Downward Facing Directional Antennas for Ultra-High Density Indoor Small Cells

The demand for wireless data is predicted to grow exponentially in the next few years, driven by the growing popularity of smartphones and tablet devices, and new data intensive services. The use of small cells in a heterogeneous network structure is a promising way of providing the required capacity in future 5G cellular networks, offering gains in capacity due to higher spatial reuse, better radio propagation conditions and the ability to target demand hotspots. Examples of these small cells include femtocells and metrocells. In this paper, the concept of deploying indoor small cells in higher densities in order to further leverage spatial reuse gains is examined. The issues and challenges involved in deploying these very small cells with coverage range of only a few meters and a novel antenna configuration providing coverage from the ceiling are discussed. Simulations of an LTE deployment are performed indicating that the proposed antenna configuration reduces interference and improves capacity by a factor of 4 compared to using traditional dipole antennas, enabling significant indoor user throughput gains. Simulations also show that the increased densities also can result in very high number of handovers, and techniques for managing mobility in such deployments are needed.