Combined OFDM Signal PAPR Reduction via Cyclic Time Shifts
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Solution Overview
Problem
The peak-to-average power ratio (PAPR) of combined OFDM signals increases when multiple channels are combined, leading to higher peak power requirements for radio-frequency power amplifiers, which can result in inefficiency and increased costs, and existing methods to reduce PAPR often require side-information or degrade system performance.
Innovation Solution
The method involves storing time-domain OFDM signals in a memory buffer and applying cyclic time shifts to select the optimal time-shift for reducing the PAPR of the combined multi-channel signal, without the need for side-information transmission, by analyzing and adjusting the signal parameters to achieve a lower PAPR without degrading system performance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multiple OFDM channels are combined for transmission, then the total data rate and spectral efficiency are improved, but the peak-to-average power ratio (PAPR) of the combined signal increases
Solution Approach 1:
The patent applies cyclic time shifts to the combined OFDM signal, which is a parameter transformation in the time domain. By adjusting the time shift parameter, the signal's peak characteristics are modified to reduce PAPR while preserving the combined multi-channel data rate capability
Solution Approach 2:
The patent introduces dynamic signal processing by applying time-varying cyclic shifts to the combined OFDM signal. This dynamic adjustment allows the system to adaptively control peak power characteristics in real-time, reducing PAPR while maintaining high data rate transmission through multiple combined channels
2Loss of energy
If PAPR reduction methods are applied to combined OFDM signals, then the power amplifier efficiency is improved, but system performance may be degraded
Solution Approach 1:
The patent converts the harmful high PAPR characteristic into a benefit by using cyclic time shifts to reshape the signal's peak structure. This transformation reduces PAPR to improve power amplifier efficiency while the method is specifically designed to preserve system performance through careful signal processing that maintains signal integrity
3Power
If conventional PAPR reduction methods are used, then the peak power is reduced, but side-information transmission or performance degradation is required
Solution Approach 1:
The patent implements a self-service PAPR reduction mechanism where the combined OFDM signal undergoes cyclic time shifts that are inherently embedded in the signal structure. This self-contained approach reduces peak power without requiring external side-information transmission or additional control channels, simplifying the overall system complexity
Data Source
AI summary
A method for controlling a combined waveform, representing a combination of at least two signals having orthogonal frequency multiplexed signal components, comprising: receiving information defining the at least two signals; transforming the information defining each signal to a representation having orthogonal frequency multiplexed signal components, such that at least one signal has at least two alternate representations of the same information, and combining the transformed information using the at least two alternate representations, in at least two different ways, to define respectively different combinations; analyzing the respectively different combinations with respect to at least one criterion; and outputting a respective combined waveform or information defining the waveform, representing a selected combination of the transformed information from each of the at least two signals selected based on the analysis.