Packet-based Network Time Synchronization Technology Research And Implementation

Time synchronous includes two kinds, frequency synchronization and phase synchronization. In the fields of data communication, measurement and automatic control, etc, it is inseparable from time synchronous. With the IP trend of mobile services, the packet network are gradually replacing traditional TDM communications network, for example PTN. From one aspect, new applications put forward higher synchronization performance to packet network, on the other hand the support for new business and the interconnection with the traditional TDM network also need the packet network provide high quality synchronization performance.IEEE1588v2, also known as PTP, which is a precision clock synchronization protocol applied to networked measurement and control system. Using master-slave clock scheme, time information will be coded and transferred safely, according to the link symmetry and delay measurement techniques, synchronous precision can reach the sub-microsecond level by drift adjustment and offset adjustment, which has fully met the required precision standards. Recently some large enterprises such as Huawei and ZTE etc. are also carrying on research in this area. With support from a communications company, this paper is to research and implement 1588v2 time synchronization protocol.Taking the synchronization problems facing in packet network as a breakthrough point, and the analysis of the synchronization demand in communication network as a starting point, the author carefully analyzed the importance of synchronization in packet network on the introduction section, and then briefly introduced the common frequency synchronization technology and phase synchronous technology. The core of this article consists of three parts: First, capture of the timestamp information, which requires special hardware support, and shall be achieved on the LPU card; Second, module design of the time protocol processing system, which needs the global time module's support, for the module division and the code implement efficiency will directly affect the accuracy of the clock synchronization; Third, design of the PTP protocol state machine, which includes switch and operation of the working state. At last, as per the time synchronization index in packet network, the author formulates a set of comprehensive test scheme in the existing test conditions, and summarizes the test result carefully. According to the test results, synchronization accuracy and precision in the sub-microsecond range can be perfectly reached by drift adjustment and offset adjustment, which can be fully complying with the required precision standards.