| Multi-Input Multi-Output (MIMO) wireless communications have received increasing attention in recent years, thanks to their potential for high spectral efficiency and improved quality of service. Albeit reasonable for wireline links, perfect-CSI-based transmissions developed for MIMO wireless systems can be justified only when the fading is sufficiently slow. On the other hand, the proliferation of space-time coding research we have witnessed lately, testifies to the efforts put towards the other extreme: conservative designs requiring no CSI to be available at the transmitter. As no-CSI leads to robust but rather pessimistic designs, and perfect CSI is probably a utopia for most wireless links, MIMO communications with partial CSI promise to have great practical value, because they are capable of offering the "jack of both trades."; Motivated by strict bandwidth constraint over the feedback link, we first study transmit beamforming with limited-rate feedback. Two fundamental questions arise in such a limited feedback beamforming system: how can we design the optimal codebook with minimum complexity? and what performance can the optimal codebook achieve? We successfully answer these two questions in this thesis by developing analytical and numerical codebook construction methods, and carrying out both theoretical and operational performance analyses. We also develop an adaptive multi-antenna transmitter that jointly adapts modulation type, transmit power and beamforming vector based on a limited number of feedback bits.; We further investigate partial CSI that can be characterized statistically. We first introduce a channel mean information (CMI) model for frequency selective fading channels. Under this CMI model, we develop an adaptive MIMO Orthogonal Frequency Division Multiplexing (OFDM) transmitter that employs simultaneous power loading across space and frequency, and results into considerable data throughput improvement. We next study a statistical channel amplitude information model and develop necessary and sufficient conditions for antenna selection schemes to achieve the ergodic channel capacity. We finally conclude the thesis by discussing some promising research directions. |
