Analysis of small cell partitioning in urban two-tier heterogeneous cellular networks

This paper presents a system model that enables the analysis of indoor downlink performance in urban two-tier heterogeneous cellular networks. The urban building topology is modeled as a process of randomly distributed circles. Each building is deployed with an indoor small cell with a certain occupation probability. Macro base stations are sited outdoors. Their signals experience distance-dependent shadowing due to the blockage of the buildings. Given a typical building at the origin, expressions for the coverage probability with- and without small cell occupation are derived. The analysis of the asymmetric interference field as observed by a typical indoor user is simplified by approximations. Their accuracy is verified by Monte Carlo simulations. Our results show that isolation by wall partitioning can enhance indoor rate, and that the improvement is more sensitive to building density, rather than penetration loss per building.