Method for identifying digital modulation signals in presence of complicated noise

Abstract

The invention provides a method for identifying digital modulation signals in the presence of complicated noise. The method comprises the following steps that fraction low-order rapid independent composite analysis is conducted on an observation vector x of a received signal, and the received signal is divided into a transmitting signal and Alpha stable distribution noise; ensemble average LMD based on interpolation is conducted on the separated transmitting signal s(n), and the transmitting signal is decomposed into multiple components; the first classification feature, namely the subsection instantaneous frequency standard deviation sigmaf of a component, is extracted, and a corresponding threshold delta 1 is set; a second classification feature, namely subsection instantaneous amplitude standard deviation sigmaa of the components, is extracted and a corresponding threshold delta1 and a corresponding threshold delta2 are set; a signal set {MSK, 2ASK, QPSK and 16QAM} is divided into two types, namely the signal set {MSK} and the signal set {2ASK, QPSK and 16QAM} through the threshold delta1, and signals in the signal set {2ASK, QPSK and 16QAM} are identified through the threshold delta 2 and the threshold delta3. By the adoption of the method for identifying digital modulation signals in the presence of complicated noise, the performance of identifying signals existing in a low-signal-to-noise-ratio environment in the presence of the Alpha stable distribution noise is high, and the stability is high.

Description

technical field [0001] The invention belongs to the technical field of communication, and in particular relates to a method for digitally modulating a signal under complex noise. It can be used to identify MSK signal, 2ASK signal, QPSK signal and 16QAM signal under Alpha stable distributed noise. Background technique [0002] The identification of digitally modulated signals is to determine the modulation mode of the transmitted signal from the given signal alternative set under the premise that the receiver does not know the modulation mode of the sender's signal, so as to provide the required information for the subsequent demodulation work. Although the signal modulation recognition originated from military reconnaissance, with the development of recognition technology, software radio and other technologies, modulation recognition technology has also been widely used in the field of civilian communications. In order to facilitate theoretical analysis, noise is usually as...

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Problems solved by technology

However, the recognition performance of this method is not ideal under the condition of low signal-to-noise ratio (Liu Mingqian, Li Bingbing, Cao Chaofeng. Digital modulation signal recognition method under non-Gaussian noise [J]. Journal of Electronics and Information Technology, 2013,35(1): 85- 91.)

Zhao Chunhui et al. used the generalized quartic spectrum to conduct modulation recognition research, but the QPSK recognition performance of this method is very poor under the condition of low signal-to-noise ratio (Zhao Chunhui, Yang Weichao. Research on MPSK signal modulation recognition algorithm under Alpha stable distribution noise [J]. Journal of Shenyang University, 2013, 25(1): 10-14.)

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