Research On Channel Estimation Of Cognitive OFDM System Based On Pilotsequence Design

Orthogonal Frequency Division Multiplexing(OFDM) is the technology of multi carrier transmission in wireless communication and the core technology of " Fourth Generation Mobile Communication". OFDM system can be used in the presence of multipath propagation and Doppler frequency shift of wireless mobile channel scene, can efficiently solve the multipath effect, the ISI code between interference and ICI carrier interference on the system performance influence, in frequency selective fading resistance, high channel utilization, so in the wireless communication system is a large number of applications.In this paper, the application of sparse channel recovery channel estimation is also proposed system background, transmission system for the end of the pilot signal insert mode research, put forward a kind of applicable to sparse channel estimation of OMP pilot insertion algorithm and save the spectrum resources and improve the system bit error rate BER and the minimum mean square error performance.Firstly, the development of orthogonal frequency division multiplexing(OFDM) technology is summarized, and the key technology is described.The application of the background cognitive orthogonal frequency division multiplexing(CR-OFDM) system is proposed.Secondly, the basic structure of OFDM system, the insertion design of the pilot frequency insertion, the channel estimation and the mathematical interpolation of channel estimation are resolved. Focus on three classical channel estimation methods, and compare the three estimation methods by simulation, and select the sparse recovery algorithm suitable for sparse channel restoration as the object of this paper.Finally, study of sparse recovery essence-compressed sensing theory, the theory of mathematical modeling shows the framework of the core technology, signal sparse representation, design of measurement matrix and algorithm for signal reconstruction. The sparse recovery effect of image and OFDM is compared with each algorithm, and the orthogonal matching pursuit(OMP) algorithm is determined as the subject channel estimation algorithm. The design algorithm of pilot insertion for CR-OFDM system is designed. Simulation of CR-OFDM system with different pilot frequency estimation algorithms is carried out, and the superiority of pil ot insertion algorithm is verified.