Research On The Technology Of Precise Timing In Wireless Packet Network

Clock Synchronization and Timing are one of the basic technologies in communication systems and communication networks, and are prerequisite for carrying circuit emulation and real-time services. With the development of wireless transmission technology, wireless packet networks require a more accurate and stable clock synchronization and timing support. Researching Packet Networks, especially clock synchronization and timing in wireless network, is an urgent issue. PTP, defined in IEEE 1588 standard, can achieve sub-microsecond accuracy. This thesis focuses on how to introduce PTP into wireless packet networks, and how to improve the precision of clock synchronization.Firstly, this thesis analyzes the architecture and synchronization mechanism of PTP, and compares clock synchronization algorithm in the Wireless Sensor Networks and Wireless Local Area Network, and find out that the precision of clock synchronization in wireline networks can be achieved sub-microsecond, while just tens of microseconds in wireless network. Secondly, the thesis explores three factors which influence the precision of clock synchronization and the methods of compensation in wireless networks and wireline networks, respectively. Thirdly, through observing and analyzing the results of experiments, it found that the variance between the master and slave clock via wireless links is worse three orders of magnitude than that via wireline links. Finally, we proposes an improve approach of PTP to wireless packet networks, and the implementation structure is to introduced into by a filter in the local side of the slave clock for filtering noise, and improve the precision of clock synchronization.The Matlab was used as simulation tool to research the effect of the Butterworth, Chebyshev and Elliptic filtering algorithm to improve synchronization performance. The simulation results show that the mean time offset between master and slave can be improved, and further the variance can be improved by an order of magnitude, in case a filter involved. And by adjusting the type, the order, the passband and stopband frequencies, and the width of stopband of filter, the synchronization performance can be optimized. It is concluded that the proposed improvement of PTP is feasible and effective.