Communication Device OFDM Trajectory Rotation PAPR Reduction
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Solution Overview
Problem
Radio communication transmitters operate at higher power levels than their average power, leading to reduced efficiency and the need for low-noise systems, with peak-to-average power ratio (PAPR) being a significant challenge, especially in digital I/Q transmitters where the PAPR penalty is high due to inefficient use of signal trajectories in the complex plane.
Innovation Solution
A method involving rotation of OFDM symbol trajectories in the complex plane to reduce the peak-to-average power ratio by aligning the maximum points with the diagonal directions, thereby reducing the required dynamic range and power consumption, while maintaining the same transmitted energy and correcting for phase shifts at the receiver.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the transmitter operates at higher power levels to maintain signal quality, then the transmitted power is sufficient, but the transmitter efficiency decreases and noise performance deteriorates
Solution Approach 1:
The patent applies preliminary action by rotating the OFDM symbol trajectory in the complex plane before transmission. This rotation aligns the maximum amplitude points with the diagonal directions, pre-adjusting the signal to reduce peak power requirements while maintaining transmission quality
Solution Approach 2:
The patent changes the parameter of signal trajectory orientation in the complex plane. By rotating the trajectory by 45 degrees to align maximum points with diagonal directions, the peak-to-average power ratio is reduced, improving transmitter efficiency without sacrificing signal quality
2Power
If the transmitter operates at higher power levels, then the signal strength is maintained, but the peak-to-average power ratio increases
Solution Approach 1:
The trajectory rotation is performed in advance before transmission, pre-aligning the signal points to reduce peak power excursions while maintaining average signal strength
Solution Approach 2:
The patent changes the orientation parameter of the signal trajectory in the complex plane, rotating it to align maximum amplitude points with diagonal directions, thereby reducing the peak-to-average power ratio while preserving signal strength
3Power
If the dynamic range of the DAC is increased to handle peak power, then the peak power can be transmitted, but the complexity and cost of the transmitter increases
Solution Approach 1:
By rotating the trajectory beforehand, the peak power requirements are reduced, allowing the use of a DAC with smaller dynamic range, thus simplifying the transmitter architecture and reducing cost
Solution Approach 2:
The trajectory rotation changes the distribution of signal amplitudes, reducing the peak-to-average power ratio and thereby reducing the required DAC dynamic range, which simplifies the transmitter design
Data Source
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AI summary
A communication device is described comprising a modulator configured to map send data to a set of quadrature amplitude modulation symbols, a determiner configured to determine a rotation of the set of quadrature amplitude modulation symbols based on a difference between an absolute value of the real component and an absolute value of an imaginary component of the quadrature amplitude modulation symbol of the set of quadrature amplitude modulation symbols having a maximum absolute value being reduced by the rotation, a symbol processor configured to apply the rotation to each quadrature amplitude modulation symbol of the set of quadrature amplitude modulation symbols and a transmission circuit configured to transmit the set of rotated quadrature amplitude modulation symbols via a radio communication channel.