PON Header-Guided FEC Decoding for Lower ONU Power Use
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Solution Overview
Problem
Passive optical networks (PONs) experience excessive and futile power consumption due to ONUs and OLTs decoding all FEC codewords, including idle frames, especially with the adoption of high-power LDPC decoding in newer standards, leading to inefficiency during low traffic periods.
Innovation Solution
ONUs and OLTs are configured to perform error correction on headers using error correction bits, identify frames intended for them, and then decode only relevant FEC codewords, reducing unnecessary decoding of idle frames.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If ONUs and OLTs decode all FEC codewords including idle frames, then complete data recovery is ensured, but power consumption increases excessively
Solution Approach 1:
The patent applies preliminary action by performing error correction on frame headers before FEC decoding. The ONU/OLT first corrects errors in the header portion of each frame using error correction bits, then checks the header to determine whether the frame is an idle frame or contains data intended for this ONU. Only frames that contain relevant data proceed to full FEC decoding. This preliminary header error correction and frame type identification prevents unnecessary FEC decoding of idle frames, thereby reducing power consumption while maintaining data recovery reliability for frames that actually contain data.
2Reliability
If LDPC decoding is implemented as per recent PON standards, then error correction capability is improved, but power consumption increases substantially
Solution Approach 1:
The patent applies partial action by performing error correction only on the header portion of frames rather than on the entire frame content. The header error correction uses a simplified approach that corrects errors in the header fields (such as frame type, length, and addressing information) without applying the full-power LDPC decoding algorithm to the entire frame. This partial error correction maintains sufficient reliability for frame identification and routing decisions, while avoiding the excessive power consumption of applying LDPC decoding to all frames including idle frames.
3Reliability
If FEC decoding is performed on all downstream frames, then all data is recovered, but processing time is wasted on idle frames
Solution Approach 1:
The patent applies preliminary action by performing header error correction and frame type identification before full FEC decoding. The system first corrects errors in the header portion of each frame, then examines the header to determine whether the frame is an idle frame or contains data intended for this ONU. Only frames that contain relevant data proceed to full FEC decoding. This preliminary processing step filters out idle frames early in the processing pipeline, preventing waste of processing time on frames that will ultimately be discarded.
Data Source
AI summary
An optical network unit, ONU, is configured to receive a stream of forward error correction, FEC, codewords comprising at least a portion of respective downstream frames broadcasted by the OLT over the PON, the respective downstream frames including a header and a payload, the header including one or more error correction bits for error correcting the header by the ONU, and an identifier indicative for which of the one or more ONUs the payload is intended; wherein the ONU is configured to perform first, error correcting the headers of the downstream frames based on the one or more error correction bits within the respective headers; then, identifying downstream frames with a payload intended for the ONU based on the identifier within the error-corrected headers; and thereafter, FEC decoding the one or more FEC codewords that comprise at least a portion of the identified downstream frames.