| Summary: | 碩士 === 輔仁大學 === 電子工程學系 === 93 === Wireless communication systems support not only voice but also multimedia in the future, It has been recognized that the capacity of a communication system can be increased by employing a space-time block code (STBC) multiple-input-multiple-output (MIMO) system. In the high data rate transmission system, the frequency selective fading due to multi-path propagation is often appeared to cause the inter-symbol interference (ISI) and increase the bit error rate (BER), and the STBC scheme supplies spatial and temporal diversities to achieve robustness against fading effects. The channel impulse response plays an important role in the estimate of the transmitted symbol.
In this paper, we utilize the Alamonti’s STBC scheme and propose a novel subspace channel estimation, and the theoretical analyses on channel estimation are also carried out. The weight analysis is obtained such that half of computational cost is reduced. Besides, both the forward backward averaging technique and the eigenspace technique are presented to enhance the performance of multiuser detection. However, due to the lengthy spreading codes, the LCMV receiver has the drawbacks of large computational complexity and slow convergence speed in computing the filter weight vector. Due to the reason, the GSC filter with partial adaptivity (PA-GSC) is proposed to take the place of LCMV filter. Based on these techniques, we implement the STBC Multi-rate DS-CDMA MIMO system, STBC MC-CDMA MIMO system and STBC Multi-rate MC-CDMA MIMO system. Computer simulations are given to demonstrate the effectiveness of the proposed channel estimation and multiuser detection techniques.
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