Decoupled Access in HetNets With Backhaul Constrained Small Base Stations

This paper investigates the uplink (UL) and downlink decoupled access in heterogeneous networks with backhaul constraints. A capacity-based user association policy is proposed for users with decoupled access, where small base stations (SBSs) connect to macro base stations via non-ideal backhaul. The UL association probabilities are derived under this policy, where the limitations of association probabilities are obtained when the density of SBSs grows to infinity. Then, the UL signal-to-interference-plus-noise ratio (SINR) coverage probabilities are derived and analyzed for different SINR thresholds. According to the analysis, the effects of the limited backhaul capacity on the average UL SINR coverage probabilities are presented, where a jump discontinuity, which can be considered as a certain SINR threshold, is shown to be brought by the backhaul capacity constraint. It is demonstrated that denser deployment of SBSs helps improve UL performance significantly for users with SINR lower than such SINR threshold while hardly benefits those with SINR higher than it. Finally, the theoretical results are validated via simulations.