OFDM Signal PAPR Reduction via Complex Symbol Correction
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Solution Overview
Problem
OFDM modulation techniques face significant challenges due to high peak-to-average power ratio (PAPR) issues, leading to distortion, interference, and increased bit error rates, particularly in wireless communication systems, where power amplifiers' non-linear characteristics exacerbate these problems.
Innovation Solution
A method and device for reducing PAPR in OFDM signals by transforming and correcting symbols through real-time accumulation and detection of peaks, using complex correction control information to adjust constellation symbols before frequency-time transformation, thereby optimizing the signal in the frequency domain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If OFDM modulation is used to achieve good spectral efficiency and robustness to multi-path channels, then spectral efficiency is improved, but peak-to-average power ratio increases causing signal distortion and transmission errors
Solution Approach 1:
The patent applies preliminary action by performing PAPR reduction processing on the OFDM signal before transmission. The method pre-processes the signal by selecting alternative signal representations or applying clipping/compensation techniques in advance, so that when the signal passes through the non-linear power amplifier, the distortion is minimized. This resolves the contradiction by preparing the signal beforehand to withstand the harmful effects of high PAPR while maintaining the spectral efficiency benefits of OFDM modulation.
2Reliability
If power amplifiers operate in linear zone to avoid distortion, then signal quality is improved, but amplifier efficiency decreases leading to increased power consumption
Solution Approach 1:
The patent converts the harmful non-linearity of power amplifiers into a beneficial approach by using non-linear PAPR reduction techniques such as clipping and compensation. Instead of forcing the amplifier to operate in its linear (inefficient) zone, the method pre-distorts the signal to compensate for the amplifier's non-linear behavior. This allows the amplifier to operate in its efficient non-linear zone while still achieving acceptable signal quality through the compensation mechanism, thus converting the harmful non-linearity into a manageable characteristic.
3Object-affected harmful factors
If PAPR is reduced by limiting amplifier operating range, then distortion is reduced, but amplifier efficiency drops significantly
Solution Approach 1:
The patent introduces an intermediary processing stage between the signal source and the power amplifier. This intermediary performs PAPR reduction operations such as signal clipping, windowing, or alternative signal selection, and applies compensation techniques to mitigate the introduced distortions. By placing this intermediary processing stage, the amplifier can operate over a wider dynamic range with higher efficiency while the intermediary components handle the distortion management, thus decoupling the distortion control from the amplifier's operating constraints.
Data Source
Figure 1A~6
Figure 2~3
Figure 4A~4B
AI summary
The invention relates to a method for the transmission of an OFDM signal, in which pre-transmission processing comprises: mapping data representative of a source signal to complex symbols Xn, 0 ≤ n < M, belonging to a constellation, n and M being integers; transforming M symbols Xn into M corrected symbols X'n, such that X'n = Xn + dn, wherein dn is a complex correction; and mapping M corrected symbols X'n to M from among N carriers of an OFDM modulator in order to generate the OFDM signal, N being an integer, M≤N, such that the transformation comprises an accumulator initialisation step, as well as comprising, for each carrier of order n, n varying between 1 and M-1: a step (1051, 1054) of accumulating, in the accumulator respectively at J samples already present, J time samples corresponding to the J samples of the n-order carrier mapped by X'n; a step (1052) of detecting a peak on the J samples resulting from the accumulation step at order n-1 and comparing said peak with the corresponding time sample from among J time samples of the n-order carrier delivering an item of complex correction control information (PoIn); and a correction step (1053) determining the complex correction value dn in order to obtain the corrected symbol X'n according to the complex correction control information (PoIn).