Impact of Placement of Small Cells on Downlink Performance for Cellular Wireless Networks

In this paper, we consider a cellular system whose downlink transmissions are managed by the use of a heterogeneous layout of macro and micro base station nodes. Our objective is to determine the impact of the addition of small cells on the throughput capacity of the downlink system in each individual cell. For this purpose, we first determine the locations in each cell at which a mobile would monitor the lowest SINR levels, which is important in evaluating the system´s scope level of global coverage. The configuration of modulation/coding sets and related code rate levels are adjusted accordingly. Assuming base station nodes to coordinate their downlink transmissions by using coloring oriented schedules, we prove that mobiles record the lowest SINR levels when they are located at the outer vertices of each cell´s region. We further prove that in fact, by using properly coordinated scheduling mechanisms, the inclusion of small cells leads to also enhanced throughput rate in each individual cell.