Conditional FEC Decoding in PON ONUs for Lower Idle-Power Use
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Solution Overview
Problem
Passive optical networks (PONs) face excessive and futile power consumption due to unnecessary FEC decoding of all FEC codewords, including idle frames, especially with the adoption of high-power LDPC decoding in newer standards, leading to inefficiencies in both optical network units (ONUs) and optical line terminals (OLTs).
Innovation Solution
Implement conditional FEC decoding in ONUs and OLTs by error-correcting headers based on error correction bits, identifying frames intended for the unit, and then decoding only those FEC codewords containing relevant data, reducing unnecessary decoding of idle frames.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If FEC decoding is performed on all received FEC codewords, then data recovery reliability is improved, but power consumption increases excessively
Solution Approach 1:
The patent applies preliminary action by performing header error correction and identifier inspection before FEC decoding. The ONU first corrects errors in the header using error correction bits, then checks the identifier to determine if the frame is intended for this ONU. Only frames that pass both checks are subjected to FEC decoding, eliminating unnecessary decoding operations and reducing power consumption while maintaining data recovery reliability for relevant frames.
2Reliability
If LDPC FEC encoding is implemented, then error correction capability is improved, but power consumption increases substantially
Solution Approach 1:
The patent applies partial action by performing only the necessary header error correction and identifier checking steps before FEC decoding, rather than decoding all frames. This partial processing approach maintains the high error correction capability of LDPC where needed while avoiding excessive power consumption by skipping decoding for frames not intended for this ONU.
3Reliability
If FEC decoding is performed on all downstream frames, then complete data recovery is ensured, but processing efficiency decreases
Solution Approach 1:
The patent extracts and processes only the relevant frames by first correcting header errors and then filtering frames based on the identifier field. This extraction approach ensures complete data recovery for frames intended for this ONU while improving processing efficiency by excluding frames for other ONUs from the computationally intensive FEC decoding process.
Data Source
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AI summary
Example embodiments describe an optical network unit, ONU (131 - 134), configured to communicate in a passive optical network, PON (100), with an optical line terminal, OLT (110); wherein the ONU is configured to receive a stream (210) of forward error correction, FEC, codewords (211) comprising at least a portion of respective downstream frames (221) broadcasted by the OLT over the PON; wherein the respective downstream frames comprise a header (222) and a payload (223); and wherein the header includes one or more error correction bits (234) for error correcting the header by the ONU, and an identifier (232) indicative for which of the one or more ONUs the payload is intended; wherein the ONU is characterized in that it is further configured to perform: first, error correcting (201, 241) the headers (222) of the downstream frames (221) based on the one or more error correction bits (234) within the respective headers; then, identifying (202, 242) downstream frames (221) with a payload (223) intended for the ONU based on the identifier (232) within the error-corrected headers; and thereafter, FEC decoding (203, 250) the one or more FEC codewords that comprise at least a portion of the identified downstream frames.