Optimizing placements of backhaul hubs and orientations of antennas in small cell networks

While small cells (SCs) are an important feature of emerging network architectures, providing backhaul to SCs is a challenging problem. Non-line-of-sight (NLOS) wireless backhaul networks provide a cost effective approach in urban areas where providing a wired- or fiber-based backhaul is difficult. An important problem in designing such networks is to optimize the position of backhaul hubs in a way that all SCs are properly serviced. However, this is a NP-complete problem requiring suboptimal, but effective, solutions. In this work, we will propose a novel suboptimal algorithm, based on dynamic programming, to solve the NP-hard problem of hub placement in backhaul networks. We will further consider an extended problem of optimizing both the placement of hubs and the orientation of the hub antennas. Our design methodology is backed up with numerical examples using deterministic channel prediction tools which leads to a robust and smart design of the backhaul network.