FEC-Framed Physical Layer Test Pattern for SerDes Stress Analysis

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Solution Overview

Problem

Existing test patterns for communication systems, such as Scrambled Idle and SSPRQ, have limitations in inducing desired impairments and stresses on devices, particularly in the low-frequency region, and do not effectively measure FEC codewords distribution.

Innovation Solution

A FEC framed physical layer test pattern is generated by embedding a physical layer test pattern, such as SSPRQ, into an FEC-encoded stream, allowing for the induction of desired stresses and impairments and enabling FEC aware testing and codewords analysis.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Object-affected harmful factors

If existing test patterns (Scrambled Idle, SSPRQ) are used, then testing can be performed, but the ability to induce desired impairments and stresses particularly in the low-frequency region is insufficient

Engineering Contradiction:

Improveinduction of impairments and stressesVSAvoideffectiveness of stress induction

Core Design Contradiction:

Object-affected harmful factorsVSReliability

Solution Approach 1:

The patent modifies the frequency spectrum parameters of test patterns by combining PRBS sequences with specific spectral characteristics with FEC-encoded test patterns. This creates a composite pattern with enhanced low-frequency content while maintaining FEC structure, thereby inducing desired impairments in the low-frequency region that existing patterns cannot achieve

Inventive Principle:

Principle #35Parameter changes

2Measurement precision

If existing test patterns are used, then testing can be performed, but FEC codewords distribution measurement is not effective

Engineering Contradiction:

ImproveFEC codewords distribution measurementVSAvoidFEC error statistics accuracy

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent segments the test pattern into distinct components: PRBS sequence portions and FEC-encoded portions with embedded delimiters. This segmentation allows the receiving end to separately analyze FEC codeword error distribution while maintaining the stress-inducing properties of the PRBS sequence, enabling precise measurement of FEC performance under stress

Inventive Principle:

Principle #1Segmentation

3Adaptability or versatility

If physical layer test pattern is embedded into FEC-encoded stream, then FEC aware testing and codewords analysis is enabled, but pattern generation complexity increases

Engineering Contradiction:

ImproveFEC aware testing capabilityVSAvoidpattern generation complexity

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The patent performs preliminary actions by pre-calculating and pre-positioning delimiters and synchronization sequences within the composite test pattern before transmission. This preliminary structuring enables the receiving end to easily identify and extract FEC codewords for analysis without requiring complex real-time processing, thus enabling FEC-aware testing while managing generation complexity

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS12339320B2Forward error correction (FEC) encoded physical layer test pattern

Publication Date: 2025.06.24 CISCO TECHNOLOGY INC

AI summary

Techniques are provided for generating a physical test pattern that is framed within an Forward Error Correction (FEC)-encoded stream or sequence. Accordingly, in one embodiment, a method is provided that includes obtaining a physical layer test pattern for testing operation of a device; generating an FEC framed test pattern that embeds the physical layer test pattern into an FEC-encoded stream; and applying the FEC framed test pattern to the transceiver device to test physical layer operation of the device and to obtain FEC error statistics.