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.