  Femtocell networks are promising for not only improving the coverage but also
increasing the capacity of current cellular networks. The interference-limited
reality in femtocell networks makes interference management (IM) the key to
maintaining the quality of service and fairness in femtocell networks.
Over-the-air signaling is one of the most effective means for fast distributed
dynamic IM. However, the design of this type of signal is challenging. In this
paper, we address the challenges and propose an effective solution, referred to
as single-tone signaling (STS). The proposed STS scheme possesses many highly
desirable properties, such as no dedicated resource requirement (no system
overhead), no near-far effect, no inter-signal interference, and immunity to
synchronization error. In addition, the proposed STS signal provides a means
for high quality wideband channel estimation for the use of coordinated
techniques, such as coordinated beamforming. Based on the proposed STS, two
distributed dynamic IM schemes, ON/OFF power control and SLNR
(signal-to-leakage-plus-noise-ratio)-based transmitter beam coordination, are
proposed. Simulation results show significant performance improvement as a
result of the use of STS-based IM schemes.
