Multi-Segment Link Training for Asymmetric Channel Tuning
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Solution Overview
Problem
Existing link-training protocols are limited to passive single-segment channels with symmetrical bi-directional connectivity, failing to optimize signal integrity in multi-segment and half-retimed channels, leading to higher bit error rates and suboptimal performance.
Innovation Solution
A method for link-training in multi-segment networks that allows non-symmetrical, non-bidirectional connectivity by using a link training frame with a training pattern and hop indicators to tune transmitter parameters across multiple nodes, enabling synchronization and completion of link training across all segments.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If link-training is performed over passive single-segment channels with symmetrical bi-directional connectivity, then the link-training protocol is simple and reliable, but it cannot optimize signal integrity in multi-segment and half-retimed channels
Solution Approach 1:
The patent divides the communication channel into multiple segments with intermediate nodes (retimers, optical engines) between transmitter and receiver. Each segment can be independently trained and optimized, allowing the system to adapt to multi-segment configurations while maintaining reliable link-training through localized optimization at each segment boundary.
Solution Approach 2:
The patent enables asymmetric link-training where the forward path (transmitter to receiver) and reverse path (receiver to transmitter) can have different characteristics and training parameters. This allows optimization for non-symmetrical channel configurations including half-retimed channels where the two directions may have different numbers of segments or different intermediate nodes.
2Reliability
If link-training is limited to symmetrical bi-directional connectivity, then the protocol complexity is low, but bit error rates increase in multi-segment channels
Solution Approach 1:
The patent introduces intermediate nodes (retimers, optical engines) that act as mediators in the link-training process. These intermediaries receive training patterns from the transmitter, process them through their respective segments, and forward them to the receiver. They also participate in the back-channel communication to report segment-specific quality metrics, enabling distributed optimization that reduces overall bit error rates while managing protocol complexity through localized processing.
Solution Approach 2:
The patent implements a back-channel feedback mechanism where the receiver measures signal quality metrics (bit error rate, signal-to-noise ratio) for each segment and sends this information back to the transmitter and intermediate nodes. This feedback enables iterative optimization of training parameters and equalization settings at each segment, systematically reducing bit error rates across the entire multi-segment channel.
3Reliability
If existing link-training protocols are used for multi-segment channels, then implementation is simple, but signal integrity optimization is insufficient
Solution Approach 1:
The patent designs a universal link-training framework that can operate across single-segment and multi-segment channels, as well as symmetrical and asymmetric configurations. The same basic training pattern transmission and back-channel communication protocol is used, but with enhanced capabilities to handle intermediate nodes and segment-specific optimization, providing signal integrity improvement without requiring completely different protocols for different channel types.
Data Source
AI summary
In one embodiment, a multi-segment communication network system includes nodes connected via links, a first node including a first receiver and transmitter, and a second node including a second receiver and transmitter, wherein the first transmitter is to transmit a link training frame including a training pattern to the second receiver, which is to receive the link training frame, the second node is to find a tuning factor to which to tune the first transmitter responsively to the training pattern, and generate a request indicative of the found tuning factor, the second transmitter is to send the request in the link training frame via a plurality of the links to the first receiver, the first receiver is to receive the request, and the first node is to tune at least one parameter of the first transmitter based on the tuning factor indicated in the request.