Quantized Feedback for Slow Fading Channels

Two topics in fading channels with a strict delay constraint and a resolution-constrained feedback link are treated in this thesis.First, a multi-layer variable-rate single-antenna communication systemwith quantized feedback, where the expected rate is chosen as the per-formance measure, is studied under both short-term and long-term powerconstraints. Iterative algorithms exploiting results in the literature of par-allel broadcast channels are developed to design the system parameters. Anecessary and sufficient condition for single-layer coding to be optimal is de-rived. In contrast to the ergodic case, it is shown that a few bits of feedbackinformation can improve the expected rate dramatically. The role of multi-layer coding, however, reduces quickly as the resolution of the feedback linkincreases.The other part of the thesis deals with partial power control systemsutilizing quantized feedback to minimize outage probability, with an empha-sis on the diversity-multiplexing tradeoff. An index mapping with circularstructure is shown to be optimal and the design is facilitated with a justifiedGaussian approximation. The diversity gain as a function of the feedbackresolution is analyzed. The results are then extended to characterize the en-tire diversity-multiplexing tradeoff curve of multiple-antenna channels withresolution-constrained feedback. Adaptive-rate communication is also stud-ied, where the concept of minimum multiplexing gain is introduced. It isshown that the diversity gain of a system increases significantly even withcoarsely quantized feedback, especially at low multiplexing gains.