Research On Channel Estimation Methods Of MIMO-OFDM System

The emergence of multiple-input multiple-output (MIMO) technology meets the demand of multimedia applications and high speed wireless access. Researches indicate that the MIMO can improve the performance of wireless system prominently, such as system capacity, data rate, and frequency efficiency. To develop a MIMO system, exact channel estimation is necessary. Channel estimation approaches are more complex than those of SISO channel, this leads to the complexity of the receivers rising.As a combination of OFDM with space-time coding technique, MIMO-OFDM has recently received considerable attentions, which can not only effectively enhance the transmission rate and capacity of the wireless communication system but also combat against multi-path fading and interference. In this paper, we discuss the principles of MIMO-OFDM system. Furthermore, the channel estimation technique in MIMO-OFDM system is investigated, with the emphasis on training sequence-based and pilot-based channel estimation methods. Also several basic and improved algorithms are given respectively. Finally, the analysis and comparison of these algorithms are made by computer simulation.This paper is organized as follow:Chapter 1 overviews the process of wireless communication developing and narrates the architecture of this work.Chapter 2 introduces the concept and structure of MIMO-OFDM system, and represents the rational of the MIMO and OFDM technology.Chapter 3 marks out the model of space-time coding. Space-time trellis code and space-time block code are discussed including their coding and decoding criterion. Their performances made by computer simulation are compared at the end of this chapter.Chapter 4 discusses the MIMO-OFDM channel estimation methods based on pilot tone, the methods based on training-sequence in Chapter 5. An efficient comb type training structures and the corresponding channel estimation technique are proposed. The simulation results show that the proposed method has smaller normalized MSE than the method that based on block type training sequences for packet-based MIMO OFDM systems in wireless local area networks.Chapter 6 summarizes all the work in this paper, and points out the future of the further study in this field.