Research On Technology Of Clock Transmitting And Recovery Over Packet Network

With the rapid development of network technology and more and more applications of IP, service carried over circuit-switched network began transferring to packet-switched network. Circuit emulation technique provides a possible way to this trend. Time-Division-Multiplex (TDM) service is time sensitive, whereas the packet-switched network does not supply clock synchronization.Consequently a high quality clock recovery is very important to TDM service transmitted over packet-switched networks, i.e., the circuit emulation technique.To provide a high quality service clock, we often need the network clock, or accurate clock signaling of network nodes, And the quality of network clock directly affects the quality of service clock. Based on the pro-research project"Research on key technology of transmitting and recovery of network clock over packet-switched network", this paper focuses on the strategy of how to recover the network clock through packet-switched networks. A network clock recovery method is put forward based on the research of IEEE1588PTP protocol. Both analysis and simulation shows that this method has been well designed.The basic idea of the network clock recovery method based on IEEE1588PTP protocol is : the distributed topology of clock synchronization relationship is established and the problem of to which node should the clock be synchronized and how to synchronize are solved according to IEEE1588PTP protocol.With the signal from the master clock, the slave clock is able to recover an accurate local clock signal using a Clock Recovery Phase Locked Loop (PLL).