P-waveform Peak Cancellation for OFDM PAPR Reduction
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Solution Overview
Problem
OFDM communication systems face high Peak-to-Average Power Ratio (PAPR) issues due to multi-carrier modulation, leading to signal distortion, increased power consumption, and reduced amplifier efficiency, which existing methods like clipping, block-coding, and phase adjustment schemes struggle to effectively address.
Innovation Solution
A tone reservation scheme using a multi-gradient algorithm that assigns reserved tones to reduce PAPR by detecting and clipping peaks in the IFFT signal, employing a P-waveform generated from reserved tones to accumulate and remove peaks, thereby reducing the PAPR below a target level.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If conventional PAPR reduction methods (clipping, block-coding, phase adjustment) are used, then some PAPR reduction is achieved, but signal distortion increases and amplifier efficiency remains reduced
Solution Approach 1:
The patent applies preliminary action by pre-generating P-waveforms with impulse characteristics before the IFFT operation. These pre-computed waveforms are then used to cancel peaks in the time-domain signal, allowing the amplifier to operate in its linear region and maintain high efficiency without introducing signal distortion through post-clipping methods
2Loss of energy
If gradient algorithm is used to reduce PAPR, then peaks are reduced, but computational complexity and processing time increase
Solution Approach 1:
The patent reduces computational complexity by performing the gradient algorithm-based P-waveform generation in advance, before the actual data transmission. The pre-computed P-waveforms are stored and directly applied during transmission, eliminating the need for real-time iterative peak detection and reduction operations
Solution Approach 2:
The patent introduces P-waveforms as an intermediary element that mediates between the reserved tones and the peak reduction objective. These P-waveforms serve as pre-computed cancellation signals that simplify the real-time processing by replacing complex iterative algorithms with direct signal addition
3Loss of energy
If multiple peaks are addressed sequentially, then each peak is reduced, but processing time increases
Solution Approach 1:
The patent merges multiple peak reduction operations into a single unified process by accumulating multiple P-waveforms into one composite cancellation signal. This accumulated waveform simultaneously addresses multiple peaks in the time-domain signal, reducing processing time while maintaining effective peak reduction
Data Source
AI summary
Provided is a method for reducing a PAPR (Peak-to-Average Power Ratio) of a transmit signal in a broadband wireless communication. The method includes the steps of: assigning information signals to remaining tones except L reserved tones that are previously appointed among N tones, and performing an IFFT operation on the tones; detecting peaks that are greater than a predefined reference value from the IFFT-ed signal; generating signals for removing the detected peaks using P-waveform having impulse characteristic, the P-waveform being produced using the L reserved tones; generating a clipping signal by accumulating the signals; and simultaneously removing the peaks by adding the IFFT-ed signal and the clipping signal.