OFDM Equalizer Using Phase Components for Scattered Pilot Symbols

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Solution Overview

Problem

Conventional OFDM demodulators struggle with demodulating signals with pilot symbols scattered among data symbols, leading to increased noise and errors in transfer path estimation, particularly in Terrestrial Integrated Services Digital Broadcasting, where existing methods fail to accurately equalize signals with changing transfer functions.

Innovation Solution

An equalizer and equalization method that extracts pilot symbols, performs inverse Fourier transformation, computes complex gains, and uses phase components to equalize the input signal, effectively mitigating noise and accurately estimating transfer paths even with scattered pilot symbols.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Adaptability or versatility

If conventional OFDM demodulators use frame structure with pattern signals for propagation path estimation, then transfer function estimation can be performed, but the demodulator cannot process signals with scattered pilot symbols among data symbols

Engineering Contradiction:

Improvesignal structure compatibilityVSAvoiddemodulation capability

Core Design Contradiction:

Adaptability or versatilityVSReliability

Solution Approach 1:

The equalizer is designed to handle multiple signal structures (both frame structure with pattern signals and scattered pilot symbol structure) through a unified processing approach using inverse Fourier transformation and path extraction, making the system universally applicable to different OFDM signal formats

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Adaptability or versatility

If scattered pilot symbols are used for transfer path estimation, then signal demodulation is enabled, but noise components in the LPF passage region cannot be removed in advance

Engineering Contradiction:

Improvepilot symbol arrangement flexibilityVSAvoidtransfer path estimation accuracy

Core Design Contradiction:

Adaptability or versatilityVSMeasurement precision

Solution Approach 1:

The invention extracts only the relevant path information from the inverse Fourier transformed pilot symbols by identifying and selecting paths with significant amplitude values, effectively filtering out noise components while preserving the essential transfer path characteristics

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The inverse Fourier transformation serves as an intermediary process that converts scattered pilot symbols in the frequency domain into time-domain path information, enabling noise reduction through subsequent threshold-based path extraction

Inventive Principle:

Principle #24Intermediary (Mediator)

3Productivity

If pilot symbols are compared with those four symbols before, then some equalization can be performed, but changes in transfer function within four symbols cannot be detected

Engineering Contradiction:

Improveequalization processing speedVSAvoidequalization accuracy

Core Design Contradiction:

ProductivityVSReliability

Solution Approach 1:

The equalizer performs preliminary inverse Fourier transformation on pilot symbols to extract path information in advance, enabling real-time detection of transfer function changes without waiting for four-symbol intervals

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS7684311B2Equalizer and equalization method

Publication Date: 2010.03.23 LAPIS SEMICON CO LTD

AI summary

There is provided an equalizer that includes: a first extracting circuit extracting a plurality of pilot symbols from an inputted signal; an inverse Fourier transform circuit inversely Fourier transforming the extracted plurality of pilot symbols, and computing a complex gain per path; a second extracting circuit extracting a plurality of paths by using the complex gains; a Fourier transform circuit Fourier transforming the extracted paths; and an equalization computing circuit extracting phase components of the Fourier-transformed paths, and carrying out multiplication by using the inputted signal and the extracted phase components.