MIMO And Its Application In Wireless LAN

Multiple Input Multiple Output (MIMO) is a key technology in the wireless communication systems of the new generation, as a result of its benefit for improving either the reliability or the speed. Therefore, the theory and the application of MIMO are the focus of this dissertation. The main problems solved here include: the design criterion and method of space-time codes for transmit diversity (TD), the encoding/decoding schemes for space multiplexing (SM) and its combination with TD, and also the applications of such techniques in Wireless LAN (WLAN) from the aspect of throughput.The main ideal of this dissertation can be expressed as follows:Firstly, the improvement of the trace criteria (TC) for space-time trellis code (STTC) is studied. Although the key ideal of the TC is correct, the upper bound of the pairwise error probability is not reasonable, and the code design method has deficiency. Thus, by re-derivation two new upper bounds, eigenvalues sum-square/square-sum ratio and squared distances sum-square/square-sum ratio, are got for slow and fast fading respectively. The code design method is also improved, and some better new codes have been found. The different performance of a code in slow and fast fading channels can be explained by the differences between the eigenvalues sum-square/square-sum ratio distribution and the squared distances sum-square/square-sum ratio distribution of that code. As the TC is the dominant factor affecting the code performance for both slow and fast fading, it can also be used to design the smart-greedy code. Some better smart-greedy codes are presented in this dissertation.Secondly, the TC, which was originally designed for flat fading channels, is extended to the frequency selective fading channels. This part of work includes two points:One is that the key ideal of the TC is proved to be also correct in frequency selective fading channels in despite of fading speed. The other is that STTCs designed by the TC also perform well when they are used as space-frequency trellis codes (SFTCs). This conclusion is made by the analysis of the corelation between STTC and SFTC. The ideal of traces distribution is suitable for SFTC too. The increase of path time delay can give evident improvement to SFTC performance when there is no interleaveing between subcarriers in orthogonal frequency division multiplexing (OFDM), but will give almost none improvement when interleaving exsits. On the other hand, the interleaving can give evident improvement when the path time delay is small, while give a little decrease when the path time delay is large. Same as STTC, increase the trellis state of SFTC will improve the performance evidently.The handcrafted design of super orthogonal space-time trellis code (SOSTTC) based on the TC is studied thirdly. The shortcoming of the rank-determinant criterion based design and the merit of the TC based design are analyzed. The factors optimization in the TC based SOSTTC design is studied. Especially the assignments of signal subsets and the space-time block coding (STBC) schemes are explained in detail accoding to the different trellis structures. Through constellation expansion, new better codes can be found. The simulation results show that the SOSTTCs designed by the TC also perform well in fast fading channels. At the end of this part, two easily made mistakes during SOSTTC decoding are pointed out.Then, the encoding/decoding schemes for Bell laborataries layered space-time (BLAST) and its combination with TD are studied. A new group interference suppression algorithm named as...