Research Of Channel Estimation In MIMO-OFDM System

Channel estimation is one of the most important and most difficult problems in the wireless mobile communication engineering. The contents of this dissertation are concentrated on the channel estimation technologies in new generation wireless communication systems.Wireless mobile communication has undergone surprising development recently. The second generation mobile communication is developing at a never appeared speed. The third generation mobile communication, which can provide voice, data, video as well as other multimedia services, is at the beginning phase of commercialization. And the research on new generation mobile communication, i.e. the fourth generation or the beyond third generation mobile communication, has also been started.The main characteristics of new generation wireless communication lie on the ability to support high data rate and large system capacity services. Demands for high data rate based mobile wireless communication services are rapidly increasing. The main driver of this development is the booming mobile Internet and multimedia market. However, physical limitations on wireless channel present a fundamental technical challenge for high data rate mobile wireless communications. So some new powerful technologies are needed to support high spectral efficiency in new generation wireless mobile communication. MIMO-OFDM is one of the most promising scheme for achieving high data rate and large system capacity over wireless mobile links.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 effectively combat multi-path fading and interfere. In this paper, we discuss the principle of MIMO-OFDM system based on the introduction of fading channels. Furthermore, the channel estimation technique in MIMO-OFDM system is investigated, describes several channel estimation schemes for multiple-input multiple-output (MIMO) orthogonal frequency division multiplexing (OFDM) systems, and focuses on minimum mean squared error (MMSE) algorithm based on training sequences, and also introduces a kind of improved algorithm based on the basic MMSE algorithm. Furthermore we analysis and compare these algorithms. Finally, a new channel estimation method, based on MMSE criterion, is proposed to improve the performance of channel estimation method using the special training pole construction and simplified low-rank estimators, furthermore we discuss the principle, performance and practicability.