Deploying Small Cells in Traffic Hot Spots: Always a Good Idea?

Abstract

We look at a very simple RAN (Radio Access Network) configuration comprising one macro cell and one small cell, the latter being strategically positioned to absorb the traffic peaks that occur in some time periods in a portion of the area covered by the macro cell. We study this two-cell system with a simple model based on a network of two queues, and we examine the system performance for variable parameter values, showing that some of the emerging behaviors can be critical. In particular, we see that when the handover rate out of the small cell increases, the blocking probability in the macro cell also increases, quickly reaching unacceptable levels. This can be a problem, since high handover rates correspond to limited dimensions of the small cell with respect to the macro cell, which is what is normally expected, unless the small cell is deployed in an area of very slow end user mobility. These behaviors (although possibly not applicable to all small cell scenarios) can have an important impact on the deployment of small cells, which are expected to become increasingly popular because of the need to provide additional capacity in RANs through densification of the cell layout.