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Quadrature amplitude modulation signal identifying method based on mixed moment and fisher discrimination

A quadrature amplitude modulation and signal identification technology, applied in the field of communication, can solve the problems of large amount of calculation and low accuracy, and achieve the effect of improving accuracy, reducing the amount of calculation, and improving the accuracy of calculation.

Inactive Publication Date: 2010-06-30
XIDIAN UNIV
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Problems solved by technology

This method needs to "estimate" the signal-to-noise ratio when identifying MQAM signals, so the amount of calculation is large, and when identifying high-order QAM signals, the accuracy rate is low

Method used

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  • Quadrature amplitude modulation signal identifying method based on mixed moment and fisher discrimination
  • Quadrature amplitude modulation signal identifying method based on mixed moment and fisher discrimination
  • Quadrature amplitude modulation signal identifying method based on mixed moment and fisher discrimination

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Embodiment Construction

[0024] see figure 1 , the implementation steps of the present invention are as follows:

[0025] Step 1. After passing through the Rayleigh fading channel, the received MQAM signal model is:

[0026]

[0027] Among them: a(t) obeys the channel influence factor of Rayleigh distribution, is the channel influence factor that obeys the uniform distribution between 0 and 2π, f d is the Doppler factor, w(t) is zero mean and variance σ g 2 The complex white Gaussian noise of , s(t) is the 32QAM, 64QAM, 128QAM signal to be identified sent by the sender.

[0028] Step 2. Oversample the received signal y(t) to obtain the sampling sequence y(n):

[0029]

[0030] = u ( n ) + w ( n )

[0031] Among them: s(n) is the sample sequence of sending MQAM signal, w(n) is the mean value is zero, and the variance is σ g 2 The sampling sequence of complex Ga...

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Abstract

The invention discloses a quadrature amplitude modulation signal identifying method based on mixed moment and fisher discrimination, mainly solving the problems of large calculation amount and low identification rate in the prior art. The method comprises the following processes: sampling a received signal; respectively calculating a secondary moment, a fourth-order moment and a sixth-order moment of a sampled sequence; normalizing and combining results of the moments to acquire new characteristic quantity; determining two threshold values which discriminate that modulation types are unequal, and comparing the characteristic quantity after the characteristic quantity of the received signal is projected with the threshold values; and determining the signal to be a 64 QAM signal if the projected characteristic quantity is more than the larger threshold value, and determining the signal to be a 128 QAM signal if the projected characteristic quantity is less than the larger threshold value and more than the smaller threshold value, and determining the signal to be a 32 QAM signal if the projected characteristic quantity is less than the smaller threshold value. The method has excellent identification performance under a Rayleigh channel and low signal to noise ratio, ensures that the identification rate can reach 98 percent under a condition of the signal to noise ratio 5dB, and can be used for automatic identification of the quadrature amplitude modulation signal without priori information.

Description

technical field [0001] The invention belongs to the technical field of communication, and in particular relates to a recognition method for high-order quadrature amplitude modulation MQAM signals under the condition of Rayleigh fading channel and low signal-to-noise ratio, which is used for automatic modulation recognition. Background technique [0002] Automatic modulation identification refers to the technology of automatically identifying the modulation type of signals by sampling, observing, and analyzing unknown signals under fading channels. Obviously, this is a core technology both for military and civilian use. In the military field, especially in electronic warfare, C 4 In the I system, obtaining the modulation mode of the signal is a key step. In the civilian field, the analysis and processing of signals by the software radio system is also based on obtaining the modulation of the signal so as to perform correct demodulation. At present, there are relatively few...

Claims

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Application Information

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IPC IPC(8): H04L27/34H04B17/00H04L27/00
Inventor 李兵兵安宁黄敏
Owner XIDIAN UNIV
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