Capacity and optimal resource allocation for fading broadcast channels - Part I: Ergodic capacity

In multiuser wireless systems, dynamic resource allocation between users an d over time significantly improves efficiency and performance. In this two- part paper, we study three types of rapacity regions for fading broadcast c hannels and obtain their corresponding optimal resource allocation strategi es: the ergodic (Shannon) capacity region, the zero-outage capacity region, and the outage capacity region with nonzero outage. In Part I, we derive t he ergodic capacity region of an M -user fading broadcast channel for code division (CD), time division (TD), and frequency division (FD), assuming th at both the transmitter and the receivers have perfect channel side informa tion (CSI), It is shown that by allowing dynamic resource allocation, TD, F D, and CD without successive decoding have the same ergodic capacity region , while optimal CD has a larger region. Optimal resource allocation policie s are obtained for these different spectrum-sharing techniques. A simple su boptimal policy is also proposed for TD and CD without successive decoding that results in a rate region quite close to the ergodic capacity region. N umerical results are provided for different fading broadcast channels. In P art II, we obtain analogous results for the zero-outage capacity region and the outage capacity region.