The Study Of Synchronization In PTN

Recent years, the concept of network integration becomes the main theme of global telecommunications industry. In pace with rapid development of data services, news modes including broadband multiple-service delivery and end to end bandwidth providing gradually spring up. As a result, traditional Synchronous Digital Hierarchy (SDH) technology, IP technology and Ethernet technology could not meet transporting and carrying needs of the next generation of network. PTN as a new tech supporting multi-services, not only meets the transport need of packet service more efficiently, but also supports traditional TDM services. TDM services have the requirement of clock synchronization which must be provided by the transport network. However, PTN provides no clock synchronization mechanism. Therefore, the research of PTN clock synchronization technology has a great significance.This paper makes a in-depth study of synchronization in PTN, based on concluding the characteristics of PTN and the key technologies in PTN. The paper also expounds the synchronization requirement in PTN and introduces the existing synchronization tech in PTN. Moreover, the merit and fault of each solution is analyzed.This paper makes the in-depth study of the self-adaptive clock recovery method based on the buffer in PTN. As the traditional buffer level clock recovery method in PTN is highly sensitive to the Packet Delay Variation (PDV), a buffer level clock recovery based on Least Mean Squares (LMS) is proposed. In this method, LMS is used to remove the jitter component of sampling buffer data. Simulation results show that the improved method can effectively remove the negative contribution of packet delay jitter and provide more accurate clock recovery at the destination than traditional scheme.In addition, the buffer size control problem is not taken into consideration in traditional method, which results that after the recovered frequency is stable, the packets will experience large buffering delay. To overcome this shortcoming, the Zigzag clock recovery method is proposed. According to the simulation results, the Zigzag method takes a good buffer size control and therefore the packet buffering delay is reduced effectively. For real time services in PTN, the delay requirement can be easily satisfied by the Zigzag method.