HICIC: Hybrid Inter-Cell Interference Coordination for Two-Tier Heterogeneous Networks With Non-Uniform Topologies

Interference coordination is regarded as one of the most significant techniques in heterogeneous networks (HetNets). In this paper, we propose a novel interference coordination framework, which is referred to hybrid inter-cell interference coordination (HICIC), for interference mitigation in HetNets with non-uniform topologies. The meaning of hybrid is two-fold: first, several techniques belong to intercell interference coordination (ICIC), enhanced ICIC (eICIC), and further eICIC (FeICIC) are considered simultaneously. We perform the resource partition in both the time-domain and the frequency-domain jointly. A novel dummy base station structure is designed to take full advantage of resources. Second, different subbands in the same cell can be configured with different almost blank subframe (ABS) ratios for diverse purposes. A novel concept, coordination willingness, is proposed for determining ABS ratios in a distributed manner with limited signaling overhead. We formulate HICIC parameters optimization as a logarithm utility maximization problem and provide a semi-distributed algorithm comprising three stages to solve it. Numerical results demonstrate the efficiency of HICIC over several comparative schemes in HetNets with two different non-uniform topologies. It achieves the maximal system utility among all schemes and improves the performance of user equipment's (UEs) who have geographical disadvantages. With HICIC, sum throughput of all UEs has a significant increase with slight losses in the fairness. Our work also verifies the fact that ICIC and eICIC/FeICIC are not either-or propositions. A reasonable combination of different techniques can mitigate interference effectively making a better HetNet.