High-capacity OFDMA femtocells by directional antennas and location awareness

In this paper, we propose a location-aware mechanism combined with a low-cost four-sector switched-beam directional antenna to enhance the spectrum efficiency of orthogonal frequency-division multiple access (OFDMA)-based femtocell systems. The considered location-awareness capability is specified in the current IEEE 802.16m WiMAX standard, but has not been applied to avoid the interference between indoor femtocells and outdoor macrocells. With the knowledge of the locations of outdoor users, the proposed four-sector switched-beam antenna in a femtocell can effectively avoid the interference among femtocells and macrocells by adjusting the number of OFDMA subcarriers used at each femtocell. Numerical results show that the proposed approach can significantly improve spectrum efficiency compared to the existing methods.