Selective Peak Reduction in Mixed-Modulation RF Signal Bands
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Solution Overview
Problem
Existing communication systems face inefficiencies in peak power reduction when combining signals from different modulation schemes, such as OFDM and TDMA or CDMA, as existing techniques are ineffective in managing the increased peak-to-average power ratio (PAPR) of combined signals.
Innovation Solution
A method is introduced to generate peak reduction distortion based on a combined input signal from different modulation types, selectively applying it to specific frequency bands where it can be tolerated, thereby reducing peak power without impacting other signals significantly.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If PAPR reduction techniques are applied to combined signals from different modulation schemes, then amplifier efficiency is improved, but the effectiveness of existing PAPR reduction techniques deteriorates due to the complex PAPR characteristics of combined signals
Solution Approach 1:
The patent segments the combined signal into multiple frequency bands, where each band contains signals from specific modulation schemes. This segmentation allows different PAPR reduction techniques to be applied to different bands according to their specific characteristics, resolving the contradiction by making the reduction process adaptive to the complex combined signal structure.
Solution Approach 2:
The patent applies different PAPR reduction techniques to different frequency bands based on the local characteristics of signals in each band. For example, OFDM bands may use one technique while CDMA bands use another, optimizing the effectiveness for each local signal type while maintaining overall system efficiency.
2Loss of energy
If different PAPR reduction techniques are applied to different modulation schemes, then the PAPR of each individual signal is reduced, but the combined PAPR increases due to signal interaction
Solution Approach 1:
The patent segments the combined signal into frequency bands and processes each band separately to reduce individual PAPR contributions before combination, preventing the interactive PAPR increase that occurs when techniques are applied after combining.
Solution Approach 2:
The patent applies PAPR reduction techniques preliminarily to individual signals or frequency bands before they are combined, rather than after combination. This preliminary action prevents the constructive interference of peaks from different modulation schemes that would otherwise increase the combined PAPR.
3Power
If peak reduction distortion is applied to the entire combined signal, then overall peak power is reduced, but signals in frequency bands that cannot tolerate distortion are degraded
Solution Approach 1:
The patent segments the frequency spectrum into bands with different distortion tolerances and applies peak reduction distortion only to bands that can tolerate it. This selective application maintains signal quality in sensitive bands while achieving peak power reduction in robust bands.
Solution Approach 2:
The patent applies different levels of peak reduction distortion to different frequency bands based on their local characteristics and tolerance levels. Frequency bands containing robust signals receive aggressive distortion-based peak reduction, while bands with sensitive signals receive minimal or no distortion application.
Data Source
AI summary
A communication system comprising signal processing circuitry and up-conversion circuitry. The signal processing circuitry is configured to: i) generate a first signal of a first modulation type and a second signal of a second modulation type; ii) combine the first and second signals to form a combined input signal; iii) generate peak reduction distortion based on the combined input signal; iv) select a portion of the peak reduction distortion that corresponds to a first frequency band; and v) apply the selected portion of the peak reduction distortion in the first frequency band of the combined input signal to provide a combined output signal. The up-conversion circuitry up-converts the combined output signal to an RF signal for transmission.