Trường Đại học Bách Khoa Hà Nội
Hanoi University of Science and Technology
© HUST 2012

Hệ thông Thông tin Hàng Không
TS. Đỗ Trọng Tuấn
Bộ môn Kỹ thuật thông tin
Trường Đại học Bách Khoa Hà Nội
Hanoi University of Science and Technology
Phân mạng HF
Chương 3
© HUST 2012

Hệ thống Thông tin Hàng Không
Teminologies
3
AM(R)S: Aeronautical Mobile (Route) Service
AM(OR)S: Aeronautical Mobile (Off-Route) Service
DSB-AM: Double Side Band - Amplitude Modulation
WRC: World Radio Conference
SARP: Standard And Recommended Practices


Introduction
4
Introduction
5
Aviation
Communication
Services
Airline

Host System
FAA/CAA
Tower Systems
ARINC
Ground
Network
(AviNet
®
)
ARINC Central
Processing
System (CPS)
VHF
Satcom
HFDL
ACARS/AOA
ATN
Air Traffic
Service
Provider
Air/Ground
Router
GLOBALink
SM
by ARINC

GLOBALink/HF Flight Tracks (9/00)
6
GLOBALink/HF Flight Tracks (2003)
7

HF Range
8
GLOBALink/HFDL Global Coverage @2000
9
HF Ground
Stations (12)

Alaska
Bolivia
California
+ Guam (12/5)
Hawaii
Iceland
Ireland
New York
New Zealand
Russia
South Africa
Thailand
Legend
HFDL ground station
Areas of
Primary coverage
Areas of
Secondary coverage
GLOBALink/HFDL Global Coverage @2001
10
Legend
HF Ground
Stations (14)


Alaska
+ Bahrain
Bolivia
California
+ Canary Islands
Guam
Hawaii
Iceland
Ireland
New York
New Zealand
Russia
South Africa
Thailand
HFDL ground station
Areas of
Primary coverage
Areas of
Secondary coverage
GLOBALink/HFDL Global Coverage @2003
11
Areas of
Primary coverage
Areas of
Secondary coverage
Legend
HFDL ground
station
HFDL Ground

Stations

Alaska
Bahrain
Bolivia
California
Canary Islands
Guam
Hawaii
Iceland
Ireland
New York
New Zealand
Russia
South Africa
Thailand
ARINC GLOBALink World Wide VHF Coverage
12
GLOBALink/HFDL Global Coverage
13
High Frequency Data Link: HFDL
14
 High Frequency Data Link, or HFDL, is part of ARINC’s
GLOBALink end-to-end communication system
 The HFDL system is a segment of the Aircraft
Communications Addressing and Reporting System
(ACARS) used to exchange Airline Operational Control
(AOC) and Air Traffic Control (ATS) messagesbetween
aircraft end systems and corresponding ground-based
stations.

 GLOBALink/HF provides HF-based, air-to-ground digital
communications with aircraft using ARINC 635 protocol.
 The HFDL system uses the principles of geographic
diversity and frequency diversity to optimize HF
propagation
High Frequency Data Link: HFDL
15
 HFDL is currently the only truly global aeronautical data
link capability, and the only data link for flight routes over
the North Pole.
 Inmarsat satellite SATCOM coverage becomes marginal
around 80 degrees north and south latitude.
LINE OF SIGHT, GROUND WAVE, SKY WAVE
16
KNOWLEDGE CHECK
17
IONOSPHERE REGIONS
18
 The ionosphere is the uppermost
part of the atmosphere and is
ionized by solar radiation.

 Ionization is the conversion of
atoms or molecules into an ion
by light (heating up or charging)
from the sun on the upper
atmosphere.

 Ionization also creates a
horizontal set of stratum (layer)

where each has a peak density and
a definable width or profile that
influences radio propagation.
IONOSPHERE REGIONS
19
IONOSPHERE REGIONS
20
The F layer: or region, is 120 km to 400 km above the surface of the Earth. It is the top
most layer of the ionosphere. Here extreme ultraviolet (UV) (10-100 nm) solar radiation
ionizes atomic oxygen (O). The F region is the most important part of the ionosphere in terms
of HF communications. The F layer combines into one layer at night, and in the presence
of sunlight (during daytime), it divides into two layers, the F1 and F2. The F layers are
responsible for most skywave propagation of radio waves, and are thickest and most
reflective of radio on the side of the Earth facing the sun.
The E layer: is the middle layer, 90 km to 120 km above the surface of the Earth. This layer
can only reflect radio waves having frequencies less than about 10 MHz. It has a negative
effect on frequencies above 10 MHz due to its partial absorption of these waves. At night the
E layer begins to disappear because the primary source of ionization is no longer
present. The increase in the height of the E layer maximum increases the range to which
radio waves can travel by reflection from the layer
The D layer: is the innermost layer, 50 km to 90 km above the surface of the Earth. when
the sun is active with 50 or more sunspots, During the night cosmic rays produce a residual
amount of ionization as a result high-frequency (HF) radio waves aren't reflected by the D
layer. The D layer is mainly responsible for absorption of HF radio waves, particularly at
10 MHz and below, with progressively smaller absorption as the frequency gets higher. The
absorption is small at night and greatest about midday. The layer reduces greatly after
sunset. A common example of the D layer in action is the disappearance of distant AM
broadcast band stations in the daytime.
HF Propagation
21

 Due to variations in height and intensities of the ionised regions,
different frequencies must be used at different times of day and night
and for different paths.
 There is also some seasonal variation (particularly between winter
and summer).
 Propagation may also be disturbed and enhanced during periods of
intense solar activity.
 The upshot of this is that HF propagation has considerable
vagaries and is far less predictable than propagation at VHF.
 Frequencies chosen for a particular radio path are usually set roughly
mid-way between the lowest usable frequency (LUF) and the maximum
usable frequency (MUF).
 The daytime LUF is usually between 4 to 6 MHz during the day,
falling rapidly after sunset to around 2 MHz.
 The MUF is dependent on the season and sunspot cycle (11 years)
but is often between 8 MHz and 20 MHz.
 Hence a typical daytime frequency for aircraft communication might
be 8 MHz whilst this might be as low as 3 MHz during the night.
HF Propagation
22
HF bands are allocated to the aeronautical service
HF Propagation
23
 Each HGS operates on 2-3 channels and is equipped with
a family of HF frequencies ranging from 2-30 MHz.
 Adaptive Frequency Management techniques are
employed to obtain weekly Active Frequency Tables (AFT).
These tables are derived from a combination of real-time
ionospheric monitoring, solar and geomagnetic
observational data and HF propagation models.

 Each week, an updated AFT is uploaded to each HGS
from the ARINC Operations Center (AOC) in Annapolis,
Maryland, USA.
 The AFT instructs the ground station on which frequencies
to operate over the course of each 24-hour period
HF Modulation: SSB modulation
24
KNOWLEDGE CHECK
25

1. Explain why HF radio is used on trans-oceanic
routes.

2. Explain why different frequencies are used for HF
aircraft communications during the day and at
night.

1. State TWO advantages of using SSB modulation
for aircraft HF communications.