Affine Projection Based Decoder In A Multiuser MIMO Downlink System

Today, with the rapid development of wireless communication technology, how to improve spectrum efficiency and improve the transmission performance of the wireless link, and how to meet the higher requirements in the wireless transmission rate and quality, has become one of the hot research topics in the current communication field. The conventional single antenna transceiver communication system has been unable to meet this growing demand, and the conventional diversity or the smart antenna technology has also not enough to solve people’s demand for high capacity and high reliability in the new generation wireless communication system. Multiple-Input Multiple-Output (MIMO) transmission technology, which can largely improve frequency spectrum utility, and effectively improve the system performance, will become the theme of the next generation mobile communication system. The MIMO technology refers to adopt multiple antennas on both ends of the wireless link, and the signals are transmitted and received through a plurality of transmit and receive antennas. Theoretical results have shown that the MIMO system can effectively improve capacity and reliability. Thus, space-time encoding and decoding technologies that can effectively achieve the system capacity and effectively improve the system performance, are always the hot research topics in the wireless field. Although many significant achievements have achieved, there are still many problems unsolved, especially for multiuser MIMO system.This thesis studies the downlink transmission and decoding technology in multiuser MIMO communication system. Based on affine projection, this thesis proposes new transmission and decoding methods to cancel the interference between the users in the multi-user MIMO system. The main contributions are as follows:First, this thesis introduces the background and channel model of the multi-user MIMO communication system. The downlink channel capacity of this system, multi-user precoding techniques and multi-antenna radio capacity with the imperfect channel information are presented.Second, for downlink of the multiuser MIMO system with M transmit antennas at the base station and one receive antenna at each user, under assumptions that the transmitter does not have channel state information (CSI), and the number of the transmitting antennas equals to the number of the users, a transmission and decoding scheme is proposed as follows:in each user, affine projection technology is applied to cancel the interference between the users, and the wanted signals are decoded from the received signals.Third, the above method is extended to more general situations. For the system where ratio of the number of the transmit antennas and the number of users is an integer, a modified method of the above transmission and decoding scheme is proposed and analyzed.Finally, all proposed methods above are confirmed by simulations.