Channel Estimation Phase Compensation for FCH and DL-MAP Demodulation

Solution Overview

Problem

In broadband wireless access systems, particularly in IEEE 802.16 communication systems, the demodulation of frame control headers (FCH) and downlink-MAP (DL-MAP) is hindered by inadequate channel estimation due to synchronization issues, frequency offsets, and varying channel conditions, leading to inter-symbol interference and suboptimal performance.

Innovation Solution

A channel estimation apparatus and method that compensates for phase differences between preamble-based and PUSC symbol-based channel estimation values, using a phase rotation correction to improve demodulation accuracy for FCH and DL-MAP, employing a channel estimator, estimation buffer, and preamble phase compensator to store and adjust channel estimates.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If channel estimation is performed using pilot subcarriers in PUSC symbols, then channel estimation can be performed for data symbols, but phase rotation errors occur due to frequency offsets and time-varying channel conditions

Engineering Contradiction:

Improvechannel estimation accuracyVSAvoiddemodulation performance

Core Design Contradiction:

Measurement precisionVSReliability

Solution Approach 1:

The patent performs preliminary channel estimation using the preamble before demodulating the FCH and DL-MAP. The preamble-based channel estimation is done in advance to establish a reference that is less susceptible to phase rotation errors, improving the reliability of critical control information demodulation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces an intermediary processing step where the preamble-based channel estimation result is used as a reference to correct the pilot subcarrier-based channel estimation. This intermediary reference helps mitigate phase rotation errors that would otherwise directly affect the demodulation accuracy.

Inventive Principle:

Principle #24Intermediary (Mediator)

2Ease of operation

If conventional channel estimation methods are used for FCH and DL-MAP demodulation, then the process is simple, but demodulation performance deteriorates due to inter-symbol interference and phase rotation

Engineering Contradiction:

Improvedemodulation process simplicityVSAvoiddemodulation accuracy

Core Design Contradiction:

Ease of operationVSMeasurement precision

Solution Approach 1:

The patent performs preliminary channel estimation using the preamble before demodulating the FCH and DL-MAP. The preamble-based channel estimation is done in advance to establish a reference that is less susceptible to phase rotation errors, improving the reliability of critical control information demodulation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent introduces an intermediary processing step where the preamble-based channel estimation result is used as a reference to correct the pilot subcarrier-based channel estimation. This intermediary reference helps mitigate phase rotation errors that would otherwise directly affect the demodulation accuracy.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Device complexity

If time-varying channel conditions are not compensated, then the channel estimation process is straightforward, but synchronization performance degrades leading to inter-symbol interference

Engineering Contradiction:

Improvechannel estimation process complexityVSAvoidsynchronization performance

Core Design Contradiction:

Device complexityVSReliability

Solution Approach 1:

The patent performs preliminary channel estimation using the preamble before demodulating the FCH and DL-MAP. The preamble-based channel estimation is done in advance to establish a reference that is less susceptible to phase rotation errors, improving the reliability of critical control information demodulation.

Inventive Principle:

Principle #10Preliminary action

Solution Approach 2:

The patent uses the preamble-based channel estimation result as feedback to correct subsequent channel estimations. This feedback mechanism allows the system to adapt to time-varying channel conditions and compensate for phase rotation, improving synchronization performance without excessive complexity.

Inventive Principle:

Principle #23Feedback

Data Source

PatentUS7801252B2Apparatus and method for channel estimation for data demodulation in broadband wireless access system

Publication Date: 2010.09.21 SAMSUNG ELECTRONICS CO LTD

AI summary

Provided is a channel estimation apparatus and method. In the channel estimation apparatus, a channel estimator performs channel estimation onto a received symbol and output a channel estimation result. The channel estimation result is stored in an estimation buffer along with a channel estimation result compensated in a preamble phase compensator. The preamble phase compensator receives a channel estimation result for pilot subcarriers of a data symbol and a preamble channel estimation result from the estimation buffer, acquires a phase rotation value between them, and compensates the preamble channel estimation result with the phase rotation value. When FCH and DL-MAP are demodulated, pilot subcarriers in the Nth PUSC symbol have been used to estimate the channel of the Nth PUSC symbol.