Backhaul-Constrained Small Cell Networks: Refunding and QoS Provisioning

Small cell access points (SAPs) can offload macrocell traffic, improve indoor coverage and cell-edge user performance, and boost network capacity. In this paper, we investigate the problem faced by the mobile network operator (MNO) on how to properly incentivize the existing private SAPs to serve extra roaming macrocell users. We propose a refunding framework for small cell networks with limited-capacity backhaul, where small cell holders (SHs) receive refunding from the MNO and then admit macrocell users. Specifically, we formulate a two-stage refunding-admission game with MNO being the leader and SHs being the followers. Our results can be summarized as follows: 1) we formulate a revenue maximization problem by allowing the MNO to set individualized refunding and interference temperature constraints to SAPs. We propose a lookup table approach to solve it; 2) for small cells with guaranteed QoS provisioning, we consider access-based refunding and propose a near-optimal joint user admission and power allocation algorithm to solve the utility maximization problem at each SAP; and 3) for small cells with best-effort QoS provisioning, we consider usage-based refunding and propose a majorization method-based power allocation algorithm. Extensive numerical results show that our proposed framework and algorithms yield significant improvements on the MNO's net revenue and SHs' utilities compared with a non-refunding case. Our research highlights the possibility of enhancing the MNO's net revenue without changing the current network structure and the importance of incentivizing SHs by taking the limited-capacity backhaul into account.