Radio Resource Management in Downlink Multi-band mMIMO Systems

Massive multiple-input multiple-output (mMIMO) antenna systems and inter-band carrier aggregation (CA)-enabled multi-band communication are two key technologies to achieve very high data rates in beyond fifth generation (beyond 5G) wireless systems. We propose a joint optimization framework for multi-user, multi-band mMIMO systems where the precoder optimization, optimum sub-carrier selection, optimum power allocation and user scheduling are carried out simultaneously. In particular, we propose a novel multi-user iterative water-filling-based sub-carrier selection and precoding/power allocation optimization algorithm. We also introduce a novel sub-carrier selection scheme which considers the physical constraints (hardware limitation) at the mobile user devices. Via computer simulations we illustrate the sum-rate performance of the proposed optimization-based framework, and its superiority over similar joint optimization frameworks presented in the literature.