Achieving the Capacity Region Boundary of Fading CDMA Channels via Generalized Iterative Waterfilling

We characterize the optimum power control policies that achieve arbitrary rate tuples on the boundary of the capacity region of a power controlled, code division multiple access (CDMA) system in a fading channel with perfect channel state information (CSI). We propose a "generalized" waterfilling approach, and provide an iterative algorithm that solves for the optimum power allocation policy, for a given arbitrary rate tuple on the boundary of the capacity region. We then investigate the effects of limited feedback on the capacity region, and demonstrate that a good power control policy may require only a very low rate feedback