Agh University of Science and Technology Faculty of Electrical Engineering , Automatics , Computer Science and Electronics the Multiple - Input Multiple - Output Systems in Slow and Fast Varying Radio Channels

Multiple-input multiple-output (MIMO) systems are well known as a technique which allows increasing the throughput of a radio link and overcoming the effects of multipath fading. However, the integration of MIMO systems into the standards of wireless networks is slow, as there are numerous problems still unsolved. This PhD thesis deals with MIMO systems in slow and fast varying radio channels. First, the general issues of MIMO systems are considered. Multiplexing gain and diversity concepts, channel knowledge, coding techniques as well as multiuser access and wideband transmission are discussed. Next, the channel aspects of MIMO systems are investigated. The phenomenon of multipath propagation, channel models, variations in the radio channel and channel estimation are addressed. Then, the author's research in the area of slow and fast varying MIMO channels is presented. The following theses are formulated and proved: 1. The throughput in slow varying radio channels of indoor MIMO systems can be significantly increased when the locations and the antennas of the access point are carefully chosen. 2. Iterative Channel Estimation (ICE) algorithm allows decreasing the bit error rate in fast varying radio channels without frequent transmissions of training sequences. The first thesis is founded on the numerical ray tracing calculations concerning slow varying MIMO channels. It is shown how the locations, the separations and the characteristics of the access point antennas can affect the system throughput. The second thesis is based on the proposed ICE algorithm for fast varying channels. ICE algorithm enables the channel estimation simultaneously with the data transmission. When ICE is applied, the bit error rate can be reduced – in some cases it is more than 50 times.