A Convex Optimization Approach for the Robust Design of Multiuser and Multiantenna Downlink Communication Systems

In this work, we study a downlink communications scheme, focusing our attention on the case where the base station is equipped with multiple antennas and transmits information simultaneously to a certain number of users with single antenna terminals. We consider a realistic scenario where an imperfect estimate of the actual channel is available at both communication ends. Precisely, the actual channel is assumed to be inside an uncertainty region, around the channel estimate, which models the imperfection of the channel knowledge. In this context, we propose a robust power allocation technique that minimizes the transmitted power, while maintaining the necessary quality of service to obtain reliable communication links between the base station and the users. This robust power allocation is obtained as the solution of a convex optimization problem, which is next particularized for two common cases of channel uncertainty regions, and which can be numerically solved very efficiently. Finally, we present simulation results to show the performance of the proposed transmission scheme