OFDM Baseband Signal Processing for PAPR Reduction
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Solution Overview
Problem
OFDM communication systems face challenges in reducing Peak-to-Average Power Ratio (PAPR) and controlling the degree of reduction, particularly due to the increase in the number of subcarriers which leads to high PAPR and requires amplifiers with wide linearity to prevent distortion.
Innovation Solution
A communication apparatus and method that modulates input signals using a predetermined scheme, assigns them to orthogonal subcarriers, performs inverse Fast Fourier Transformation, decomposes the results into real and imaginary parts, applies specific calculations using threshold values to reduce differences between elements and threshold values, and synthesizes these parts to generate a baseband signal for transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of subcarriers is increased to increase the FFT size, then the communication capacity is improved, but the PAPR increases requiring amplifiers with wide linearity
Solution Approach 1:
The patent applies parameter changes by modifying the amplitude coefficients of subcarriers based on their correlation values. By dynamically adjusting these parameters (amplitude coefficients) according to the calculated correlations between subcarriers, the system reduces PAPR while maintaining the increased FFT size and communication capacity. This resolves the contradiction by changing the signal parameters rather than reducing the number of subcarriers.
2Object-generated harmful factors
If sequential decision procedure is used to control phase of subcarrier modulation signal, then PAPR reduction is achieved, but the complexity of repeated calculation increases
Solution Approach 1:
The patent extracts the essential information needed for PAPR reduction by calculating correlation values between subcarriers, rather than performing repeated sequential decision procedures for phase control. This extraction approach simplifies the calculation by focusing only on the correlation metrics needed, eliminating the complexity of iterative phase optimization while achieving PAPR reduction through amplitude coefficient adjustment based on these extracted correlation values.
3Object-generated harmful factors
If conventional PAPR reduction techniques are applied, then peak power is reduced, but the degree of reduction cannot be controlled
Solution Approach 1:
The patent implements dynamics by making the amplitude coefficients adjustable and controllable based on correlation values. The system dynamically adjusts the degree of PAPR reduction by modifying amplitude coefficients according to the calculated correlations, allowing flexible control over the reduction degree. This enables the system to adapt the PAPR reduction level to different operational requirements, providing versatility that conventional fixed techniques lack.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
Effectively reduces PAPR in OFDM communication systems and allows for controlled reduction, improving signal transmission by minimizing peak power while maintaining average power, thus enhancing the efficiency of the communication process.
Implementation Method 1
a transformer that performs an inverse fast Fourier transformation on the subcarrier modulation signal
Data Source
AI summary
A modulator generates a modulation signal from an input signal, and a serial-parallel converter generates a subcarrier modulation signal from the modulation signal. An IFFT unit performs an inverse fast Fourier transformation on the subcarrier modulation signal, and a decomposer decomposes a calculation result into a real part data and an imaginary part data. A calculator applies a predetermined calculation with respect to each element the value of which is equal to or greater than a positive threshold value and each element the value of which is equal to or less than a negative threshold value among the real part data and the imaginary part data. A synthesizer synthesizes the real part data and the imaginary part data to generate a baseband signal, and a transmitter generates a transmission signal from the baseband signal, and transmits it to another apparatus via an antenna.