OFDM Spectrum Shaping via Constellation Point Alteration
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Solution Overview
Problem
Existing spectral suppression methods either achieve modest suppression performance with acceptable signal distortion or high suppression performance with significant signal distortion, failing to provide both effective spectrum shaping and distortion-free transmission in communication systems.
Innovation Solution
A method and device for spectrum shaping that alter a subset of constellation points in a signal's frequency-domain representation while maintaining the minimum distance between points, transforming the signal into a time-domain representation to achieve distortion-free spectrum shaping with good suppression capabilities, specifically applicable to OFDM and DMT modulation techniques.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If existing spectral suppression methods are used to achieve high suppression performance, then out-of-band suppression is improved, but signal distortion increases significantly
Solution Approach 1:
The patent applies parameter changes by modifying the constellation points in the frequency domain while maintaining the minimum distance between them. Specifically, the method alters the amplitude and/or phase parameters of selected constellation points to achieve spectrum shaping, thereby improving out-of-band suppression without compromising signal integrity or increasing distortion.
2Reliability
If existing spectral suppression methods are used to maintain acceptable signal distortion, then spectrum shaping capability is limited, but out-of-band suppression remains modest
Solution Approach 1:
The patent applies local quality by selectively altering only a proper subset of constellation points rather than all points uniformly. This localized modification allows precise control over the spectrum shape while preserving the minimum distance property for unmodified points, thereby achieving both good spectrum shaping and acceptable signal distortion.
3Object-generated harmful factors
If constellation points are altered to achieve spectrum shaping, then out-of-band suppression is improved, but minimum distance between constellation points may be compromised
Solution Approach 1:
The patent ensures that parameter changes to constellation points are made in a way that preserves the minimum distance property. By carefully selecting which points to modify and how much to modify them, the method achieves spectrum shaping while maintaining the geometric integrity of the constellation, thus avoiding bit-error-rate penalties.
Data Source
AI summary
There is provided spectrum shaping of a signal. A frequency-domain representation of the signal to be spectrum-shaped is provided. The signal is associated with a set of constellation points having a minimum distance. A spectrum-shaped signal is determined by altering a proper subset of the constellation points while maintaining the minimum distance between all of the constellation points. The spectrum-shaped signal is transformed into a time-domain signal.