave Massive MIMO

ABSTRACTThis research aims to design hybrid analog and digital beamforming to improve the signal‐to‐noise ratio (SNR) and spectral efficiency (SE) of communication links. Considering the complexity and cost associated with fully connected multiple‐input multiple‐output (MIMO) communication models, a partially connected system model is adopted for the downlink millimeter‐wave (mmWave) communication model. The analog beamforming utilizes the adaptive search (AdaLS) algorithm to minimize interference and enhance user power, whereas digital beamforming is optimized using the proposed Chaotic Chebyshev Aquila Optimization (CCAO) algorithm. The CCAO algorithm integrates chaotic Chebyshev–based solution mapping with the conventional Aquila Optimization Algorithm to enhance exploration capability. The system model is illustrated, and the problem is formulated to maximize the signal‐to‐interference‐plus‐noise ratio (SINR) through the selection of the required signal at the receiver. The digital beamformer is designed using Lagrange's multiplier, and the analog beamformer is optimized using AdaLS. The proposed CCAO algorithm is detailed, incorporating chaotic dynamics to explore the solution space effectively. The research evaluates the performance of the proposed method against conventional approaches, showcasing improved normalized beam gain and SINR.

The channel capacity of the free space communication link based on Bessel-like beams

Abstract This study investigates the information channel capacity of free-space communication links based on Bessel-like beams (BLBs) and compares it to that of conventional Gaussian beams (GBs). We examine optical communication links employing amplitude coding for beams with BLB spatial field distribution and orbital angular momentum (OAM)-based coding for single-photon optical communication. Our study explores both unperturbed and perturbed propagation scenarios, considering random phase fluctuations caused by atmospheric turbulence and amplitude attenuation due to absorbing obstacles. Our results show that BLBs provide higher channel capacity than GBs at short distances (within a few kilometers of propagation distance), but GBs outperform BLBs at longer distances. In turbulent environments, BLBs experience more significant capacity degradation than GBs, though they maintain higher capacity in OAM-based single-photon links for distances under 1–2 km.

Jamming and Spoofing Techniques for Drone Neutralization: An Experimental Study

This study explores the use of electronic countermeasures to disrupt communications systems in Unmanned Aerial Vehicles (UAVs), focusing on the protection of airspaces and critical infrastructures such as airports and power stations. The research aims to develop a low-cost, adaptable jamming device using Software Defined Radio (SDR) technology, targeting key UAV communication links, including geolocation, radio control, and video transmission. It applies jamming techniques that successfully disrupt UAV communications. GPS spoofing techniques were also implemented, with both static and dynamic spoofing tested to mislead the drones’ navigation systems. Dynamic spoofing, combined with no-fly zone enforcement, proved to be particularly effective in forcing drones to land or exhibit erratic behavior. The conclusions of this study highlight the effectiveness of these techniques in neutralizing unauthorized UAVs, while also identifying the need for future research in countering drones that operate on alternative frequencies, such as 4G/5G, to enhance the system’s robustness in evolving drone environments.

Secure Drone Communications using MQTT protocol

With the revolutionary change in emerging technologies, the usage of drones or unmanned aerial vehicles (UAV) has exponentially increased in different sectors like Industry, healthcare, military, agriculture, real estate, manufacturing, logistics, energy and many more utilities. This rapid growth creates a concern for the secure communication between the internal communication modules and the ground based computer system used for controlling the UAV. Intruder can hack into the device and attack the internal communication device with the injection of the malicious code which can lead to the malfunction of the aircraft. Security issues related to the communication between the internal modules of the drone and the ground based computer system is of major concern and is crucial. UAVs have to operate in constrained networks with limited bandwidth. In such a constrained environment MQTT protocol can be an excellent protocol. No cryptographic techniques are used to retain the simplicity and the light weight of the MQTT protocol. This contributes for the large scope for emerging with new solutions in the protection issues of MQTT communications. This paper mainly focuses on Armstrong number encryption standard algorithm for providing a computationally simple yet a secure and strong algorithm for UAVs encryption and decryption process on the communication links using MQTT protocol.