Pointer Offset Mechanism for SONET/SDH Clock Recovery
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Solution Overview
Problem
The existing technologies for mapping and demapping SONET/SDH frames over Ethernet are complex and costly, requiring intricate circuitry for clock recovery and synchronization, which hinders the migration of legacy TDM network core technology to packet network core technology.
Innovation Solution
A method that involves storing SONET/SDH frames in a FIFO and adjusting the pointer offset based on the difference between a reference clock and a client clock, allowing for software-based calculation and reducing the need for complex hardware, thereby simplifying the demapping process and integrating it into a single card solution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If existing technologies for mapping and demapping SONET/SDH frames over Ethernet are used, then clock recovery and synchronization can be achieved, but device complexity and cost increase due to intricate circuitry requirements
Solution Approach 1:
The patent replaces complex hardware circuitry for clock recovery and synchronization with software-based processing. The pointer offset adjustment is performed through software algorithms that calculate and modify pointer values based on clock differences, eliminating the need for intricate hardware PLLs and clock recovery circuits while maintaining reliable synchronization.
Solution Approach 2:
The patent changes the approach from hardware-based clock synchronization to parameter-based adjustment. By modifying pointer offset values as software parameters rather than using fixed hardware circuits, the system achieves flexible clock synchronization. The pointer offset is dynamically adjusted based on calculated differences between reference and client clocks, transforming a hardware problem into a software parameter adjustment problem.
2Reliability
If complex hardware circuitry is used for clock recovery and synchronization, then reliable SONET/SDH mapping can be achieved, but migration cost to packet networks increases
Solution Approach 1:
The patent replaces expensive hardware circuitry with software-based solutions, significantly reducing migration costs. By implementing clock recovery and synchronization through software algorithms rather than hardware circuits, the cost of migrating legacy SONET/SDH networks to packet-based Ethernet networks is dramatically reduced while maintaining mapping reliability.
Solution Approach 2:
The patent uses software-based pointer offset adjustment as a cost-effective alternative to expensive hardware circuits. This software approach provides sufficient functionality for SONET/SDH mapping without requiring costly hardware infrastructure, making the migration process economically feasible for network operators.
3Device complexity
If software-based pointer offset adjustment is used, then hardware complexity is reduced, but processing speed may be affected
Solution Approach 1:
The patent applies partial action by adjusting only the pointer offset values rather than performing complete hardware clock recovery operations. This selective software-based adjustment maintains processing speed adequacy while significantly reducing hardware complexity. The software algorithms perform sufficient pointer modifications to achieve synchronization without the overhead of full hardware circuit processing.
Data Source
AI summary
In one embodiment, a SONET/SDH over Ethernet demapping point utilizes a pointer offset mechanism for clock recovery and timing. The pointer offset is determined by the difference between a client clock and a reference clock.