Rate-free modulation and demodulation method approaching capacity limit in wide-range SNR

Abstract

The invention discloses a rateless modulation and demodulation method approaching a capacity limit in a wide-range SNR, and belongs to the technical field of modulation and demodulation in wireless communication. The method comprises the following steps: firstly, a group of constellation points close to Gaussian distribution is fit by using non-uniform interval points with equal probability; secondly, the mapping performance of a constellation diagram is optimized through a BSA algorithm, and a local optimal mapping scheme between information code elements and constellation points is designed; at a sending end, a sparse mapping matrix is used for carrying out random sampling on an information sequence to obtain information code elements, the information code elements are directly modulated to constellation points according to a mapping scheme, and the sampling and mapping times are increased along with the reduction of the channel SNR, so that the adaptive SNR range is expanded; and a receiving end carries out demodulation by adopting a BP iterative algorithm. The method provided by the invention does not need to design a weight set to realize the Gaussian forming of the symbol, can obtain the performance close to the capacity limit in a large-range SNR (Signal to Noise Ratio), and is a modulation and demodulation method with a rate-free characteristic.

Description

technical field [0001] The invention belongs to the technical field of modulation and demodulation in wireless communication, and more specifically relates to a rateless modulation and demodulation method close to the capacity limit within a large range of SNR. Background technique [0002] According to information theory, under the AWGN (Additive White Gaussian Noise) channel, for a power-limited communication system, when the channel input signal has a Gaussian distribution, Gaussian shaping gain can be obtained, thereby improving the channel transmission capacity. The modulation schemes in which the constellation points are uniformly arranged in the current commonly used communication systems cannot obtain shaping gain, but by designing non-uniformly arranged constellation points, making the modulated signal close to Gaussian distribution, shaping gain can be obtained. In order to make the arrangement of the modulation constellation points close to the Gaussian distributi...

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Problems solved by technology

However, the Euclidean distance between the constellation points of high-order modulation is small, and it is susceptible to noise interference, resulting in a high demodulation error rate, so it is only suitable for communication scenarios with high SNR (Signal Noise Ratio)

If the modulation order is reduced and the number of constellation points is reduced, although the Euclidean distance between constellation points can be enlarged to make it applicable to lower SNR conditions, it is difficult to accurately fit the Gaussian distribution with fewer constellation points. There will be a large fitting error between the position distribution and the Gaussian distribution, resulting in a loss of Gaussian shaping gain

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