\n\n In recent research, time synchronization has a great importance in the various\napplication of wireless sensor network. Localization, tracking, message passing using contention-based\nschemes and communication are some of the fields where synchronization between sensor clocks is\nhighly required. Therefore, several algorithms were designed to achieve a rational and reliable frame of\ntime within the wireless sensor network. Patents related to time synchronization in WSN were also analyzed.\n\n\n\n This paper discusses the powerful statistical tool using maximum probability theory for synchronizing\nthe time within the sensor's clock. In this paper, maximum probability theory is applied to\nestimate the best value of clock offset between two sensor clocks. The proposed algorithm is analyzed\nby exchanging timing messages between nodes using two-way message exchange schemes.\n\n\n\nThe proposed algorithm is also implemented along with a Time-Sync Protocol for Sensor Network.\nIt reduces error deviation from 2.32 to 0.064 ms as compared with Time-Sync Protocol for Sensor\nNetwork without proposed works.\n\n\n\n It was observed that for a small network, proposed work gives better and efficient results\nwith Time-Sync Protocol for Sensor Network.\n

A Statistical Tool for Time Synchronization Problem in WSN

Collaborative body sensor network (CBSN) is formed of several body sensor networks (BSNs) moving in a given area and able to exchange data between each other. One of the challenges in CBSN is to design a Medium Access Protocol that efficiently supports nodes mobility, and at the same time, guarantees immediate delivery of urgent data, and maintains high energy efficiency during regular observation. In this paper, a hybrid traffic and mobility aware MAC (TMA-MAC) is proposed to satisfy CBSN's traffic requirements through adopting a hybrid DS-CDMA/DTDMA technique, and to support CBSN's nodes mobility through ensuring efficient transmission of intracluster mobile nodes data and proposing a mechanism to handle inter-cluster nodes joining requests. TMA-MAC was compared to other existing protocols under both traffic and mobility variations. Simulations were conducted using OPNET to evaluate TMA-MAC with respect to packet delay, packet drop percentage, and energy consumption.

https://hal.archives-ouvertes.fr/hal-02993836/document

Mobility aware and traffic adaptive hybrid MAC protocol for collaborative body sensor networks

Wireless Sensor Networks (WSNs) is one of the hot topics in the field of information, which can be used in the special environment to realize the signal acquisition, processing and transmission. As a key technology of WSNs, time synchronization has achieved a wide range of attention and many scholars have come up with lots of methods to solve the problems for different applications. Among these problems the consistency of multi hop error in large scale networks is one of the key difficulties that need to be further considered. In this paper, a mobile node and many fixed nodes form a mobile wireless network. Furthermore the mobile node is used as the time source. In our method the synchronization process does not depend on any special network topology because fixed nodes directly synchronized to the mobile node that traverse the whole network periodically. For the nodes synchronize to the mobile node directly, the time synchronization of nodes in the network keeps in good consistency. Experiments and analysis suggest that our method has greatly improved the stability and consistency of the time synchronization in compare with the traditional hop by hop synchronization method.

A Consistent and Low-Overhead Time Synchronization Method for Wireless Sensor Networks

Existing time synchronization protocols for Wireless Sensor Networks (WSN) have already focused on lot of time synchronization issues like accuracy, energy efficiency, security and time synchronization itself etc for static wireless sensor networks but best of our knowledge time synchronization for mobile wireless sensor networks has not been fully explored yet, so there is need to design protocols that can assist to time synchronize mobile wireless sensor networks in a simple way to achieve better time synchronization accuracy. In this paper we propose mathematical model that is basically an extension of pair-wise time synchronization protocol and it aims to synchronize mobile wireless sensor node with the help of nearby static wireless sensor node. This model can be used to achieve network wide time synchronization. Proposed model has kept the track of direction and velocity of mobile nodes. Proposed protocol has been simulated and results are compared with existing pair-wise time synchronization protocol. Results show that pair-wise time synchronization protocol introduces significant error that will keep increasing with the moving velocity of mobile node. In contrast proposed algorithm performed very well in terms of accuracy, energy and computational cost and was able to synchronize mobile nodes with the help of static sensor nodes successfully.

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Asma Khan

Papers

Time Synchronization for Mobile Wireless Sensor Network