| High data rates give rise to frequency-selective propagation, while carrier frequency-offsets and mobility-induced Doppler shifts introduce time-selectivity in wireless communication links. As the transmission rates and mobility increase, future generations of wireless communication systems will have to cope with critical performance-limiting challenges that originates from propagation channels exhibiting time- and frequency-selectivity (double-selectivity). This research investigation focuses on the basic properties and principles of doubly-selective channels: modeling, estimation, diversity, and capacity. In a nutshell, the research in this dissertation includes: (i) derivation of a basis expansion to model physical doubly-selective channels; (ii) design of linearly coded transmissions with maximum diversity to combat fading of doubly-selective channels; (iii) development of data-aided (training-based) channel estimation and delineation of information-theoretic aspects of doubly-selective propagation with non-coherent receivers; (iv) study of multi-antenna space-time coded transmissions over doubly-selective channels to collect multi-dimensional diversity; and (v) design for multi-antenna systems to achieve full rate and full diversity. The findings impact the basic research, and facilitate the design of mobile wireless systems communicating over interference-rich propagation media. |
