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 broadband
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 transportation
owners hire contractors to install the cabling over which the repeaters are connected
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.