On the Expected Rate of Slowly Fading Channels with Quantized Side Information

A multiple-layer variable-rate system employing quantized feedback to maximize the expected rate over slowly fading channels is studied. The transmitter utilizes partial channel-state information, obtained via an optimized resolution-constrained feedback link, to adapt the power and to assign code layer rates, under different power constraints. We develop an iterative algorithm to optimize the system parameters, which successfully exploits results from the study of parallel broadcast channels. Unlike in the ergodic case, even coarsely quantized feedback improves the expected rate considerably. Our results indicate that with as few as one bit of feedback information, the role of multi-layer coding reduces significantly