Joint sub-carrier allocation and 3D beamforming design in OMA-NOMA based mmWave heterogeneous networks under channel uncertainties

Abstract

In this paper, we investigate a new radio resource allocation, three-dimensional (3D) multiple input single output (MISO) beamforming and cross-tier interference mitigation in a millimeter wave (mmWave) heterogeneous cellular network. To manage the cross-tier interference, a scheme based on the combination of orthogonal multiple access (OMA) and non-orthogonal multiple access (NOMA) is proposed. To this end, the total bandwidth is divided into OMA-based and NOMA-based sub-carriers in which the macro-cell base station (MBS) uses OMA-based sub-carriers and the total bandwidth is considered for small cell base stations (SBSs). For maximizing the sum-rate of OMA-NOMA based system, a non-convex optimization problem is formulated where the channel state information (CSI) is not known perfectly. The proposed optimization problem is solved by introducing auxiliary variables, alternate search method (ASM) and successive convex approximation (SCA) technique. Then, an iterative algorithm is adopted where sub-carrier, beamforming and BS tilt angle sub-problems are sequentially obtained. The simulation results confirm the effectiveness of the proposed scheme compared with 2D beamforming and OMA-based schemes.