Coordinate update algorithms for robust power loading for the MISO downlinkwith outage constraints and Gaussian uncertainties

We consider the problem of power allocation for the multiple-input single-output (MISO) downlink with uncertain channel state information at the transmitter. The uncertainty is modeled probabilistically and the receivers specify quality-of-service (QoS) constraints in terms of a target signal-to-interference-and-noise ratio that is to be achieved with a given outage probability. The proposed approach is based on a deterministic characterization of the outage probability, and mildly conservative approximations thereof. Although the resulting optimization problems are not convex, the good solutions that we obtain using straightforward coordinate update algorithms provide significantly better performance than the existing convex approaches because the approximations are less conservative.