The Research Of Channel Estimation Technology In OFDM System

Orthogonal Frequency Division Multiplexing (OFDM) is a high-speed transmission technology under the wireless communication. Its basic principle is to transmit high-speed serial data broken down into multiple parallel low-rate data, and separately for different carrier modulation. Orthogonal frequency division multiplexing due to good performance of anti-frequency selective fading and high bandwidth utilization. Has been a wide range of wireless LAN standards (such as IEEE802.11a HIPERLAN,MMAC,etc.) use. And the OFDM has become the next-generation mobile communication system, one of the key technologies.This paper mainly studies OFDM system channel estimation techniques. OFDM system, first introduced the development status and prospects, and then an analysis of its basic principles, as well as OFDM systems in several key technologies; for OFDM Systems Channel Estimation in key technologies, describes the channel estimation method of classification, and various classification methods The key algorithm, several commonly used algorithms, such as the LS algorithm and RLS algorithms, LMS and RLS adaptive algorithms, as well as channel estimation in several interpolation algorithms are compared, and compared the performance of the algorithm graph. Then channel estimation is studied two key ways:The first method is based on pilot channel estimation method. First introduced the pilot selection and insertion methods, gives the pilot channel estimation based on a system model, and then on this basis proposed adaptive algorithm RLS channel estimation method using LS algorithm to estimate the first pilot at the channel response value, and then use the RLS adaptive processes of the channel response of recursive channel estimation algorithm, the final adoption of interpolation the location of all sub-carrier channel frequency response. Simulation results show that RLS-based adaptive algorithm outperforms the channel estimation algorithm based on the LS channel estimation method.The second method is based on the virtual sub-carrier subspace blind channel estimation method. In this section, first introduced the virtual sub-carrier technology and common sub-space algorithm; and then in the literature based on the introduction of a virtual sub-carrier technology, the introduction of a virtual sub-carrier technology to make up the system using the cyclic prefix of the system performance. The method used to receive signals directly SVD decomposition in this paper, in order to avoid the original received signal second-order statistics, reducing the system's computational complexity. The simulation results show that the method is not only better than the original method is convergence, and the system performance is better than the original method.