Analog-Distorted Test Data Generation for 400 Gbps FEC Systems
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Solution Overview
Problem
Conventional test systems face challenges in generating realistic high-speed forward error correction (FEC) encoded test data with analog distortion, particularly in synchronizing multiple data streams for creating a 400 Gbps data stream, as they lack the necessary capabilities for analog distortion or fuzzing.
Innovation Solution
A test system configured with at least one processor and memory, capable of receiving configuration information to generate replacement data streams, distorting them at an analog level, and combining them with other data streams using a multiplexer to create a synchronized 400 Gbps FEC encoded test data stream.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If a packet data generator is used to generate multiple high-speed data streams for testing, then the data stream generation capability is improved, but the ability to introduce analog distortion is lost
Solution Approach 1:
The system divides the data stream generation function into two independent parts: a packet data generator for creating multiple high-speed data streams, and a separate analog distortion device for introducing physical layer impairments. This segmentation allows each component to specialize in its function while working together through the multiplexer.
Solution Approach 2:
A multiplexer serves as an intermediary device that combines the output from the packet data generator and the analog distortion device into a single unified data stream. This mediator enables the integration of digitally generated data with analog-distorted data without requiring the packet data generator to have native analog distortion capabilities.
2Reliability
If FEC encoding is performed across all data lanes to create a high-speed data stream, then the encoding capability is improved, but the ease of modifying individual data streams is reduced
Solution Approach 1:
The system performs FEC encoding at the individual lane level rather than across the entire aggregated stream, allowing each data lane to be independently encoded and modified. This segmentation enables selective replacement of specific lanes with analog-distorted versions without affecting the encoding of other lanes.
Solution Approach 2:
Instead of applying analog distortion to all data lanes, the system selectively applies distortion to only those lanes that need to represent realistic channel impairments. This partial action approach maintains the integrity of lanes that don't require distortion while introducing realistic impairments where needed.
3Measurement precision
If multiple data streams are synchronized using a master clock, then the synchronization accuracy is improved, but the device complexity increases
Solution Approach 1:
The system uses identical copies of the same base data pattern across multiple lanes, generated by the packet data generator. This copying approach ensures inherent synchronization since all lanes originate from the same source, reducing the need for complex master clock synchronization mechanisms.
Solution Approach 2:
The synchronization function is merged into the packet data generator itself, which generates all lanes from a single unified data source. This integration eliminates the need for separate synchronization hardware between lanes, as the generation process inherently maintains timing alignment.
Data Source
AI summary
Conventional test systems can experience issues when attempting to test network nodes or system with realistic high speed forward error correction (FEC) encoded test data. For example, a test system may use a packet data generator to generate eight data streams or lanes of 50 Gigabits per second (Gbps) test data and may then use a multiplexer to combine the eight lanes into a 400 Gbps data stream for transmission using 4-level pulse amplitude modulation (PAM4). To generate a high speed data stream comprising multiple data lanes, the test system may be required to use a master clock or other time synchronization technique to keep the data lanes in sync. Further, to generate an FEC encoded high speed data stream comprising multiple data lanes, the test system may perform FEC encoding across all of the data lanes comprising the high speed data stream, which can make test data modifications difficult afterwards.Hence, issues can arise if a packet data generator lacks capabilities, e.g., analog distortion or analog fuzzing features, that are needed for testing some aspect of network node functionality.