nd by the enterprise IP network to smaller sites. Using Distributed Antenna Systems for In-Building Coverage Distributed Antenna Systems (DAS) are an alternative to picocells for coverage within buildings. DASs consist of repeaters connected to coaxial, twisted-pair, or fiber-optic cabling in buildings. A repeater amplifies cellular signals transmitted into buildings by equipment that the cellular carrier supplies. Repeaters are located throughout the building and transmit Radio Frequency (RF) signals to the macrocell. Unlike super femtocells, they don't actually offload traffic from the larger cellular network because they are not capable of reusing spectrum. They also are connected to building broad- band services to offload traffic from a carrier's backhaul network. DASs are also located in subway systems and sports stadiums for which traditional cell sites don't generally reach or provide adequate coverage. Building and transporta- tion owners hire contractors to install the cabling over which the repeaters are con- nected and the signals travel. The carrier installs its own antenna that provides the cellular signals. In some of these systems, particularly public spaces such as subways and airports, multiple carriers are connected to the DAS. For enterprises, gaining their carrier's agreement to connect to either a DAS or a microcell solution is a major challenge. Even large enterprises have experienced long delays in receiving permission or making upgrades to these in-building coverage installations. The advent of lower-cost solutions, more efficient spectrum re-use, and increased revenue from usage fees might provide the impetus to increase the speed and number of these implementations. Importantly, enterprises with in-building wireless systems are more likely to be "sticky" clients. They are less likely to drop their carrier after their investments of time and money in a DAS. Mobile and Wi-Fi Networks Deploying Femtocells for Improved Coverage Femtocells are essentially miniaturized base stations on a chip