Zhulin An

Nonidentical Linear Pulse-Coupled Oscillators Model With Application to Time Synchronization in Wireless Sensor Networks

Similar to other cyber infrastructure systems, as wireless sensor networks become larger and more complex, many classic algorithms may no longer work efficiently. This paper presents a wireless sensor network time synchronization model that was initially inspired by synchronous flashing of fireflies. Synchronous flashing of fireflies is an interesting phenomenon that has been studied for decades. A variety of models have been proposed to explain this phenomenon, among which is the pulse-coupled oscillators model that models fireflies as oscillators. The oscillators in such a model interact only through discrete pulses, similar to the flashing of fireflies. In this paper, we propose a new nonidentical linear pulse-coupled oscillators model and use the model to analyze synchronization of pulse-coupled oscillators with different frequencies. The conditions to achieve and maintain synchronization are derived, and then, the results are used to prove that the oscillators in the model can achieve synchronization eventually, except for a set of frequencies with zero Lebesgue measure. Furthermore, through simulations and implementation on a wireless sensor network testbed, we demonstrate that the proposed nonidentical linear pulse-coupled oscillators model can be used in designing lightweight scalable time synchronization protocols for distributed systems.

Improving both energy and time efficiency of depth-based routing for underwater sensor networks

Underwater Sensor Network (UWSN) is a representative three-dimensional wireless sensor network. Due to the unique characteristics of underwater acoustic communication, providing energy-efficient and low-latency routing protocols for UWSNs is challenging. Major challenges are water currents, limited resources, and long acoustic propagation delay. Network topology of UWSNs is dynamic and complex as sensors have always been moving with currents. Some proposed protocols adopt geographic routing to address this problem, but three-dimensional localization is hard to obtain in underwater environment. As depth-based routing protocol (DBR) uses depth information only which is much more easier to obtain, it is more practical for UWSNs. However, depth information is not enough to restrict packets to be forwarded within a particular area. Packets may be forwarded through multiple paths which might cause energy waste and increase end-to-end delay. In this paper, we introduce underwater time of arrival (ToA) ranging technique to address the problem above. To maintain all the original advantages of DBR, we make the following contributions: energy-efficient depth-based routing protocol that reduces redundancy energy cost in some blind zones; low-latency depth-based routing protocol that is able to deliver a packet through an optimal path. The proposed protocols are validated through extensive simulations.

Distributed Multi-Target Tracking Based on the K-MTSCF Algorithm in Camera Networks

It is a challenging task to develop an effective multi-target tracking algorithm for camera networks due to the factors, such as spurious measurement, limited field of view, complexity of data association algorithm, and so on. In a real-life environment, the system model for camera networks is usually nonlinear, and hence, a Kalman filter may be inappropriate for modeling this system. Besides, the main drawback of traditional joint probabilistic data association (JPDA) is prone to raise the combinatorial explosion problem when the association probabilities have to be calculated. To solve these problems, a multi-target square-root cubature information weighted consensus filter (MTSCF) combined with a K-best joint probabilistic data association algorithm is proposed in this paper. The proposed K-MTSCF algorithm can not only reduce the effect of data association uncertainty stemming from the ambiguity of measurements and computation complexity of data association algorithm by K-best JPDA, but also increase tracking accuracy and stability using MTSCF algorithm. The experimental results demonstrate that the proposed approach performs favorably against the state-of-the-art methods in terms of accuracy and stability for tracking multiple targets in camera networks.

DTMAC: A Delay Tolerant MAC Protocol for Underwater Wireless Sensor Networks

Unlike radio communication in terrestrial wireless sensor networks, acoustic channel in underwater wireless sensor network (UWSN) is challenged by long propagation delay and swarm mobility. The long propagation delay causes the deterioration of network throughput and unfairness. Moreover, the swarm mobility causes unreliable access and the failure of channel reservation. In this paper, we propose a novel delay tolerant MAC protocol (DTMAC) inspired by the coupon collectors problem. It proposes a distributed coupon collection algorithm in UWSNs. If a node needs to send a packet, the packet will be repeatedly transmitted

TDMA Versus CSMA/CA for Wireless Multihop Communications: A Stochastic Worst-Case Delay Analysis

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Poster abstract: human tracking based on LRF and wearable IMU data fusion

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A Reliable Depth-Based Routing Protocol with Network Coding for Underwater Sensor Networks

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TDMA versus CSMA/CA for wireless multi-hop communications: A comparison for soft real-time networking

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DBR-MAC: A Depth-Based Routing Aware MAC Protocol for Data Collection in Underwater Acoustic Sensor Networks

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