Receiver Demodulation for Nonlinear Amplifier Distortion
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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 wireless communication system and method that includes a reception device with an estimation unit to estimate signal points, an equalization unit for initial correction, a correction unit to adjust for non-linear amplification, and a demodulation unit to demodulate based on likelihood calculations, using training signals with varied amplitudes to compensate for non-linear amplification characteristics.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If a transmission device uses a non-linear region of an amplifier to transmit signals, then transmission power and signal strength are improved, but signal distortion occurs and demodulation accuracy deteriorates
Solution Approach 1:
The system performs preliminary actions by transmitting training signals with known values before actual data transmission. The reception device uses these training signals to estimate the communication path and characterize the non-linear amplification effects in advance, enabling accurate demodulation of subsequent signals despite the non-linear amplification used during transmission.
Solution Approach 2:
The system implements feedback mechanisms where the reception device continuously estimates the communication path based on received training signals and uses this information to correct for non-linear amplification effects. The estimated communication path characteristics are fed back to guide the demodulation process, allowing the system to compensate for the non-linear distortion introduced by the amplifier.
2Measurement precision
If a reception device performs initial equalization on a received signal, then signal quality is improved, but residual distortion from non-linear amplification remains
Solution Approach 1:
The correction process is segmented into multiple stages: initial equalization using estimated communication path, followed by additional correction based on the specific characteristics of non-linear amplification. This segmentation allows the system to address different types of distortion systematically, with the first stage handling general channel effects and the second stage specifically targeting non-linear amplification distortion.
Solution Approach 2:
The system changes parameters dynamically by adjusting equalization coefficients and correction values based on the estimated communication path characteristics. The reception device modifies the equalization parameters according to the specific non-linear amplification effects detected from training signals, enabling adaptive correction that maintains reliability while improving signal quality.
3Measurement precision
If a transmission device transmits training signals with multiple signal points of different amplitudes, then the reception device can accurately estimate the communication path, but the training signal occupies additional transmission resources
Solution Approach 1:
The training signals serve multiple functions: they are used to estimate the communication path, characterize non-linear amplification effects, and enable the reception device to perform accurate equalization and demodulation. By making the training signals multi-functional, the system maximizes the utility of the additional transmission resources they occupy.
Solution Approach 2:
The training signals are transmitted periodically at predetermined intervals rather than continuously. This periodic transmission allows the reception device to estimate communication path characteristics at appropriate intervals without requiring constant training signal transmission, thereby reducing the overall quantity of transmission resources consumed while maintaining estimation accuracy.
Data Source
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AI summary
A wireless communication system according to an embodiment is a wireless communication system in which a reception device demodulates a signal on the basis of a training signal transmitted by a transmission device that performs single-carrier multi-level modulation, in which the transmission device transmits the training signal to the 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, on the basis of characteristic information indicating an input-output characteristic including a non-linear region of an amplification unit that is provided in the transmission device and amplifies a signal to be transmitted, an input-output characteristic in a non-linear region of the amplification unit 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 amplification unit amplifies a signal, a likelihood of a signal corrected by the correction unit; and a demodulation unit that demodulates a signal on the basis of the likelihood calculated by the likelihood calculation unit.