Downlink outage probability of co-channel femtocells in hierarchical 3-Sector macrocells

In this letter, we analyze the outage probability (OP) of orthogonal frequency division multiple access (OFDMA) based downlink (DL) for femtocells under co-channel deployment in hierarchical 3-sector macrocells. We first derive a closed-form expression of the femto DL OP, and then devise a distributed scheme for femtocells to control their DL transmit power according to femto users' locations within the macrocell network. Numerical and simulation results show that the femtocell exclusion region (FER) around a 3-sector macro base station (MBS) shrinks at edges between macro sectors, giving more space for co-channel femtocell deployment, and the proposed distributed femto DL power control is able to stop co-channel femto DL transmissions inside the FER and maintain reliable DL services for all femtocells outside the FER, while effectively reducing macrocell DL OP, especially at edges between macro sectors.