Multi-Carrier Transmitter Peak Compensation for OFDM PAPR Reduction
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Solution Overview
Problem
In multi-carrier communication systems, particularly those using Orthogonal Frequency Division Multiplexing (OFDM), the non-linear amplitude and phase transfer functions of power amplifiers cause distortions, leading to increased bit error rates due to high peak-to-average power ratios (PAPR), which existing methods like backing off or linearizing circuitry are inefficient or costly to address.
Innovation Solution
A technique that extracts peak signals from the modulated signal, transforms them into the frequency domain, and processes selected subcarriers to generate a peaks compensation spectrum, which is then combined with the modulated signal to reduce PAPR, either in the time or frequency domain, before amplification and transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If non-constant amplitude signal modulation schemes are used to achieve higher bit rates, then data transmission efficiency is improved, but power amplifier non-linearity distortions increase
Solution Approach 1:
The patent applies preliminary action by extracting peak signals from the modulated signal before power amplification and generating compensation signals in advance. These compensation signals are then combined with the original modulated signal to pre-correct peak distortions, allowing the power amplifier to operate without significant non-linearity effects while maintaining high bit rates from non-constant amplitude modulation schemes.
Solution Approach 2:
The patent extracts the harmful peak components from the modulated signal by identifying and isolating peak signals that exceed a threshold. These extracted peaks are then processed separately to generate compensation signals, effectively removing the source of distortion before the signal enters the non-linear power amplifier.
2Object-generated harmful factors
If backing off is used to reduce peak-to-average power ratio, then power amplifier distortion is reduced, but power conversion efficiency decreases
Solution Approach 1:
Instead of reducing the overall signal power (backing off), the patent extracts only the peak components that cause distortion and processes them separately. This allows the main signal to pass through the power amplifier at full power with high efficiency, while only the problematic peaks are corrected through the compensation mechanism.
Solution Approach 2:
The patent applies local quality by treating only the specific problematic peak portions of the signal differently from the rest of the signal. Rather than uniformly reducing the entire signal power, the compensation mechanism selectively addresses only the peak components that exceed the distortion threshold, leaving the rest of the signal unchanged and maintaining overall power efficiency.
3Object-generated harmful factors
If linearizing circuitry is used to compensate for power amplifier non-linearity, then distortion is reduced, but device complexity and cost increase
Solution Approach 1:
The patent extracts only the peak distortion components from the signal and processes them separately through a simplified compensation mechanism. This selective approach avoids the need for complex linearizing circuitry that would be required to handle the entire signal spectrum, reducing both device complexity and cost while still effectively compensating for power amplifier non-linearity.
Solution Approach 2:
The patent employs a computationally efficient peak extraction and compensation method that can be implemented with relatively simple processing circuits rather than expensive analog linearizing circuitry. The compensation signals are generated through mathematical operations that can be performed with standard digital signal processing components, providing an affordable alternative to complex linearizing hardware.
Data Source
AI summary
A multi-carrier transmitter and transmission technique are described for transmitting payload data during a transmission time interval with reduced peak-to-average power ratio (PAPR). A multi-carrier modulator modulates subcarrier frequencies with payload data and provides a modulated signal for transmission during the transmission time interval. Excessive peaks in the modulated signal are extracted. The extracted peaks signal is transformed into the frequency domain to generate a peaks frequency spectrum which is processed using the frequency spectrum of certain subcarriers selected for reducing PAPR to produce a peak compensation spectrum. In one approach, that spectrum is transformed into the time domain before being modified by the modulated signal in the time domain to reduce PAPR. Alternatively, that peak compensation spectrum is modified using a modulated frequency spectrum provided by the modulator in the frequency domain and the result is then transformed into the time domain to produce a modified modulated signal with reduced PAPR.