OFDM Communication Device PAPR Reduction via Matrix Shifting
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Solution Overview
Problem
In OFDM communication, high Peak-to-Average Power Ratio (PAPR) due to increased FFT size leads to signal distortion, requiring efficient methods to reduce PAPR while controlling the degree of reduction.
Innovation Solution
A communication device and method that modulates input signals, generates subcarrier modulation signals, and arranges them in a compound matrix, shifts matrix rows, performs IFFT, detects peak-to-average power ratios, and repeats processing to find optimal shifts, resulting in reduced PAPR and controlled PAPR reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the number of subcarriers is increased to improve communication capacity, then the FFT size increases, but the PAPR becomes high causing signal distortion
Solution Approach 1:
The patent applies preliminary action by performing phase rotation on subcarrier modulation signals before IFFT transformation. The phase rotation is calculated in advance based on the relationship between subcarrier indices and column indices, and applied to modify the phase of each subcarrier signal before the main signal processing. This preliminary phase adjustment prevents high PAPR from occurring during the IFFT process, thereby avoiding signal distortion while maintaining high communication capacity through increased subcarrier numbers.
2Object-affected harmful factors
If sequential decision procedure is used to control phase for PAPR reduction, then PAPR is reduced, but repeated calculation processing is required finding optimal phase
Solution Approach 1:
The patent applies parameter changes by transforming the phase control approach from sequential decision-making to a direct parameter-based calculation. Instead of repeatedly searching for optimal phases through sequential decisions, the invention uses a closed-form mathematical relationship between subcarrier indices and column indices to directly calculate the required phase rotation. This changes the problem from an iterative optimization task to a direct parameter computation, significantly reducing calculation time while achieving effective PAPR reduction.
3Object-affected harmful factors
If phase control is performed for each subcarrier to reduce PAPR, then PAPR is reduced, but device complexity increases
Solution Approach 1:
The patent applies universality by creating a unified phase rotation mechanism that handles all subcarriers through a single mathematical framework. The phase rotation amount is determined by a universal formula that relates subcarrier indices to column indices, allowing the same processing logic to be applied across all subcarriers simultaneously. This multi-functional approach replaces the need for separate phase control operations for each subcarrier, reducing device complexity while maintaining effective PAPR reduction across the entire signal spectrum.
Data Source
AI summary
A modulator generates modulation signals from input signals. A combiner arranges subcarrier modulation signals based on the modulation signals in order thereby to generate a compound matrix. The shifter shifts elements of each row of the compound matrix to generate shift matrix. An IFFT calculator subjects the shift matrix to inverse fast Fourier transformation to generate inverse transformation matrix. A maximum detector detects a column with a highest peak-to-average power ratio among columns of the inverse transformation matrix. A minimum detector detects an inverse transformation matrix including a column with a lowest peak-to-average power ratio among columns of inverse transformation matrices detected by the maximum detector. A transmitter generates a transmission signal based on baseband signals generated from each column of the inverse transformation matrix detected by the minimum detector, and transmits the transmission signal.