OFDM PAPR Reduction via Iterative Frequency Domain Clipping
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Solution Overview
Problem
Existing methods for reducing peak-to-average power ratio (PAPR) in OFDM signals, such as soft clipping, often degrade other important system parameters like error vector magnitude (EVM) and spectral mask, limiting the achievable PAPR reduction.
Innovation Solution
A system and method that processes OFDM signals through iterative transformations between time and frequency domains, clipping absolute values and guard bins to set PAPR thresholds while maintaining EVM and spectral mask within desired limits, followed by additional iterations to achieve target PAPR reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If soft clipping is used to reduce PAPR, then PAPR is reduced, but EVM and spectral mask are degraded
Solution Approach 1:
The patent segments the frequency domain signal into data bins and guard bins, applying different processing to each segment. The guard bins are clipped to reduce PAPR while the data bins are preserved to maintain signal quality metrics like EVM and spectral mask.
Solution Approach 2:
The patent applies local quality by treating different portions of the frequency spectrum differently. The guard bins (which contribute to PAPR) are clipped, while the data bins (which carry information and affect EVM) are protected. This localized processing allows PAPR reduction without degrading overall signal quality.
2Loss of energy
If aggressive PAPR reduction is applied, then PAPR decreases, but signal quality parameters deteriorate
Solution Approach 1:
The patent employs an iterative feedback process where the signal is processed through multiple cycles of clipping and transformation. In each iteration, the PAPR is reduced while monitoring signal quality parameters. The process continues until both PAPR and signal quality requirements are satisfied, ensuring reliable operation.
Solution Approach 2:
The patent performs preliminary clipping of the guard bins before the final signal generation. By pre-reducing the peak values in the frequency domain and then transforming to time domain, the system achieves PAPR reduction without requiring aggressive post-processing that would degrade signal quality.
3Loss of energy
If conventional soft clipping is used, then PAPR reduction is achieved, but the amount of reduction is limited
Solution Approach 1:
The patent moves the clipping operation from the time domain to the frequency domain by transforming the signal using DFT/IDFT. This dimensional change allows clipping to be applied to individual frequency bins independently, enabling much more aggressive PAPR reduction without affecting the time-domain signal envelope and associated quality metrics.
Data Source
AI summary
A method includes processing an input sequence of samples of an orthogonal frequency division multiplexing signal (OFDM) to reduce a peak to average power ratio (PAPR) of the OFDM signal with given constraints of an error vector magnitude (EVM) parameter and a spectral mask parameter for the OFDM signal during a first processing iteration. The method includes performing at least one other iteration of the first processing iteration on a subsequent time domain sequence generated in the first processing iteration to reduce the PAPR of the OFDM signal below a system target PAPR threshold and below threshold limits for the EVM parameter and the spectral mask parameter.