Receiver Equalization for Nonlinear Amplifier Signal Demodulation
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Solution Overview
Problem
Existing wireless communication systems struggle to accurately demodulate signals when transmission devices use non-linear amplification regions, leading to signal distortion and demodulation errors.
Innovation Solution
A reception device employs a method that includes estimating signal points based on non-linear amplification characteristics, performing initial equalization, correcting signal distortions, and calculating likelihoods to demodulate signals accurately, using training signals with varied amplitudes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a non-linear amplification region is used to transmit signals, then transmission power efficiency is improved, but signal distortion increases and demodulation accuracy deteriorates
Solution Approach 1:
The system performs preliminary actions by transmitting training signals with known amplitude values before actual data transmission. The reception device uses these training signals to estimate the non-linear amplification characteristic in advance, enabling subsequent accurate demodulation of data signals despite the non-linear distortion.
Solution Approach 2:
The system implements feedback by having the reception device calculate a communication path based on the difference between expected and actual amplitude values of training signals. This estimated communication path is then used to correct the amplitude values of received data signals, compensating for the non-linear amplification distortion.
2Measurement precision
If conventional linear amplification is used, then signal distortion is minimized, but transmission power efficiency decreases
Solution Approach 1:
The system changes the parameter of amplification characteristic from linear to non-linear by utilizing the non-linear region of the amplifier. Combined with parameter compensation through the correction unit that adjusts amplitude values based on the estimated non-linear characteristic, this enables both high power efficiency and maintained signal integrity.
3Device complexity
If signal correction is performed without considering non-linear amplification, then processing complexity is reduced, but demodulation accuracy deteriorates
Solution Approach 1:
The system performs preliminary estimation of the non-linear amplification characteristic using training signals before actual communication begins. This advance preparation allows the reception device to store the estimated characteristic and use it during demodulation, reducing the complexity of real-time processing while maintaining high accuracy.
Solution Approach 2:
The system creates a copy of the expected signal characteristics through training signals and uses this copy to compare against actual received signals. The difference between these copies provides the basis for estimating the non-linear characteristic and correcting signal amplitude values during demodulation.
Data Source
AI summary
A wireless communication system according to an embodiment is a wireless communication system, in which a transmission device transmits the training signal to a reception device such that a plurality of signal points having different amplitudes on a constellation is included, and the reception device includes: an estimation unit that estimates the signal points included in the training signal of a case where it is assumed that, an input-output characteristic in a non-linear region of an amplifier is also linear; an equalization unit that performs initial equalization on a received signal; a correction unit that corrects a signal subjected to initial equalization by the equalization unit on the basis of the signal points estimated by the estimation unit; a likelihood calculation unit that calculates, with respect to a constellation before the amplifier amplifies a signal, a likelihood of a signal corrected by the correction unit.