Transmit Diversity And Beamforming Optimization Of Design And The Blind Receive

From the invention of the telegram to the commercial use of the third Generation (3G) communications, and from the emergence of wired communications to the rush of wireless communications, communication techniques are influencing people's lives deeply and transforming the whole society. As the developmental tendency of the communications, wireless communications has become an important sign of the social development. The future communication systems are expected to satisfy higher requirements, it needs offer not only large coverage and reliable transmission but also high data rate and spectrum efficiency, etc.However, practical communication systems are facing lots of complicated problems, such as multi-path fading, time variation of channel, noise, multi-access interference (MAI), inter-symbol interference (ISI) and the limitation of bandwidth, which affect the quality of communication links and system capacity greatly, and also become the key factors obstructing the development of wireless communications. Meanwhile, how to optimize the assignment of system resources without increasing the consumption of transmission power and sacrificing the bandwidth, and how to fulfill the quality of service (QoS) of different users in a multiuser system are practical problems to be solved.Space time processing technique offers an effective way to solve the above-mentioned problems, and it has become a hot research topic during these years. Multi-antenna space time processing theory belongs to the field of information science, which relates to temporal domain signal processing, spatial domain signal processing, adaptive signal processing and blind signal processing, etc.Transmitter and receiver are the main parts to construct the space time system, and it is a very challenging task to change and optimize the traditionalsystem construction and signal processing methods in order to improve the system performances. Whereas diversity and beamforming are two important space time processing techniques, and it is more feasible to exploit them at the base station other than at the mobile terminal, therefore, this dissertation focuses on studying these two downlink transmission techniques and their joint optimization schemes. In addition, due to the problems stemming from the channel estimation used in the traditional receivers, a novel blind detection approach for space time systems is presented as well. In general, this dissertation mainly discussed as follows:1) The joint design approaches of transmit diversity (TD) and beamforming (BF) are investigated, and mainly focus on the joint scheme between space-time block coding (STBC) based TD and BF — beam space-time block coding (BSTBC). In the light of different system configuration, the dissertation studies two representative kinds of BSTBC schemes: discrete beam space-time block coding (D-BSTBC) and integrated beam space-time block coding (I-BSTBC). In addition, a new structure of transmitter using antenna array is designed for I-BSTBC scheme, and an adaptive downlink transmission strategy which considers the idea of joint design is also presented. Hence, the adaptive ability for the complex channel conditions is improved and the re-configurable performance of the system is also increased.2) An independent component analysis (ICA) based blind detection approach for multi-antenna system is proposed to solve the problems related to the traditional channel estimation based methods. By comparing the models between the multiple input multiple output (MIMO) system and ICA system, the inherent relation between them is established. After constructing three kinds of transformed models for the space time systems based on blind source separation (BSS) theory, some effective ICA algorithms are employed to implement the blind detection. What is more, auniform blind extraction method is presented for both STBC and vertical Bell Labs layered space time (V-BLAST) systems, and it also takes the real and complex constellation into account for the transmitted signals during the extracting process. Finally, the ICA technique is extended to other downlink transmission schemes, such as BSTBC, etc., and is also considered to be an auxiliary means for the traditional receiver. 3) An orthogonal transmit beamforming (OTBF) scheme is proposed to solve the problem of interference in the multi-user system, and three different strategies of OTBF are investigated, i.e., minimum transmission power strategy, maximin signal-to-interference-plus-noise ratio (SINR) strategy and maximin common information rate strategy. Specially, in order to increase the feasibility and efficiency of system modeling and solution, a powerful mathematical tool — convex optimization (mainly semidefinite programming (SDP)) is exploited in the analysis. What is more, a robust design is also proposed to solve the problems of channel estimation errors so that the ability to overcome the CSI errors is improved dramatically.In sum, the joint design between diversity and beamforming as well as the OTBF scheme at the transmitter side and the ICA based blind detection approach at the receiver side are investigated in this dissertation, and the new mathematical tools including ICA and convex optimization are used in the modeling and solution of the proposed schemes. Finally, the problems to be solved related to this research field and future research topics are summarized, furthermore, the prospect of the developing tendency is analyzed as well.