Receiver Equalizer Training Using Channel Slope Lookup
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Solution Overview
Problem
Existing PCIe link training methods are slow and inefficient, requiring 10 seconds or more for equalizer training due to strict latency limitations and signal integrity issues, which hinder fast linkup times in high-speed data transmission.
Innovation Solution
Implement a continuous time linear equalizer with high-frequency boost, an analog-to-digital converter, and a channel estimation module to measure spectral density, using the difference in spectral densities to set operating parameters and retrieve optimized settings from a lookup table for expedited training.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a step-by-step parameter-by-parameter optimization process is used for equalizer training, then the reliability of signal integrity is improved, but the linkup time increases to 10 seconds or more
Solution Approach 1:
The patent applies preliminary action by pre-computing and storing optimal equalizer parameters in lookup tables during manufacturing or system initialization. During linkup, the receiver measures channel characteristics and directly retrieves pre-optimized parameters from the lookup table, bypassing the need for time-consuming real-time parameter optimization. This resolves the contradiction by performing the computationally intensive optimization work in advance, enabling fast linkup while maintaining signal integrity through use of pre-calibrated optimal parameters.
Solution Approach 2:
The patent implements parameter changes by transitioning from a continuous parameter optimization approach to a discrete lookup table approach. Instead of iteratively adjusting equalizer parameters during linkup, the system changes the operational mode to query pre-stored parameter sets based on measured channel conditions. This parameter paradigm shift enables rapid convergence while preserving signal integrity through use of optimized parameters for different channel scenarios.
2Reliability
If PCIe link training follows strict latency limitations, then the protocol compliance is improved, but the training speed is reduced due to frequent retransmissions
Solution Approach 1:
The patent applies preliminary action by pre-determining optimal equalizer parameters for various channel conditions before actual link training occurs. During the training phase, the system only needs to measure channel characteristics and retrieve corresponding parameters from pre-computed lookup tables, rather than performing iterative optimization that would violate latency constraints. This enables compliance with PCIe protocol timing requirements while achieving fast training speeds.
3Productivity
If high symbol rates are used to increase data throughput, then the productivity is improved, but signal integrity deteriorates due to noise and interference
Solution Approach 1:
The patent implements parameter changes by using lookup tables that store optimized equalizer parameters specifically tuned for high symbol rate operation. The system measures channel characteristics and retrieves parameters optimized for the specific data rate and channel conditions, enabling maintenance of signal integrity at high throughput speeds. This resolves the contradiction by having pre-computed parameters that account for the increased noise and interference inherent in high symbol rate transmission.
Data Source
AI summary
To expedite training and achieve fast linkup times, one illustrative receiver includes: a continuous time linear equalizer configured to provide a controllable amount of high frequency boost to an analog receive signal; an analog to digital converter configured to convert the analog receive signal into a digitized receive signal; a channel estimation module configured to obtain a spectral density measurement of the digitized receive signal at each of two different frequencies, the spectral density measurements having a difference indicating a slope of a channel response; and a microcontroller configured to set at least one operating parameter of the continuous time linear equalizer based on said difference. An illustrative method includes: estimating a slope of frequency dependence of a channel response; using the slope to retrieve a set of equalization parameters from a look-up table; and employing the set of equalization parameters to exit a receiver training mode.