Wireless Signal Recognition In Complex Electromagnetic Environment

Wireless communication is the most widely used communication method.The iden-tification and analysis of wireless signals are urgent issues in both military and civilian fields.The digital communication system transforms information symbols to transmission signals by channel coding and carrier modulation.Affected by the complex electromag-netic environment and non-cooperative channels,unknown signals' recognition results of modulation type and channel coding type directly affect the signal demodulation and de-coding.This article takes the wireless signal in complex electromagnetic environment as the research object,and proposes the identification method of the signal modulation type and channel coding type by the main steps of the digital communication system and the measured data under the condition of small samples.The main work of this paper is as follows:1.Thie thesis first introduces the channel coding module and modulation module of the digital communication system.This part elaborates the modulation principles of differ-ent modulation types,signals' differences and coding principles of different code types,then clarifies the purpose and application prospects.2.This thesis proposes a modulation signal recognition method based on multi-dimensional features,and the recognition method is verified in both the simulated ex-perimental environment with a large number of samples and the actual experimental envi-ronment with an extremely limited number of samples.This method uses the time domain information,high-order cumulant information and transform domain information of the modulation signals to complete the feature extraction,and uses both the back propaga-tion(BP)neural network and decision tree theory to design the classifier.The experimental results prove that multi-dimensional features are better than single-dimensional feature,and it also proves that this method still has a better signal recognition effect under the condition of a small number of samples.3.This thesis proposes a channel coding identification method based on the ran-domness of data.Through the analysis of sequence randomness theory and cryptographic randomness theory,the channel coding characteristic parameters are designed.The exper-imental results show that the proposed channel coding related features have a good distin-guishing effect on different channel coding types,and verify the correctness and feasibility of the proposed method.