Network Clock Frequency Reference Distribution via Packet Protocol
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Solution Overview
Problem
In mobile networks, synchronization failures in the physical synchronization chain lead to disruptions in frequency reference distribution, causing call drops and handover failures, especially in the access part of the mobile backhaul network where redundant synchronization cards are not feasible due to cost optimization and capillary topology, and existing workarounds like deploying backup PTP paths result in bandwidth waste and performance degradation.
Innovation Solution
A method that detects synchronization failures and activates a packet-based protocol (like PTP) between neighbor network clocks to transmit the frequency reference, using a physical-layer-based protocol as the primary method and a packet-based protocol as a backup, allowing seamless distribution even in cases of synchronization card failures, with mechanisms for role assignment, message transmission, and forwarding rules to maintain network topology.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a physical-layer-based synchronization mechanism (SyncE/SDH/SONET) is used for frequency distribution, then synchronization accuracy and robustness are improved, but the system becomes vulnerable to single-point failures in capillary topologies where redundant paths are unavailable
Solution Approach 1:
The system dynamically switches between physical-layer-based synchronization (SyncE/SDH/SONET) and packet-based PTP synchronization based on the operational status of the physical synchronization chain. When a failure is detected in an intermediate network clock, the system automatically activates PTP as a backup mechanism, allowing the synchronization method to adapt to changing network conditions and maintain reliability without compromising accuracy during normal operation
Solution Approach 2:
The invention prepares a packet-based PTP synchronization mechanism in advance as a backup cushion against potential failures in the primary physical-layer-based synchronization chain. This backup mechanism is readied but not actively used during normal operation, providing protection against synchronization failures without incurring continuous bandwidth costs, thus resolving the contradiction between maintaining high reliability and avoiding resource waste
2Reliability
If backup frequency distribution paths or redundant synchronization cards are deployed, then system reliability is improved, but hardware cost and device complexity increase significantly
Solution Approach 1:
Instead of deploying physical redundant synchronization cards or backup frequency distribution paths, the invention creates a virtual copy of the synchronization function using packet-based PTP protocol over the existing data path. This software-based approach replicates the synchronization capability without requiring additional hardware components, thus improving reliability while avoiding the complexity and cost of physical redundancy
Solution Approach 2:
The packet-based PTP mechanism serves multiple functions: it acts as a backup synchronization path when the physical synchronization chain fails, and simultaneously utilizes the existing data communication infrastructure for its operation. This multi-functionality allows the system to improve reliability without adding dedicated backup hardware, as the same data network carries both data traffic and synchronization packets
3Reliability
If PTP is deployed permanently as a backup mechanism, then synchronization reliability is improved, but network bandwidth is wasted and Packet Delay Variation increases
Solution Approach 1:
The PTP backup mechanism operates periodically only when needed - specifically when a synchronization failure is detected in the physical-layer-based chain. During normal operation, PTP packets are not transmitted, avoiding continuous bandwidth consumption. The system checks the status of the physical synchronization chain and activates PTP periodically only during failure conditions, thus maintaining reliability without permanent bandwidth occupation
Solution Approach 2:
Instead of deploying full PTP synchronization permanently across the entire network, the invention applies PTP partially - only in the specific network segments affected by synchronization failures and only when the physical synchronization chain is compromised. This partial deployment approach provides the necessary backup reliability while minimizing bandwidth waste by limiting PTP packet transmission to only the necessary conditions and locations
Data Source
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AI summary
A method is intended for distributing a frequency reference to network clocks (NC1-NC5), comprising a synchronization card (SC) and an interface card (IC), and belonging to a mobile network (MN) having a physical-layer-based protocol for distributing the frequency reference to the network clocks according to a chosen topology, and a packet-based protocol for distributing this frequency reference to the network clocks respecting this chosen topology. This method comprises a step (i) during which one detects a synchronization failure in a synchronization card (SC) of a failed network clock (NC2) connected to neighbour network clocks (NC1,NC3-NC5), a step (ii) during which one activates a mechanism of the packet-based protocol between a master neighbour network clock (NC1) and slave neighbour network clocks (NC3-NC5), and a step (iii) during which one uses the activated protocol to transmit the frequency reference recovered by the master (NC1) to the slaves (NC3-NC5) by following the topology.