| Transmission technology plays a very important role in the wireless communication systems, especially when the band resource is becoming more and more limited. Effective transmission is able to increase data rate and improve spectral efficiency. With the development of multiple input multiple output (MIMO) and orthogonal frequency division multiplexing (OFDM), the research on transmission has been extended to frequency domain and space domain besides time domain. It is the tendency to combine the advantages of both MIMO and OFDM, in order to establish high-rate reliable wireless systems.On the basis of international current research works, this thesis investigates some transmission technology in the MIMO wireless communication systems in depth, especially at base coordination in MIMO cellular broadcast channels, power allocation combined optimized coordinated transmission, code division multiplexing access (CDMA) in MIMO-OFDM systems, space-time-frequency spreading code design and dynamic resource allocation in grouped multiple carrier (MC) CDMA. Main work and innovations in this thesis are:Firstly, coordinated transmission based on max-min rate criterion in MIMO broadcast channel (BC) is investigated.The ranges of sum data rate of zero-forcing (ZF) and minimum mean square error (MMSE) coordinated transmissions are given, and the corresponding mathematic forms of power allocation of users' symbols are presented. Based on block diagonalized (BD) and with MMSE criterions, BD coordinated transmission with MMSE criterion is proposed. BD coordinated transmission with MMSE effectively mitigates co-channel interference and significantly decrease the implemental complexity. Thus it ensures the desirable feasibility with high spectral efficiency.Secondly, optimized coordinated transmission in MIMO broadcast channel is investigated. Different from that based on max-min rate criterion, optimized coordinated transmission allocates users' symbol power according to their channel information, in order to increase data rate. It has efficiently improved spectral efficiency of the systems to jointly optimize the power allocation of users' symbol and coordinated transmission. Moreover, in accordance to the optimized coordinated scheme, user selection criterion for multiple user scenarios has been proposed.Thirdly, CDMA and space-time-frequency spreading MIMO-OFDM systems have been investigated. The three-dimensional spreading scheme in downlink MIMO-OFDM systems has been introduced. Motivated by the existing double orthogonal code (DOC), extended double orthogonal spreading code (E-DOSC) has been proposed. E-DOSC breaks the "2 square" limit on spreading length while keeping the double orthogonality. It could be used in the real systems more flexibly.Furthermore, non-limited pair-orthogonal code (NPOC) is investigated in downlink MIMO-OFDM systems.The code design of NPOC has been proposed, which satisfies design criterion of non-limited pair-orthogonality, suppresses multi-user interference (MUI) by balancing users' performance, ensures the improvement of system performance. It explores the advantages of multiple antennas and realizes full space diversity among transmit antennas.Meanwhile, it has quite flexible code length and can save lots of band resource while performance is ensured.Finally, dynamic resource algorithms in downlink grouped MC-CDMA are investigated. By grouping sub-carriers into several sub-bands and allocating users to different sub-bands, MUI is decreased and performance is improved. The optimal user-grouping criterion is proposed, which is impractical because power allocation is included. With MMSE detection, equivalent SINR is proposed to be used as the grouping criterion. Two user-grouping algorithms are also proposed, which achieve ideal spectral efficiency and bit error rate, with low implemental complexity.
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