Research On Parameters Estimation Methods For OFDM Systems

OFDM is widely used in military communications for the numerous technical advantages. In military communication, inorder to intercept the enemy intelligence for surveillance, tracking, threaten confirmation, and interfering efficiently, the parameters of the received signals must be estimated first. This dissertation aims to estimating the parameters of the received OFDM signals accurately, which belongs to the communication reconnaissance.Based on the discussion of the principles, characteristics and key technologies of OFDM, this paper studied the methods for estimating the SNR and code rate in detail. For the SNR estimation in OFDM systems, this paper firstly analyzed the shortcomings of virtual carrier estimation and channel temporal correlation methods, then the symbol synchronization was employed in recceiving end to improve the estimation precision. Simulation results shown effectiveness of the improved algorithm.In the traditional code rate estimation methods, the auxiliary function was established and analyzed by wavelet transform based on the estimation of the sub-carrieres. Because of the high sensitivity to frequency shift in OFDM systems, the error of sub-carrier estimation would affect the performance of code rate estimation. To solve this problem, the blind synchronization was introduced in this paper before the sub-carrier estimation, which improved the estimation accuracy greatly. The simulation results verified the effectness of the improved algorithm.