Frequency Offset Estimation Using Adjacent Subcarrier Interference Cancellation

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Solution Overview

Problem

Existing frequency offset estimation methods for OFDM technology are inefficient when using discontinuously distributed pilot symbols, leading to loss of estimation precision due to interference between users.

Innovation Solution

A method and apparatus that reconstructs channel values for target and non-target users, cancels interference in the frequency domain using adjacent subcarrier data, and determines frequency offset using conjugate correlation and orthogonalization techniques, improving precision by leveraging frequency domain data from adjacent subcarriers.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If continuous pilot symbols are used for frequency offset estimation, then estimation precision is maintained, but resource overhead increases and spectral efficiency decreases

Engineering Contradiction:

Improvefrequency offset estimation precisionVSAvoidpilot symbol quantity

Core Design Contradiction:

Measurement precisionVSQuantity of substance

Solution Approach 1:

The patent segments the frequency domain into multiple subcarriers and uses comb-type pilot distribution where pilots are placed at specific intervals rather than continuously. This segmentation allows frequency offset estimation to be performed using only selected subcarriers, reducing the total number of pilot symbols while maintaining estimation capability through the use of adjacent subcarrier interference information.

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent transitions from time-domain continuous pilot sequencing to frequency-domain comb-type pilot distribution. By changing the dimension of pilot distribution from continuous time sequence to discrete frequency intervals, the system achieves frequency offset estimation with reduced pilot overhead while utilizing the frequency domain structure of OFDM signals.

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Quantity of substance

If comb-type pilot symbols are used to reduce overhead, then resource efficiency improves, but frequency offset estimation precision deteriorates due to interference

Engineering Contradiction:

Improvepilot symbol quantityVSAvoidfrequency offset estimation precision

Core Design Contradiction:

Quantity of substanceVSMeasurement precision

Solution Approach 1:

The patent converts the harmful interference from adjacent subcarriers into a beneficial resource for estimation. Instead of treating adjacent subcarrier interference as noise to be eliminated, the method utilizes this interference information as additional observation data for frequency offset estimation, thereby improving precision despite using fewer comb-type pilot symbols.

Inventive Principle:

Principle #22Blessing in disguise (Convert harm into benefit)

Solution Approach 2:

The patent introduces channel state information as an intermediary element that mediates between the comb-type pilot symbols and the frequency offset estimation. By using reconstructed channel values from adjacent subcarriers as intermediate data, the system can extract frequency offset information even when direct pilot symbols are sparsely distributed, thus maintaining precision with reduced overhead.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Measurement precision

If adjacent subcarrier data is used for interference cancellation, then estimation precision improves, but computational complexity increases

Engineering Contradiction:

Improvefrequency offset estimation precisionVSAvoidcomputational complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent performs preliminary channel estimation and reconstruction of adjacent subcarrier data before the frequency offset estimation process. By pre-processing and organizing the channel state information and adjacent subcarrier interference data in advance, the actual estimation computation is simplified, reducing the real-time computational burden while maintaining the ability to utilize interference information for improved precision.

Inventive Principle:

Principle #10Preliminary action

Data Source

PatentUS10148463B2Method and device for estimating frequency offset

Publication Date: 2018.12.04 XIAN ZHONGXING NEW SOFTWARE

AI summary

The present disclosure discloses a method and apparatus for estimating a frequency offset. The method includes: reconstructing an estimated channel value of a target user and an estimated channel value of a non-target user to obtain a reconstructed estimated channel value of the target user and a reconstructed estimated channel value of the non-target user; calculating frequency domain received data of a target user's local pilot frequency at which interference has been cancelled by using frequency domain data of a subcarrier occupied by the target user, frequency domain data of a subcarrier occupied by the adjacent non-target user, and the reconstructed estimated channel value of the target user and the reconstructed estimated channel value of the non-target user; and determining an estimated frequency offset value by using the target user's local pilot frequency at which interference has been cancelled and the frequency domain received data.