DAFT-Spread AFDM Signal Waveform for Low PAPR Wireless Transmission
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Solution Overview
Problem
Conventional wireless communication systems face challenges in achieving high signal-to-quantization-noise ratio (SQNR) due to non-linear distortions caused by power amplifiers and large peak-to-average power ratio (PAPR) in signals, especially in high-mobility scenarios with significant Doppler frequency shifts, leading to degraded performance in data detection.
Innovation Solution
The implementation of discrete affine Fourier transform (DAFT)-spread-affine frequency division multiplexing (AFDM) signals, which utilize a precoder and inverse DAFT to generate chirped Dirichlet pulse-shaped single-carrier signals with reduced PAPR, enabling robust data detection and channel estimation even in doubly dispersive channels with high carrier frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If OFDM waveforms are used to handle Doppler frequency shifts, then data detection capability is improved, but PAPR performance degrades
Solution Approach 1:
The patent applies parameter changes by transitioning from conventional OFDM waveforms to AFDM waveforms with modified time-frequency localization parameters. This change in waveform parameters maintains orthogonality under Doppler shifts while reducing peak power occurrences, thereby improving PAPR performance without sacrificing data detection capability in high-mobility scenarios
2Reliability
If OFDM waveforms are tuned to conserve orthogonality in presence of Doppler frequency shifts, then reliability is improved, but spectral efficiency is reduced
Solution Approach 1:
The patent employs dynamics by designing AFDM waveforms with time-varying frequency characteristics that adapt to Doppler shifts. The chirp modulation introduces dynamic frequency progression within each symbol, allowing the waveform to maintain orthogonality under mobility conditions without requiring conservative tuning that would reduce spectral efficiency
3Power
If power amplifiers operate at high carrier frequencies, then transmission capability is improved, but non-linear distortions increase
Solution Approach 1:
The patent converts the harmful effect of high PAPR into a benefit by using AFDM waveforms that inherently exhibit lower peak power characteristics. This waveform design transforms what would be a problematic high-power scenario into a more manageable transmission condition, reducing non-linear distortions while maintaining transmission capability at high carrier frequencies
Data Source
AI summary
A wireless transmitting device to transmit a signal on a wireless communication channel. The wireless transmitting device obtains a set of Mu input symbols from a user u and apply a precoder to generate a set of precoded input symbols. The precoder includes an Mu-point discrete affine Fourier transform (DAFT) based on a bivariate polynomial that includes a first quadratic term of the time index and a second quadratic term of the input symbol index associated with a same coefficient based on a system parameter. The wireless transmitting device further apply an N-point inverse discrete affine Fourier transform (IDAFT) to a vector formed by placing the Mu precoded input symbols on Mu consecutive entries of an N-long vector with the entries ranges assigned to different users being non-overlapping. Finally, the wireless transmitting device is configured to transmit the signal on the wireless communication channel with low PAPR performance.