The Simulations Of MATLAB And OMNeT++ For IEEE1588 Precious Time Protocol In WSN

Wireless Sensor Network (WSN) is a typical low-cost and self-organization distributed network, which has advantages in deployment flexibility, while has disadvantages in energy limitation and low stability. As a key technique in distributed systems, time synchronization plays an important role in high-precision modern industrial Wireless Local Area Networks (WLAN). Many applications of wireless network depend on time synchronization, such as data fusion, time division multiple access (TDMA), times of arrival (TOA), etc. The IEEE 1588 precise time protocol (PTP) based on time packet exchange technology can achieve high precision and low power consumption time synchronization in wired Ethernet.Compared to the wired Ethernet, WSN takes more challenges from wireless channel sharing, data fading and data packet collision, which may lead to overwhelming transmission delay jitters. Therefore, it is difficult for the wireless sensor nodes to acquire accurate time-stamps and evaluate PTP’s performance. It is a meaningful research to evaluate PTP’s performance by realistic simulation in WSN.The WSN and IEEE 1588 PTP are analyzed in this thesis, as well as the application of IEEE 1588 PTP in WSN. A simulator of WSN based on OMNeT++, which is an opening source network simulation tool is developed. And a Kalman filter is used to improve the performance and the behavior of the PTP’s time synchronization. The OMNeT++ simulation results and the factors that affect the PTP performance are presented and evaluated when compared to MATLAB simulation.The main works of the thesis are shown as follows:1) IEEE 1588 PTP is studied and applied into WSN, and the factors of time synchronization are analyzed.2) The clock of WSN’s node and the PTP synchronization packet exchange process are modeled respectively, and the system of PTP is modeled based on the channel characteristics of WSN. Then a Kalman filter is used to improve the performance and the behavior of the PTP’s time synchronization.3) On account of previous studies, the parameters and regulation mechanism of the system are reconstructed based on the characteristics of WSN. Simulation systems of IEEE 1588 PTP are developed on two different simulation platforms, named MATLAB and OMNeT++, and the results are comparatively analyzed.The simulator results show that the noise of offset and skew have a great influence on protocol precision when the uncertainties of time stamping keeps in a low range. On the other hand, the proposed Kalman filter can improve the performance of PTP when the uncertainties of time stamping get higher. And the results in OMNeT++reflect the real networks more than in MATLAB; the simulator on OMNeT++ is more suited to expand research in real WSN.