Chih-Yu Wen

Automatic decentralized clustering for wireless sensor networks

We propose a decentralized algorithm for organizing an ad hoc sensor network into clusters. Each sensor uses a random waiting timer and local criteria to determine whether to form a new cluster or to join a current cluster. The algorithm operates without a centralized controller, it operates asynchronously, and does not require that the location of the sensors be known a priori. Simplified models are used to estimate the number of clusters formed, and the energy requirements of the algorithm are investigated. The performance of the algorithm is described analytically and via simulation.

Distance Estimation Using Bidirectional Communications Without Synchronous Clocking

A fundamental problem when locating sensors in a network is to estimate the distance between pairs of sensors. This paper considers a variety of time-of-arrival and phase-shift approaches that use bidirectional signaling to bypass the need for accurate synchronous clocking. The measurement techniques are simulated and analyzed to assess the accuracy of the distance estimation. The analysis demonstrates tradeoffs between the accuracy of the oscillators, the accuracy of the subsequent distance estimation, and the complexity of the methods

Distributed Clustering With Directional Antennas for Wireless Sensor Networks

This paper proposes a decentralized algorithm for organizing an ad hoc sensor network into clusters with directional antennas. The proposed autonomous clustering scheme aims to reduce the sensing redundancy and maintain sufficient sensing coverage and network connectivity in sensor networks. With directional antennas, random waiting timers, and local criterions, cluster performance may be substantially improved and sensing redundancy can be drastically suppressed. The simulation results show that the proposed scheme achieves connected coverage and provides efficient network topology management.

Adaptive Decentralized Re-Clustering for Wireless Sensor Networks

This paper discusses a dynamic decentralized algorithm for re-clustering the sensors of an ad hoc sensor network. Each sensor uses a random waiting timer and local criteria to determine whether to form a new cluster or to join a current cluster. A localized clusterhead reselection process is triggered when the energy reserves of the clusterhead falls below a threshold. The algorithm operates without a centralized controller, it operates asynchronously, and does not require that the location of the sensors be known a priori. An analysis of cluster lifetime, the energy requirements of the algorithm, and a simplified model are used to study the behaviors of the proposed algorithm. The performance of the algorithm is described analytically and via simulation.

A Secure Scheme Against Power Exhausting Attacks in Hierarchical Wireless Sensor Networks

Security and energy efficiency are critical concerns in wireless sensor network (WSN) design. This paper aims to develop an energy-efficient secure scheme against power exhausting attacks, especially the denial-of-sleep attacks, which can shorten the lifetime of WSNs rapidly. Although various media access control (MAC) protocols have been proposed to save the power and extend the lifetime of WSNs, the existing designs of MAC protocol are insufficient to protect the WSNs from denial-of-sleep attacks in MAC layer. This is attributed to the fact that the well-known security mechanisms usually awake the sensor nodes before these nodes are allowed to execute the security processes. Therefore, the practical design is to simplify the authenticating process in order to reduce the energy consumption of sensor nodes and enhance the performance of the MAC protocol in countering the power exhausting attacks. This paper proposes a cross-layer design of secure scheme integrating the MAC protocol. The analyses show that the proposed scheme can counter the replay attack and forge attack in an energy-efficient way. The detailed analysis of energy distribution shows a reasonable decision rule of coordination between energy conservation and security requirements for WSNs.

Adaptive AOA/TOA Localization Using Fuzzy Particle Filter for Mobile WSNs

Location-awareness is crucial and becoming increasingly important to many applications in wireless sensor networks. This paper presents a network-based positioning system and outlines recent work in which we have developed an efficient principled approach to localize a mobile sensor using time of arrival (TOA) and angle of arrival (AOA) information employing multiple seeds in the line-of-sight scenario. By receiving the periodic broadcasts from the seeds, the mobile target sensors can obtain adequate observations and localize themselves automatically. Based on the distance measurements and the initial position estimate, adaptive fuzzy control scheme is applied to solve the localization adjustment problem. The simulations show that the proposed approach provides adaptive flexibility and robust improvement in position estimation.

Decentralized anchor-free localization for wireless ad-hoc sensor networks

This paper proposes algorithms for establishing connectivity and location estimation in wireless sensor networks. The algorithms exploit the information flow while coping with distributed signal processing and the requirements of network scalability. Once the estimation procedure and communication protocol are performed, sensor clusters can be merged to establish a single global coordinate system without GPS sensors using only distance information. In order to adjust the sensor positions, the refinement schemes are applied to reduce the estimation error such that the propagation error can be suppressed. This paper outlines the technical foundations of the localization techniques and presents the tradeoffs in algorithm design. The feasibility of the proposed schemes is shown to be effective under certain assumptions and the analysis is supported by simulation and numerical studies.

A secure scheme for power exhausting attacks in wireless sensor networks

Security and energy efficiency are the most important concerns in wireless sensor networks (WSNs) design. To save the power and extend the lifetime of WSNs, various media access control (MAC) protocols are proposed. Most traditional security solutions can not be applied in the WSNs due to the limitation of power supply. The well-known security mechanisms usually awake the sensor nodes before the sensor nodes can execute the security processes. However, the Denial-of-Sleep attacks can exhaust the energy of sensor nodes and shorten the lifetime of WSNs rapidly. Therefore, the existing designs of MAC protocol are insufficient to protect the WSNs from Denial-of-Sleep attack in MAC l ayer. The practical design is to simplify the authenticating process in order to enhance the performance of the MAC protocol in countering the power exhausting attacks. This paper proposes a cross-layer design of secure scheme integrating the MAC protocol. The analyses show that the proposed scheme can counter the replay attack and forge attack in an energy-efficient way.

Adaptive Distributed Topology Control for Wireless Ad-Hoc Sensor Networks

This paper presents a decentralized clustering and gateway selection algorithm for wireless ad-hoc sensor networks. Each sensor uses a random waiting timer and local criteria to determine whether to form a new cluster or to join a current cluster and utilizes the messages transmitted during hierarchical clustering to choose distributed gateways such that communication for adjacent clusters and adaptive distributed topology control can be achieved. The algorithm operates without a centralized controller, it operates asynchronously, and does not require that the location of the sensors be known a priori. A performance analysis of the topology management and the energy requirements of the algorithm are used to study the behaviors of the proposed algorithm. The performance of the algorithm is described analytically and via simulation.

Adaptive AOA-Aided TOA Self-Positioning for Mobile Wireless Sensor Networks

Location-awareness is crucial and becoming increasingly important to many applications in wireless sensor networks. This paper presents a network-based positioning system and outlines recent work in which we have developed an efficient principled approach to localize a mobile sensor using time of arrival (TOA) and angle of arrival (AOA) information employing multiple seeds in the line-of-sight scenario. By receiving the periodic broadcasts from the seeds, the mobile target sensors can obtain adequate observations and localize themselves automatically. The proposed positioning scheme performs location estimation in three phases: (I) AOA-aided TOA measurement, (II) Geometrical positioning with particle filter, and (III) Adaptive fuzzy control. Based on the distance measurements and the initial position estimate, adaptive fuzzy control scheme is applied to solve the localization adjustment problem. The simulations show that the proposed approach provides adaptive flexibility and robust improvement in position estimation.