Waveform Generation With DFT Precoding and Zero Padding
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Solution Overview
Problem
Orthogonal Frequency Division Multiplexing (OFDM) waveforms have high peak-to-average-power-ratio (PAPR), leading to power inefficiency and the need for high power amplifier back-off, which is not effectively addressed by existing methods like DFT precoded OFDM.
Innovation Solution
A method and transmitter system that perform constellation rotation, convolution, and pulse shaping using discrete Fourier transforms to generate a waveform with optimized PAPR, involving prefixing and post-fixing data with zeros, circular or linear convolution, and frequency domain filtering to reduce PAPR.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If OFDM waveform is used for modulation, then data transmission capability is improved, but PAPR increases leading to power inefficiency
Solution Approach 1:
The patent segments the OFDM signal processing into distinct stages: DFT precoding divides the time-domain signal into frequency components, followed by IFFT that segments these into parallel subcarriers. This segmentation allows independent processing of signal components to reduce peak power while maintaining data transmission capability.
Solution Approach 2:
The patent transforms the signal from time domain to frequency domain through DFT precoding, then back to time domain via IFFT. This dimensionality change between time and frequency domains enables PAPR reduction by distributing signal energy across multiple frequency components rather than concentrating it in time domain peaks.
2Use of energy by moving object
If high power amplifier back-off is applied to reduce PAPR, then PAPR is reduced, but transmission power decreases
Solution Approach 1:
The patent applies preliminary PAPR reduction through DFT precoding and frequency domain filtering before the signal reaches the power amplifier. By pre-processing the signal to eliminate peaks in advance, the system avoids the need for aggressive power amplifier back-off, thereby maintaining high transmission power while achieving low PAPR.
3Use of energy by moving object
If DFT precoded OFDM is used, then PAPR is reduced, but signal discontinuities and side lobes increase
Solution Approach 1:
The patent changes the filtering parameters by applying frequency domain filtering with optimized window functions and filter coefficients. This parameter optimization smooths the spectral transitions, reducing side lobes and signal discontinuities while preserving the PAPR reduction benefits of DFT precoding.
4Device complexity
If conventional OFDM processing is used, then implementation is simple, but PAPR optimization is insufficient
Solution Approach 1:
The patent implements a universal processing framework where the same DFT-IFFT structure serves multiple functions: it enables PAPR reduction, facilitates frequency domain filtering, and maintains compatibility with standard OFDM operations. This multi-functionality achieves PAPR optimization without significantly increasing implementation complexity.
Data Source
AI summary
Embodiments of the present disclosure disclose method and transmitter to generate and transmit a waveform with an optimized peak to average power (PAPR) in a communication network. The method comprises performing a constellation rotation on input data symbols to create a rotated data symbols, wherein the input data symbols is obtained by performing at least one of prefixing a modulation data with first predefined number (N1) of zero's and post-fixing the modulation data with second predefined number (N2) of zero's. Also, the method comprises performing convolution operation on the input data symbols using one or more filter coefficients to produce a symbol level filtered data. Further, the method comprises pulse shaping the symbol level filtered data to generate a pulse shaped data sequence and processing the pulse shaped data sequence to generate a waveform.