Joint Secure User Association, Power and Subcarrier Allocation in Decoupled 5G Heterogeneous Network

Coverage, capacity and throughput can be enhanced significantly by offering a hybrid solution consisting of microwave high power base station (HPB) underlaid millimeter wave low power base station (LPB) augmented by the downlink uplink decoupled (DU-De) user association strategy in N-tier heterogeneous networks (HetNets). However, secure user association, power and microwave and millimeter wave sub-carriers allocation employing DU-De strategy has not been investigated in the past. This work formulates mathematical models for DU-De strategy and downlink uplink coupled (DU-Co) strategy to investigate secure user association, power and sub-carrier in microwave and millimeter wave band allocation for secrecy rate maximization in N-tier HetNets. Nature of the formulated problems is complex, challenging and NP-hard. Outer approximation algorithm, with less complexity, is used to solve the formulated problems for optimal solution. Extensive simulation results in terms of secure user association and average secrecy rate show the effectiveness of DU-De strategy over DU-Co strategy in HetNets.