A Time Synchronization Method for Hierarchical Heterogeneous Networks

Abstract

The invention relates to a heterogeneous network technology of industrial real-time application, in particular to a time synchronization method oriented to a hierarchical heterogeneous network. A three-layer heterogeneous network consisting of an Internet backbone network, a wireless mesh backhaul network and a field Ethernet sub-network is constructed on the basis of hierarchical thought. An One_step time synchronization mechanism is adopted on the basis of the time synchronization principle of IEEE1588 and a hardware timestamp concept, so that a quarter of synchronization information packet transmission in a network is reduced; the network load is reduced; a hardware timestamp of a wireless network is introduced; and the time synchronization accuracy is increased. A boundary clock positioned on an interface between the wireless mesh backhaul network and a local Ethernet sub-network is designed on the basis of the abovementioned content in order to coordinate the time synchronization between the wireless mesh backhaul network and the local Ethernet sub-network, so that the problem of low time synchronization accuracy of the heterogeneous network due to different network protocols, synchronization information exchange and port inconsistency is solved. At last, whole-network time synchronization is realized by adopting a hierarchical synchronization mechanism. On the basis of existing IEEE1588 and IEEE802.11 protocols, extra protocol overhead is not introduced.

Description

technical field [0001] The invention relates to a heterogeneous network technology for industrial real-time application, in particular to a time synchronization method for hierarchical heterogeneous networks. Background technique [0002] The large-scale application of wired Ethernet technology in the industry has brought great economic benefits, and related technologies have become mature, but problems such as wiring environment, cost, and communication range limit the application of wired Ethernet technology. However, with the development of wireless network technology, the characteristics of low cost, high reliability, and mobility of wireless network technology make its application in the industry possible. effect. However, due to the real-time, stability, and reliability requirements of industrial field control, the inherent link instability of wireless networks, and the vulnerability to external electromagnetic environments make it impossible for industrial wireless n...

AI Technical Summary

Problems solved by technology

For example, the IEEE1588 synchronization protocol of the wired Ethernet has a synchronization accuracy of sub-microsecond level, which has met the application requirements of most factories; the TSF (Time Synchronization Function) provided by the 802.11 wireless network realizes synchronization at the application layer, and its accuracy is very low. , although the synchronization mechanism of the driver layer has been realized, its precision can only reach the microsecond level

Moreover, due to differences in communication technologies, and the lack of unified infrastructure, information exchange ports and mechanisms, and synchronization information formats, the synchronization accuracy and reliability of heterogeneous networks are often lower

[0004] Although the IEEE1588 protocol is based on wired Ethernet, it is possible to apply IEEE1588 to wireless networks because it is based on the UDP / IP protocol.

However, the high-precision synchronization of IEEE1588 is based on the hardware layer time stamp, and the existing wireless chip is highly integrated and does not provide a hardware layer time stamp interface, so the synchronization accuracy of directly applying IEEE1588 to the heterogeneous network is not high : The accuracy of the existing solution to compensate channel access delay by increasing the synchronization packet sending rate only reaches the order of ms

In the synchronization mechanism of the traditional IEEE1588 protocol, the time synchronization of master and slave nodes requires four time information transmissions. For limited network bandwidth, a large amount of time information will increase the bandwidth burden; and the transmission of follow_up information is very important for 802.11 wireless networks. is not advisable

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