Study on Spectral Efficiency Improvement by Space Time Coding Technique for High-speed High-capacity Mobile Radio Communications

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In this research, space-time coding and MIMO channel transmission are investigated in order to further improve the spectral efficiency of radio communication systems. In these techniques, multiple co-channel signals are transmitted at the same time from different transmitting antennas. This transmission technique offers diversity effect when the signals carry the same information; otherwise this scheme improves the spectral efficiency by simultaneous radiation of multiple signals modulated by different information. The trellis-coded co-channel interference canceller (TCC), which is proposed by our research group, is a form of space-time coding and MIMO channel transmission in multiuser communication scenarios. In this research, the number of antennas assumed in TCC is enlarged to extend the TCC to a more aggressive MIMO transmission scenario. Then the signal processing technique and coding technique areinvestigated for MIMO-TCC. Also inlab experiments using RF equipments are conducted to confirm the performance of the TCC. The major results of this research are as follows:1) In spatial multiplexing systems, TCC can outperform the well-known BLAST scheme because the TCC is based on the optimum signal processing approach, even when the complexity of TCC is reduced.2) TCC is confirmed to be robust against correlation among receiving antennas owing to its trellis coding technique.3) The coding scheme for TCC has much space to improve. In this research, new coding scheme is found to lower the bit error rate.4) The computational complexity of the TCC can be greatly reduced with a small penalty of performance.5) With channel estimation, TCC outperforms space-time coding, which offers good diversity gain by the multiple transmission of the same information.6) In-lab experiments of TCC are conducted, and the results agree well with that of computer simulations.