Channel Estimation via Segmented IFFT for CMMB

Solution Overview

Problem

Conventional OFDM channel estimation methods require large-scale IFFT operations, which are inefficient and costly, particularly in China Multimedia Mobile Broadcasting (CMMB) systems, and result in high power consumption and complex operations.

Innovation Solution

A novel channel estimation method that reduces the scale of IFFT operations by adaptively adjusting operation formulas based on the characteristics of the preliminary frequency-domain channel response, using a 512-sampling-point IFFT operation instead of the conventional 4096-sampling-point IFFT, and incorporates time-domain windowing and smoothing to generate a frequency-domain channel response.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Measurement precision

If conventional 4096-sampling-point IFFT operation is used for channel estimation, then channel estimation accuracy is maintained, but operation complexity and power consumption increase significantly

Engineering Contradiction:

Improvechannel estimation accuracyVSAvoidoperation complexity

Core Design Contradiction:

Measurement precisionVSDevice complexity

Solution Approach 1:

The patent segments the 4096-point frequency-domain channel response into multiple 512-point segments. Each segment undergoes separate 512-point IFFT operation instead of one large 4096-point IFFT. This segmentation reduces the computational complexity from O(4096²) to multiple O(512²) operations, while maintaining channel estimation accuracy through proper reconstruction of the time-domain CIR from segmented results

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent transforms the problem from a single large-dimensional IFFT operation to multiple smaller-dimensional operations by introducing a segmentation dimension. The frequency-domain response is divided along the frequency axis into segments, and the time-domain processing is performed on each segment separately, then combined through appropriate mathematical operations to reconstruct the full channel response

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

2Measurement precision

If conventional 4096-sampling-point IFFT operation is used for channel estimation, then channel estimation accuracy is maintained, but power consumption increases

Engineering Contradiction:

Improvechannel estimation accuracyVSAvoidpower consumption

Core Design Contradiction:

Measurement precisionVSUse of energy by moving object

Solution Approach 1:

The patent segments the 4096-point frequency-domain channel response into multiple 512-point segments. Each segment undergoes separate 512-point IFFT operation instead of one large 4096-point IFFT. This segmentation reduces the computational complexity from O(4096²) to multiple O(512²) operations, while maintaining channel estimation accuracy through proper reconstruction of the time-domain CIR from segmented results

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent changes the key parameter of IFFT operation size from 4096 points to 512 points. This parameter change fundamentally reduces the number of computational operations required, directly lowering power consumption. The accuracy is maintained through mathematical reconstruction techniques that combine the results from multiple 512-point operations to equivalent the channel information that would be obtained from a single 4096-point operation

Inventive Principle:

Principle #35Parameter changes

3Reliability

If pilot symbols are distributed across 4096 sub-carriers, then channel coverage is comprehensive, but IFFT operation scale remains large

Engineering Contradiction:

Improvechannel coverageVSAvoidIFFT operation scale

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent segments the frequency-domain processing into multiple 512-point segments. Pilot symbols are distributed across the full 4096 sub-carriers for comprehensive channel coverage, but the IFFT operation is performed on segmented 512-point subsets. This allows maintaining complete channel information while reducing the operational scale of each IFFT computation

Inventive Principle:

Principle #1Segmentation

Solution Approach 2:

The patent transforms the problem from a single large-dimensional IFFT operation to multiple smaller-dimensional operations by introducing a segmentation dimension. The frequency-domain response is divided along the frequency axis into segments, and the time-domain processing is performed on each segment separately, then combined through appropriate mathematical operations to reconstruct the full channel response

Inventive Principle:

Principle #17Another dimension (Dimensionality change)

Data Source

PatentUS8615048B2Channel estimation method and an associated apparatus

Publication Date: 2013.12.24 MEDIATEK INC

AI summary

A channel estimation method, applied to an orthogonal frequency comprises performing a first number of sampling points inverse fast Fourier transformation (IFFT) operation on a preliminary frequency-domain channel response having a second number of response values to generate a first time-domain channel impulse response (CIR), the second number being greater than the first number; performing a time-domain windowing operation on the first time-domain CIR to generate a second time-domain CIR; performing a smoothing operation on a plurality of second time-domain CIRs of successive time points to generate a smooth time-domain CIR; and performing FFT operation on the smooth time-domain CIR to generate a frequency-domain channel response.