Research On Adaptive Multi-mode MIMO-SCFDE Transmission System

Next-generation wireless communication systems have higher requirements for data rate and transmission quality. Fading caused by multipath transmission is the main factor which affects the transmission rate and transmission quality. MIMO-OFDM and MIMO-SCFDE systems can combat the multipath fading effectively and have high spectral efficiency at the same time. They become the key techniques for the physical layer of the next-generation wireless communication systems.Adaptive transmission technique is the one which exploiting the channel state information, adaptively adjust its transmission strategy to improve the effectiveness and /or reliability of communications systems. For MIMO systems, adaptive techniques such as pre-coding and antenna selection are commonly exploited.This thesis first gives a brief introduction of the system structures and the principles of the MIMO-OFDM and MIMO-SCFDE systems. Then some existing adaptive MIMO-OFDM transmission schemes are introduced, including the adaptive algorithms based on full channel state information as well as the one based on partial channel state information and on limited feedback. The codebook based precoding MIMO-OFDM systems are described, especially in terms of the contradictory relationship amount the amount of feedback, the complexity and the spectral efficiency. In order to make a good compromise among these contradiction factors, we propose an efficient adaptive multi-mode MIMO-SCFDE transmission system to obtain a rather simple compromise. According to the performance analysis of the system, we give some methods of selecting the frequency domain loading points, based on SNR criteria, the Gaussian criteria and channel capacity criteria. Through simulation we found that under the same BER performance different criteria select different number of frequency domain loaded points. But the difference is slight. Each frequency sub-channel of the systems needs only[log2(NT+1] bits feedback. To compare with interpolation-based MIMO-OFDM multi-mode precoding systems, we found that under the same transmission rate and transmit power, the BER performance of the system we proposed is better with less amount of feedback. To further improve the spectral efficiency, we add antenna selection technique to the system, and propose an adaptive multi-mode MIMO-SCFDE transmission system with the antenna selection. This system requires NT bits per frequency sub-channel to feedback. Although needing more feedback information than the one without antenna selection, this system has obvious advantages in term of spectral efficiency.