Cable Network Timing Synchronization Using External Time References
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Solution Overview
Problem
Existing timing synchronization methods in mobile networks using hybrid fiber-coaxial (HFC) networks face challenges due to asymmetry in packet delay variation (PDV) and asymmetrical network delays, which affect frequency and phase synchronization, particularly in DOCSIS systems, leading to errors in handover performance.
Innovation Solution
A reference cable modem uses an external timing source to calculate the delay from the CMTS to itself, eliminating the need to measure asymmetries in the network, thereby simplifying synchronization by reducing the number of measurements and calculations, and ensuring accurate frequency and phase synchronization across mobile network devices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If multiple measurements are made to address asymmetry in DOCSIS network, then timing synchronization accuracy is improved, but device complexity and calculation complexity increase
Solution Approach 1:
The patent extracts and eliminates the need to measure asymmetrical delays by using an external timing source that provides absolute timing references. Instead of measuring multiple parameters to calculate synchronization, the system directly obtains timing information from an external source, removing the complex calculation requirements while maintaining synchronization accuracy.
Solution Approach 2:
The patent introduces an external timing source as an intermediary that provides timing synchronization information to the DOCSIS network. This mediator eliminates the need for complex internal measurements and calculations by providing ready-to-use timing references, thereby reducing device complexity while improving timing synchronization accuracy.
2Adaptability or versatility
If timing synchronization is performed over DOCSIS network, then network compatibility is improved, but timing accuracy deteriorates due to packet delay variation asymmetry
Solution Approach 1:
The patent introduces an external timing source as an intermediary that provides timing synchronization information to the DOCSIS network. This mediator eliminates the need for complex internal measurements and calculations by providing ready-to-use timing references, thereby reducing device complexity while improving timing synchronization accuracy.
Solution Approach 2:
The patent changes the approach from measuring relative delays within the DOCSIS network to using absolute timing references from an external source. This parameter change from relative to absolute timing measurement eliminates the impact of PDV asymmetry while maintaining compatibility with DOCSIS network infrastructure.
Data Source
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AI summary
In one embodiment, a method receives a first time from a network device. The first time is derived from a first timing source in a first domain. The method receives a second time in a second domain from a second timing source. A difference time value is calculated between the first time and the second time. The method then sends the difference time value to the network device where the network device uses the difference time value to send a delay value to other computing devices to synchronize timing of the other computing devices in the second domain. The other computing devices are configured to synchronize the respective time using the delay value with mobile network devices to allow timing synchronization between the mobile network devices.