Dual Communications in MIMO SCMA-Based Secure HetNets

This paper studies a novel dual-mode scheduling framework that jointly performs power allocation, beamforming, and sparse code multiple access (SCMA) based scheduling over microwave and millimeter wave (mmW) bands. We propose a robust secure transmission scheme assuming imperfect channel state information for the eavesdropper links. The proposed scheduling framework allows users to schedule simultaneously on each dual-mode BS, based on SCMA, to maximize the joint access secrecy and backhaul rates under transmit power constraints. It is shown that the proposed scheduling framework can find an effective scheduling solution over both microwave and mmW in polynomial time. Simulation results show that the dual connectivity, and joint solutions have 22.5%, and 20% performance gain compared to only microwave, and the disjoint solution, respectively.