Downlink Antenna And User Selection Algorithms For MIMO System

The 3rd Generation mobile communication systems will bloom soon in China, and the key technologies of the beyond 3rd Generation or 4th Generation mobile communication systems are becoming perfect as time goes by. The hundreds years history of communication has experienced from mail delivery to broadband fibre-optic cables, and also from the personal letter to mobile web cam. It has already been the truth that the era of information is comes.The aim of wirless communication will continue to be faster and better. However, the frequency band of the wirless communication system is limited, and also the transmit power can not be as large as we want it to be. As the user's requirement for the quality of serverice increases with the aim of better life, the communication technologies which can improve the performance of the communication systems notably are starved for. The OFDM technology doubles the utilization rate of frequency band, which makes this technology the dominant method used in the 4th Generation mobile communication systems. However, such performance improvement still can not satisfy the requirement of the users for the future communication systems.In the 1990s, the wireless communication technology named Multiple Input Multiple Output (MIMO) has springed up, which equipped with multiple RF chains both at the transmitter and receiver. Because of the space variables inducted by this technology, the system throughput and service quality can be improved notably, which makes the MIMO technology becomes one of the hot topics in the study of communication rapidly. However, with the increase of RF chains, the hardware and signal processing complexity of the system increases exponentially, which makes the system realization difficult. How to decrease the system realization complexity while remain the system performance is now an urgent problem for solution.Antenna selection technology is applied in MIMO systems which equipped with larger number of antennas than the RF chains at transmitter or receiver. By alloting the best antenna subset to those RF chains, the MIMO systems realization complexity will be simplified while the system performance can be maintained. When the transmit antenna number equale to the number of RF chains, using antenna shuffling technology, the performance of the DSTTD system still can be improved.In the other hand, the MIMO systems which serve multiple users in the same time, named MU-MIMO systems, also can improve the system throughput and service quality through multiuser diversity gain. With the aim of eliminating the interference of different users, the number of the users can be served simultaneously is limited by the number of transmit antennas of MU-MIMO systems. When there exist a large number of users, user and receive antenna selection is needed. For the optimization of the system performance, user and antenna selection algorithms have been studied for various precoding schemes. The MSLNR precoding scheme can serve all the users in the same time, because this scheme does not eliminate all the interference of different users. However, with the number of users increasing, the interference between different users becomes serious and the system performance becomes bad. So user selection is necessary for the MSLNR precoding systems. Recently communication systems usually set the quality of service for all the users equal with ZF precoding scheme, which also known as EQoS-ZF systems. So how to satisfy all the users' requirement with the least power consumption or how to maximize the system throughput when the transmit power is limited are the problems need to be studied.So, to slove these problems, this dissertation is mainly discussed as follows:1) The fast antenna selection algorithms for MIMO system. Through space vector analysis, the space vector character which the better antenna subset should have is obtained. Based on the character, the fast antenna selection algorithm which has lower computational complexity is proposed. As the study of nonlinear algorithms spring up and the convex optimization algorithm is used in the wireless communication systems widely, for the MIMO system with the same rate of each transmit antenna, we then analysize this nonlinear problem and solve it effectively using convex optimization algorithm. Finnally, based on the channel capacity analysis, the antenna selection algorithm for one side or both sides of MIMO system is studied, these algorithms have almost the same performance as the optimal while the realization complexity is very low.2) Atenna shuffling and antenna selection technologies realized in DSTTD systems. The DSTTD systems combine space multiplexity and diversity technologies together and the performance is better than the general MIMO systems. Combined with antenna selection in the receiver side, the system performance can be improved notablely with neglectable hardware complexity. Through limited feedback, the system performance can be further improved when the transmitter combined with antenna shuffling scheme.3) Antenna and user selection realized in multiuser systems. With the aim of optimizing the performance of MSLNR precoding MU-MIMO systems, three different user selection algorithms are proposed: round robin algorithm, Norm based algorithm and capacity based user selection algorithm. After that, for the purpose of all the users having the same chance to be served, the adjusted fair scheduling algorithm for norm based algorithm and capacity based user selection algorithm are proposed. In the end, for the EQoS-ZF systems with transmit antenna and user selection, fast transmit antenna and user selection algorithms are proposed, these algorithms can improve the service quality when the transmit power is limited or save the transmit power when all the users are satisified with the service quality.In sum, after studying the antenna selecton algorithm through the point of space vector, convex optimization and capacity expressions, different low computational complexity antenna selection algorithms are proposed. When the DSTTD systems combined with antenna shuffling scheme, the system performance can be improved especially in the IID channel, further combined with receive antenna selection, the system peroformance can be improved greatly. With the aim of improving the system performance of the MSLNR precoding systems, three different user selection algorithms are proposed. Furthermore combined with user scheduling algorithm, the fairness between users can be guaranteed. In the case of adding neglectable hardware and computational complexity, the EQoS-ZF system performace can be improved with transmit antenna and user seleetion. In the last part of the dissertation, the problems to be solved related to these research fields and future research topics are summarized, meanwhile, the prospect of the developing tendency is analyzed as well.