Transcript Slide 1

‫‪HFDL‬‬
‫‪HF Data Link‬‬
‫گردهمائی ارتباطات هوانوردی‬
‫‪ 19‬آذر ‪86‬‬
‫محمود صادقيان‬
‫از شرکت فرودگاههای کشور‬
Communication
 Communication
 Air-Ground –air
 Ground –Ground
 Communication Requirements
 Voice
 HF – VHF
 Data
 AMSS - CPDLC - VDL - HFDL
Role of HFDL in CNS/ATM
 HFDL system can :
 Satisfy future ATS & AOC communication
requirements in :
 Oceanic areas
 land areas Where Other data link Implementation
may be impractical
 Reduce growth For voice services
requirements
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Role of HFDL in CNS/ATM
 HFDL fulfills several key roles:
 1) provides aircraft that are not SATCOMequipped with a long-range, cost-effective
data link;
 2) serves as a data link for polar regions
 3) acts in combination with SATCOM as very
high performance system
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HFDL
propagation
For aeronautical purposes, the
important bands are HF, VHF, and UHF
(SATCOM).
 HF :
 enables TO cover beyond-line-of-sight (BLOS)
communication ranges
 VHF :
 its coverage is restricted to line-of-sight (LOS) ranges.
 UHF :
 SATCOM coverage is determined by line-of-sight
conditions
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HFDL
propagation
 HF Radio Signal Propagation depends upon
ionospheric layer shape and densities
 Ionosphere affected by :
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eleven-year sunspot cycle
seasonal variations
day-to-day changes
diverse variations
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HFDL
Networked sites
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HFDL
Automatic frequency management
 The HFDL system on the aircraft
automatically searches for a suitable
frequency from all HFDL operational
ground station frequencies.
 Each HFDL ground station broadcast
squitters every 32 seconds on its
operational frequencie
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HFDL
Automatic frequency management
 The GS configures each frame to support the
expected uplink and downlink traffic.
 HFDL Frame
 32 Second
 13 Slot
 Squitter
 Uplink Slots
 Downlink Slots
 random access downlink slots
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HFDL
Automatic Selection of Data rate
 Data rates :
 300, 600, 1 200, and 1 800 bits/s.
 In HFDL each link will have a maximum
downlink and uplink data rate
 maximum uplink rate is determined by
the aircraft
 maximum downlink rate is determined by
the ground station
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HFDL

HFDL system comprise following subsystems
a) HFDL aircraft station sub-system
b) HFDL ground station sub-system
c) HFDL ground communications sub-system
d) HFDL ground management sub-system
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HFDL aircraft sub-system
 HFDL aircraft sub-system components
a) HFDL transmission and HF data unit
(HFDU);
b) Data modulation and demodulation;
c) HFDL protocol and frequency selection; and
d) Interface to the [airborne data link
processor].
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HFDL
Ground station sub-system
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a) HF transmission and reception
b) data modulation and demodulation
c) HF protocol and frequency selection
d) interface to the ground
communications sub-system.
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HFDL
HFDL ground communications sub-system
A ground communications infrastructure is
required to interconnect
 HFDL ground stations
 end users
 HFDL management sub-system
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 HFDL ground management subsystem provides :
a) aircraft log-on status table management;
b) system table management; and
c) frequency management.
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HFDL
Antennas for HFDL ground stations
 A given ground station may be able to use
several antennas to provide required short
to long-range Communications.
 Antenna selections may include a shortrange omnidirectional antenna combined
with several moderate to long range
directive antennas
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‫با تشکر‬
‫پايان‬
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HFDL
Ground station synchronization
 The HFDL system is designed to take
advantage of time synchronization
 squitters are used to
 mark the beginning of the 32 second frames
 determine availability of a communication channel
 transmit system management information
 Ground stations synchronize their squitter
transmissions to UTC
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HFDL
Digital signal processing
The modems employed
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PSK modulation
forward error correction
interleaving of coded data
adaptive channel equalization of received data.
 These techniques enabled the modems to
compensate for the distortion of the HF channe
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HFDL
Performance
 Availability
 Integrity
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HFDL
Performance
HFDL system relationship to HF voice
 HFDL makes more efficient use of the available HF
spectrum
 HFDL employs less than 2.2 seconds duration in time slots
of 2.47 seconds duration to send data packets
 using digital signal processing techniques to combat effects
such as multipath, fading,
 more useable spectrum is available with HFDL than
with HF voice.
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2 4 6
8 10
1011
electrons/m3
Magnetosphere
(50000 Km)
F2
F1
Es
E
D
iono
(400/1000 Km)
tropo
(8/15)
IONOSPHERE CHARACTERISTICS
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Different Phase of Flight
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 The range of usable frequencies will
vary:
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• throughout the day;
• with the seasons;
• with the solar cycle;
• from place to place;
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OWF : Optimum Working Frequency
MUF : Maximum Usable Frequency
EMUF E layer MUF
ALF : Absorption Limiting Frequency
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