Adaptive Equalizer Tap Switching for Sparse Echo Cancellation
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Solution Overview
Problem
Conventional adaptive equalizers face inefficiencies in channel echo cancellation, particularly in digital television systems where sparsely separated echoes lead to most coefficients being close to zero, resulting in ineffective equalization.
Innovation Solution
The adaptive equalizer incorporates a controller that switches tap cells between normal and estimation modes, using a power meter and mode switcher to manage coefficients, allowing for recursive updates and channel parameter estimation, thereby optimizing coefficient usage and equalizer output.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional adaptive equalizers use all coefficients for equalization, then the equalization process covers all channel effects, but most coefficients are close to zero and do not contribute effectively to channel echo cancellation
Solution Approach 1:
The patent extracts and identifies only the non-zero coefficients from the set of all coefficients. The controller detects which coefficients are non-zero and selectively applies only those coefficients to the received signal for equalization, excluding the zero coefficients. This extraction principle directly resolves the contradiction by eliminating computational waste on ineffective coefficients while maintaining equalization effectiveness.
Solution Approach 2:
Instead of applying all coefficients (excessive action), the patent applies only the necessary subset of non-zero coefficients (partial action). The controller determines the actual number of non-zero coefficients and limits the equalization process to only those coefficients, avoiding unnecessary computations on zero coefficients while achieving complete channel echo cancellation.
2Reliability
If the equalizer processes all coefficients, then comprehensive channel compensation is achieved, but the processing time and complexity increase unnecessarily
Solution Approach 1:
The patent extracts the essential information (non-zero coefficients) from the complete coefficient set and uses only that extracted subset for equalization. This reduces the processing time by eliminating iterations over zero coefficients while maintaining comprehensive channel compensation accuracy through the use of all relevant non-zero coefficients.
Solution Approach 2:
The patent applies partial action by processing only the necessary non-zero coefficients rather than all coefficients. This reduces adaptation settling time by limiting processing to the actual number of non-zero coefficients while maintaining reliable channel compensation through the inclusion of all significant channel effects.
3Device complexity
If all tap cells operate continuously in normal mode, then the equalizer structure is simple, but coefficients close to zero cannot be identified and utilized efficiently
Solution Approach 1:
The patent introduces dynamic mode switching for each tap cell, allowing cells to transition between normal mode and estimation mode based on their coefficient values. This dynamic behavior enables the system to identify non-zero coefficients efficiently while maintaining a relatively simple overall structure. The controller dynamically determines which tap cells are active based on coefficient magnitude.
Solution Approach 2:
The patent applies local quality by giving different operational characteristics to different tap cells based on their individual coefficient values. Non-zero coefficients remain in normal mode for active equalization, while zero coefficients are identified and excluded. This local differentiation improves coefficient utilization efficiency without requiring complete structural redesign.
Data Source
AI summary
An exemplary embodiment of an adaptive equalizer is provided, receiving symbols to generate an equalizer output. The adaptive equalizer comprises a plurality of tap cells, a coefficient updater, a plurality of multiplexers, a controller and an integrator. Each tap cell generates a filter value from a tap data value and a coefficient. The coefficient updater provides a coefficient vector comprising a plurality of coefficients updated recursively. Each multiplexer is coupled to a corresponding tap cell and the coefficient updater, switching between a normal mode and an estimation mode. The controller coupled to the multiplexers controls mode switching of each multiplexer based on each corresponding coefficient. The integrator coupled to the tap cells collects the filter values to generate an equalizer output.