| The rapid development of wireless mobile communication systems follows the quest for high data rates and high spectral efficiency which brings a wide range of study for distributed wireless communication systems(DWCS). To improve the system capacity and reliability, multiple input and multiple output(MIMO) technology is introduced into DWCS. Linear disperse codes(LDC) can get a trade-off between diversity gain and multiplexing gain, and can be flexibly used for any antenna configurations, so the study of LDC in DWCS is very important.On the one hand, traditional LDC codewords designed based on centralized MIMO systems are not suitable for DWCS. On the other hand, as for the enhancement technologies in MIMO systems, traditional LDC transmit antenna selection (LDC-TAS) algorithms are based on a high-order equivalent MIMO system and have high complexity. Hybrid space-time coding can further make use of some poorest channels moved by TAS via coexistence of several codec links but brings system complexity. Form the point of modulation, existed adaptive modulation and space time coding(AM-STC) suggests that lower modulation is a good choice only through simulation. So we first propose the distributed LDC(D-LDC) codeword design in this thesis, and further in response to the above enhancement technologies, TAS with lower complexity, multi-rate LDC and AM-STC based on theory are proposed.First, a method of distributed LDC codeword design based on different average channel gain between distributed transmission antennas and receiver in DWCS is proposed. Compared with the traditional random search algorithm, the complexity of minimizing the column correlation of linear transformation matrix(LTM) to approximate the trace orthogonal requirements is significantly reduced. Simulation results show that the performance of D-LDC is prior to that of traditional LDC in the edge of DWCS.To study the transmit antenna selection algorithm with lower complexity in LDC systems, the max-min post-SNR and maximum capacity transmit antenna selection algorithm are analyzed. And then, the max-min eigenvalue TAS and maximum approximate capacity TAS based on the subset channel matrix are proposed. To further reduce complexity, we propose an algorithm based on matrix cancellation. Simulation results suggest that the TAS based on matrix cancellation has lower complexity and the approximate performance with the optimal maximum capacity TAS. Unlike the max-min eigenvalue TAS which is affected by the minimum average channel gain in the edge of cross-coverage in DWCS, the TAS based on matrix cancellation is affected less and can get a good performance.Multi-rate LDC transmission is proposed to effectively use the channels moved by TAS. First, the multi-rate LDC with symbols from different modulations is considered which is realized by the power allocation among different symbols based on the BER formula and has high complexity. Further, we propose an algorithm of multi-rate LDC codeword design with symbols from the same modulation subset. Compared with the traditional LDC, there is no additional complexity based only on the replace of LDC basis matrix. To further improve the reliability, the adaptive of multi-rate LDC and traditional LDC-TAS is introduced and can get better performance than tradition dual-mode transmit antenna selection without additional complexity.Considering the point of modulation, we theretically prove that the lower order modulation is more effective than the higher order modulation under a given transmission rate base on the approximate constellation constrained capacity formula. Further, the AM-STC based on instantaneous channel information is proposed and can effectively improve the spectral efficiency at low SNRs. Finally, D-LDC, LDC-TAS with lower complexity, multi-rate LDC and AM-STC are compared from the aspects of BER performance, feedback bits, complexity and codeword storage space. An algorithm with lower complexity and higher reliability is selected and has a good practical in DWCS.
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