Symbol-Multiplexing PMA for Error-Burst Handling

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Solution Overview

Problem

High ratio bit multiplexing in Ethernet communication reduces the capability of Forward Error Correction (FEC) to handle error bursts, leading to Signal-to-Noise Ratio (SNR) penalties and increased Bit Error Rate (BER), and is incompatible with existing optical modules using bit multiplexing.

Innovation Solution

Implement a Physical Medium Attachment (PMA) that converts between bit multiplexing and symbol multiplexing, using alignment markers to align symbols and correct de-multiplexing or re-multiplexing, enabling transparent interoperability with existing devices.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Productivity

If high ratio bit multiplexing is used to increase bit rate, then productivity is improved, but reliability deteriorates due to reduced FEC capability and increased error bursts

Engineering Contradiction:

Improvebit rateVSAvoiderror correction capability

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The patent changes the multiplexing parameter from bit-level to symbol-level. By multiplexing symbols instead of bits, the system achieves high bit rates while maintaining better error correction capability, as symbols are more resilient to error bursts than individual bits.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent introduces an intermediary conversion process between bit multiplexing and symbol multiplexing. This intermediary layer allows the system to interface with existing bit-multiplexed optical modules while internally using symbol multiplexing to improve reliability and reduce SNR requirements.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Productivity

If high ratio bit multiplexing is used to increase bit rate, then productivity is improved, but signal quality deteriorates due to SNR penalties

Engineering Contradiction:

Improvebit rateVSAvoidSNR penalty

Core Design Contradiction:

ProductivityVSObject-affected harmful factors

Solution Approach 1:

The patent changes the multiplexing parameter from bit-level to symbol-level. Symbol multiplexing reduces SNR penalties compared to high ratio bit multiplexing, allowing higher bit rates to be achieved with better signal quality and lower error rates.

Inventive Principle:

Principle #35Parameter changes

3Reliability

If symbol multiplexing is implemented to improve reliability, then adaptability deteriorates due to incompatibility with existing bit-multiplexed devices

Engineering Contradiction:

Improveerror correction capabilityVSAvoidinteroperability

Core Design Contradiction:

ReliabilityVSAdaptability or versatility

Solution Approach 1:

The patent introduces an intermediary conversion process between bit multiplexing and symbol multiplexing. This intermediary layer enables the system to interface with existing bit-multiplexed optical modules while internally using symbol multiplexing to improve reliability and reduce SNR requirements.

Inventive Principle:

Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent implements a universal interface that can handle both bit-multiplexed and symbol-multiplexed signals. This multi-functionality allows the system to maintain compatibility with existing devices while supporting the improved symbol multiplexing mode for new connections.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Data Source

PatentUS12438755B2Symbol multiplexing physical medium attachment (PMA)

Publication Date: 2025.10.07 CISCO TECHNOLOGY INC

AI summary

Symbol multiplexing Physical Medium Attachment (PMA) may be provided. A plurality of first lanes may be received and then Alignment Markers (AMs) from the plurality of first lanes may be used to determine symbol boundaries and identify the plurality of first lanes. Next, groups of the plurality of first lanes may be de-skewed and checkerboard patterns in the plurality of first lanes may be undone. Then the plurality of first lanes may be symbol-wise multiplexed to a plurality of second lanes. The plurality of second lanes may then be sent.