OFDM Communication Apparatus Reducing PAPR via Frequency Domain Phase Rotation
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Solution Overview
Problem
In OFDM communication, the increase in the number of subcarriers leads to a higher Peak-to-Average Power Ratio (PAPR), requiring more linear amplifiers to prevent signal distortion, which complicates the process of reducing PAPR.
Innovation Solution
A communication apparatus and method that uses a modulator to assign input signals to orthogonal subcarriers, performs inverse Fast Fourier Transformation, shifts data using a predetermined sequence with high autocorrelation properties, and repeats processes to generate baseband signals with reduced PAPR, simplifying the suppression of PAPR increases without needing phase control for each subcarrier.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the number of subcarriers is increased to increase the FFT size, then the data transmission capacity is improved, but the PAPR increases requiring more linear amplifiers
Solution Approach 1:
The patent applies preliminary action by performing PAPR reduction processing before the IFFT operation. The phase rotation is applied to the frequency domain data prior to transformation, allowing the system to prepare for and prevent high peak occurrences before they manifest in the time domain signal, thus reducing the amplifier linearity requirement while maintaining high data transmission capacity
Solution Approach 2:
The patent changes parameters by applying phase rotation to subcarriers based on calculated optimal phase values. This parameter modification in the frequency domain transforms the signal characteristics to reduce peak amplitude in the time domain, effectively lowering PAPR while preserving the increased data capacity provided by more subcarriers
2Object-generated harmful factors
If sequential decision procedure is used to calculate optimal phase for each subcarrier, then PAPR reduction is achieved, but the processing complexity increases
Solution Approach 1:
The patent segments the PAPR reduction process into distinct functional blocks: an optimal phase calculation unit that computes phase rotation values for each subcarrier, and a phase rotation application unit that implements the rotation. This segmentation allows for modular implementation and optimization of each stage independently, reducing overall processing complexity while maintaining effective PAPR reduction
Solution Approach 2:
The patent replaces the traditional mechanical iterative adjustment approach with a computational system that calculates optimal phase values using decision procedures. This substitution of mechanical tuning with algorithmic calculation enables more efficient and automated phase control, reducing processing complexity while achieving the same PAPR reduction effect
Data Source
AI summary
A modulator generates a modulation signal from an input signal by, and a serial-parallel converter generates a subcarrier modulation signal from the modulation signal. A shifter shifts a predetermined data series to generate a shift sequence. Two IFFT units perform an IFFT on data sent thereto to generate first data and second data. An operator generates baseband signals from at least one of the sum of the first data and the second data and the difference therebetween. The foregoing processing is repeated with a predetermined number of times to shift the predetermined data series being changed. A PAPR determiner sends the baseband signal matching with a predetermined reference for determining a transmission signal to a transmitter. The transmitter generates a transmission signal from the baseband signal, and transmits the transmission signal to another communication apparatus via an antenna.