The Research Of Precoding Technology In LTE And LTE-A System

Precoding technology can improve the performance of MIMO system, by adjusting the transmit single according to the channel condition. It is now widely applied in the next generation communication systems, such as LTE and LTE-A. The research of precoding technology in LTE system will help to evaluate the system performance. The research of precoding in LTE-A system will promote the process of standardization. It'll also increase the voice of our country in the field of communication.In practical systems, limited feedback precoding based on codebook is used, due to the limited capacity of the feedback channel. For limited feedback precoding, the most important two problems are codebook design and codeword selection. We will discuss these two problems in LTE and LTE-A system.LTE system has already given the precoding codebook for different scenarios. So, the research of precoding in LTE system is focused on designing an appropriate codeword selection method. We propose a codeword selection approach based on system throughput, which fits the features of LTE system. EESM is used to realize this approach. The simulation results shows that LTE system can archive the desired peak transmit rate and peak spectral efficiency with the help of precoding technology.The precoding codebook for LTE-A system is under discussion. We focus on the precoding codebook in high order SU-MIMO scenario. A novel codebook design approach is proposed. The codebook of rank 1 is constructed first. Then the whole codebook is designed based on Householder transformation and matrix aggregation according to rank 1 codebook. The codebook constructed by this method has good structure properties which can reduce the complexity of precoding. Link level simulation is used to compare the performance of different codebook methods. The simulation result shows that the codebook designed by the novel approach performs best in variety scenarios and achieves a good tradeoff between performance and complexity. So, the codebook can be proposed to be the candidate of LTE-A system.