Coded QAM Modulation Reducing Envelope Fluctuation
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Solution Overview
Problem
Higher order QAM modulation in digital communications leads to increased envelope fluctuation and cycle skipping issues, affecting transmission performance due to more amplitudes and phases, which prior methods like offset-QAM do not adequately address.
Innovation Solution
A method involving a sending apparatus that performs serial-to-parallel conversion, delay control, and QAM mapping to generate synchronized quadrature and in-phase electrical signals, reducing envelope fluctuation and symbol reverse rates, thereby suppressing nonlinear effects and improving cycle skipping during transmission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If higher order QAM modulation is used to increase spectrum utilization efficiency, then spectrum utilization efficiency is improved, but envelope fluctuation increases and transmission performance deteriorates
Solution Approach 1:
The patent changes the mapping relationship between bits and constellation points by introducing a specific coding scheme that maps bits to adjacent constellation points with smaller phase differences. This parameter change in the mapping strategy reduces envelope fluctuation while maintaining higher order QAM's spectrum efficiency, thereby resolving the contradiction between productivity and reliability.
2Loss of information
If higher order QAM modulation is used to provide more phases, then more information can be transmitted, but cycle skipping frequency increases and system performance is affected
Solution Approach 1:
The patent modifies the phase distribution parameters by designing a coding scheme where consecutive bits map to constellation points with minimized phase transitions. This parameter optimization reduces cycle skipping during phase retrieval while preserving the high information capacity of higher order QAM, resolving the contradiction between information transmission capacity and phase retrieval accuracy.
3Reliability
If offset-QAM is used to reduce envelope fluctuation, then envelope fluctuation degree is reduced to some extent, but signal spectrum is not essentially improved and cycle skipping effect cannot be improved
Solution Approach 1:
The patent introduces a novel coding scheme that changes the bit-to-constellation mapping parameters, achieving both reduced envelope fluctuation and improved spectral efficiency simultaneously. Unlike conventional offset-QAM that only addresses envelope fluctuation, this parameter change in mapping strategy optimizes both reliability and productivity, resolving the contradiction between envelope fluctuation control and signal spectrum efficiency.
Data Source
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AI summary
The present invention relates to the field of signal processing, and discloses code modulation and demodulation methods, apparatuses, and a system, so as to reduce an envelope fluctuation degree of a signal and improve system performance. A specific implementation method includes: receiving, by a sending apparatus, N channels of bit signals, and performing serial-to-parallel conversion on any channel of bit signal of the N channels of bit signals, to generate two channels of first bit signals; performing delay control on the two channels of first bit signals, to generate two channels of code bit signals; performing QAM mapping on the two channels of code bit signals and other N-1 channels of bit signals, to generate a channel of quadrature electrical signal and a channel of in-phase electrical signal, where four quadrants of the in-phase electrical signal and the quadrature electrical signal are determined by bit values that correspond to the two channels of code bit signals at a same moment; and modulating the quadrature electrical signal and the in-phase electrical signal, to obtain a transmit signal, and sending the transmit signal. The present invention is applied to signal modulation and demodulation.