Coax Media Converter Timestamp Re-stamping for HFC Timing Mismatches
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Network systems face timing mismatches between different clock domains in Hybrid Fiber Coaxial (HFC) cable access networks, leading to underscheduling and overscheduling conditions that affect the scheduling of upstream burst transmissions.
Innovation Solution
A Coax Media Converter (CMC) is used to extract and re-stamp timestamps in bandwidth allocation messages from a network termination system's time domain to a local time domain, allowing for consistent scheduling of upstream burst transmissions and mitigating timing mismatches by adjusting clock speeds or eliminating contention regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a Coax Media Converter (CMC) is used to re-stamp timestamps in bandwidth allocation messages from a network termination system's time domain to a local time domain, then timing mismatches between different clock domains are mitigated and scheduling consistency is improved, but device complexity increases
Solution Approach 1:
The CMC acts as an intermediary device between the network termination system and cable modems, translating bandwidth allocation messages from the system's time domain to the local time domain. It extracts timestamps from incoming messages, re-stamps them with locally synchronized timestamps, and inserts the updated messages into the downstream data stream, thereby mediating timing differences without requiring changes to existing systems.
Solution Approach 2:
The CMC creates a copy of the bandwidth allocation message, modifies the timestamps in the copy to match the local time domain, and inserts this copied and modified message into the downstream stream. This allows the original message structure to be preserved while providing time-domain-specific timing information to cable modems.
2Measurement precision
If the CMC re-stamps timestamps to accommodate clock differences, then timing errors are reduced and upstream burst transmission scheduling is improved, but processing time and computational resources increase
Solution Approach 1:
The CMC pre-synchronizes its local clock with the network termination system's clock before timestamp re-stamping occurs. This preliminary synchronization establishes a known reference relationship between the two time domains, allowing the CMC to calculate appropriate timestamp adjustments without requiring complex real-time analysis or iterative processing.
Solution Approach 2:
The CMC changes the timestamp parameters from the system time domain to the local time domain by applying a calculated offset based on clock frequency differences and synchronization information. This parameter transformation is performed through direct calculation rather than iterative adjustment, minimizing processing time while maintaining timing accuracy.
Data Source
Figure 1~2
Figure 3~4
Figure 5
AI summary
One embodiment of the invention includes a coax media converter (CMC) system communicatively coupled to at least one modem in a network system. The system includes a frequency reference configured to generate a clock signal in a local time domain. The system also includes a scheduling processor configured to extract a bandwidth allocation message from a data stream and to re-stamp each of at least one timestamp in the bandwidth allocation message in the local time domain based on the clock signal to generate a corresponding updated bandwidth allocation message comprising a respective at least one re-stamped timestamp. The system further includes a downstream physical interface configured to transmit the updated bandwidth allocation message to the at least one modem to schedule upstream burst transmissions from the respective at least modem based on the at least one re-stamped timestamp.