QoS feasibility for the MIMO broadcast channel: Robust formulation and multi-carrier systems

Based on recent results for the multiple-input multiple-output (MIMO) broadcast channel (BC), the feasibility of the quality of service (QoS) requirements of multi-carrier systems is investigated. Allowing for a precoding operation with arbitrary structure, the feasibility test for multi-carrier systems is analogous to that for MIMO systems with linear transceivers. However, if the precoder is restricted to be applied separately to the different carriers, additional conditions must be fulfilled for feasibility. After stating these conditions, we propose a simple test which is sufficient, but not necessary for feasibility. For a robust QoS formulation that is appropriate for erroneous channel state information, the feasibility results for the MIMO BC can be reused as long as all possible channel realizations fulfill a regularity condition.