Multiuser MISO beamforming and interference cancellation in two-tier femtocell networks

Transmit beamforming can be performed to achieve capacity gains by spatially multiplexing multiple users and reduce outages by spatial interference mitigation. In this paper, we investigate the multiuser multiple input single output (MU-MISO) transmission in a two-tier femtocell network where base stations in each tier follow an independent Poisson point process (PPP), and provide insights into the spatial interference mitigation at the transmitter. A joint frequency and spatial interference cancellation (JFSIC) scheme is proposed to eliminate the dominant downlink interference from closed access femto access points to severely impacted macrocell users. Using stochastic geometric tools, the performances of both tiers are evaluated in terms of success probability and area spectral efficiency. Monte Carlo simulations are performed to verify our analytical results and demonstrate the effectiveness of JFSIC scheme compared to the conventional zero-forcing beamforming.