OFDM Receiver Interference Cancellation via Component Extraction
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Solution Overview
Problem
Existing OFDM systems face challenges in correcting Doppler shift-induced inter-carrier interference, leading to reduced receiving sensitivity due to high computational complexity and incorrect handling of leak-in and leak-out components.
Innovation Solution
A receiving device and method that estimates transmission path properties, transforms signals using FFT, calculates leak-in coefficients, and subtracts interference components to isolate desired signal components, while combining them to improve sensitivity without requiring inverse matrix calculations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the MMSE algorithm is used to calculate weighting coefficients for inter-carrier interference suppression, then receiving sensitivity is improved, but computational complexity increases due to inverse matrix calculations
Solution Approach 1:
The patent extracts and processes only the necessary signal components (desired signal and interference signal) separately, avoiding the need to process all carrier signals simultaneously through inverse matrix calculations. By isolating the specific components needed for interference suppression, the computational burden is significantly reduced while maintaining effectiveness.
Solution Approach 2:
The received signal is segmented into distinct components: desired signal components and interference signal components from adjacent carriers. This segmentation allows independent processing of each component type, eliminating the need for complex full-matrix inverse calculations required by the MMSE algorithm while achieving similar interference suppression results.
2Object-generated harmful factors
If inter-carrier interference cancellation is performed by eliminating leak-in components from adjacent carriers, then inter-carrier interference is suppressed, but receiving sensitivity deteriorates due to elimination of leak-out components
Solution Approach 1:
Instead of simply eliminating leak-in components from adjacent carriers (which also removes useful leak-out components), the patent converts the harmful interference into a beneficial signal by extracting and processing the leak-out components separately. These components are then added back to the desired signal, transforming what was previously considered interference into a useful signal enhancement.
Solution Approach 2:
The patent introduces an intermediary processing step where leak-out components are extracted, processed through interference cancellation, and then recombined with the desired signal. This intermediary approach allows selective removal of harmful interference while preserving and even enhancing useful signal components that would otherwise be lost.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution effectively corrects Doppler shift with reduced computational load, enhancing receiving sensitivity by accurately isolating and combining signal components, thus addressing the limitations of existing methods.
Implementation Method 1
an FFT computation means for transforming the received signal to a frequency domain, thereby outputting a signal of the frequency domain
Implementation Method 2
changes in transmission path property over time modify the orthogonality among the carriers, producing inter-carrier interference... a Doppler shift causes each carrier frequency to shift by a Doppler frequency
Data Source
Figure 1A~1B
Figure 2
Figure 3
AI summary
The receiving device, which can correct a Doppler shift by a small amount of calculation and can improve receiving sensitivity by combining components leaking into adjacent carriers, includes: a transmission path estimation means (1); an FFT computation means (2); a correction means (3) for correcting distortion of a signal of a frequency domain; a leak-in coefficient calculation means (4) for calculating an inter-carrier interference leak-in coefficient; an interference component estimation means (5) for estimating an interference component included in a carrier to be demodulated on the basis of a signal indicating the leak-in coefficient and a corrected signal of the frequency domain; a subtraction means (8) for subtracting the interference component from the signal of the frequency domain; a signal component estimation means (6, 7) for estimating a desired second signal component included in a plurality of carriers other than the carrier to be demodulated; a subtraction means (9, 10) for subtracting the interference component estimated by the signal component estimation means (6, 7) from the signal of the frequency domain; and a combining means for combining an output from the subtraction means (8) and an output from the subtraction means (9, 10).