Modeling And Simulation Of Communication Reconnaissance For OFDM

With the rapid development of communication science,great revolutions have taken place in its application field in both breadth and depth.As one of the core technique of the fourth generation communication,OFDM has also been fully applied in practice,which brings new challenges to the works of electronic reconnaissance.This thesis intends to study on the modeling and Simulation of communication reconnaissance with the OFDM signal under an entirely blind condition,including study on blind estimation methods,formulation of communication reconnaissance schemes,and modeling and simulation engineering.The detailed work of this thesis is as follows.1.The OFDM system and signal characteristics are analyzed,and a OFDM signal model is established.Based on the standardized simulation platform,the simulation software architecture for OFDM is proposed.2.The blind estimation methods for the system parameters and synchronization parameters of OFDM is studied.Based on the cyclostationary characteristic of OFDM signal,a method for estimating the symbol length by combining the cyclic prefix and the cyclostationary stability is proposed.The simulation result shows that the proposed method has a better performance than the method which only used the autocorrelation of cyclic prefix.And a method which takes advantage of wavelet subtraction and cosine roll-off approximation filter is used to improve the traditional Welch spectrum estimation method for estimating frequency band and oversampling rate.The effective subcarrier subspace and noise subspace are established and the effective separation of these subspace was done.The carrier number is estimated.The delay and frequency offset are estimated by using periodic stationary characteristics.3.In this paper the characteristics of OFDM channel parameters are also been analyzed and several kinds of commonly blind estimation methods are compared.A subspace estimation method based on improved-ICA is proposed.The simulation results show that the method has a better performance in estimating the noise subspace,especially the non-Gaussian noise,which improves the blind estimation performance of channel parameters when facing low SNR conditions.4.By taking advantage of the hierarchical and structured design ideas,a modeling and simulation work on signal level of every sub-system and every sub-module is carried out,which calls for some modeling-skills of segment and encapsulation.Based on this standardized modeling and simulation platform,a set of OFDM signal reconnaissance simulation system is proposed,which starts from the simulation of the interception signal and ends at obtaining all the results of blind character estimation and blind channel estimation.The whole system is divided into six main branches.Four of which are used to complete the parameters estimation,respectively,pre-processing,frequency and over-sample rate estimation,length comprehensive estimation,carrier number comprehensive estimation.And the other two branches,by using the parameter estimation results,complete the synchronization and balanced tasks respectively.For the simulation system,it is convenient,fast and repeatable to estimate the parameters of the OFDM system.