OTN Frame Restructuring for Low-Latency Forward Error Correction
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Solution Overview
Problem
Existing OTN frames for communication between OTN cards suffer from high latency, low robustness, and high transmission rate due to limitations in FEC methods, particularly the G.709 FEC, which results in poor performance under burst errors and high coding rates, reducing the maximum backplane length and tolerance to errors.
Innovation Solution
Modifying the OTN frame structure before transmission by removing FEC parity, re-structuring data, and using alternative Reed Solomon codes such as RS (627,613, m=10, t=7) or RS (528,514, m=10, t=7) to create a new frame format with reduced latency and increased robustness, while compensating for bit shuffling done by the OTL through bit shuffling and de-shuffling circuitry, thereby enhancing error tolerance and coding efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If G.709 FEC is used for OTN frame transmission, then error correction capability is provided, but latency increases and robustness against burst errors decreases
Solution Approach 1:
The patent changes the FEC parameters by using alternative Reed Solomon codes (RS (627,613, m=10, t=7) or RS (528,514, m=10, t=7)) instead of the standard G.709 FEC. This parameter change achieves lower coding rates (reducing overhead from 6.7% to approximately 4.5-5%) and improved Net Coding Gain, thereby reducing latency while maintaining or improving error correction capability against burst errors.
2Reliability
If G.709 FEC is used for OTN frame transmission, then error correction is achieved, but coding rate increases reducing maximum backplane length
Solution Approach 1:
The patent applies parameter changes by selecting alternative Reed Solomon codes with optimized coding rates. The new codes reduce the coding rate from the standard G.709 6.7% overhead to approximately 4.5-5% overhead, allowing for longer maximum backplane lengths while maintaining or improving tolerance to burst errors through enhanced Net Coding Gain.
3Productivity
If bit shuffling is done by OTL, then data is redistributed across lanes, but frame structure complexity increases
Solution Approach 1:
The patent applies preliminary action by performing bit shuffling and de-shuffling operations as integral parts of the frame restructuring process before transmission. The transmitter performs bit shuffling to redistribute data bits across lanes, and the receiver performs corresponding de-shuffling to restore the original sequence. This preliminary arrangement of bits simplifies the overall frame structure handling by pre-compensating for the lane distribution effects.
Data Source
AI summary
There are various drawbacks by using existing OTN (Optical Transport Network) frames for communication between OTN cards. Such drawbacks might for example include high latency, low robustness, and/or high coding rate. According to embodiments of the present disclosure, systems and methods are provided for modifying an OTN frame (or creating a new frame with data from the OTN frame) prior to transmission by an OTL (Optical channel Transport Lane) in order to address some or all of the foregoing drawbacks. Note that this embodiment can make use of existing hardware (e.g. hardware used for generating the OTN frame, and the OTL used for transmission).