Abstract
This research aims to analyze the effects of different parameter estimation on the recognition performance of satellite modulation signals based on deep learning (DL) under low signal to noise ratio (SNR) or channel non-ideal conditions. In this study, first, the common characteristics of broadband satellite modulation signal and the commonly used signal feature extraction algorithm are introduced. Then, the broadband satellite modulation signal pattern recognition model based on deformable convolutional neural networks (DCNN) is built, and the broadband satellite signal simulation is conducted based on Matlab software. Next, the signal characteristics of binary phase shift keying (BPSK), quadrature phase shift keying (QPSK), 8 phase shift keying (PSK), 16 quadratic amplitude modulation (QAM), 64QAM, and 32 absolute phase shift keying (APSK) are extracted by the constellation map, and the ratio changes of T1 and T2 with SNR are compared. When SNR is given, it is compared with VGG model, AlexNet model, and ResNe model. The results show that the constellation points of satellite signals with different modulations are evenly distributed. T1 of PSK modulation signals increases significantly with the increase of SNR. When SNR is greater than 10, PSK modulation signals can be identified. When T2 is set and SNR is greater than 15dB, 16QAM and 32APSK signals can be distinguished. In the model, the Relu activation function, mini-batch gradient descent (MBGD) algorithm, and Softmax classifier have the best recognition accuracy. PSK modulation signals have the best recognition rate when the SNR is 0dB, and the recognition accuracy of different modulation signals at 20dB is over 98%. When the data length reaches 4000, the recognition accuracy of different modulation signals is higher than 97%. Compared with other algorithms, this algorithm has the highest recognition accuracy (99.83%) and shorter training time (3960s). In conclusion, the broadband satellite modulation signal pattern recognition algorithm of DCNN constructed in this study can effectively identify the patterns of different modulation signals.
Highlights
Nowadays, the development of communication technology shows the trend of rapid growth, and the traditional ground communication technology can’t meet people’s daily needs gradually, so more and more experts and scholars focus on the research of satellite communication technology
In the case of signal to noise ratio (SNR) of 20dB, constellation maps of different modulation signals without frequency deviation have a common characteristic, that is, the different points are distributed in concentric circles with the same radius, the constellation points of different signals are evenly distributed, and the boundaries between the constellation points are clear
The characteristic parameters T1 of 64QAM and 32APSK modulation signals will gradually decrease as the SNR increases
Summary
The development of communication technology shows the trend of rapid growth, and the traditional ground communication technology can’t meet people’s daily needs gradually, so more and more experts and scholars focus on the research of satellite communication technology. When improving the performance of satellite communication system, the recognition of satellite communication modulation mode is the key, but the modulation mode of different signals needs to be determined according to the current channel environment. The density of satellite signals has been greatly increased, so in order to increase the carrying capacity of satellite signals, it is necessary to use different modulation methods for signal modulation. The recognition technology of modulation signals is between receiving and demodulating. After receiving the satellite signals, the method of extracting the modulation signals from the noisy signals can lay a foundation for the subsequent demodulation, parameter estimation, and signal information extraction of the satellite signals [3]
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