This technical scenario works not only for cellular service but also other
wireless services. For example, the RFs used for public safety can be
“extended” into a building’s DAS allowing public emergency responders to
readily communicate. The DAS-type infrastructure for cellular services can
also be leveraged to provide in-building Wi-Fi. Some commercial real estate
owners are finding that complete in-building Wi-Fi is less expensive and pre-
sents fewer issues than dealing with tenant-provided Wi-Fi systems that inter-
fere with each other.
Pico Cells
Pico cell systems are small radios, similar to the outdoor cellular base stations,
but limited in capacity and power. They are manufactured by the major cell
equipment companies and are best suited for apartment complexes and small
office buildings. They are typically connected back to a cell base station using
an IP network; the base station controls the pico cells, thus managing the
communication traffic to and from the small cells in the buildings.
The pico cells can compete with the outdoor macro cell for coverage. That
is, a cellular handset could possibly hunt from the small pico cells to the macro
cells for service. To prevent this, the pico cells have to provide a strong and
dominant signal. The strength of their signal affects the area that will be
covered and the system’s caller capacity.
Multiple pico cells used in a building can provide better coverage but
because each cell uses the same frequency more interference or noise is created.
The result is decreased capacity of the system to carry higher data rates. Pico
cells combined with a DAS can provide better overall system performance.
Figure 10.2 Simple distribution antenna system.
Voice Networks and Distributed Antenna Systems 119