PAM4 Erasure Decoding for Burst Error Correction in PCIe
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Solution Overview
Problem
Existing error correction methods in Peripheral Component Interconnect Express (PCIe) systems using PAM-4 modulation struggle with correcting multiple errors in a burst, leading to increased retransmission rates and reduced system performance.
Innovation Solution
An electronic device with an improved error correction function that performs erasure decoding by selecting symbols with high error probability and recalculating using an erasure decoding unit, reducing the need for retransmissions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional ECC decoding is used for PAM-4 signals, then the decoding process is simple, but multiple errors in a burst cannot be corrected leading to increased retransmission rates
Solution Approach 1:
The patent performs preliminary actions by calculating LLR values for all PAM-4 symbols before ECC decoding, identifying unreliable symbols in advance. This preliminary identification of error-prone symbols enables the system to prepare for potential corrections without waiting for decoding failures, thereby improving reliability and reducing retransmission rates.
Solution Approach 2:
The patent introduces an intermediary mechanism between conventional ECC decoding and retransmission by implementing erasure decoding for identified unreliable symbols. This intermediary step allows the system to attempt correction of multiple errors within the burst without immediately resorting to retransmission, effectively bridging the gap between simple decoding and reliable error correction.
2Reliability
If erasure decoding is performed for all symbols, then error correction performance improves, but calculation complexity and processing time increase
Solution Approach 1:
The patent applies local quality by performing erasure decoding selectively only on unreliable PAM-4 symbols identified through LLR calculation, rather than processing all symbols uniformly. This localized approach concentrates computational resources on the specific symbols most likely to contain errors, improving error correction performance while avoiding the excessive complexity of processing all symbols with the same intensity.
Solution Approach 2:
The patent implements partial action by performing erasure decoding on only a subset of symbols (those identified as unreliable) rather than all symbols. This partial application of the computationally intensive erasure decoding technique achieves effective error correction for the critical symbols while keeping the overall calculation complexity manageable.
Data Source
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AI summary
Disclosed is an electronic device, which includes an ECC decoder that performs ECC decoding on a flit including a plurality of PAM-4 symbols for each of a plurality of ECC groups, a CRC decoder that performs CRC decoding on the ECC decoded flit to obtain data, and an erasure decoding unit that calculates an LLR for each of the PAM-4 symbols when the CRC decoding fails, extracts an error symbol candidate from among the plurality of PAM-4 symbols for each of the plurality of ECC groups based on the LLR, and performs the ECC decoding again after erasing the error symbol candidate.