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connections, and manages the media access control
sublayer and physical layer. An aircraft LME tracks how
Data circuit-terminating equipment (DCE). A DCE is a net- well it can communicate with the ground stations of a
work provider equipment used to facilitate communications single ground system. An aircraft VME instantiates an
between DTEs. LME for each ground station that it monitors. Similarly, the
ground VME instantiates an LME for each aircraft that it
Data link entiry (DLE). A protocol state machine capable of monitors. An LME is deleted when communication with
setting up and managing a single data link connection. the peer system is no longer viable.
Data link service (DLS) sublayer. The sublayer that resides M burst. A management channel data block of bits used in
above the MAC sublayer. For VDL Mode 4, the DLS VDL Mode 3. This burst contains signalling information
sublayer resides above the VSS sublayer. The DLS manages needed for media access and link status monitoring.
ANNEX 10 - VOLUME III 279 25/11/04
No. 79
Annex 10 - Aeronautical Telecommunications Volume 111
Media access control (MAC). The sublayer that acquires the
data path and controls the movement of bits over the data
path.
Mode 2. A data-only VDL mode that uses D8PSK modulation
and a carrier sense multiple access (CSMA) control
scheme.
Mode 3. A voice and data VDL mode that uses D8PSK
modulation and a TDMA media access control scheme.
Mode 4. A data-only VDL mode using a GFSK modulation
scheme and self-organizing time division multiple access.
Subnetwork layer. The layer that establishes, manages and
terminates connections across a subnetwork.
System. A VDL-capable entity. A system comprises one or
more stations and the associated VDL management entity.
A system may either be an aircraft system or a ground
system.
Time division multiple access (TDMA). A multiple access
scheme based on time-shared use of an RF channel
employing: (1) discrete contiguous time slots as the
fundamental shared resource; and (2) a set of operating
protocols that allows users to interact with a master control
station to mediate access to the channel.
Physical layer. The lowest level layer in the Open Systems
Interconnection protocol model. The physical layer is User group. A group of ground and/or aircraft stations which
concerned with the transmission of binary information over share voice and/or data connectivity. For voice communithe
physical medium (e.g. VHF radio). cations, all members of a user group can access a11
communications. For data, communications include
point-to-point connectivity for air-to-ground messages, and
Quality of service. The information relating to data transfer point-to-point and broadcast connectivity for ground-to-air
characteristics used by various communication protocols to messages.
achieve various levels of performance for network users.
VDL management entity (VME). A VDL-specific entity that
Reed-Solomon code. An error correction code capable of provides the quality of service requested by the ATNcorrecting
symbol errors. Since symbol errors are defined SN-SME. A VME uses the LMEs (that it creates
collections of bits, these codes provide good burst error and destroys) to enquire the quality of service available
correction capabilities. from peer systems.
Self-organizing time division multiple access (STDMA). A VDL Mode 4 bunt. A vHF digital ]ink (VDL) Mode 4 burst
multiple access scheme based on time-shared use of a radio is composed of a sequence of source address, burst ID,
frequency (RF) channel employing: (I) discrete contiguous information, slot reservation and frame check sequence
time slots as the fundamental shared resource; and (2) a set (FCS) fields, bracketed by opening and closing flag
of operating protocols that allows users to mediate access to sequences.
these time slots without reliance on a master control station.
Slot. One of a series of consecutive time intervals of equal
duration. Each burst transmission starts at the beginning of
a slot.
Subnetwork connection. A long-term association between an
aircraft DTE and a ground DTE using successive virtual
calls to maintain context across link handoff.
Subnetwork dependent convergence function (SNDCF). A
function that matches the characteristics and services of a
particular subnetwork to those characteristics and services
required by the internetwork facility.
Subnetwork entity. In this document, the phrase "ground
DCE" will be used for the subnetwork entity in a ground
station communicating with an aircraft; the phrase
"ground DTE" will be used for the subnetwork entity in a
ground router communicating with an aircraft station; and,
　
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