Peak Reduction Tone Selection for OFDM PAPR
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Solution Overview
Problem
Wireless communication systems face challenges in reducing peak-to-average power ratio (PAPR) in OFDM signals, leading to non-linearity in power amplifiers and distortion, especially in 5G NR systems with higher data rates, where existing PAPR reduction techniques are computationally expensive and inefficient.
Innovation Solution
The method involves determining a predetermined sequence of peak reduction tones (PRTs) and fixing their locations in advance, allowing for non-computationally complex optimization of tone phases and magnitudes to minimize PAPR, and using these PRTs to cancel peaks in the time domain representation of data tones, thereby reducing PAPR without degrading error vector management (EVM).
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If clipping and filtering (CF) is used to reduce PAPR, then peak power reduction is achieved, but in-band distortion occurs and the method may not converge to a desirable solution
Solution Approach 1:
The patent segments the frequency domain resources by dividing subcarriers into two distinct sets: data subcarriers and peak reduction tone (PRT) subcarriers. This segmentation allows independent optimization of each set, where data subcarriers carry information and PRT subcarriers are specifically designed to reduce peaks in the time domain signal, thereby reducing PAPR without degrading data integrity or causing in-band distortion.
Solution Approach 2:
The patent introduces peak reduction tones (PRTs) as intermediary elements that mediate between the data signal and the power amplifier non-linearity. These PRTs act as a buffer that can be optimized to cancel peak excursions in the time domain signal, protecting the main data signal from causing power amplifier non-linearity while maintaining signal quality.
2Power
If data-dependent PAPR reduction techniques are used, then PAPR reduction effectiveness is improved, but computational complexity increases making them undesirable for real-time implementation
Solution Approach 1:
The patent applies preliminary action by pre-determining the phases and magnitudes of peak reduction tones (PRTs) based on the data subcarriers before inverse fast Fourier transform (IFFT) processing. This pre-optimization eliminates the need for complex iterative algorithms during real-time transmission, as the PRT parameters are calculated in advance and can be stored in lookup tables, significantly reducing computational complexity for real-time implementation while maintaining PAPR reduction effectiveness.
3Reliability
If power amplifier is operated at mean input power level several dB lower than saturation point, then non-linearity is avoided, but power efficiency decreases due to input back off
Solution Approach 1:
The patent applies preliminary anti-action by pre-canceling peak excursions in the frequency domain through optimized peak reduction tones (PRTs) before the signal reaches the power amplifier. By removing peak components that would cause non-linearity in advance, the power amplifier can operate closer to its saturation point without entering the non-linear region, thereby improving power efficiency while maintaining signal fidelity and avoiding non-linearity.
Data Source
AI summary
Aspects of the disclosure relate to selection and use of peak reduction tones (PRTs) including obtaining a predetermined sequence of PRTs corresponding to a set of granted resources including a plurality of tones, mapping a set of data to a first subset of the plurality of tones outside of the predetermined sequence of PRTs and mapping a set of PRTs to a second subset of the plurality of tones within the predetermined sequence of PRTs. At least one peak of a time domain representation of the first subset of the plurality of tones is canceled using a time domain representation of the second subset of the plurality of tones. A transmitted waveform comprising the first subset of the plurality of tones and the second subset of the plurality of tones is transmitted.