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Self-organizing time division lnulti~le access (STDMA). A VDL Mode 4 burst. A VHF digital link (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: (1) discrctc 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 consecu~ivc lime 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 WE using successive virtual
calls to maintain contcxt across link handoff.
Subnetwork dependent convergence function (SNDCF). A
function that matches the characteristics and services of a
particular subnelwork 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
stalion communicating with an aircraft; the phrase
"ground DTE" will be used for the subnetwork entity in a
ground router communicating wjth an aircraft station; and,
the phrase "aircraft DTE" will. be used for the subiletwork
entity in an aircraft communicating with thc station. A
subnetwork entity is a packet layer entity as defined in
IS0 8208.
Note.-- The start of a burst map occur only at quantized
time intervals and this construint allows the propagution deluy
between the trunsmission and reception to be derived.
VDL Mode 4 DLS system. A VDL system that implements the
VDL Mode 4 DLS and subnetwork protocols to carry ATN
packets or other packets.
VDL Mode 4 specific services (VSS) sublayer. The sublayer
that resides above the MAC sublayer and provides VDL
Mode 4 specific access protocols including reserved,
random and fixed protocols.
VDL station. An aircraft-based or ground-based physical
entity, capable of VDL Mode 2, 3 or 4.
Note.- In the context of this chapter; a VDL station is also
referred to as u "station".
Vocoder A low bit rate voice encoder/decodcr.
Voice unit. A device that provides a simplex audio and
signalling interface between the uscr and VDL.
Part I Annex 10 - Aeronautical Telecommunications
VSS user. A user of the VDL Mode 4 specific services. The lowest assignable frequency shall be 118.000 MHz and the
VSS user could be higher layers in the VDL Mode 4 highest assignable frequency shall be 136.975 MHz. The
SARPs or an external application u.sing VDL Mode 4. separation between assignablc frequencies (channel spacing)
shall be 25 kHz.
6.1.2 Radio channels and
functional channels
6.1.2.1 Aircraft station radio frequency range. An aircraft
station shall be capable of tuning to any of the channels in the
range specified in Section 6.1.4.1 within 100 milliscconds after
the reccipt of a11 autotunc command. In addition, for VDL
Mode 3, an aircraft station shall be able to tune to any channel
in the range specified in Section 6.1.4.1 within 100
milliseconds after the receipt of any tuning command.
6.1.2.2 Ground stution rudio frequency mnge. A ground
station shall be capable of operating on its assigned channel
within the radio frequency range dctailed in 6.1.4.1.
6.1.2.3 Common signulling channel. Frequency
136.975 MHz shall be reserved as a world-wide common
signalling channel (CSC) for VDL Mode 2.
6.1.3 System capabilities
6.1.3.1 Durn trampamncy. The VDL system shall provide
code-independent, byte-independent transfer of data.
6.1.3.2 Broadcast. The VDL system shall provide link
layer data broadcast services (Mode 2) andlor voice and data
broadcast services (Mode 3). For VDL Mode 3, the data
broadcast service shall support network multicasting capability
originating from the ground.
6.1.3.3 Connection murulgement. The VDL system shall
establish and maintain a reliable communications path
between the aircraft and the ground SyStEm while allowing but
not requiring manual intervention.
Note.- In this context "reliable" is defined by the BER
requirement specified in 6.3.5.1.
Note.- Volume V specifies that the block of frequencies
from 136.9 - 136.975 MHz inclusive is reserved for VHF
air-ground digitul cornn~unications.
6.1.4.2 The design polarization of emissions shall be
vertical.
6.2 SYSTEM CHARACTERISTICS OF
THE GROUND INSTALLATION
　
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