Energy efficiency of a heterogeneous network using millimeter-wave small-cell base stations

For fifth generation (5G) cellular systems, various approaches are studied including millimeter-wave (mm-wave) communications and heterogeneous networks (HetNets) with small cells. In mm-wave bands, since a much wider bandwidth is available, higher data rates can be achieved. However, mm-wave transmissions suffer from blockage. In this paper, in order to take advantage of a wide bandwidth in mm-wave bands with mitigating the blockage problem, we consider a HetNet consisting of micro-wave base stations (BSs) for macro cells and mm-wave BSs for small cells and study its energy efficiency. We show that the energy efficiency of the considered HetNet can be maximized by choosing the optimal communication range of mm-wave BSs.