Research On Multi-carrier Mixed Signal Identification And Parameter Estimation

In various wireless communication systems,Orthogonal Frequency Division Multiplexing technology is widely used due to its high spectral efficiency and strong ability to withstand multipath propagation.In some large-scale public events,a large number of wireless terminals using OFDM technology come together to form a complex wireless electromagnetic environment,and mutual interference between devices occurs from time to time.How to correctly identify multi-carrier mixed signals and estimate their parameters,and then find the interference equipment,is the key to eliminating interference and maintaining communication order.This paper studies some related technologies in multi-carrier mixed-signal processing,and focuses on the detection and identification technology and parameter estimation technology of OFDM mixed signal.The main research results include:1.A multi-carrier mixed-signal identification method based on fractional wavelet transform is proposed.Multi-carrier mixed-signal detection and identification is the first step in multi-carrier mixed-signal processing.Different types of multi-carrier mixed-signal processing methods are different.Here we mainly consider the mixing of two signals and use one OFDM signal in the OFDM mixed signal as the target signal.The other signal is an interference signal.The specific method is to first perform a Hilbert transform on the multi-carrier mixed-signal,then perform a fractional wavelet transform,then use the fractional domain wavelet coefficients to construct the eigenvalues,and finally use a decision tree classifier for OFDM mixing signals' identification.The simulation results show that by selecting the appropriate transform order,the algorithm can not only identify single-carrier interference and multi-carrier interference but also distinguish the modulation types of single-carrier interference and multi-carrier interference.Moreover,the algorithm does not rely on any prior knowledge.Conducive to practical application.2.A multi-carrier mixed-signal carrier frequency and symbol rate estimation algorithm based on cyclic spectral density is proposed.To further distinguish and identify multi-carrier mixed signals,parameter estimation of multi-carrier mixed signals is studied.Parameter estimation is the second-largest technology for mixed-signal processing.Parameter estimation can not only further identify multi-carrier mixed signals,but also accurately estimate multi-carrier mixed signals carrier frequency,symbol rate,and the number of subcarriers,and then recover modulation information,is one of the important contents of non-cooperative communication.Based on this,a carrier frequency and symbol rate estimation algorithm for multi-carrier mixed signals based on cyclic spectral density is proposed.The specific method is to first use the smoothed FAM algorithm in the time domain to estimate the cyclic spectral density and then intercept the two-dimensional cross-section of the cyclic frequency equal to zero.There are two obvious peaks on the plane.Based on the peak values,the OFDM signal carrier frequency can be estimated.Followed by intercept the two-dimensional cross-section of the f equal tocf,which can estimate the symbol rate of a mixed OFDM signal.Simulation results show that the proposed algorithm can accurately estimate carrier frequency and symbol rate.3.A multi-carrier mixed-signal sub-carrier number estimation algorithm based on oversampling and cyclic stationery are proposed.Aiming at the problem that the number of sub-carriers of mixed OFDM signals is difficult to study,a sub-carrier number estimation algorithm based on oversampling and cyclically stable multi-carrier mixed signals are proposed.The idea of the algorithm is to firstly use auto-correlation estimates the oversampling rate q of the hybrid OFDM signal,and then estimates the two effective symbol lengths of the hybrid OFDM signal based on the auto-correlation after oversampling,and finally estimates the number of subcarriers of the hybrid OFDM signal.Research shows that the proposed algorithm can accurately estimate the number of subcarriers of a multi-carrier mixed signal.4.Experimental verification of multi-carrier mixed-signal identification and parameter estimation was carried out.Use AD9361 signal acquisition card to collect single multi-carrier signal(DJI Elf 4 UAV image transmission signal,WiFi signal),and multi-carrier mixed-signal(DJI Elf 4 UAV image transmission signal and WiFi signal mixed signal).Using these collected measured signals to verify the effectiveness of the algorithm based on fractional wavelet transform identification,carrier frequency,symbol rate estimation of multi-carrier mixed signals,and blind sub-carrier number estimation.The actual verification proves the effectiveness of these algorithms.