Selective Peak Reduction for Mixed-Modulation PAPR Control
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Solution Overview
Problem
Existing techniques are ineffective in reducing peak power ratio (PAPR) for combined signals from different modulation schemes, such as OFDM and TDMA or CDMA, as they require different PAPR techniques and can result in undesirable PAPR when signals are combined.
Innovation Solution
A selective peak power reduction technique that applies peak reduction distortion only to specific frequency bands of a combined signal, where the distortion can be tolerated, minimizing impact on other signals, thereby reducing peak power without affecting signals intolerant to distortion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If PAPR reduction techniques are applied to combined signals from different modulation schemes, then peak power is reduced, but signal distortion increases for intolerant modulation types
Solution Approach 1:
The combined signal is segmented into different frequency bands corresponding to different modulation schemes. The signal processor identifies which frequency bands contain which modulation types and applies PAPR reduction selectively only to bands that can tolerate distortion (like OFDM), while leaving bands with distortion-intolerant modulations (like TDMA or CDMA) unchanged. This segmentation approach resolves the contradiction by reducing peak power overall while preserving signal integrity for sensitive modulation types.
Solution Approach 2:
Different quality levels of PAPR reduction are applied to different parts of the signal. Specifically, aggressive peak reduction is applied locally to frequency bands containing only distortion-tolerant modulations, while minimal or no reduction is applied to bands containing distortion-intolerant modulations. This local differentiation allows the system to achieve peak power reduction where safe while maintaining signal integrity where required.
2Power
If different PAPR techniques are applied to different modulation schemes, then each signal's PAPR is reduced, but the combined signal's PAPR increases
Solution Approach 1:
The patent merges the PAPR reduction process into a single unified signal processing operation that handles multiple modulation schemes simultaneously. Instead of processing each modulation type separately and then combining them (which increases PAPR), the system processes the combined signal in one pass, using frequency band identification to selectively apply reduction techniques. This merging approach reduces overall PAPR while managing complexity through efficient frequency-domain processing.
Solution Approach 2:
The signal processor is designed with multi-functionality to handle multiple modulation schemes (OFDM, TDMA, CDMA) within a single processing architecture. It can identify different modulation types in different frequency bands and apply appropriate PAPR reduction strategies to each, making the system universal rather than requiring separate processing chains for each modulation type. This universality reduces both PAPR and overall system complexity.
3Power
If peak reduction distortion is applied to the entire combined signal, then peak power is reduced, but performance of distortion-intolerant signals deteriorates
Solution Approach 1:
The combined signal is divided into frequency band segments, each corresponding to a specific modulation scheme. The signal processor identifies which segments contain distortion-intolerant modulations (TDMA, CDMA) and which contain distortion-tolerant modulations (OFDM). Peak reduction distortion is then applied selectively only to the tolerant segments, while leaving the intolerant segments unchanged. This segmentation resolves the contradiction by achieving peak power reduction without degrading the performance of sensitive signals.
Solution Approach 2:
Different levels of peak reduction distortion are applied to different frequency band segments based on their modulation type. Frequency bands containing OFDM signals receive aggressive peak reduction, while bands containing TDMA or CDMA signals receive minimal or no reduction. This local differentiation in distortion application allows the system to reduce overall peak power while maintaining excellent performance for distortion-intolerant modulation types.
Data Source
AI summary
The present invention provides a technique for reducing the peak power of a combined signal that has a first signal of a first modulation type and a second signal of a second modulation type. Based on the combined signal, peak reduction distortion is determined. The peak reduction distortion is configured such that, if applied to the entirety of the combined signal, excessive peaks throughout the combined signal would be reduced. However, instead of applying the entirety of the peak reduction distortion, a selected portion of the peak reduction distortion is applied to a corresponding portion of the combined signal to reduce the peak power of the combined signal.