Air Traffic Management Concept Baseline Definition - The Boeing ...

the ATN ADS specification. This will allow a greater reliance on aircraft-detected
deviation from the planned flight to initiate reports and less dependence on periodic
reports and controller detection of those deviations. This will allow the periodic reports
to be less frequent, resulting in more efficient use of radio bandwidth with equal or better
conformance monitoring.
Flight Information Services (FIS) is a collector for a potential group of applications, such
as weather and Notice to Airmen (NOTAM) reporting. At this time, the only function
which has been defined is ATIS. FIS may be described as an ‘inverted ADS’ in that the
aircraft can request a contract with a ground-based database for specific information. For
instance, an aircraft may ask for the arrival ATIS information for a specific airport, with
the contract specifying that an update be sent to the aircraft whenever the information is
modified. This would allow the aircraft to maintain current ATIS information with no
further pilot intervention.
Context Management Application (CMA) is functionally equivalent to the AFN function
of FANS-1. The aircraft and ground share information about function and version
availability for each of the applications. The intent is that future versions of the
applications will be backward compatible, allowing the applications to down-mode to a
lower version to maintain compatibility with their peer at the other end.
The ATN protocol consists of a family of protocols derived from those specified by the
International Standards Organization. The protocol family is partitioned into seven layers
of functionality, called the Open Systems Interconnection.
The key protocols of ATN are found in the Network layer. The movement of data
packets is performed by the Connection-Less Network Protocol. The exchange of routing
data to ensure that the packets get forwarded to their destination is performed by the
Inter-Domain Routing Protocol. Other members of the protocol support the functionality
provided by these two protocols.
The primary media for ATN are the same as for FANS-1, that is, VHF, SATCOM, and
HF. The subnetwork protocols for these three media are different from those in an
ACARS environment in that they are optimized to support the bit-oriented network
protocol data units which they convey. In addition, a couple of other media have been
proposed for ATN.
Mode S data link was proposed as a medium early on in the development of ATN.
Although some European countries continue to plan for Mode S data link, the FAA has
removed Mode S data link from their plans, in favor of VHF.
When the aircraft is parked at the gate, on the open ramp, or in a hangar, an umbilical
cable may prove to be a more efficient way to convey data to and from the aircraft. This
would save precious radio bandwidth for mobile aircraft, which have no choice but to use
radio frequencies, and would allow a larger bandwidth than is technically feasible over
available radio bands. The Gatelink concept has been proposed to fill this need. The
current definition is based on the 100 Mbps Fiber Distributed Data Interface network.
Gatelink has not been implemented in other than prototype so it may change if, and when,
it is finally built.
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