Constrained Peak Cancellation for OFDM PAPR Reduction
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Solution Overview
Problem
Orthogonal Frequency Division Multiplexing (OFDM) transmission schemes face inefficiencies due to high peak-to-average power ratio (PAPR), requiring linear amplifiers and struggling with peak cancellation, especially at high clipping rates where subcarriers are out-of-band and clipping noise power is at data-carrying frequencies.
Innovation Solution
A method for constrained peak cancellation in OFDM symbols, which identifies sets of clipping noise samples, determines cancellation pulses based on the center-of-mass, phase, and in-band energy constraints, and subtracts these pulses from the OFDM symbol to reduce PAPR, utilizing a bank of pulses with different spectral characteristics cyclically shifted to the clipping noise locations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If conventional peak cancellation methods are used in OFDM, then PAPR reduction is achieved, but in-band energy distortion increases and error rates worsen
Solution Approach 1:
The patent changes the parameters of cancellation pulses by optimizing their amplitude, phase, and time-location characteristics. It introduces constrained optimization that adjusts pulse parameters to reduce PAPR while maintaining in-band energy integrity, thereby reducing error rates compared to conventional methods
Solution Approach 2:
The patent implements feedback mechanisms by calculating the actual PAPR reduction effect and in-band energy distortion after applying cancellation pulses. This feedback is used to iteratively adjust the cancellation pulse parameters to achieve optimal PAPR reduction while maintaining signal integrity and minimizing error rates
2Reliability
If linear amplifiers are used to handle high PAPR, then signal fidelity is maintained, but power efficiency deteriorates
Solution Approach 1:
The patent applies preliminary action by reducing PAPR through cancellation pulses before the signal enters the power amplifier. This pre-processing allows the use of non-linear, high-efficiency amplifiers while maintaining signal fidelity, as the harmful peaks are already suppressed and will not cause amplifier saturation or distortion
3Loss of energy
If clipping rate is increased for higher efficiency, then power efficiency improves, but clipping noise power at data-carrying frequencies increases
Solution Approach 1:
The patent converts the harmful clipping noise into a beneficial signal by treating the clipping noise peaks as targets for cancellation. The cancellation pulses are specifically designed to target and suppress these noise peaks at data-carrying frequencies, thereby converting the harmful clipping effect into an opportunity for selective noise reduction while maintaining high power efficiency
Data Source
AI summary
Embodiments include a method, computer program product, and system for utilizing a system for peak cancellation for a received Orthogonal Frequency Division Multiplexing (OFDM) symbol to reduce the peak-to-average power ratio (PAPR). The system detects M sets of clipping noise samples of the symbol where each set includes one of the M highest clipping noise peaks of the symbol, determines cancellation pulses that correspond to the highest clipping noise peaks of the M sets in the time domain, and subtracts the cancellation pulses from the corresponding highest clipping noise peak samples to reduce the PAPR. The cancellation pulses are determined at least in part from the center-of-mass of each set of the clipping noise samples, the phase of some samples of each set, and the in-band energy limitation associated with the OFDM symbol.