Adaptive PAPR Reduction for Multi-Carrier Modulation Schemes
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Solution Overview
Problem
Multi-carrier transmission systems face challenges with high peak-to-average power ratio (PAPR) due to the need for large power amplifier back-off, which reduces power efficiency and requires costly amplifiers, and existing PAPR reduction techniques either introduce distortions, reduce data rate, or require complex receiver designs.
Innovation Solution
A method to select and apply PAPR reduction methods based on the modulation scheme used for each set of sub-carriers, utilizing Partial Transmit Sequences (PTS) for higher order modulation and alternative methods like clipping or tone injection for lower order modulation, while maintaining reliable channel estimation and minimizing overhead.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If multi-carrier transmission is used, then data transmission capacity is improved, but peak-to-average power ratio increases
Solution Approach 1:
The transmit signal is divided into N nonoverlapping subvectors, and each subvector is multiplied by a different rotation factor. This segmentation allows independent manipulation of signal segments to reduce peaks while maintaining overall data transmission capacity.
Solution Approach 2:
Rotation factors are applied to subvectors to change the phase parameters of signal segments. By optimizing these rotation factors from a discrete set, the patent reduces peak power while preserving average power and data rate.
2Reliability
If power amplifier back-off is increased to handle high PAPR, then signal linearity is improved, but power efficiency deteriorates
Solution Approach 1:
PAPR reduction is applied at the transmitter before power amplification. By preprocessing the signal to reduce peaks in advance, the power amplifier can operate closer to its maximum power without suffering from non-linear distortion, thereby improving power efficiency while maintaining signal linearity.
3Power
If clipping is used to reduce PAPR, then peak power is reduced, but in-band and out-of-band distortions are introduced
Solution Approach 1:
Rotation factors serve as intermediaries that modify the phase of signal subvectors to reduce peaks without directly clipping or distorting the signal. This intermediary approach achieves PAPR reduction while avoiding the harmful distortions associated with direct clipping methods.
4Power
If adaptive constellation extension or tone injection is used, then PAPR is reduced, but receiver complexity increases
Solution Approach 1:
The PAPR reduction function is extracted and implemented entirely at the transmitter through rotation factor application. This removes the need for complex receiver processing, as the signal modifications are predetermined and do not require sophisticated detection or compensation at the receiver end.
5Power
If tone reservation or partial transmit sequences are used, then PAPR is reduced, but data rate decreases
Solution Approach 1:
The rotation factors are dynamically optimized for each transmit signal configuration, allowing maximum PAPR reduction without permanently reserving tones or reducing the number of active subcarriers. This dynamic adaptation maintains data transmission capacity while achieving effective PAPR control.
Data Source
Figure 1
AI summary
A disclosed method of reducing peak to average power ratio (PAPR) includes selecting a PAPR reduction method dependent on a modulation scheme used for a set of sub-carriers. One type of modulation scheme is more suitable for at least one possible PAPR reduction method while another modulation scheme is more suitable for a different PAPR reduction method. Disclosed examples apply a different PAPR reduction technique to accommodate differing features of different modulation schemes.