The Research Of User Scheduling And Transmission Technology For Uplink And Downlink Of Multiuser MIMO

As the mobil equipments are becoming smarter and thinner, it poses a great challenge to apply multiple antennas on the teminal equipment. In order to take advantage of the MIMO technology so that the spectrum performance can be largely improved, the virtual MIMO technology is proposed. By unifying the spatially-seperated terminals into a group, a special MIMO system is formed between the grouped terminals and the multiple antennas installed at the base station. In this way, the throughput of the cellular network and the communication quality has been tremendously increased. The crucial problem of virtual MIMO lies in the design of the user pairing algorithm, namely how to choose the optimal terminal group so that the system performance is improved while the co-channel interference is mitigated.As the user moves around, the channel continuously changes due to fast or slow fading and other factors, so it is necessary to adjust the transmitting power of the base station or the terminals in real time by power control, in order to ensure a reliable connection. Most of the present research on the user scheduling algorithm is conducted assuming that each user is allocated with equal power. However, if the user transmits at the same power all the time in practical systems, it will probably experience bad QoS over time. Therefore, it is worthwhile designing jointly the algorithm of the user scheduling and power allocation.By taking the necessary steps to process transmitting signal and receiving signal,the beamforming technology can increase the SINR considerably, which helps to enlarge system capacity and suppress interference. It can be viewed as a filtering processing on the signal, on one hand by designing the transmitting matrix at the transmitter, it directs the signal to the desired user as possible as it can to mitigate the interference; on the other hand by designing the receiving matrix, it contributes to increase the power of the desired signal so that the power of the interference signal is subdued. While the co-channel interference among users is the crucial problem which needs to be tackled, it is therefore of great significance to take a joint research on thebeamforming and user scheduling.Based on the above analysis, this paper takes into consideration user pairing in virtual MIMO, power allocation and beamforming to design the scheme jointly, the main tasks are as follows:The first chapter introduces the latest research of the multiuser MIMO scheduling and power control, and analyzes the existing problem.The second chapter gives the system model of the uplink virtual MIMO,demonstrates in details the principle and characteristics of four traditional user pairing algorithm, and expand the algorithms to schedule more than two users, and conducts the simulation verification and analasis at the end of the chaper.The third chapter proposes a joint user pairing and power allocation algorithm with the goal of maximizing the sum rate of all users, based on the uplink virtual MIMO model combined with power control. The optimal solution can be obtained by the Lagrange multiplier of convex optimization. The simulation verification and analasis is conducted at the end of the chaper.The fouth chapter builds the multiuser MIMO model of broadcasting channel, and optimizes the existing design on the precoding vector, and proposes a successive precoding and user scheduling algorithm. At the end of the chapter the propoesed scheme is compared with other algorithms and its superiority is verified and the corresponding analysis is conducted.Finally the fifth chapter concludes the dissertation and discusses the future research work.