Equalizer Coefficient Scaling During AGC Gain Changes
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Solution Overview
Problem
In communication systems, especially those adhering to 3GPP release 5 or 6 standards, the automatic gain controller (AGC) adjustments lead to delays in equalizer adaptation, resulting in errors and potential retransmissions due to the slow response of the NLMS equalizer to gain changes.
Innovation Solution
Implementing a method that involves an equalizing filter with a filter coefficient updater, which applies a scaling factor to the filter coefficients based on the gain change, and freezing coefficient updates during the AGC adjustment period to quickly adapt to gain changes, thereby reducing adaptation time and errors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the equalizer uses traditional NLMS adaptation to adjust to gain changes, then the equalization accuracy is maintained, but the adaptation time increases causing delays and errors
Solution Approach 1:
The patent applies preliminary action by detecting gain changes before they fully impact the equalizer output and pre-adjusting the filter coefficients using a scale factor. The system monitors AGC gain adjustments and proactively scales the equalizer coefficients in response to detected gain changes, allowing the equalizer to adapt faster than traditional NLMS would naturally converge.
Solution Approach 2:
The patent changes the parameters of the equalizer by introducing a scale factor that directly modifies the filter coefficients based on detected gain changes. Instead of relying on the gradual parameter adaptation of traditional NLMS, the system dynamically scales the coefficients using the formula: new_coefficient = old_coefficient × scale_factor, where the scale factor is derived from the detected gain change magnitude.
2Loss of time
If the equalizer adapts quickly to gain changes by updating coefficients rapidly, then the adaptation time decreases, but errors may occur during the transition period
Solution Approach 1:
The patent implements feedback by continuously monitoring the AGC gain adjustments and using this information to dynamically adjust the equalizer coefficients. The system detects when gain changes occur and feeds this information back to the coefficient scaling mechanism, which then applies appropriate scale factors to maintain equalization accuracy during transitions.
Solution Approach 2:
The patent applies dynamics by making the coefficient update process adaptive and responsive to real-time gain changes. The system dynamically adjusts the scaling behavior based on the detected gain change magnitude and timing, allowing the equalizer to flexibly adapt to varying channel conditions without introducing errors during transitions.
3Device complexity
If traditional equalizer adaptation is used without gain change detection, then the system complexity is low, but retransmissions increase due to errors from slow adaptation
Solution Approach 1:
The patent applies self-service by enabling the equalizer to automatically detect and respond to gain changes without external intervention. The system monitors its own input signal characteristics and AGC adjustments, then autonomously adjusts its coefficients using scale factors, eliminating the need for complex external control mechanisms while improving throughput.
Data Source
AI summary
In one embodiment, a receiver comprises an automatic gain controller (AGC), an equalizer, a controller, and a register interface. The AGC makes gain adjustments to compensate for changes in the average amplitude of a received signal. The equalizer has a coefficient updater that calculates coefficients and a finite impulse response (FIR) filter that applies the coefficients to the received signal to generate an equalized signal. During gain adjustments by the AGC, the register interface provides a weight freeze signal to the coefficient updater, which subsequently freezes the updating of the coefficients for a freeze duration period. Then, register interface provides a scaling factor, generated by the controller based on the size of the gain adjustment, to the coefficient updater. At the end of the freeze period, coefficient updater applies the scaling factor to the coefficients and unfreezes the coefficient updating.