Rate Adaptation, Power Control, and Diversity Combining in Wireless Systems

The present dissertation consists of a collection of six papers preceded by an introduction. The papers investigate the design and performance analysis of communication systems operating over wireless fading channels. Wireless communication systems carry great expectations for future services. They are expected to give users both reliable high data rate transmission and the freedom of mobility. However, due to the limited available spectral resources and the random nature of the wireless channel, these systems also constitute formidable challenges to the designer. This thesis explores some modern analysis and design tools that can help overcome these challenges to meet the great expectations. Specifically, the thesis is concerned with adaptive transmission schemes for both single link and multi-link communication systems. Key adaptive techniques investigated are those of: i) Adaptive modulation, increasing the spectral efficiency by adapting the signal constellation to the channel state, ii) power control, providing a flexible tool for exploiting the degrees of freedom offered by the wireless channel, e.g., by throughput enhancing powerallocation for single-link transmission, or to provide battery savings at the mobile unit and interference management for multi-link scenarios, and iii) (adaptive) diversity combining, improving and stabilizing link quality by utilizing multiple independent signal paths for communication.