Research On Precoding In MIMO-OFDM System

Future mobile communication brings forward higher call for wireless communication system in the field of transmission rate, system performance and system business capacity. Multiple input multiple output (MIMO) communication system adopts multiple antennas structure both at the transmitter and the receiver, not only being able to make system capacity and frequency spectrum utilization ratio several times linear increase, which satisfies the high transmission rate and high system business capacity demands, but also can fully utilize spatial diversity to improve the system performance. The OFDM technology can effectively overcome the inter-symbol interference (ISI) that induced by the wireless channel's time scattering and frequency selection characteristic. Therefore, in modern wireless communication system,the MIMO and the OFDM technologies are combined to improve the system performance and transmission rate further. The key technology in MIMO wireless communication, precoding is studied in this paper, and the limited feedback precoding based codebook is mainly focused on, which stores the same codebook both at the transmitter and the receiver, the precoder is designed at the receiver and conveyed to the transmitter using a limited number of bits. The receiver selects one of these codebook matrices using a modified version of a previously proposed full channel knowledge precoder selection criterion.The main body of the paper is:The ideal precoding method when the transmitter has perfect channel knowledge, and the precoding matrix selection criterion when the transmitter dose not have perfect channel knowledge are both studied in this paper;The precoding system based CDD is studied in this paper. The precoding based zero delay CDD, small delay CDD and large delay CDD is respectively analized, then the precoding system based large delay CDD is mainly studied in the paper and it's performance is compared with the traditional precoding system;To the open-loop precoding system based large delay CDD system, this paper has studied it's realization methods and analized it's impact over the system performance, finally is the simulation results and analysis;A new codebook subset selection algorithm to reduce the system feedback cost is proposed in this paper, according to the channel state information and the relation between the precoding matrices, then using the four antenna ports codebook in the LTE agreement, this paper has gived the realization method and the simulation results of the codebook subset selection algorithm to verify that the alogrothm proposed in this paper can effectively reduce the system feedback cost, on the premise that the system performance loss is very little.