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overall communications plan. Therefore, it is becoming more common to see neutral Distributed
Antenna Systems (DAS) within airport communications topologies.
Cellular base stations are sized for typical operating conditions within the coverage of a cell.
During emergency operations, on- or off-airport, the traffic load can easily overload a base station and
prevent critical calls from being completed. In anticipation of these situations, airport operators should
either have capacity agreements with the local carriers, or arrange for mobile base stations to be deployed
to the airport during emergencies.
Cellular traffic is transmitted “in the clear” and is not considered secure. Protocols like GSM do incorporate
voice security means, and voice encryption applications are available for most types of phones.
Basic cell phones provide limited feature sets. Smartphone’s enable the user to do a variety of functions
including accessing the Internet, over which video as well and voice traffic can be delivered. Smartphone’s
are mobile extensions of the airport’s IT network, in addition to providing cellular telephone services, and
should be considered network appliances during system design. It is for the airport operator to decide how
far to extend these services and what security measured are required to protect both the Smartphone and
the IT network.
Trunked Radio Systems and Interoperability
A trunked radio system is a specialized repeater system with one or more towers, and multiple frequencies,
which allows channelized, semi-private conversations between many more groups of users than it actually
has allocated RF channels; and is made possible by statistical multiplexing. There are many different
implementations of trunked business and public-safety radio, using different trunking protocols; two types
of systems commonly found on airports are described below.
In 1987, the FCC set aside six megahertz of spectrum in the 800 MHz band for exclusive use by local,
regional and state public safety agencies. The banding consists of spectrum at 806-824 MHz paired with
spectrum at 851-869 MHz
In 2004, because of interference issues, the FCC reconfigured the band plan to separate public safety
systems from commercial cellular wireless systems. The FCC later added paired public safety frequencies
in the 700 MHz band.
Trunked radios at airports generally serve multiple users on and off-airport including public safety, fire,
and emergency response organizations. The ability to interoperate with and coordinate the activities of
diverse groups over a wide area is a primary driver in adopting trunked radio services, although on-airport
functional coordination, e.g., maintenance activities, is also important.
Trunked radios coordinate multiple users by means of talk groups. Individuals subscribe to one or more
talk groups depending on their responsibilities and needs for communication.
Whereas large airports likely have dedicated trunked radio systems; smaller airports may be served by a
municipal or county system in which the airport is assigned a number of channels. The roles and
responsibilities of the parties are typically spelled out in a Mutual Aid Agreement or in Memoranda of
Trunked radio coverage depends on the distance of the user from the master transmitter, environmental
factors such as foliage which can attenuate the signals, and building construction where steel reinforcements
can also attenuate signals. The 800 MHz band signals are more susceptible to such attenuation than radios
operating at longer wavelengths. For this reason, airport users should perform radio frequency surveys of
their areas of operation, and particularly on the lower levels of terminals, to map where signals cannot be
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