OFDM Peak Cancellation via Weighted Gradient Algorithm
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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 that are less efficient.
Innovation Solution
A weighted gradient-based adaptive peak cancellation algorithm is employed to generate a peak cancellation signal, reducing PAPR and error rates by scaling peak reduction tones based on power spectral density and transmission constraints.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If OFDM signals are transmitted with high PAPR, then the transmission bandwidth utilization is improved, but the amplifier efficiency deteriorates due to requirement of linear amplifiers
Solution Approach 1:
The patent extracts and removes the peak amplitude components from the OFDM signal through peak cancellation techniques. By identifying and subtracting peak values from the time-domain signal, the system reduces PAPR while maintaining the overall signal structure and bandwidth utilization characteristics.
Solution Approach 2:
The patent modifies the amplitude parameters of the OFDM signal by applying clipping and peak cancellation operations. The peak values are reduced through parameter transformation, converting high-amplitude peaks into lower-amplitude components, thereby improving amplifier efficiency without fundamentally changing the signal's bandwidth properties.
2Loss of energy
If peak cancellation signals are applied to reduce PAPR, then the amplifier efficiency is improved, but the induced error rates such as PER and BER increase
Solution Approach 1:
The patent employs feedback mechanisms where the peak cancellation signal is generated based on the detected peak values of the OFDM signal. The cancellation amount is adjusted according to the actual peak characteristics, and the process iterates to achieve optimal PAPR reduction while monitoring and controlling error rate performance.
Solution Approach 2:
The patent applies partial peak cancellation rather than complete elimination of peaks. By canceling only a portion of the peak amplitude or selectively canceling certain peaks, the system achieves sufficient PAPR reduction to improve amplifier efficiency while minimizing the distortion introduced to the signal, thereby controlling error rate increase.
3Device complexity
If clipping operation is used to reduce PAPR, then the computational complexity is reduced, but the spectral density properties and error rates deteriorate
Solution Approach 1:
The patent performs preliminary clipping operations on the OFDM signal before peak cancellation. By pre-processing the signal to remove extreme peaks through clipping, the subsequent peak cancellation operates on a signal with already-reduced peak values, simplifying the overall computational process while maintaining better spectral properties than clipping alone.
Data Source
AI summary
Embodiments include a system, method, and computer program product that receives an Orthogonal Frequency Division Multiplexing (OFDM) symbol, and utilizes a weighted gradient-based adaptive peak cancellation convergence algorithm to create a peak cancellation signal to reduce a peak-to-average power ratio (PAPR) as well as induced error rates of the OFDM symbol. Iterations of the weighted gradient-based adaptive peak cancellation convergence algorithm produce a peak cancellation signal that converges to a desired peak cancellation signal that satisfies a targeted PAPR. Some embodiments utilize a priori knowledge of a power spectral density of clipping noise and pre-defined transmission constraints in the frequency domain to create a peak cancellation signal with specific and desired spectral density properties. For example, some peak reduction tones (PRTs) may be scaled to take advantage of available power resources associated with the pre-defined transmission constraints, where the scaling is specific to each PRT.