Adaptive Filter Pole Control for Low-Complexity Channel Estimation

Solution Overview

Problem

Current channel estimation methods in wireless communication systems, such as those used in WCDMA and UMTS, face high complexity and power consumption, making them costly to implement and inefficient in third-generation mobile communication scenarios.

Innovation Solution

A filter apparatus with a fixed portion for selectivity and an adaptive portion that adjusts pole values to change the frequency response, maintaining selectivity while reducing complexity, using a constrained linear filter structure and second-order statistic-based adaptation to cope with third-generation mobile environments.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If adaptive filtering methods (Wiener filtering, Kalman filtering) are used for channel estimation, then channel estimation performance is improved, but device complexity increases significantly

Engineering Contradiction:

Improvechannel estimation performanceVSAvoidalgorithm complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The filter is segmented into a fixed portion (for selectivity) and an adaptive portion (for frequency response adaptation). This segmentation allows the complex adaptive filtering function to be divided into manageable parts, reducing overall device complexity while maintaining estimation performance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different parts of the filter have different qualities: the fixed portion provides predetermined selectivity with simple structure, while the adaptive portion provides frequency response adaptation with controlled complexity. This local differentiation resolves the contradiction by assigning specific functions to specific parts.

Inventive Principle:

Principle #3Local quality

2Adaptability or versatility

If fully adaptive filter structure is used for channel estimation, then adaptability to changing conditions is improved, but power consumption increases

Engineering Contradiction:

Improvefrequency response adaptationVSAvoidpower consumption

Core Design Contradiction:

Adaptability or versatilityVSUse of energy by moving object

Solution Approach 1:

The filter is segmented into a fixed portion (for selectivity) and an adaptive portion (for frequency response adaptation). This segmentation allows the complex adaptive filtering function to be divided into manageable parts, reducing overall device complexity while maintaining estimation performance.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

Different parts of the filter have different qualities: the fixed portion provides predetermined selectivity with simple structure, while the adaptive portion provides frequency response adaptation with controlled complexity. This local differentiation resolves the contradiction by assigning specific functions to specific parts.

Inventive Principle:

Principle #3Local quality

3Device complexity

If non-adaptive low-pass filter is used with cut-off frequency dimensioned to maximum Doppler frequency, then device complexity is reduced, but channel estimation performance deteriorates

Engineering Contradiction:

Improvealgorithm complexityVSAvoidchannel estimation performance

Core Design Contradiction:

Device complexityVSMeasurement precision

Solution Approach 1:

The filter transitions from a static non-adaptive low-pass filter to a dynamic adaptive filter where the frequency response can change based on channel conditions. The adaptive portion adjusts pole values to optimize performance for different Doppler frequencies and signal conditions, resolving the contradiction between simplicity and performance.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS7602845B2Adaptive filter

Publication Date: 2009.10.13 CALLAHAN CELLULAR LLC

AI summary

The present invention relates to a filter apparatus and method having a fixed aspect for providing a predetermined selectivity and having an adaptive aspect for determining the frequency response of said filter apparatus. The adaptive aspect is controlled to change the frequency response. Predetermined zero values of the filter characteristic are set to provide a predetermined filter selectivity; and at least one filter parameter is controlled to change pole values of the filter characteristic so as to provide frequency response adaptation. Thereby, the frequency response of the filter operation can change while the filter selectivity can be maintained. The filter apparatus is thus able to cope with advanced system requirements while keeping the complexity and power consumption low.