The Research On Tomlinson-Harashima Precoding And Limited Feedback Technique For Multi-User Mimo Systems

Multiple-input multiple-output systems can effectively improve the channel capacity, especially, spatial multiplexing technology can linearly increase the system throughput with the minimum of input and output antennas. However, spatial multiplexing unavoidably incurred the co-channel interference among different users and different data streams within the same user. Precoding technology can effectively eliminate the co-channel interference introduced by the MIMO spatial multiplexing, especially the Tomlinson-Harashima precoding (THP) performed well among all precoding schemes.Owning to the good performance of multiple-user MIMO (MU-MIMO) systems compared with single-user MIMO (SU-MIMO) systems, in this paper, much attention will be paid to THP precoding for MU-MIMO systems. The focus of this paper will be the research of limited feedback for Tomlinson-Harashima precoding, which got little attention in the past. The main contents of the paper were as follows:The first part of the paper focus on the theory of THP precoding for MU-MIMO systems. The derivation of the channel capacity of THP precoding and linear zero-forcing precoding under non-perfect channel condition has been developed. It has been found that the channel capacity of THP precoding has drastic improvement compared with that of linear zero-forcing precoding.Then, the second part of the paper focus on the research of limited feedback issue of THP precoding for MU-MIMO systems. It has been found that the right characteristic matrix of the channel matrix met the demand of the THP precoding for MU-MIMO systems. The paper also put forward an orthogonal quantization method which quantizes the right characteristic matrix of the channel matrix which reduced the unnecessary expenditures.The third part of the paper evaluated the performance of THP precoding for MU-MIMO systems with the channel capacity and bit error rate. The evaluation found that MU-MIMO THP precoding had the potential to be the next generation mobile communication standard.The last part of the paper evaluated the possibility of THP precoding for MU-MIMO systems in indoor scenarios in the first place. It had been found that the high SNR of indoor scenarios was propitious to the application of THP precoding for MU-MIMO systems in indoor scenarios. Based on the discovery above, a dynamic switch scheme between the THP precoding and linear zero-forcing precoding was put forward with the aim of the maximization of the channel capacity of MU-MIMO systems. The bright point of the scheme was to keep the compatibility between the THP precoding and linear zero-forcing precoding, which laid the foundation for the standardization of THP precoding for the MU-MIMO systems.