Research On Channel Estimation Algorithms In OFDM System

Communication service in wireless channels with high speed and quality is required for future wireless communication systems. OFDM(orthogonal frequency division modulation) has gained more and more attraction in recent years due to its high bandwidth efficiency and robustness against frequency selective fading channels.Wireless channel characteristic is firstly introduced in this paper. Secondly, the principle and main techniques of OFDM system are analyzed. Lastly, the channel estimation algorithms in OFDM system are investigated in detail. Channel estimation methods can be sorted into two basic categories: training sequence/pilot aided methods and blind methods. The main task of this paper is the research on blind channel estimation algorithms in OFDM systems. Since the pilot aided methods are used widely in practice, so some common algorithms are also studied in this paper.Compared to pilot aided channel estimation methods, blind methods have better transmission efficiency. In this paper, a subspace method based on second-order statistics is proposed for blind channel identification in order to conquer the complication and imprecision of blind estimation methods in OFDM system. We derive a sufficient condition that guarantees all the channels to be identifiable no matter what their zero locations are. In the process of calculating the correlation, the concept of signal vector acquisition and smoothing is introduced to improve the performance of the algorithm. The method does not require any modification of the existing OFDM systems. The method is simple. It has fast speed of convergence. Simulations show the superior performance of the proposed algorithm.