| Summary: | 碩士 === 國立成功大學 === 電腦與通信工程研究所 === 98 === In the 3rd generation mobile communication system, as a result of Multiple Access Interference (MAI) caused by multi-users and inter-symbol interference (ISI) due to multipath propagation delay, those interferences limit the capacity of multiple users in the cellular system and affect the transmission quality of communication, decreasing the system performance seriously. Besides, the orthogonal condition of spreading sequences in MIMO-CDMA system is destroyed and cause interference in multipath environment and non-quasi static channel. So as to decrease the complexity of system and overcome the multipath fading, the parallel rake receivers to despread orthogonal- and cyclic- inherent space-time code and multipath interference cancellation to enhance the signal signature are proposed in this thesis.
The system design is a combination of our proposed decoding structure and using the correlation characteristic of M-sequence to separate multipath signals caused by spatial diversity in MIMO system. To overcome the time dispersion of the transmitted signal due to multipath effect, we utilize rake receivers with time diversity and achieve the maximal diversity gain from the independent multipath component. After that, we use the proposed multipath interference mechanism to reconstruct the several replicas of the same information signal which is transmitted over transmit antennas, eliminating the ISI before maximum ratio combining. We analyze the different transmission rate and diversity order for different transmit antennas. Furthermore, the exact error probability of the proposed scheme is also derived.
Mathematical analysis and simulation results show that the proposed scheme in multipath environment over non-quasi static channel, it can be decoded by a significant low complexity ML decoder. Comparing to conventional STBC with single rake receiver in MIMO-CDMA scheme, it obtains the better system performance and suitable to use in the wireless mobile communication.
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