An algorithm for WSN clock synchronization: Uncertainty and convergence rate trade off

Performance Analysis for a Wireless Sensor Network of Star Topology with Random Nodes Deployment

Abstract: A wireless sensor network is applied for detecting information, by nodes, then generates and transfers the packets to the clustering head for further transmission. In practice, due to the influence of environmental factors, traffic loads of nodes and barrier, a node may fail to detect the information which occurs within its sensing area. Thus, the redundant deployment is often conducted. There are some frequent questions need to be considered when deploying the WSN: (1) how many nodes are required for obtaining a confident coverage of the area; (2) how well does the WSN perform as time goes by, because it is an energy consumption technique; (3) when is the best opportunity to reallocate the nodes. To answer the above questions, we conduct this research. We use $$k$$ -out-of- $$n$$ model to calculate the $$k$$ -coverage probability, which determines the minimal number of nodes that are needed to be deployed in the monitored area. We formulate the node availability and WSN availability with the assumption that the information arrival is a Poisson process. By applying the age-based replacement model, we obtain the optimal reallocation interval with lowest long run expected cost rate.

RiSeG: A logical ring based secure group communication protocol for Wireless Sensor Networks

Abstract: It is worth noting that securing group communication in Wireless Sensor Networks (WSNs) has recently been extensively investigated. Although many works have addressed this problem, they have considered the concept of grouping differently. In this paper, we consider a group as being a set of nodes sensing the same type of data and we alternatively propose an efficient secure group communication scheme that enables group management and secure group key distribution. The proposed scheme is based on a logical ring architecture, which permits to alleviate the task of the group controller in maintaining the group key. The proposed scheme also provides backward and forward secrecy, addresses the node compromise attack and gives solution to detect and eliminate the compromised nodes. Finally, our implementation shows that the proposed scheme is highly efficient and secure.

Reliability analysis for a data flow in event-driven wireless sensor networks using a multiple sending transmission approach

Abstract: Reliability analysis is an important issue in wireless sensor networks (WSNs). This paper aims to study the reliability of a data flow in event-driven wireless sensor networks with multiple sending transmission approach without acknowledgments. Initially, an event-driven wireless sensor network model is described in terms of limited node battery energy and shadowed fading channels. Then, in order to analyze the network reliability, the wireless link reliability and the node energy availability are investigated, respectively. Furthermore, the analytical expressions of the instantaneous network reliability and the mean time to failure (MTTF) are derived. Finally, the simulation results validate the correctness and accuracy of the analytical results.

Towards master-less wsn clock synchronization with a light communication protocol

Abstract: Time synchronization of Wireless Sensor Network (WSN) nodes is essential in those applications requiring distributed task scheduling or data aggregation and fusion. In this paper, a new synchronization procedure based on a distributed Proportional Integral (PI) consensus controller is described. Compared to other similar solutions, the proposed approach keeps into account the effect of random communication and processing delays and it is expected to have lower communication overhead. Also, it is designed to avoid the election of any fixed time reference node, thus potentially improving the robustness of the whole synchronization procedure. Some simulation results show that the procedure works correctly even in different network traffic conditions.

Master-less time synchronization for wireless sensor networks with generic topology

Abstract: Time synchronization in wireless sensor networks (WSN) is essential to schedule communication and distributed measurement tasks. In this paper a consensus-based synchronization algorithm is used to compensate dynamically both time offsets and clock frequency skews, thus driving all WSN clocks towards a common time scale. The proposed approach does not require either the election of a master node as a time reference for the whole network, or a specific synchronization protocol. Some simulation results show that the algorithm converges within a reasonable time, regardless of timestamping jitter, random communication latencies and incomplete node visibility.

Fine-grained network time synchronization using reference broadcasts

Abstract: Recent advances in miniaturization and low-cost, low-power design have led to active research in large-scale networks of small, wireless, low-power sensors and actuators. Time synchronization is critical in sensor networks for diverse purposes including sensor data fusion, coordinated actuation, and power-efficient duty cycling. Though the clock accuracy and precision requirements are often stricter than in traditional distributed systems, strict energy constraints limit the resources available to meet these goals.We present Reference-Broadcast Synchronization, a scheme in which nodes send reference beacons to their neighbors using physical-layer broadcasts. A reference broadcast does not contain an explicit timestamp; instead, receivers use its arrival time as a point of reference for comparing their clocks. In this paper, we use measurements from two wireless implementations to show that removing the sender's nondeterminism from the critical path in this way produces high-precision clock agreement (1.85 ± 1.28μsec, using off-the-shelf 802.11 wireless Ethernet), while using minimal energy. We also describe a novel algorithm that uses this same broadcast property to federate clocks across broadcast domains with a slow decay in precision (3.68 ± 2.57μsec after 4 hops). RBS can be used without external references, forming a precise relative timescale, or can maintain microsecond-level synchronization to an external timescale such as UTC. We show a significant improvement over the Network Time Protocol (NTP) under similar conditions.

The flooding time synchronization protocol

Abstract: Wireless sensor network applications, similarly to other distributed systems, often require a scalable time synchronization service enabling data consistency and coordination. This paper describes the Flooding Time Synchronization Protocol (FTSP), especially tailored for applications requiring stringent precision on resource limited wireless platforms. The proposed time synchronization protocol uses low communication bandwidth and it is robust against node and link failures. The FTSP achieves its robustness by utilizing periodic flooding of synchronization messages, and implicit dynamic topology update. The unique high precision performance is reached by utilizing MAC-layer time-stamping and comprehensive error compensation including clock skew estimation. The sources of delays and uncertainties in message transmission are analyzed in detail and techniques are presented to mitigate their effects. The FTSP was implemented on the Berkeley Mica2 platform and evaluated in a 60-node, multi-hop setup. The average per-hop synchronization error was in the one microsecond range, which is markedly better than that of the existing RBS and TPSN algorithms.

Discrete-time control systems

Abstract: Discrete-time control systems , Discrete-time control systems , مرکز فناوری اطلاعات و اطلاع رسانی کشاورزی

Perspectives and results on the stability and stabilizability of hybrid systems

Abstract: This paper introduces the concept of a hybrid system and some of the challenges associated with the stability of such systems, including the issues of guaranteeing stability of switched stable systems and finding conditions for the existence of switched controllers for stabilizing switched unstable systems. In this endeavour, this paper surveys the major results in the (Lyapunov) stability of finite-dimensional hybrid systems and then discusses the stronger, more specialized results of switched linear (stable and unstable) systems. A section detailing how some of the results can be formulated as linear matrix inequalities is given. Stability analyses on the regulation of the angle of attack of an aircraft and on the PI control of a vehicle with an automatic transmission are given. Other examples are included to illustrate various results in this paper.

Standard for a Precision Clock Synchronization Protocol for Networked Measurement and Control Systems

Abstract: A protocol is provided in this standard that enables precise synchronization of clocks in measurement and control systems implemented with technologies such as network communication, local computing, and distributed objects. The protocol is applicable to systems communicating via packet networks. Heterogeneous systems are enabled that include clocks of various inherent precision, resolution, and stability to synchronize. System-wide synchronization accuracy and precision in the sub-microsecond range are supported with minimal network and local clock computing resources. Simple systems are installed and operated without requiring the management attention of users because the default behavior of the protocol allows for it.