3. System architecture and problem description
Here, a UDN environment is considered, where small cells are overlaid by macro cells. The
set of BSs can be turned on/off based on the statistics and characteristics of flows associated
with them by a cell-level energy manager. The BSs which are turned on are referred as active
BSs and the BSs which are turned off, are referred as inactive BSs. In Fig. 1, we define an
architecture of software defined UDN.