Backhauling in Heterogeneous Cellular Networks: Modeling and Tradeoffs

Consumer demand for data has increased tremendously over the last years, and small cell networks are increasingly being considered as one of the key technologies to cope with this demand. Small cell network deployments within the conventional macro cellular networks are creating a significant amount of heterogeneity compared to traditional cellular networks. Nevertheless, the backhaul link is often the bottleneck in terms of system performance and cost. In this paper, we consider the backhaul issue in heterogeneous cellular networks and propose a hierarchical network model using superimposed independent homogeneous Poisson point processes. We derive the total expected delay by taking into account retransmissions over the wireless link, as well as the backhaul delay incurred from both wired and wireless backhaul. For the total expected deployment cost, we take into account infrastructure cost and the construction cost of wired backhaul deployment. Specifically, we are able to characterize the behavior of delay and deployment cost using our simple and tractable model. Furthermore, we propose a delay-based access control policy, which can provide better latency performance especially in dense deployments. Our theoretical framework provides a fundamental understanding of the tradeoff between wired and wireless backhaul and the effect on deployment cost and system performance in heterogeneous cellular networks.