On The Research Of Channel Estimation And Equalization In OFDM Based Mobile Televion System

Orthogonal Frequency Division Multiplexing (OFDM) is one of the most promising wireless communication techniques, which is robust to ISI (inter-symbol interference) and has been widely used in wideband wireless communication area. Mobile multimedia technology has been the focus of research in the recent years and there are lots of existing mobile television standards now. China has delivered the mobile multimedia industry standard, CMMB system on Oct 2006. Tsinghua University has also proposed a mobile television standard based on TDS-OFDM.Channel estimation and equalization is one of the key techniques in the wireless communication area and one of the most important modules as well. The thesis is to study, analyze and simulate the channel estimation and equalization in OFDM based mobile television system including CP-OFDM based system and TDS-OFDM based system.The thesis analyzes and summarizes all kinds of channel estimation and equalization algorithm in CP-OFDM based mobile television system, which is the basis of the study on CMMB system. After studying and analyzing its system structure, frame structure and pilot pattern, a simulation platform of CMMB system is built by MATLAB simulink and classic channel estimation algorithms are realized on the platform. The thesis proposes a method to solve the problem caused by the discontinuous of CMMB scattered pilots when applying the LMMSE based algorithm. Meanwhile, an improved method based on DFT simplified algorithm is proposed. Simulation shows that the improved method has a better performance for the same complexity.For TDS-OFDM based mobile television system, the thesis proposes a method based on proper correlation window which needs not eliminate ISI by correlation and convolution repeatedly. It has a good performance and can realize low-complexity channel estimation even in the long multipath channel. The thesis also proposes the hardware architecture for channel estimation and cyclic restoration algorithm in TDS-OFDM system. An approximate algorithm of interference cancellation has been proposed to reduce the complexity and resource of hardware implementation. And simulation shows that it has little lose in performance. The clock frequency and the use of hardware resources got from hardware simulation are also given in the thesis.