FFE Tap Adaptation Using Channel Estimation for Joint ISI Reduction
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Solution Overview
Problem
Existing communication systems face challenges in adapting feed forward equalizer (FFE) tap weights without access to digital input signals, particularly in analog delay lines, and in achieving joint optimization between FFE and decision feedback equalizer (DFE) for effective inter-symbol interference (ISI) reduction.
Innovation Solution
A method and apparatus that utilize channel estimation to adapt FFE tap weights, enabling joint optimization between FFE and DFE, allowing the FFE to remove precursor ISI or work with DFE to reduce post cursor ISI, by generating error signals and controlling adaptation loops without digital input signal access.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If channel estimation-based adaptation is used, then FFE can be adapted without digital input signal access, but implementation complexity increases
Solution Approach 1:
The patent introduces channel estimation as an intermediary mechanism that allows the adaptation algorithm to indirectly obtain channel information without direct access to digital input signals. The channel estimator acts as a mediator between the analog delay line and the adaptation logic, converting analog channel characteristics into usable estimation data for tap weight adjustment.
Solution Approach 2:
The patent replaces the conventional mechanical/digital signal sampling approach with an analog-based channel estimation mechanism. Instead of requiring digital samples of the input signal, the system uses analog channel estimation techniques to derive the necessary information for adaptation, substituting the digital sampling mechanism with an analog estimation approach.
2Device complexity
If FFE is used only for precursor ISI removal, then implementation is simpler, but post cursor ISI reduction capability is lost
Solution Approach 1:
The patent makes the FFE universal by enabling it to perform multiple functions: removing precursor ISI and reducing post cursor ISI when used jointly with DFE. The channel estimation-based adaptation mechanism allows the FFE to be configured dynamically for different ISI reduction tasks, making it a multi-functional component rather than a single-purpose device.
Solution Approach 2:
The patent introduces dynamic adaptability to the FFE through channel estimation-based tap weight adjustment. The equalizer can dynamically change its configuration and functionality based on channel conditions, transitioning between precursor ISI removal mode and joint post-cursor ISI reduction mode with DFE, rather than being fixed in a single configuration.
3Reliability
If joint optimization between FFE and DFE is implemented, then ISI reduction performance improves, but adaptation complexity increases
Solution Approach 1:
The patent merges the adaptation mechanisms of FFE and DFE into a unified channel estimation-based framework. Instead of separate adaptation algorithms for each equalizer, the system combines them into a joint optimization process where both FFE and DFE tap weights are adapted simultaneously based on common channel estimation data, reducing overall system complexity.
Solution Approach 2:
The patent implements feedback mechanisms where the channel estimation results are fed back to both FFE and DFE adaptation processes. This feedback loop allows joint optimization by continuously adjusting both equalizers based on the estimated channel characteristics and actual performance, enabling coordinated adaptation without requiring complex independent control mechanisms.
Data Source
AI summary
An apparatus including a receiver having a feed forward equalizer (FFE) coupled to a communication channel. The receiver may be configured to adjust the FFE using information based on an estimate of one or more characteristics of the communication channel.