Unreliable Communication Network Research Articles

Robust fusion filter for networked uncertain descriptor systems with colored noise and cyber-attacks

The robust fusion filtering problem of multi-sensor networked uncertain descriptor systems (NUDSs) with colored noise, uncertain noise variances and cyber-attacks is investigated. During data transmission in unreliable communication networks, the data can be maliciously attacked by attackers. In other words, the local filters (LFs) may receive false data or may not receive data because of the cyber-attacks. By adopting the singular value decomposition (SVD) method, the original NUDSs can be converted into two reduced-order subsystems with uncertain correlated fictitious white noises, and the cyber-attacks are transformed into the fictitious noises. Cross-covariance matrices between local filtering errors are derived. The robust LFs are obtained according to the minimax robust estimation principle. Under the linear unbiased minimum variance criterion, three weighted fusion algorithms are applied to fuse the LFs. For all allowable uncertainties of noise variances and cyber-attacks, the minimal upper bounds of covariance matrices of the local and distributed fusion filters are guaranteed. The proof of their robustness is established through the minimax estimation principle and Lyapunov equation method. Finally, the correctness and effectiveness of the proposed algorithms are verified by a circuit system example.

Resilient distributed model predictive control of state‐delayed linear parameter varying systems with quantitative communication against denial of service attacks

AbstractThis work presents a resilient distributed model predictive control (MPC) method for linear parameter varying (LPV) systems with state delays and attacks in communication networks. Coordinations are required for distributed MPC (DMPC) to achieve the global performance of centralized MPC (CMPC). However, control performance can be severely degraded by unreliable communication networks, for example, with denial of service (DoS) attacks. A resilient control framework is derived to address the unreliable communications in DMPC. A global system is divided into subsystems for the distributed control purpose. To deal with the model uncertainties and state delays, a “min‐max” DMPC algorithm is presented with a buffer to ensure resilience against DoS attacks. A quantization scheme is introduced to quantize the control information exchanged between subsystems. An iterative interaction scheme is proposed to exchange feedback control laws among subsystems. The stability of the closed‐loop system under the proposed algorithm is ensured by using a Lyapunov function method. The effectiveness of the proposed DMPC is demonstrated through two simulation examples.

A reliable cluster-based opportunistic routing protocol for underwater wireless sensor networks

Underwater Acoustic Sensor Networks (UASNs) have gained significant popularity and application in various marine engineering exploration scenarios, driven by the global evolution of the ocean ecosystem. However, UASNs face numerous challenges arising from the unique characteristics of the underwater environment and acoustic channels, such as limited energy resources, unreliable communication, and dynamic network topology in uncertain environments, all of which impact the network lifetime and transmission reliability. To address these challenges and enable efficient underwater data packet transmissions, this paper proposes a reliable cluster-based routing method called RCRP. The RCRP organizes sensor nodes into clusters, where cluster heads transmit the fused data to the sink node through multi-hop forwarding. To overcome routing voids caused by node failures during packet transmission, a prediction model based on the Markov chain is introduced to identify void nodes and inform neighboring nodes about the routing holes. Furthermore, a connection prediction mechanism is developed to tackle changes in the uncertain network topology, taking into account node mobility and the received SNR. For packet transmissions, a waiting mechanism inspired by the opportunistic routing (OR) paradigm is proposed, which determines the optimal forwarding route based on the calculated probability of successful connection between nodes. Simulation results demonstrate that RCRP outperforms existing routing protocols in terms of packet delivery ratio, surviving time, and energy consumption, highlighting its effectiveness in enhancing the performance of UASNs.

Attack-Resilient Distributed Nash Equilibrium Seeking of Uncertain Multiagent Systems Over Unreliable Communication Networks.

This article investigates the distributed Nash equilibrium (NE) seeking problem of uncertain multiagent systems in unreliable communication networks. In this problem, the action of each agent is subject to a class of nonlinear systems with uncertain dynamics, and the communication network among agents will be affected by the nonperiodic denial of service (DoS) attacks. Note that, in this insecure network environment, the existence of DoS attacks will directly destroy the connectivity of the network, which leads to performance degradation or even failure of the most existing distributed NE seeking algorithms. To address this problem, we propose a two-stage distributed NE seeking strategy, including the attack-resilient distributed NE estimator and the neuroadaptive tracking controller. The estimator based on the projection subgradient method and the consensus protocol can converge exponentially to virtual NE against DoS attacks. Then, the neuroadaptive tracking controller is designed for uncertain multiagent systems with the output of the estimator as the reference signal such that the actual action of all agents can reach NE. Based on the Lyapunov stability theory and improved average dwell time automaton, the stability of the estimator and the controller is proven, and all signals in the closed-loop system are uniformly bounded. Numerical examples are presented to verify the effectiveness of the proposed strategy.

Adaptive fault‐tolerant platooning control for nonlinear homogeneous multiple autonomous vehicles under unreliable communication networks

AbstractThis article presents a fault‐tolerant platooning control algorithm for a class of nonlinear homogeneous multi‐vehicle systems under unreliable network communication environment. The considered types of actuator failures in individual vehicle are loss‐in‐effectiveness, and bias faults. Suppose the communication network among vehicles is here described as a switching graph subject to intermittent communications. Unlike the existing results dealing with vehicle platoon under continuous communications, this article develops a hierarchical fault‐tolerant platooning control approach, under which, the multiple vehicle coordination platooning objective is ensured even in the cases of discontinuous communication faults and actuator failures. First, each following vehicle can estimate the desire reference information via cooperative adaptive virtual estimator even in intermittent communications. Second, the local fault‐tolerant controller with adaptive parameter update mechanism can guarantee the practical position and velocity of following vehicles asymptotically track the desire estimations. Finally, a simulation example of a team of autonomous vehicles is given to verify the effectiveness of the proposed method.

Event-Based Secure Consensus Control for Multirobot Systems With Cooperative Localization Against DoS Attacks

In this article, we investigate the secure consensus control problem for multirobot systems with event-triggered communication strategy under aperiodic energy-limited denial-of-service (DoS) attacks, where DoS attacks prevent the transmission of information between robots. Each robot is equipped with onboard sensors to estimate its position cooperatively by taking relative measurements and exchanging the local positioning information with other robots through the unreliable communication network. In the meantime, each robot determines its consensus control based on transmitted position estimates and steers the robot to the desired consensus position. Therefore, our goal is to design a secure control scheme for each robot based on cooperative localization with an event-triggered mechanism and obtain a sufficient condition for the upper bound of duration and the maximum number of attacks such that <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$N$</tex-math></inline-formula> robots can move to the desired secure consensus position in the presence of DoS attacks. Finally, simulation and experimental results are presented to show the effectiveness of obtained theoretical results.

Retracted: Power Tracking and Energy Balancing of Energy Storage Systems under Unreliable Communication Network

Retracted: Power Tracking and Energy Balancing of Energy Storage Systems under Unreliable Communication Network

Distributed energy resource coordination for a microgrid over unreliable communication network with doS attacks

This article studies the coordination economic dispatch problem (EDP) for distributed energy resources. To minimise the total operating cost under various constraints, a switched distributed coordination algorithm is presented to solve the EDP over the unreliable communication network with the Denial-of-Service (DoS) attacks. In this situation, the proposed algorithm integrates the normal mode and the attack mode. The attackers can make the communication network unconnected and destroy the convergence and optimality in the attack mode. In order to explore under what conditions the optimal solution can still be obtained, we model the attack modes by differential inclusions and use an average dwell-time automaton and time-ratio monitor to limit the DoS attacks. Then, the switched distributed algorithm is modelled as a hybrid dynamical system. Furthermore, some conditions are derived to guarantee the exponential convergence of the proposed algorithm under DoS attacks. Finally, simulation results tested on the IEEE 30-bus power system illustrate the effectiveness of the proposed algorithm.

Asynchronous secure controller design for singularly perturbation stochastic semi-Markov jump CPSs with the memory-based dynamic event-triggered scheme against complex cyber-attacks

In this paper, the problem of asynchronous secure controller design for singular perturbation stochastic semi-Markov jump systems (SPSS-MJSs) against complicated cyber-attacks is addressed. Firstly, the unified framework for multi-channel spoofing attacks and DoS attacks is properly established for CPSs with the unreliable communication network. Then, by introducing a register, we propose the memory-based dynamic event-triggered scheme (MDETS), which can save resources for the bandwidth limited network to a certain degree. Since the mode information of Markov chain for the secure controller is often unavailable, a hidden Markov model (HMM) is used to formulate the asynchronous situation between the mode of original system and the constructed controller. Further, by constructing Lyapunov functionals and utilizing linear matrix inequality (LMI) techniques, the obtained closed-loop SPSS-MJSs are endowed with an exponential stability criterion. And the co-design of the asynchronous secure controller and MDETS is presented. Finally, a practical example of the specific small capacitance circuit system is offered to verify the feasibility and superiority of the developed method.

Newly qualified registered nurses’ and midwives’ experiences from rural health district placement in Namibia

BackgroundThe transition period for newly qualified registered nurses/midwives (NQRN/Ms) is a fundamental phase in their career. Yet, transition experiences have been studied mostly within urban and/or specialised healthcare settings in high-resource countries. This study aimed to explore and describe the experiences of NQRN/Ms in a rural health district in Namibia.MethodsA qualitative, descriptive, explorative, and contextual design was followed. The sample consisted of eight participants who were purposively selected. Data were collected via in-depth individual interviews and analysed following a reflexive thematic analysis. The researchers were guided by Lincoln and Guba’s strategies for establishing trustworthiness.FindingsThemes conceptualised from the analysis include encounters with rural community members; encounters with colleagues; staffing, management, and supervision; shortage of resources; poor infrastructure; unreliable communication networks; and the lack of social life.ConclusionThe NQRN/Ms had mixed experiences related to a variety of aspects such as social life, resources, colleagues and community members. These findings can be used to improve undergraduate nursing curricula, as well as to create graduate job preparation workshops and support networks.

Fixed-Time Resilient Edge-Triggered Estimation and Control of Surface Vehicles for Cooperative Target Tracking Under Attacks

This paper is concerned with the cooperative target tracking of under-actuated unmanned surface vehicles (USVs) with event-triggered communications subject to denial-of-service (DoS) attacks. The target position information can be sensed by a fraction of follower USVs only. A fixed-time resilient cooperative edge-triggered estimation and control architecture is presented for achieving cooperative target tracking under DoS attacks. Specifically, a distributed edge-triggered fixed-time extended state observer (ESO) is designed to recover the position and velocity of the target with a prescribed time regardless of the unreliable communication network subject to DoS attacks. Moreover, the communication burden of the network is reduced by the proposed edge-triggered mechanism. In the control law design, a fixed-time ESO is designed for estimating the model uncertainties and external disturbances in an earth-fixed reference frame. Then, a fixed-time target tracking control law is proposed for each follower USV based on the fixed-time ESO. It is proven that the error signals in the closed-loop control system of USVs are convergent to the origin in a fixed time. An example is provided to substantiate the effectiveness of the proposed fixed-time resilient cooperative edge-triggered estimation and control architecture for USVs.

Power Tracking and Energy Balancing of Energy Storage Systems under Unreliable Communication Network

In this paper, we consider the distributed power tracking and energy balancing problem of a general energy storage system subject to unreliable switching communication network. In order to deal with the uncertainty of the network topology, a distributed observer-based approach has been proposed. First, an adaptive distributed observer is employed to recover the reference power for the entire energy storage system for each energy storage unit. Second, based on the estimated reference power, a certainty equivalent control law is synthesized to simultaneously achieve power tracking and energy balancing. Numerical simulations are provided to validate the proposed control approach.

Cooperative Control of UAVs Over an Unreliable Communication Network

This article proposes a method for the cooperative control of two unmanned aerial vehicles (UAVs) to guarantee collision avoidance. The UAVs are locally controlled and are able to change their trajectories at any time. They are connected over an unreliable communication network that may induce packet losses and transmission delays. The network has no coordinator and necessary information for collision avoidance can solely be communicated. In order to reduce the communication effort, information are only transmitted at discrete time instants when they are necessary. Depending on the current situation, one UAV is responsible for avoiding the collision by adjusting its trajectory. To this aim, a control unit is introduced for the UAVs that uses the idea of event-based control and combines methods from communication technology and control theory. The control unit has to execute four tasks: estimation of the current network properties, prediction of the movement of the neighboring object, invocation of communication in an event-based fashion, and planning of the collision avoiding trajectory. It is proved that the control aims are satisfied even in the presence of time delays and packet losses induced by the communication network. A simulation study with two quadrotors shows the suitability of the method.

Resilient Secure Control of Networked Systems Over Unreliable Communication Networks

This article considers the secure consensus of networked nonlinear multiagent systems (MASs) under denial-of-service attacks via unreliable communication networks in a directed graph. Different from existing consensus results in an undirected graph, the case that the communication topology of MASs may be frequently attacked by attackers in a directed graph is considered. The existence of attackers leads to the entire communication topology of MASs having no directed spanning tree that plays a key role in consensus analysis. Besides, to ease the communication load between agents, a resilient leader-following event-triggered control protocol and corresponding to the static triggering policy are first proposed, respectively. Then, an extra key variable is adopted to develop the dynamic triggering policy for the directed graph case to achieve secure consensus while reducing triggering instants, which subsumes several existing static ones as special cases. A unified hybrid framework is established to derive new sufficient conditions of achieving secure consensus without continuous communications among neighboring agents. Besides, parameters of sufficient conditions are designed by solving optimization problems. Finally, the theoretical analysis is verified by a robot manipulator system example.

Decentralized dynamic event‐triggered control for networked control systems under unreliable communication network and actuator saturation

AbstractIn this paper, the stochastic stability of networked control systems (NCSs) with nonlinear perturbation and parameter uncertainties is studied. A decentralized dynamic event triggering scheme (DDETS) is introduced to reduce energy consumption and network transmission burden. Each channel can decide whether to transmit signals sampled by corresponding sensors through this mechanism. Due to the unreliability of communication network, a new mathematical model of NCSs based on multi‐channel fading and hybrid cyber attacks is established, and the actuator is constrained by saturation. A sufficient condition for stochastic stability based on static controller is derived through Lyapunov stability theory, and two numerical examples are given to demonstrate the effectiveness of the method.

Dynamic Event-Triggered Predictive Control for Interval Type-2 Fuzzy Systems with Imperfect Premise Matching.

This paper investigates the dynamic event-triggered predictive control problem of interval type-2 (IT2) fuzzy systems with imperfect premise matching. First, an IT2 fuzzy systems model is proposed, including a dynamic event-triggered mechanism, which can save limited network resources by reducing the number of data packets transmitted, and a predictive controller, which can predict the state of the system between the two successful transmitted instants to deal with unreliable communication networks. Then, according to the Lyapunov stability theory and imperfect premise matching method, sufficient conditions for system stabilization and the controller gain are obtained. Finally, the validity of the proposed method is demonstrated by the numerical examples.

Event‐triggered stabilization of multi‐dimensional nonlinear systems under communication constraints

AbstractThis article investigates the input‐to‐state stability of a multi‐dimensional nonlinear system, which transmits feedback information through an unreliable communication network with bounded network delay and occasional dropouts. In order to stabilize the system and save the occupied communication resources, we propose a model‐based periodic event‐triggered control strategy which can make full use of feedback packets, especially the information contained in their triggering time instants. However, both the network delay and feedback dropouts will reduce the amount of information extracted from triggering/sampling time instants, and significantly degrade the system performance. To handle them, this article provides a novel encoding and decoding method to make use of the timing information and the bits inside each feedback packet for both state and output feedback cases. Compared with the conventional time‐driven strategies, the proposed event‐triggered one can stabilize the concerned nonlinear system at a lower bit rate. The effectiveness and bit rate advantage of the proposed strategy are further illustrated through simulations.

Design-for-Trust Techniques for Digital Microfluidic Biochip Layout with Error Control Mechanism.

Among recent technological advances, microfluidic biochips have been leading a prominent solution for healthcare and miniaturized bio-laboratories with the assurance of high sensitivity and reconfigurability. On increasing more unreliable communication networks day-by-day, technological shifts in the fields of communication and security are now converging. In today's cyber threat landscape, these microfluidic biochips are ripe targets of powerful cyber-attacks from different hackers or cyber-criminals. Hence, securing such systems is of paramount importance. This paper presents the security aspects of digital microfluidic (DMF) biochip layout to protect the confidentiality of layout data from unscrupulous people and man-in-the-middle attacks. We propose an authentication mechanism with an error control mechanism that provides reliability, authentication, trustworthy and safety for both storage and communication of GDS, i.e., Graphical Design System, file generally used for DMF biochip layouts. Simulation results articulate the efficacy of the proposed security model without the overhead of the bioprotocol completion time. The proposed scheme, which used AES as an encryption algorithm with a 256-bit encryption key, has also shown a speedup of 6.0 (with 85% efficiency) faster than the prior efficient scheme. We hope to develop a secure layout design flow for DMF biochips to achieve better resistance to any attack.

Fixed-Time Distributed Secondary Control for Islanded Microgrids With Mobile Emergency Resources Over Switching Communication Topologies

Mobile emergency resources (MERs) are critical to the resilience of distribution systems for an emergency response to natural disasters. However, after disasters, the communication network of MERs may be unreliable. For example, the communication topology switches in different modes randomly. The conventional centralized control algorithms may not converge. As a result, the instability of frequency and voltage happened. To alleviate the impacts of the unreliable communication network on the second control performance, this paper regards the distribution system after disasters as multiple microgrids. A distributed secondary control algorithm is designed to regulate frequency and voltage in islanded microgrids over switching communication topologies. The algorithm is guaranteed to converge in a fixed time. Case studies are carried out to demonstrate the effectiveness and robustness of the proposed control algorithm under switching communication topologies.

Fuzzy-Model-Based Control for Singularly Perturbed Systems With Nonhomogeneous Markov Switching: A Dropout Compensation Strategy

This article addresses the asynchronous control for singularly perturbed systems with nonhomogeneous Markov switching approximated by T–S fuzzy models. The transition probabilities of the nonhomogeneous Markov process are supposed to be time-varying and distinguished by of a polytopic set. As distinct from some reported works, to abate the effect of missing packets in unreliable communication network, a novel dropout compensation strategy is constructed, where the packet arriving rate is assumed to be uncertain. Meanwhile, to describe the asynchronizations of the dropout compensation strategy and the controller, the hidden Markov models are absorbed. By resorting to the fuzzy-rule-dependent and the parameter-dependent Lyapunov–Krasovskii functional, novel sufficient conditions of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"><tex-math notation="LaTeX">$\mathcal {H}_{\infty }$</tex-math></inline-formula> performance are formulated and the fuzzy-based asynchronous controller gains are realized. Finally, to testify the efficiency and applicability of the proposed results, a numerical example and practical tunnel diode circuit system are provided.