  The surest way to increase the system capacity of a wireless link is by
getting the transmitter and receiver closer to each other, which creates the
dual benefits of higher quality links and more spatial reuse. In a network with
nomadic users, this inevitably involves deploying more infrastructure,
typically in the form of microcells, hotspots, distributed antennas, or relays.
A less expensive alternative is the recent concept of femtocells, also called
home base-stations, which are data access points installed by home users get
better indoor voice and data coverage. In this article, we overview the
technical and business arguments for femtocells, and describe the
state-of-the-art on each front. We also describe the technical challenges
facing femtocell networks, and give some preliminary ideas for how to overcome
them.
