  This paper proposes a self-optimized coverage coordination scheme for
two-tier femtocell networks, in which a femtocell base station adjusts the
transmit power based on the statistics of the signal and the interference power
that is measured at a femtocell downlink. Furthermore, an analytic expression
is derived for the coverage leakage probability that a femtocell coverage area
leaks into an outdoor macrocell. The coverage analysis is verified by
simulation, which shows that the proposed scheme provides sufficient indoor
femtocell coverage and that the femtocell coverage does not leak into an
outdoor macrocell.

Networking and Internet Architecture