The Technology Research On Time Synchronization In Wire-Less Network Based On IEEE1588

As the increase of real-time application, the time synchronizationbetween nodes in the network becomes important. Time synchronizationcan help raising the efficiency of resources and improving the userexperience and performance of the systems. Nowadays GPS and IEEE1588can realize highly precise time synchronization. But the GPS systemhas the following shortages: high expenses, and safety risk. And usingGPS to synchronize the nodes in a small-size network is not practicalespecially in an indoor environment. As with IEEE1588, it has a goodapplication in Ethernet but for wireless network it’s not suitable. So how torealize the time synch of relatively high precision in wireless environmentis very important.This paper build a hardware platform to realize the IEEE1588protocol and design the clock nodes in the network based on theADSP-BF518chip. Two clocks are connected through Ethernet, one ofwhich is master clock and the other is slave one. Usually, the master clockin network has a relatively high precision compared to the slave clocks.This paper models the clock and utilizes data fusion to deal with twogroups of local time information generated by two low-precise oscillators,reaching the goal of improving the local clock stability. The essential ofslave clock synchronization is to estimate the offset and skew of it relativeto the master clock and then adjust the local time. The method ofestimation defined in IEEE1588doesn’t consider the noise which willhave a bad effect on the estimation. Kalman filer is considered to estimatethe offset and skew and it can eliminate the effect of noise, improving theprecision of time synchronization. When the exchange of time information between slave and master is based on the wireless environment and the multipath in the wireless will make the network delay between master and slave asymmetric which will affect the synchronization error which is simulated in the paper. When the situation comes to the wireless network, CSMA/CA is introduced to avoid signal conflict but the mechanism results in the time random of channel contention and it may reach several hundred μs or even ms, which will hinder the precision of time synchronization. To eliminate the contention time influence, an assistant time synch protocol is advised and an assistant clock node is used to realize the time synchronization. The simulation result shows that the protocol can reduce the bad effect of channel content on time synchronization.