Research On Single-User And Multi-User Precoding Technologies

Multiple-Input and Multiple-Output (MIMO) is a multi-antenna transmission technology, which can improve communication system's capacity and reliability without requiring any more transmission power and system bandwidth. It is considered as one of the key technologies in future mobile communication systems. Currently, MIMO has been widely used in broadband wireless communication systems, including LTE, HSPA, WiMAX and 802.11n.The error propagation can be avoided and the complexity of the user equipment can be greatly reduced by MIMO precoding technology. Therefore, how to design the MIMO precoding algorithms to improve the transmission rate and bit error rate performance becomes to be the hot spot on researching field of communication. Base station can transmit multiple data streams to the same user or different users, according to this, MIMO precoding can be divided into single-user and multi-user MIMO precoding; also MIMO precoding can be divided into linear and nonlinear precoding, according to whether the nonlinear operation is used.This paper deeply researched the MIMO precoding technology, based on the project "Performance analysis and optimization technology of MU-MIMO nonlinear precoding", which is a joint research project of Beijing University of Posts and Telecommunications and ZTE Corporation. Main works are listed as follows:1. The key technologies in the LTE system have been described. This paper focuses on MIMO technology, the single-user and multi-user MIMO system models and the channel capacity have been analyzed. The OFDM, precoding and beamforming technologies have also been described.2. The existing technologies of single-user MIMO linear and nonlinear precoding have been researched. The design principles of the codebook have been summarized. The existing single-user spatial multiplexing MIMO precoding schemes have been analyzed too.3. The existing technologies of multi-user MIMO linear and nonlinear precoding have been researched. The advantages, disadvantages and improvements of the existing multi-user MIMO precoding schemes have been analyzed and summarized. Two precoding schemes are proposed in this paper, one is the ZF-based block diagonalization geometric mean decomposition THP precoding scheme, and the other is the better performance multi-user MIMO adaptive precoding scheme. The limited feedback techniques have also been summarized.4. The LTE physical layer simulation platform's structure has been introduced. The process of MU-MIMO precoding simulation is mainly described. The performance of the single-user and multi-user MIMO precoding schemes have been simulated. The framework of the LTE hardware system has been introduced, and an improvement of the DSP chip's DFT operations has been proposed.5. A summary of this paper has been given, and a suggestion for future research directions and prospects has been proposed.