A method for synchronizing frequency between a master clock and a slave clock

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The invention provides a method for better synchronizing the frequency between a master clock and a slave clock in packet-switched networks, particularly tree-shaped topologies commonly found in mobile backhaul or similar networks. By enlarging the size of synchronization packets sent from the master clock so they are at least as large as the average or maximum background traffic packet size, the solution dramatically reduces packet delay variation caused by the queuing and transmission of large background packets ahead of synchronization packets. This is achieved, for example, by adding padding to standard synchronization messages such as those used in the IEEE 1588 Precision Time Protocol (PTP).

Use CasesContent extracted from patent full text and abstract with AI.

• Synchronizing clocks in mobile network base stations where accurate timing is required but satellite or other clock sources are unavailable or too expensive.
• Providing reliable frequency synchronization over Ethernet-based or packet-switched backhaul networks, especially for telecommunications operators transitioning from circuit-switched to packet-switched infrastructure.
• Deploying cost-effective, high-precision synchronization in industrial automation and power grid monitoring systems that rely on precise timing over packet networks.
• Improving synchronization for distributed systems or data centers that use tree-shaped network topologies without requiring extensive hardware upgrades.

BenefitsContent extracted from patent full text and abstract with AI.

• Reduces the main source of packet delay variation in synchronization—ensuring more accurate timing over packet-switched networks without costly hardware changes.
• Enables cost-effective deployment by allowing use of less expensive slave clocks, as high-quality oscillators do not need to be installed at every node.
• Simple adaptation to existing protocols like IEEE 1588 PTP by adding standardized padding, minimizing compatibility issues and making implementation easy.
• Applicable to a wide range of industry-standard packet-switched networks, including Ethernet, IP, and those using microwave radio links.
• Improves network quality and service reliability for telecommunication providers, especially in settings where alternative synchronization methods are impractical.

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Patent Abstract

The inventions provides for a method for synchronizing frequency between a master clock (50) and a slave clock (60), wherein the master clock (50) and the slave clock (50) are connected through a tree-shaped packet-switched network, in which the master clock (50) is connected to a root node (25) of the network and the slave clock (60) is connected to a leaf node (40) of the network, synchronization packets (70) are sent from the master clock (50) to the slave clock (60), and background traffic packets (75) are routed from the root node (25) of the network to the leaf nodes (40) of the network. According to the invention, the synchronization packets (70) sent out by the master clock (50) have a packet size at least about equal to the average packet size of the background traffic packets (75). This way, packet delay variations that are based on remainder-of-packet delays are reduced. In one embodiment, the synchronization packets (70) are modified standard synchronization messages which were modified by adding padding information enlarging the standard synchronization messages. The invention further regards a network suitable to carry out such method and a master clock for use in such method and network.