| Summary: | 博士 === 國立交通大學 === 電信工程系所 === 93 === Recently, there has been a substantial increase in the development of multi-input multi-output (MIMO) technologies for evolving wireless mobile Internet services and next-generation cellular systems. These technologies must be able to cope with the challenging wireless environment, and antenna systems in the form of adaptive array or smart antennas can provide an effective and promising solution while achieving reliable and high data-rate transmission. Research and development in this area have significantly increased, and many commercial products are now readily available for wireless communication systems.
This thesis is concerned with the use of multiple antennas at the transmitter and receiver in wireless communication systems. We attempt to provide an overview of all these antenna systems for wireless communications and introduce some of the important issues surrounding them. The key points are that the system must be adaptive and consist of multiple antennas. Several aspects of space-time (ST) processing related to the ST signaling and interference suppression for MIMO based wireless communications will be discussed. In this thesis, we first focus on developing the interference suppression scheme based on an ST receiver. We study an ordered successive interference cancellation (OSIC) based MIMO equalizer over the frequency selective multipath channels. The MIMO equalizer is developed as a reduced-rank (RR) realization of the conventional minimum mean square error (MMSE) decision feedback equalizer (DFE). The MMSE weight vectors at each stage of the OSIC are computed based on the "generalized sidelobe canceller (GSC)" technique and RR processing is incorporated by using the "conjugate gradient (CG)" algorithm for reduced complexity implementation. After that, we then work on the design of MIMO transceiver over the frequency flat channels. In this part, we first study a general MU dual-signaling system, in which each user's data stream is either orthogonal ST block encoded for transmit diversity (TD) or spatially multiplexed for high spectral efficiency (SE) based on its own channel condition. Second we develop an efficient MIMO transceiver architecture (ST encoding/decoding design) with a slight amount of feedback information that optimizes the ST codeword with respect to the BER performance for a grouped orthogonal ST block coded system to achieve both the high SE and link quality (LQ). In particular, the receiver in the two MIMO systems is also designed based on the OSIC scheme. By exploiting the algebraic structure of orthogonal codes, it is shown that the OSIC based detector in the above considered two systems allows for an attractive "group-wise" implementation. The group-wise detection property, resulting uniquely from the use of orthogonal codes, potentially improves the signal separation efficiency. Moreover, the imbedded structure of the channel matrix is also exploited for deriving a computationally efficient "recursive based" detector implementation.
In summary, the main advantages of the proposed ST receivers over the popular existing ones lie in its lower implementation complexity, much faster convergence behavior and better BER performance. On the other hand, we provide a smart and robust solution for transmitter and receiver designs better matched to the channel condition and system requirement in MIMO wireless communications. Mathematical analysis and computer simulations show that the proposed methods can achieve high LQ and high SE and offer excellent immunity to interference and noise.
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