Signal processing techniques for synchronization of wireless sensor networks

Plenary PaperClock synchronization is a critical component in wireless sensor networks, as it provides a common time frame to different nodes. It supports functions such as fusing voice and video data from different sensor nodes, time-based channel sharing, and sleep wake-up scheduling, etc. Early studies on clock synchronization for wireless sensor networks mainly focus on protocol design. However, clock synchronization problem is inherently related to parameter estimation, and recently, studies of clock synchronization from the signal processing viewpoint started to emerge. In this article, a survey of latest advances on clock synchronization is provided by adopting a signal processing viewpoint. We demonstrate that many existing and intuitive clock synchronization protocols can be interpreted by common statistical signal processing methods. Furthermore, the use of advanced signal processing techniques for deriving optimal clock synchronization algorithms under challenging scenarios will be illustrated. © 2010 SPIE.published_or_final_versio

A Time Synchronization Protocol for TDMA Based Wireless Sensor Networks

학위논문 (석사)-- 서울대학교 대학원 : 전기공학부, 2013. 8. 이정우.There has been much interest in wireless sensor networks recently, due to their diverse range of possible applications. Although there have been much research in MAC layer protocols for wireless sensor networks, these works are mainly focussed on the power savings and efficiencies of the protocols. For sensor networks which are in-situ and do not require much flexibility, such as a battery management system, energy is not always the most important factor, but rather reliability and scalability (where sensing periods are known). As such, a traditional TDMA protocol can be considered as a good option. Time synchronization in wireless sensor networks have also been considered by many academics, but work related to time synchronization in TDMA networks have been much less popular. In this thesis, a time synchronization protocol for TDMA based wireless sensor networks is proposed, Propagating Chain Time Synchronization. Propagating Chain Time Synchronization is a novel protocol for synchronizing TDMA based networks. The scheme achieves improved synchronization errors compared to traditional beacon synchronization methods, through skew correction estimated from chained two-way message exchanges, which employ piggybacking and overhearing.1 Introduction 1 1.1 Wireless Sensor Networks 1 1.1.1 Challenges in Designing Wireless Sensor Networks 2 1.2 Thesis Motivation 7 1.2.1 Wireless Sensor Networks in Battery Management Systems 7 2 Time Synchronization 10 2.1 Overview 10 2.2 Models of Clock Synchronization 11 2.2.1 Typical Synchronization Errors 13 2.3 Related Work 14 2.3.1 Sender-Receiver Synchronization 14 2.3.2 Receiver-Receiver Synchronization 16 2.3.3 Receiver-Only Synchronization 17 2.3.4 Clock Skew Estimation and Correction 18 2.3.5 Clock Synchronization in TDMA Based Networks 19 3 Propagating Chain Time Synchronization for TDMA Based Wireless Sensor Networks 21 3.1 Overview 21 3.2 System Model 21 3.2.1 Basic Assumptions 22 3.2.2 Topology 22 3.2.3 Chained Synchronization 23 3.2.4 Overhearing and Piggybacking 24 3.2.5 Propagating Skew Correction 28 4 Theoretical Error Analysis 31 4.1 System Models 31 4.2 Node Clock Modelling 32 4.3 TSF 34 4.4 Chained Synchronization 36 4.5 Two-Way Message Exchange Synchronization Error 38 5 Simulation 42 5.1 Simulation Parameters 42 5.2 Simulation Results 46 6 Conclusion 52 Bibliography 54Maste

Adaptive Time Synchronization for Homogeneous WSNs

Wireless sensor networks (WSNs) are being used for observing real‐world phenomenon. It is important that sensor nodes (SNs) must be synchronized to a common time in order to precisely map the data collected by SNs. Clock synchronization is very challenging in WSNs as the sensor networks are resource constrained networks. It is essential that clock synchronization protocols designed for WSNs must be light weight i.e. SNs must be synchronized with fewer synchronization message exchanges. In this paper, we propose a clock synchronization protocol for WSNs where first of all cluster heads (CHs) are synchronized with the sink and then the cluster nodes (CNs) are synchronized with their respective CHs. CNs are synchronized with the help of time synchronization node (TSN) chosen by the respective CHs. Simulation results show that proposed protocol requires considerably fewer synchronization messages as compared with the reference broadcast synchronization (RBS) protocol and minimum variance unbiased estimation (MUVE) method. Clock skew correction mechanism applied in proposed protocol guarantees long term stability and hence decreases re‐ synchronization frequency thereby conserving more energ

Preliminary OFDM based acoustic communication for underwater sensor networks synchronization

This work presents a first approach to wireless underwater sensor networks UWSN time synchronization, using OFDM (Orthogonal Frequency Division Multiplexing) acoustic communication and time reference served by a synchronization protocol. This synchronization and type of modulation allows getting a low drift clock on each sensor, on a high efficiency underwater communication network.Peer ReviewedPostprint (author’s final draft

Clock Synchronization in Wireless Sensor Networks: An Overview

The development of tiny, low-cost, low-power and multifunctional sensor nodes equipped with sensing, data processing, and communicating components, have been made possible by the recent advances in micro-electro-mechanical systems (MEMS) technology. Wireless sensor networks (WSNs) assume a collection of such tiny sensing devices connected wirelessly and which are used to observe and monitor a variety of phenomena in the real physical world. Many applications based on these WSNs assume local clocks at each sensor node that need to be synchronized to a common notion of time. This paper reviews the existing clock synchronization protocols for WSNs and the methods of estimating clock offset and clock skew in the most representative clock synchronization protocols for WSNs

Distributed clock synchronization for wireless sensor networks using belief propagation

In this paper, we study the global clock synchronization problem for wireless sensor networks. Based on belief propagation, we propose a fully distributed algorithm which has low overhead and can achieve scalable synchronization. It is also shown analytically that the proposed algorithm always converges for strongly connected networks. Simulation results show that the proposed algorithm achieves better accuracy than consensus algorithms. Furthermore, the belief obtained at each sensor provides an accurate prediction on the algorithm's performance in terms of MSE. © 2011 IEEE.published_or_final_versio

Clock Synchronization in Wireless Sensor Networks: Analysis and Design of Error Precision Based on Lossy Networked Control Perspective

Motivated by the importance of the clock synchronization in wireless sensor networks (WSNs), due to the packet loss, the synchronization error variance is a random variable and may exceed the designed boundary of the synchronization variance. Based on the clock synchronization state space model, this paper establishes the model of synchronization error variance analysis and design issues. In the analysis issue, assuming sensor nodes exchange clock information in the network with packet loss, we find a minimum clock information packet arrival rate in order to guarantee the synchronization precision at synchronization node. In the design issue, assuming sensor node freely schedules whether to send the clock information, we look for an optimal clock information exchange rate between synchronization node and reference node which offers the optimal tradeoff between energy consumption and synchronization precision at synchronization node. Finally, simulations further verify the validity of clock synchronization analysis and design from the perspective of synchronization error variance