Performance Evaluation of a Wireless Sensor Network

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Dr. Kovácsházy Tamás
Department of Measurement and Information Systems

A fundamental requirement of distributed systems is the presence of a communication network between its nodes. In case of a sensor system, care must be taken not only to the data transfer but also to the timing, as the measured value and the measurement time are both important. Handling of the timing conditions requires the clock synchronization of the measurement units. For this purpose, several examples can be found in the literature considering wired and wireless applications. However, the synchronization accuracy requirements of the examined sensor system were too high for the application of a present standard. Therefore, the implementation of an own protocol was demanded. After the examination of the more generally applicable solutions designed for wired networks, I decided to have my protocol based on one of them.

The self-designed wireless communication protocol implements embedded clock synchronization, ensuring the appropriately accurate knowledge of message timing. It is designed for sensor systems, where high precision clock synchronization is demanded. Therefore, the synchronization messages in my solution have higher priority than the data messages. Furthermore, the system supports real time application, where the presence of continuous supervision is crucial. It uses time-sharing communication that periodically grants service time for the message sending demand of the nodes, thus each unit has the opportunity for communication. The embedded clock synchronization is based on the IEEE 1588 standard and operates with almost the same accuracy. It is made possible by utilizing the specific functionalities of the applied hardware, increasing the recording precision of the time stamps.

The topic of this final project was partly elaborated in my Scientific Students’ Associations work this year, where the theoretical fundamentals of clock synchronization was developed in a cooperation with my colleague, Sámuel Várallyay. He also helped with the design of the physical system. The implementation of the communication protocol and synchronization on the embedded system was solely my responsibility.


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