The Research On Detections And Channel Estimation In MIMO-OFDM Systems

The next generation mobile communication systems are expected to provide high data rate up to 100Mbps or even 1Gbps in order to support the multimedia services, such as www, ftp or Video On Demand (VOD). Generally, the next generation mobile communication systems are called B3G or 4G systems. Many key technologies can be candidates for B3G or 4G systems. Orthogonal Frequency Division Multiplexing (OFDM) is an efficient and simple technique to overcome the effect of frequency selectivity caused by multipaths. Therefore, OFDM is generally accepted by 3GPP Long Term Evolution (3GPP LTE) and many B3G or 4G systems. It is indicated by information theoretic studies that the channel capacity of Multiple Input Multiple Output (MIMO) systems increases approximately linearly with the minimum of the numbers of the transmit and receive antennas at high SNR. Therefore, MIMO-OFDM is accepted generally in B3G or 4G systems. Now, China's Future Technology for Universal Radio Environment (FuTURE) project and Europe's Wireless World Initiative New Radio (WINNER) project also accept MIMO-OFDM as the base of physical layer.This dissertation is based on the National 863 project and focuses on the key technologies in MIMO-OFDM. The design and optimization of MIMO receiver, the effect of Signal-to-Noise Ration (SNR) mismatch and channel estimation on the performance of MIMO-OFDM systems are studied deeply.In the first chapter, the progress of the mobile communications is reviewed. The current progress of 3G, B3G/4G is introduced. The key techniques and the problems lying in B3G/4G are denoted.In the second chapter, the system model is introduced first. Some MIMO detections are shown and compared. The advantage and disadvantage of lattice reduction based linear detection is denoted. Based on this MIMO detection, two improved detections are proposed. One is called Decision Feedback aided Detection based on Lattice Reduction (DF-DLR). Simulation shows that DF-DLR can improve the performance of lattice...