Adaptive Equalizer Coefficient Control During Link Speed Negotiation
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Solution Overview
Problem
The existing Fibre Channel standard's Link Speed Negotiation method, which involves sending training signals at progressively lower speeds, is not effectively addressed when using a receiver with an adaptive equalizer, as it may lead to improper adaptation of coefficients and divergence in signal energy, especially at lower speeds.
Innovation Solution
A communications method and device that filter the receive signal, detect the baud rate, and adapt filter coefficients only if the baud rate is above a predetermined rate, while inhibiting adaptation at lower rates to prevent coefficient divergence and ensure proper equalization during link speed negotiation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If adaptive equalizer coefficients are continuously adapted during link speed negotiation, then equalization performance is improved, but coefficient divergence occurs at lower baud rates
Solution Approach 1:
The equalizer adaptation is made dynamic by enabling it only when the detected baud rate exceeds the threshold, and disabling it when the baud rate is at or below the threshold. This dynamic switching resolves the contradiction by adapting the equalizer's operational state to the current signal conditions, allowing coefficient adaptation at high speeds while preventing divergence at low speeds.
Solution Approach 2:
The invention changes the operational parameter of the adaptive equalizer (adaptation enabled/disabled) based on the detected baud rate. By monitoring the baud rate and switching the adaptation state accordingly, the system optimizes equalization performance at high speeds while maintaining coefficient stability at low speeds, thus resolving the technical contradiction.
2Adaptability or versatility
If link speed negotiation uses progressively lower training speeds, then compatibility across generations is improved, but signal energy divergence occurs
Solution Approach 1:
The system dynamically adjusts the equalizer adaptation state based on the current training speed being negotiated. During link speed negotiation, as the baud rate transitions through different generations, the equalizer adapts its behavior accordingly - remaining active for high-speed training signals while becoming inactive at lower speeds, thus maintaining signal energy stability across generation transitions.
Solution Approach 2:
The baud rate detector acts as an intermediary between the link speed negotiation process and the adaptive equalizer. It monitors the training signal speed and mediates the equalizer's adaptation behavior, enabling the system to maintain compatibility across Fibre Channel generations while preventing signal energy divergence through appropriate equalizer state management.
Data Source
AI summary
An illustrative digital communications method includes: filtering a receive signal to provide a filtered receive signal; deriving symbol decisions from the filtered receive signal; detecting a baud rate of the receive signal; adapting one or more coefficients of the filter if the baud rate is above a predetermined rate; and inhibiting coefficient adaptation if the baud rate is below the predetermined rate. The method may be implemented in a receiver having: a filter to convert a receive signal into a filtered receive signal; a decision element coupled to the filter to derive symbol decisions; a baud rate detector to detect a baud rate of the receive signal; and an adaptation module to adapt one or more coefficients of the filter if the baud rate is above a predetermined rate, the baud rate detector inhibiting adaptation if the baud rate is below the predetermined rate.