Outage performance of opportunistically placed low-powered base stations in heterogeneous cellular networks

Due to the recent deployment of various low-powered base stations (BSs) within the macro cells, intra-cell interference has increased. This adversely effects the network performance of users within the cells. Considering a closed access system, a user can only connect to the BS it belongs to and the rest of the BSs act purely as interferers. So, in order to avoid excessive interference, opportunistic placement of BSs becomes necessary. Recent literature on heterogeneous cellular networks consider the placement of all BSs according to some random distribution. Although this consideration is realistic for low-powered BSs, it is not feasible for macro BSs. The macro BSs are generally placed after careful network planning with a minimum separation between them. In this work, we consider a heterogeneous network model where the macro BSs are placed on a hexagonal grid lattice rather than in random. We propose to use the low-powered BSs opportunistically rather than randomly within the macro cells. We show that, instead of using the low-powered BSs randomly within the cell, placing them opportunistically near the macro cell boundary can improve user performance while reducing network interference.