Quantum Bacterial Foraging Optimization Based Interference Coordination in 3D-MIMO Systems

Interference coordination can effectively suppress interference to improve communication quality and is one of the fundamental problems in three-dimension multiple-input multiple-output (3D MIMO) wireless communication systems, especially in multi-cell multi-user multiple-input multiple-output (MIMO) systems. Previous works on interference coordination only consider system spectral efficiency, which may result in departmental users' throughput approaching zero. In this paper, we design an efficient transmission scheme to suppress the interference in multi-cell multi-user 3D MIMO downlink system, taking both the spectral efficiency and fairness into account. In this scheme, cell-center user and cell-edge user specific downtilts and power are jointly optimized and each user can reach an acceptable sum rate. The target problem is a combinatorial non-convex optimization problem that cannot be solved by the traditional KKT-based (Karush-Kuhn-Tucker) Lagrangian algorithm, here the improved quantum bacterial foraging optimization (IQBFO) algorithm is used to solve it due to its fast convergence. Finally, simulation results show that the proposed scheme has a larger system throughput when considering the user fairness, i.e., all of the users can transmit at an acceptable rate. Moreover, our IQBFO algorithm has a fast convergence.