Interference mitigation in femtocell networks using single-radio parasitic antennas

The femtocell networks provide a promising solution to increase system capacity and improve indoor coverage. However, inter-cell interference becomes enormous in femtocells due to dense deployment and cell-size reduction. This paper proposes the interference mitigation method for the downlink of femtocells, using the electronically steerable parasitic array radiator (ESPAR) antenna at both femto-base stations (FBSs) and user terminals (UTs), which relies on a single radio-frequency (RF) chain; thus meets the demanding low-power, low-cost and small-size requirements of modern wireless terminals - FBSs and UTs. We first exploit the ESPAR antenna as a switched-beam array capable of predefining directional beampatterns accessing to different angular sectors. Then each FBS/UT dynamically selects an appropriate beampattern according to its measurement of desired direction. We also consider an optimal way to employ the ESPAR antenna by adaptively designing the beampattern steering to desired direction while placing nulls to interferers. The results show significant gains obtained by using ESPAR antennas at both FBSs and UTs.