The Research Of Channel Estimation And Equalization Technology In OFDM System

High-rate and high-quality service is needed in wireless and mobile communication system, whereas, Due to a variety of advantages, such as high bandwidth efficiency and excellent anti-multipath performance, Orthogonal Frequency Division Multiplexing (OFDM) has received considerable attentions and been widely used in many fields.This paper deals with the technologies of channel estimation and equalization for OFDM system. The principle and characteristics of OFDM system are introduced first. Then several key technologies of channel estimation and equalization for OFDM are discussed in detail. An adaptive implementation of minimum mean square error (MMSE) estimation approach for multi-path channel taps estimation is proposed in a convenient representation of the multi-path channel taps by the Karhunen-Loeve (KL) series expansion. With the application of KL expansion, rather than estimating correlated channel taps, uncorrelated series expansion coefficients are adaptively estimated. The performance of the proposed approach is studied through analytical and experimental results. Based on the oversampling of OFDM frequency response, this paper proposes a method called LS+LPF. Comparing with si(sin(x)/x) interpolator, cubic interpolator with low pass filter, and Winner interpolator both in mean square error and bit error rate without encoding, the results of the method proposed by this thesis show that the performance is better than si interpolator and cubic interpolator with low pass filter, and close to the Winner interpolator but the complexity is much lower than the latter. At last the techniques of time domain equalization and frequency domain equalization are discussed, at the same time, time domain train algorithm and its coefficients are studied.