OFDM Pilot Removal via Frequency Domain Magnitude Estimation

Solution Overview

Problem

Existing techniques for removing distributed pilot signals from OFDM signals require complex, iterative time domain estimation algorithms, which are resource-intensive and inefficient.

Innovation Solution

A method that converts the received OFDM signal into a frequency domain signal, determines the average magnitude of populated frequency bins, and uses this information along with the known pilot signal structure to remove the distributed pilot signal, eliminating the need for complex time domain estimation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If complex iterative time domain estimation algorithms are used to remove distributed pilot signals, then pilot signal removal accuracy is improved, but processing complexity and resource consumption increase

Engineering Contradiction:

Improvepilot signal removal accuracyVSAvoidprocessing complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent extracts the pilot signal removal operation from the time domain to the frequency domain, where the pilot signal can be directly separated from data subcarriers based on their distinct frequency locations. This extraction approach eliminates the need for complex iterative time domain estimation algorithms while maintaining accurate pilot signal removal.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces the mechanical iterative time domain estimation process with a simpler frequency domain operation. By transforming the signal to the frequency domain and utilizing the known pilot signal structure, the system substitutes complex iterative computation with direct frequency bin manipulation and subtraction.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

2Measurement precision

If complex iterative time domain estimation algorithms are used to remove distributed pilot signals, then pilot signal removal accuracy is improved, but processing resources consumed increase

Engineering Contradiction:

Improvepilot signal removal accuracyVSAvoidprocessing resources

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent extracts the pilot signal removal operation from the time domain to the frequency domain, where the pilot signal can be directly separated from data subcarriers based on their distinct frequency locations. This extraction approach eliminates the need for complex iterative time domain estimation algorithms while maintaining accurate pilot signal removal.

Inventive Principle:

Principle #2Taking out (Extraction)

Solution Approach 2:

The patent replaces the mechanical iterative time domain estimation process with a simpler frequency domain operation. By transforming the signal to the frequency domain and utilizing the known pilot signal structure, the system substitutes complex iterative computation with direct frequency bin manipulation and subtraction.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Ease of operation

If frequency domain processing is used to remove pilot signals, then processing simplicity is improved, but pilot signal removal accuracy may worsen

Engineering Contradiction:

Improveprocessing simplicityVSAvoidpilot signal removal accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent applies preliminary action by transforming the time domain signal to the frequency domain before performing pilot signal removal. This preliminary transformation enables direct separation of pilot and data components based on their frequency locations, simplifying the removal process while maintaining accuracy through proper use of frequency domain characteristics.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses copying by creating a frequency domain representation of the received signal and manipulating copies of the signal in the frequency domain. This allows the pilot signal to be identified and removed based on its known frequency structure without affecting the original time domain signal, ensuring both simplicity and accuracy.

Inventive Principle:

Principle #26Copying

Data Source

PatentUS8665973B2Removal of a band-limited distributed pilot from an OFDM signal

Publication Date: 2014.03.04 L3HARRIS GLOBAL COMMUNICATIONS INC

AI summary

A technique for removing a band-limited distributed pilot signal from an orthogonal frequency division multiplexed (OFDM) signal involves converting a received OFDM signal, which includes a distributed pilot signal and an OFDM data signal, into a frequency domain signal having populated frequency bins containing respective subcarrier signals, each including a constituent data signal of the OFDM data signal and component pilot signal of the distributed pilot signal. An average magnitude of the populated frequency bins is determined based on the absolute values of the complex components of the populated frequency bins of the frequency domain signal, and the average magnitude of the populated frequency bins is used to estimate a pilot signal magnitude. The distributed pilot signal is removed from the frequency domain signal using a stored replica of the pilot signal scaled in conjunction with the pilot signal magnitude to yield the OFDM data signal.