Research On IEEE 1588 Time Synchronization Technology In PTN

With the rapid development of communication technology,the increase of realtime applications,and the demand of large bandwidth and high speed transmission,the clock nodes in the network have increasingly strict requirements on the accuracy of time synchronization.However,the Network Time Protocol(NTP),which is widely used in computer networks,can only provide millisecond precision.Although GPS can provide high time accuracy of nanosecond,but it is subject to cost and security problems.In this case,IEEE 1588 protocol is called an ideal scheme of high precision time synchronization due to its advantages of low cost,high adaptability and high subnanosecond accuracy.This paper firstly introduces the development process and synchronization requirements of Packet Transport Network(PTN),then introduces the Precision Time Protocol(PTP)IEEE 1588 of clock synchronization technology in PTN,and analyzes the characteristics of different clock types through IEEE 1588 Network simulation.Then,the influencing factors of synchronization performance were analyzed.Aiming at the influence of temperature on clock stability,and the clock state was estimated based on kalman filter.Finally,a clock servo control method based on Beetle Antennae Search(BAS)algorithm to optimize Proportion Integration Differentiation(PID)was adopted to control the clock frequency.Then,main work of this paper as follow:(1)Research on the principle of IEEE 1588 protocol,analyzes different clock types characteristics,and use OMNe T++ to construct the simulation of master and slave synchronize for three linear topologies of cascading boundary clock,cascading transparent clock,the hybrid clock system with a switching device.Then,analyzes the main factors that limit the synchronization accuracy of IEEE 1588 system: stack delay jitter,packet delay variation,asymmetry,timestamp quantization error,and clock instability,and puts forward some countermeasures.(2)For clock instability: the rate of aging caused by temperature,and then the frequency skew and clock offset error are brought,a three-state clock model is established.Meanwhile,the errors introduced by IEEE 1588 observation are modeled as gaussian white noise,then the clock state and errors were eventually eliminated and eliminated by kalman filter.(3)In order to improve the synchronization accuracy and convergence speed of the slave clock servo control system based on PID,BAS optimized PID control method(BAS-PID)was adopted to control the slave clock frequency.Compared with the traditional PID control method based on back propagation neural network and particle swarm optimization,BAS-PID control method has slightly higher synchronization accuracy and slightly faster convergence speed,making synchronization more efficient.