INDUSTRIAL TRAINING
PROJECT REPORT
AT
ACKNOWLEDGEMENT
I express my deep gratitude to Ms. Rama Gupta
,Jt.G.M.(Comm.),Airports Authority of India Jaipur
Airport for providing me this golden opportunity to
attend the Industrial/Vocational training.
My sincere thanks to Sh.Kamlesh Kumar,
Manager (Elex), our training co-ordinator for
providing the proper guidance and continuous
encouragement for making this training successful .
I am also thankful to all the CNS faculty
members for their keen interest and at last my
coordinal thanks to my batch mates and friends for
their cooperation.
Dated : / / 2013
TABLE OF CONTENTS
Name Page No.
1. Brief Description of Jaipur 03
2. General Information 05
3. Brief Description of CNS Department 06
4. Classification of CNS Facilities 08
5. Basic Communication system 13
6. VCCS/Tape recorder/DATIS 18
7. Frequency bands uses in comm.. 20
8. AFTN/AMSS 21
9. Nav-aids DVOR/DME 28
10. Instrument Landing System (ILS) 32
11 .Security Equipments 42
12. Automation system 45
13. ADS-B 49
14.Intranet/LAN/WAN 56
15.Figures
Brief Description of JAIPUR
Jaipur is the Capital city of Rajasthan and is also called the PINK CITY.
(Zero mile point). It is well connected with other major cities by Rail/Road
and air.
Area: 3, 42,237Sq Km
Population: 2.6 Million as per 2001 census
Tourist Places: -
(i) Amber Palace: 20 Km from Airport, in Red sandstone with
marble interiors famous for fascinating blend of Rajput and
Mughal architecture.
(ii) Hawa Mahal: Palace of wind with latticed Jharokhas 14 Km
away from Airport. Heart of city, is a fusion of Rajputana and
Mughal Acrtitecture
(iii) City Place: Fabulous museum displays possessions of the
Jaipur Royal family.
(iv) Jantar Mantar: An Unique open air observatory built by the
founder of Jaipur- Sawai Jai singh. It is complex instruments
used for measuring local time ,the altitude of stars, meridian etc.
(v) Jai Garh :The victory forts-world’s largest cannon Jaivan.
Perched atop the hill Jaigarh.
Distance from Railway Station: 12 Km
Jaipur Runway strip 15/33 with one terminal office and two Hanger was
constructed by Maharaja Mansingh II in 1932 named as Sanganer
Airport. Dakota Aircraft was used for domestic and International flight
from Jaipur to Karachi/Lahore. New Runway with orientation 09/27 of
length 9000 feet has been constructed and de-used Runway 15/33 is
being used for parking the Aircrafts. The salient features of the New
Terminal Building (Terminal-2) are: -
Glass and steel structure with passenger friendly facilities such as:
(a) Most modern security system
(b) Centrally air-conditioning system. Passenger Boarding Bridge
(Aerobridges),
(c) Two glass aerobridges with visual docking system.
(d) On Line Baggage conveyer system.
(e) Escalator and Glass Lifts.
(f) Large Duty Free Shoe Area.
(g) Twin-Level connection segregating arrival and Departure area.
(h) Underground pedestrian link to/from car parking area to
Concourse.
(i) Peak Pax-500 (250 Departure, 250 Arrival)
The Airlines operating at this airport are: -
(a) International: Indian , Air Arabia, & Air India Express
(b) Domestic: Indian, Jet Airways, Jet lite, Indigo, Kingfisher, Go Air,
Spice Jet.
All domestic flights are to be operated from new terminal building (T-2)
and all International flights are to be operated from the existing old
terminal building (T-1).
Technical Data of the Airport:
a) Aerodrome Reference Code: 4D
b) Elevation: 1263.10 Feet (385 meter)
c) ARP coordinates: 26°49′26.3″N 075°48′′12.5″E
d) Main RWY orientation: 27/09
e) RWY dimension: 2797.05m X 45m
f) Apron dimension 230 m X 196 m
g) Parking Bays
GENERAL INFORMATION
1. Name of Airport : Jaipur Airport, Jaipur
2. Type of Airport : Civil Aerodrome
3. Address : OIC, AAI, Jaipur Airport
Jaipur - 302029
4. Operational Hours : 24 hours
5. Name & Designation of : Rama Gupta
Officer-in-Charge Jt.GM (Com)
6. Region : Northern Region
7. RHQ : New Delhi
8. Nature of Station : Non Tenure
JAIPUR AIRPORT – VIJP IST=(UTC + 0530)
Geographical Coordinates (WGS–84) : 26º 49' 26.3” N
75º 48' 12.5” E
Aerodrome Reference Code : 4 D
Aerodrome Reference Point (ARP) Elevation : 384.96 M
BRIEF DESCRIPTION / ROLE OF CNS DEPARTMENT 1.To provide uninterrupted services of Communication, Navigation
and Surveillance (CNS) facilities for the smooth and safe movement of
aircraft (over flying, departing & landing) in accordance with ICAO
standards and recommended practices.
2. To maintain Security Equipments namely X-Ray Baggage systems
(XBIS), Hand Held Metal Detectors (HHMD) and Door Frame Metal
Detectors (DFMD).
3. To provide and maintain inter-unit communication facility i.e.
Electronic Private Automatic Exchange Board (EPABX)
4. To maintain the Computer systems including peripherals like
printers, UPS etc. provided in various sections connected as
standalone as well as on Local Area Network (LAN).
5. To maintain the passenger facilitation systems like Public Address
(PA) system, Car Hailing System and Flight Information Display
System (FIDS).
6. To maintain and operate Automatic Message Switching system
(AMSS) used for exchange of messages over Aeronautical Fixed
Telecommunication Network (AFTN).
7. To provide Communication Briefing to pilots by compiling NOTAM
received from other International NOF.
8. To maintain and operate Fax machine.
9. To co-ordinate with telephone service providers for provision and
smooth functioning of auto telephones/ hotlines/ data circuits.
Classification of CNS facilities Name of the Equipment Make QTY FREQ POWER
COMMUNICATION EQUIPMNET
VHF AM Sets
Transmitters
OTE
DT-100
PARKAIR
125.25
126.6
50W
Receivers
OTE
DR-100
PARKAIR
125.25
126.6
VHF AM Transreceivers PAE 5610
PAE BT6M
125.25
DS-Radio
JORTON
I-COM
125.25
125.25
125.25
DVR RETIA
64
Chnl NA
64 kbps line
NA NA
FIDS
IDDS
SOLARI NA NA
Digital Clock
Bihar
Commn. NA NA
DSCN VIASAT
LAN/WAN Cisco Tele NA NA
EPABX
Coral
Panasonic
NA
NA
NA
NA
VCCS SCHMID NA NA
Mobile Radio (FM)
Communication
(BASE STATION)
MOTORO
LA
161.825
Mhz
For
CISF
166.525
Mhz
For
AAI
--
10W
--
VERTEX
Standard
Mobile Radio (FM)
Communication
(Hand Held Sets)
MOTORO
LA
SIMCO)
Vertex
Standard
KENWOO
D
161.825
Mhz
166.525
Mhz
--
--
--
AUTOMATION INDRA NA NA TYPE B1
ADS-B COMSOFT 1090
Mhz
NA
NAVIGATION EQUIPMENT
DVOR (JJP)
THALES
420
112.9
Mhz. 100W
HP DME(JJP)
(Collocated with D-VOR)
THALES
Airsys-435
1100
1163
Mhz
1 KW
LOCALIZER (IJIP)
NORMAC-
7013
109.9
Mhz 15W
GLIDE PATH
NORMAC-
7033
333.8
Mhz 5W
LP DME (IJIP Collocated
with GP)
THALES
Airsys -415
997
1060
Mhz
100W
Locator Outer SAC 100 295 Khz 50W
SECURITY EQUIPMENTS
X-BIS SYSTEM
Departure Lounge 100100V
Heimann (Ger)
Security Hold Area
6040i Heimann (Ger)
Departure Lounge 100100V
Heimann (Ger)
Security Hold Area
6040i Heimann (Ger)
Explosive Trace
Detectors
Smith 500 DT
Smith
IONSCAN500DT
(Singapore)
DFMD
METOR-200
CEIA
CCTV INFINOVA
PA SYSTEM
BOSCH
BASIC COMMUNICATION SYSTEM
1.1 Introduction: Transmitter, Receiver & Channel
Introduction
Communication is the process of sending, receiving and processing of
information by electrical means. It started with wire telegraphy in 1840
followed by wire telephony and subsequently by radio/wireless
communication. The introduction of satellites and fiber optics has made
communication more widespread and effective with an increasing
emphasis on computer based digital data communication. In Radio
communication, for transmission information/message are first converted
into electrical signals then modulated with a carrier signal of high
frequency, amplified up to a required level, converted into
electromagnetic waves and radiated in the space, with the help of
antenna. For reception these electromagnetic waves received by the
antenna, converted into electrical signals, amplified, detected and
reproduced in the original form of information/message with the help of
speaker.
Transmitter
Unless the message arriving from the information source is electrical in
nature, it will be unsuitable for immediate transmission. Even then, a lot
of work must be done to make such a message suitable. This may be
demonstrated in single-sideband modulation, where it is necessary to
convert the incoming sound signals into electrical variations, to restrict
the range of the audio frequencies and then to compress their amplitude
range. All this is done before any modulation. In wire telephony no
processing may be required, but in long-distance communications,
transmitter is required to process, and possibly encode, the incoming
information so as to make it suitable for transmission and subsequent
reception.
Eventually, in a transmitter, the information modulates the carrier, i.e., is
superimposed on a high-frequency sine wave. The actual method of
modulation varies from one system to another. Modulation may be high
level or low level, (in VHF we use low level modulation) and the system
itself may be amplitude modulation, frequency modulation, pulse
modulation or any variation or combination of these, depending on the
requirements. Figure 1.1 shows a low-level amplitude-modulated
transmitter type.
Antenna
AUDIO IN
Channel
The acoustic channel (i.e., shouting!) is not used for long-distance
communications and neither was the visual channel until the advent of
the laser. "Communications," in this context, will be restricted to radio,
wire and fiber optic channels. Also, it should be noted that the term
channel is often used to refer to the frequency range allocated to a
CRYSTAL
OSC & AMP
MODULATOR
& DRIVER PA
RF OUTPUT
POWER AMP
AUDIO
AMPLIFIER
Figure 1.1 Block diagram of typical radio transmitter
particular service or transmission, such as a television channel (the
allowable carrier bandwidth with modulation).
It is inevitable that the signal will deteriorate during the process of
transmission and reception as a result of some distortion in the system,
or because of the introduction of noise, which is unwanted energy,
usually of random character, present in a transmission system, due to a
variety of causes. Since noise will be received together with the signal,
it places a limitation on the transmission system as a whole. When
noise is severe, it may mask a given signal so much that the signal
becomes unintelligible and therefore useless. Noise may interfere with
signal at any point in a communications system, but it will have its
greatest effect when the signal is weakest. This means that noise in the
channel or at the input to the receiver is the most noticeable.
Receiver
There are a great variety of receivers in communications systems,
since the exact form of a particular receiver is influenced by a great
many requirements. Among the more important requirements are the
modulation system used, the operating frequency and its range and the
type of display required, which in turn depends on the destination of the
intelligence received. Most receivers do conform broadly to the super
heterodyne type, as does the simple receiver whose block diagram is
shown in Figure 1.2.
Antenna
Speaker
Mixer
Figure 1.2 Block diagram of AM super heterodyne receiver
RF Stage
Intermediate
Frequency
Amplifier
Demodulator
Audio Voltage
and Power
amplifiers
Local
Oscillator
Receivers run the whole range of complexity from a very simple crystal re-
ceiver, with headphones, to a far more complex radar receiver, with its
involved antenna arrangements and visual display system, which will be
expanded upon in Chapter 6. Whatever the receiver, it’s most important
function is demodulation (and sometimes also decoding). Both these processes
are the reverse of the corresponding transmitter modulation processes.
As stated initially, the purpose of a receiver and the form of its output
influence its construction as much as the type of modulation system
used. The output of a receiver may be fed to a loudspeaker, video
display unit, teletypewriter, various radar displays, television picture
tube, pen recorder or computer: In each instance different arrangements
must be made, each affecting the receiver design. Note that the
transmitter and receiver must be in agreement with the modulation and
coding methods used (and also timing or synchronization in some
systems).
Transmitter (or equipment) modulation.
Transmitter modulation is one in which, the carrier and total sideband
components are combined in a fixed phase relationship in the equipment
(say transmitter) and the combined wave follow a common RF path from
the transmitting antenna through space to the receiver ensuring no
introduction of phase difference between the carrier and the TSB on its
way. It is obvious that the mixing (multiplication) of the carrier and the
modulating signal has to be taken place to produce the TSB within the
equipment only, before combining (adding) it with carrier within or
outside the equipment.
Space Modulation
Another type of amplitude modulation process may be required to be
used in many places like Navaids where the combination (addition) of
sideband only (SBO comprising one or more TSB(s)) and the carrier with
or without the transmitter modulated sidebands takes place in space.
Note that both of the SBO or carrier with sidebands (CSB) are
transmitter modulated but when all the required signals out of these
three namely SBO, CSB or carrier are not radiated from the same
antenna the complete modulation process will be realized rather the
composite modulated waveform will be formed at the receiving point by
the process of addition of all the carriers and all the sidebands (TSBs).
The process of achieving the complete modulation process by the
process of addition of carriers and sidebands (TSBs) at the receiving
point in space is called the “Space Modulation” which means only that
modulation process is achieved or completed in space rather than in
equipment itself but not at all that space is modulated.
VOICE COMMUNICATION CONTROL SYSTEM
INTRODUCTION AND NEED OF VCCS AT AIRPORTS
The Voice Communication Control System (VCCS) is a Voice Switch and Control System for networking an airport VHF
communication system. It is an electronic switching system, which controls the complex flow of speech data between air
traffic controllers on ground and aircraft. The system has been designed using Complementary Metal Oxide Semiconductor
(CMOS) digital circuits and is very easy to operate.
The VCCS is based on a modular architecture. The heart of the system is a Central Switching Unit (CSU) in which the data
inputs from various controller workstations are separately processed. The controller workstation installed at the ATS units
works as a command centre from which the air traffic controller operates the VHF RT. Each Controller Workstation is assisted
by a Radio Telephony Display Console, Audio Interface and Headset Interface Units. A multibus data link connects the CSU
with each controller workstation.
INTRODUCTION TO TAPE RECORDING
PURPOSE OF TAPE RECORDER
The purpose of tape recorder is to store the Sound by recording
of sound either by Disc Recording, Film Recording or Magnetic
Recording. In our Department, we are using Magnetic
Recording to record the communications/speech between Air
(Aircraft) to Ground, Ground to Ground, telephones, Intercom’s
etc. For any miss happening or any other reason, the
conversations of past period can be checked to find out the root
cause so that in future such types of mistakes can be avoided.
DIGITAL AIRPORT TERMINAL INFORMATION SYSTEM (DATIS)
Introduction
Digital Airport Terminal Information System (DATIS) is an
intelligent announcing system used for Automatic Terminal
Information Service (ATIS) – for the automatic provision of
current, routine information (weather, runway used etc.) to
arriving and departing aircraft throughout 24 hrs or a specific
portion thereof. The System is Completely solid-state,
without any moving parts. The design is based around
advanced digital techniques viz., PCM digitization, high
density Dynamic RAM Storage and microprocessor control.
This ensures reproduction of recorded speech with high
quality and reliability. Storage capacity normally supplied is
for 4 minutes Announcement, and as the system design is
modular, it can be increased by simply adding extra memory.
The system is configured with fully duplicated modules,
automatic switch-over mechanism and Uninterrupted Power
Supply to ensure Continuous System availability.
Frequency band and its uses in communications
Table 1.1 Radio Waves ClassificatioN
Band Name Frequency Band
Ultra Low Frequency (ULF) 3Hz - 30 Hz
Very Low Frequency (VLF) 3 kHz - 30 kHz
Low Frequency (LF) 30 kHz - 300 kHz
Medium Frequency (MF) 300 kHz - 3 MHz
High Frequency (HF) 3 MHz - 30 MHz
Very High Frequency (VHF) 30 MHz - 300 MHz
Ultra High Frequency (UHF) 300 MHz -3 GHz
Super High Frequency (SHF) 3 GHz - 30 GHz
Extra High Frequency (EHF) 30 GHz - 300 GHz
Infrared Frequency 3 THz- 30 THz
Frequencies band uses in communication
NAME OF
THE
EQUIPMENT
FREQUENCY
BAND
USES
NDB 200 – 450 KHz Locator, Homing & En-route
HF 3 – 30 MHz Ground to Ground/Air Com.
Localizer 108 – 112 MHz Instrument Landing System
VOR 108 – 117.975 MHz Terminal, Homing & En-route
VHF 117.975 – 137 MHz Ground to Air Comm.
Glide Path 328 – 336 MHz Instrument Landing System
DME 960 – 1215 MHz Measurement of Distance
UHF LINK 0.3 – 2.7 GHz Remote Control, Monitoring
RADAR 0.3 – 12 GHz Surveillance
AFTN SWITCHING SYSTEM & COMMUNICATION
INTRODUCTION
In AFTN, information is exchanged between many stations. The
simplest form of communication is point-to-point type, where
information is transmitted from a source to sink through a medium.
The source is where information is generated and includes all
functions necessary to translate the information into an agreed
code, format and procedure. The medium could be a pair of wires,
radio systems etc. is responsible for transferring the information.
The sink is defined as the recipient of information; it includes all
necessary elements to decode the signals back into information.
CLASSIFICATION OF AFTN SWITCHING SYSTEM
A switching system is an easy solution that can allow on demand
basis the connection of any combination of source and sink
stations. AFTN switching system can be classified into 3 (three)
major categories:
1. Line Switching
2. Message Switching
3. Packet Switching.
LINE SWITCHING
When the switching system is used for switching lines or circuits it
is called line-switching system. Telex switches and telephones
exchanges are common examples of the line switching system.
They provide user on demand basis end-to-end connection. As
long as connection is up the user has exclusive use of the total
bandwidth of the communication channel as per requirement. It is
Interactive and Versatile.
MESSAGE SWITCHING
In the Message Switching system, messages from the source are
collected and stored in the input queue which are analysed by the
computer system and transfer the messages to an appropriate
output queue in the order of priority.
The message switching system works on store and forward
principle. It provides good line utilization, multi-addressing,
message and system accounting, protects against blocking
condition, and compatibility to various line interfaces.
PACKET SWITCHING SYSTEM
This system divides a message into small chunks called packet.
These packets are made of a bit stream, each containing
communication control bits and data bits. The communication
control bits are used for the link and network control procedure and
data bits are for the user.
A packet could be compared to an envelope into which data are
placed. The envelope contains the destination address and other
control information. Long messages are being cut into small
chunks and transmitted as packets. At the destination the network
device stores, reassembles the incoming packets and decodes the
signals back into information by designated protocol. It can handle
high-density traffic. Messages are protected until delivered. No
direct connection required between source and sink. Single port
handles multiple circuits access simultaneously and can
communicate with high speed.
AERONAUTICAL TELECOMMUNICATION NETWORK
(ATN)
The basic objective of CNS/ATM is ‘Accommodation of the users preferred
flight trajectories’. This requires the introduction of automation and adequate
CNS tools to provide ATS with continuous information on aircraft position and
intent . In the new CNS/ATM system, communications with aircraft for both
voice and data (except for polar region) will be by direct aircraft to satellite
link and then to air traffic control (ATC) centre via a satellite ground earth
station and ground-ground communication network . voice communication
(HF) will be maintained during the transition period and over polar region until
such time satellite communication is available. In terminal areas and in some
high density airspaces VHF and SSR mode S will be used.
The introduction of data communication enables fast exchange of
information between all parties connected to a single network. The
increasing use of data communications between aircraft and the various
ground systems require a communication system that gives users close
control over the routing of data, and enables different computer systems
to communicate with each other without human intervention.
In computer data networking terminology, the infrastructure required to
support the interconnection of automated systems is referred to as an
Internet. Simply stated, an Internet comprises the interconnection of
computers through sub-networks, using gateways or routers. The inter-
networking infrastructure for this global network is the Aeronautical
Telecommunication Network (ATN).
The collection of interconnected aeronautical end-system(ES),
intermediate-system(IS) and sub-network (SN) elements administered
by International Authorities of aeronautical data-communication is
denoted the Aeronautical Telecommunication Network (ATN).
The ATN will provide for the interchange of digital between a wide
variety of end-system applications supporting end-users such as Aircraft
operation, Air traffic controllers and Aeronautical information specialists.
The ATN based on the International organization for standardization
(ISO). Open system interconnection (OSI) reference model allows for the
inter- operation of dissimilar Air-Ground and ground to ground sub-
networks as a single internet environment.
End-system attached to ATN Sub-network and communicates with End
system with other sub-networks by using ATN Routes. ATN Routes can
be either mobile (Aircraft based) or fixed (Ground based).
The router selects the logical path across a set of ATN sub-networks that
can exists between any two end systems. This path selection process
uses the network level addressing quality of service and security
parameters provided by the initiating en system. Thus the initiating end
system does not need to know the particular topology or availability of
specific sub-networks. The ATN architecture is shown in the figure.
Present day Aeronautical communication is supported by a number of
organizations using various net working technologies. The most eminent
need is the capability to communicate across heterogeneous sub-
networks both internal and external to administrative boundaries. The
ATN can use private and public sub-net works spanning organizational
and International boundaries to support aeronautical applications. The
ATN will support a data transport service between end-users which is
independent of the protocols and the addressing scheme internal to any
one participating sub-networks. Data transfer through an Aeronautical
internet will be supported by three types of data communication sub-
networks.
a. The ground network – AFTN,ADNS,SITA Network
b. The Air-ground network – Satellite, Gate-link, HF, VHF, SSR
Modes
c. The Airborne network – the Airborne Data Bus, Communication
management unit.
THE GROUND NETWORK
It is formed by the Aeronautical Fixed telecommunication network
(AFTN), common ICAO data interchange network (CIDIN) and Airline
industry private networks
THE AIR-GROUND NETWORK
The Air-Ground sub networks of VHF, Satellite, Mode S, gate link, (and possibly
HF) will provide linkage between Aircraft-based and ground-based routers
(intermediate system).
THE AIRBORNE NETWORK
It consists of Communication Management Unit (CMU) and the Aeronautical
radio incorporation data buses (ARINC). Interconnectivity to and inter
operability with the Public data Network (PDN) will be achieved using gate-
ways to route information outside the Aeronautical environment.
ADNS (AIRNC DATA NETWORK SERVICE)
The backbone of the ARINC communication services s the ARINC Data Network
Service. The network provides a communication interface between airlines,
AFTN, Air-route Traffic Control Centres ( ARTCC) and weather services. ADNS is
also used to transport air ground data link messages and aircraft
communication addressing and reporting system (ACARS).
SITA NETWORK
SITA’s worldwide telecommunication network is composed of switching
centers interconnected by medium to high speed lines including international
circuits. The consolidated transmission capacity exceeds 20 Mbps and the
switching capacity exceeds 150 million data transactions and messages daily.
THE AIR_GROUND COMMUNICATION SYSTEM
The available/planned air-ground communication systems are-
a. Satellite
b. Gate link
c. HF radio
d. SSR Mode S
e. VHF
NAVIGATIONAL AIDS
VHF Omni Range (V.O.R)
VOR, short for VHF Omni-directional Range, is a type of radio
navigation system for aircraft. VORs broadcast a VHF radio signal
encoding both the identity of the station and the angle to it, telling
the pilot in what direction he lies from the VOR station, referred to
as the radial. Comparing two such measures on a chart allows for
a fix. In many cases the VOR stations also provide distance
measurement allowing for a one-station fix.
It operates in the VHF band of 112-118 MHz, used as a medium to
short range Radio Navigational aid. It works on the principle of
phase comparison of two 30 Hz signals i.e. an aircraft provided
with appropriate Rx, can obtain its radial position from the range
station by comparing the phases of the two 30 Hz sinusoidal
signals obtained from the V.O.R radiation. Any fixed phase
difference defines a Radial/Track (an outward vector from the
ground station into space). V.O.R. provides an infinite number of
radials/Tracks to the aircrafts against the four provided by a LF/MF
radio range.
PURPOSES AND USE OF VOR:
1. The main purpose of the VOR is to provide the navigational signals for an aircraft receiver, which will allow the pilot to determine the bearing of the aircraft to a VOR facility.
2. In addition to this, VOR enables the Air Traffic Controllers in the Area Control Radar (ARSR) and ASR for identifying the aircraft in their scopes easily. They can monitor whether aircraft are following the radials correctly or not.
3. VOR located outside the airfield on the extended Centre line of the runway would be useful for the aircraft for making a straight VOR approach. With the help of the AUTO PILOT aircraft can be guided to approach the airport for landing.
4. VOR located enroute would be useful for air traffic 'to maintain their PDRS (PRE DETERMINED ROUTES) and are also used as reporting points.
5. VORs located at radial distance of about 40 miles in different directions around an International Airport can be used as holding VORs for regulating the aircraft for their landing in quickest time. They would be of immense help to the aircraft for holding overhead and also to the ATCO for handling the traffic conveniently.
DISTANCE MEASURING EQUIPMENT(DME)
As early as 1946 many organisations in the West took an active
part in the development of DME system. The Combined Research
Group (CRG) at the Naval Research Laboratory (NRL) designed
the first experimental L band DME in 1946.
The L band, between 960 MHz and 1215 MHz was chosen for
DME operation mainly because:
a. Nearly all other lower frequency bands were occupied.
b. Better frequency stability compared to the next higher
frequencies in the Microwave band.
c. Less reflection and attenuation than that experienced in the
higher
Frequencies in the microwave band.
d. More uniform omni directional radiation pattern for a given
antenna height than that possible at higher frequencies in the
microwave band.
PURPOSES AND USE OF DME
PURPOSE OF DME INSTALLATION
Distance Measuring Equipment is a vital navigational Aid, which
provides a pilot with visual information regarding his position
(distance) relative to the ground based DME station. The facility
even though possible to locate independently, normally it is
collocated with either VOR or ILS. The DME can be used with
terminal VOR and holding VOR also. DME can be used with the
ILS in an Airport; normally it is collocated with the Glide path
component of ILS.
Association of DME with VOR
Associated VOR and DME facilities shall be co-located in
accordance with the following:
a. Coaxial co-location: the VOR and DME antennas are located
on the same vertical axis; or
b. Offset co-location:
For those facilities used in terminal areas for approach purposes or other procedures where the highest position fixing accuracy of system capability is required, the separation of the VOR and DME antennas does not exceed 30 m (100 ft) except that, at Doppler VOR facilities, where DME service is provided by a separate facility, the antennas may be separated by more than 30 m (100 ft), but not in excess of 80 m (260 ft);
For purposes other than those indicated above, the separation of the VOR and DME antennas does not exceed 600 m (2,000 ft).
Association of DME with ILS
Associated ILS and DME facilities shall be co-located in
accordance with the following:
a. When DME is used as an alternative to ILS marker beacons, the DME should be located on the airport so that the zero range indication will be a point near the runway.
b. In order to reduce the triangulation error, the DME should be sited
to ensure a small angle (less than 20 degrees) between the approach
path and the direction to the DME at the points where the distance
information is required.
c. The use of DME as an alternative to the middle marker
beacon assumes a DME system accuracy of 0.37 km (0.2
NM) or better and a resolution of the airborne indication such
as to allow this accuracy to be attained.
The main purposes of DME installations are summarised as
follows:
For operational reasons
As a complement to a VOR to provide more precise navigation service in localities where there is:
o High air traffic density
o Proximity of routes
As an alternative to marker beacons with an ILS. When DME is used as an alternative to ILS marker beacons, the DME should be located on the Airport so that the zero range indication will be a point near the runway.
As a component of the MLS
The important applications of DME are:
Provide continuous navigation fix (in conjunction with VOR);
Permit the use of multiple routes on common system of airways to resolve traffic;
Permit distance separation instead of time separation between aircraft occupying the same altitude facilitating reduced separation thereby increasing the aircraft handling capacity;
Expedite the radar identification of aircraft; and
INSTRUMENT LANDING SYSTEM
Purpose and use of ILS:
The Instrument Landing System (ILS) provides a means for safe landing of
aircraft at airports under conditions of low ceilings and limited visibility.
The use of the system materially reduces interruptions of service at
airports resulting from bad weather by allowing operations to continue at
lower weather minimums. The ILS also increases the traffic handling
capacity of the airport under all weather conditions.
The function of an ILS is to provide the PILOT or AUTOPILOT of a landing
aircraft with the guidance to and along the surface of the runway. This
guidance must be of very high integrity to ensure that each landing has a very
high probability of success.
COMPONENTS OF ILS:
The basic philosophy of ILS is that ground installations, located in the
vicinity of the runway, transmit coded signals in such a manner that pilot is
given information indicating position of the aircraft with respect to correct
approach path.
To provide correct approach path information to the pilot, three different
signals are required to be transmitted. The first signal gives the
information to the pilot indicating the aircraft's position relative to the
center line of the runway. The second signal gives the information
indicating the aircraft's position relative to the required angle of descent,
where as the third signal provides distance information from some
specified point.
These three parameters which are essential for a safe landing are Azimuth
Approach Guidance, Elevation Approach Guidance and Range from the
touch down point. These are provided to the pilot by the three
components of the ILS namely Localizer, Glide Path and Marker Beacons
respectively. At some airports, the Marker Beacons are replaced by a
Distance Measuring Equipment (DME).
This information is summarized in the following table.
ILS Parameter ILS Component
a. Azimuth Approach Guidance Provided by Localizer
b. Elevation Approach
Guidance
Provided by Glide Path
c. Fixed Distances from
Threshold
Provided by Marker Beacons
d. Range from touch down
point
Provided by DME
Localizer unit:
The localizer unit consists of an equipment building, the transmitter
equipment, a platform, the antennas, and field detectors. The antennas
will be located about 1,000 feet from the stop end of the runway and
the building about 300 feet to the side. The detectors are mounted on
posts a short distance from the antennas.
Glide Path Unit :
The Glide Path unit is made up of a building, the transmitter equipment,
the radiating antennas and monitor antennas mounted on towers. The
antennas and the building are located about 300 feet to one side of the
runway center line at a distance of approximately 1,000 feet from the
approach end of the runway.
Figure 2. shows the typical locations of ILS components
Marker Units :
Three Marker Units are provided. Each marker unit consists of a
building, transmitter and directional antenna array. The system will be
located near the runway center line, extended. The transmitters are 75
MHz, low power units with keyed tone modulation. The units are
controlled via lines from the tower.
The outer marker will be located between 4 and 7 miles in front of th e
approach end of the runway, so the pattern crosses the glide angle at
the intercept altitude. The modulation will be 400 Hz keyed at 2 dashes
per second.
The middle marker will be located about 3500 feet from the approach
end of the runway, so the pattern intersects the glide angle at 200 feet.
The modulation will be a 1300 Hz tone keyed by continuous dot, dash
pattern.
Some ILS runways have an inner marker located about 1.000 feet from
the approach end of the runway, so the pattern intersects the glide
angle at 100 feet. The transmitter is modulated by a tone of 3000 Hz
keyed by continuous dots.
Distance Measuring Equipment (DME):
Where the provision of Marker Beacons is impracticable, a DME can be
installed co-located with the Glide Path facility.
The ILS should be supplemented by sources of guidance information which will
provide effective guidance to the desired course. Locator Beacons, which are
essentially low power NDBs, installed at Outer Marker and Middle Marker
locations will serve this purpose.
Aircraft ILS Component :
The Azimuth and Elevation guidance are provided by the Localizer and Glide
Path respectively to the pilot continuously by an on-board meter called the
Cross Deviation Indicator (CDI).Range information is provided continuously in
the form of digital readout if DME is used with ILS. However range information
is not presented continuously if Marker Beacons are used. In this condition
aural and visual indications of specific distances when the aircraft is overhead
the marker beacons are provided by means of audio coded signals and lighting
of appropriate colored lamps in the cockpit.
FUNCTIONS OF ILS COMPONENTS :
A brief description of each of the ILS components is given in this section.
Function of Localizer unit :
The function of the Localizer unit is to provide, within its coverage
limits, a vertical plane – o f c o u r s e a l i g n e d with the extended
center-line of the runway for azimuth guidance to landing aircraft. In
addition, it shall provide information to landing aircraft as to whether
the aircraft is offset towards the left or right side of this plane so as
to enable the pilot to align with the course.
Function of Glide Path unit :
The function of the Glide Path unit is to provide, within its coverage limits, an
inclined plane aligned with the glide path of the runway for providing elevation
guidance to landing aircraft. In addition, it shall provide information to landing
aircraft as to whether the aircraft is offset above or below this plane so as to
enable the pilot to align with the glide path.
Function of marker Beacon / DME :
The function of the marker beacons,/DME is to provide distance information
from the touch down point to a landing aircraft.
The marker beacons, installed at fixed distances from the runway threshold,
provide specific distance information whenever a landing aircraft is passing
over any of these beacons so that the pilot can check his altitude and correct it if
necessary.
The DME, installed co-located with the Glide Path unit, will provide a continuous
distance information from the touch down point to landing aircraft.
Function of Locators:
The function of locators, installed co-located with the marker beacons, is to
guide aircraft coming for landing to begin an ILS approach.
Different models used in AAI:
Different models of ILS used in AAI are as follows:
1. GCEL ILS :In this ILS mechanical modulator is used and both the near field monitoring system is utilized.
2. NORMARC ILS :In this system advance technology is used and for monitoring purpose along with near field monitoring integral monitoring has been utilized .Now a days 2 models viz. NM 3000 series and NM 7000 series are mostly used in AAI.
3. ASI ILS : In Mumbai and Delhi airport these ILS are used under modernization programme. One of the ILS model at Delhi is a CAT III ILS.
GENERAL CONCEPTS ON
SECURITY EQUIPMENTS
&
PUBLIC ADDRESS SYSTEM
MULTI ENERGY MACHINES
The machine used in airports usually is based on a dual-energy X-ray system.
This system has a single X-ray source sending out X-rays, typically in the range
of 140 to 160 kilovolt peak (KVP). KVP refers to the amount of penetration an
X-ray makes. The higher the KVP, the further the X-ray penetrates.
After the X-rays pass through the item, they are picked up by a detector. This
detector then passes the X-rays on to a filter, which blocks out the lower-
energy X-rays. The remaining high-energy X-rays hit a second detector. A
computer circuit compares the pick-ups of the two detectors to better
represent low-energy objects, such as most organic materials.
Since different materials absorb X-rays at different levels, the image on the
monitor lets the machine operator see distinct items inside your bag. Items are
typically colored on the display monitor, based on the range of energy that
passes through the object, to represent one of three main categories:
1. Organic 2. Inorganic 3. Metal
While the colours used to signify "inorganic" and "metal" may vary between
manufacturers, all X-ray systems use shades of orange to represent "organic."
This is because most explosives are organic. Machine operators are trained to
look for suspicious items -- and not just obviously suspicious items like guns or
knives, but also anything that could be a component of an improvised
explosive device (IED). Since there is no such thing as a commercially available
bomb, IEDs are the way most terrorists and hijackers gain control. An IED can
be made in an astounding variety of ways, from basic pipe bombs to
sophisticated, electronically-controlled component bombs.
While the colours used to signify "inorganic" and "metal" may vary between manufacturers, all X-ray systems use shades of orange to represent "organic."
This is because most explosives are organic. Machine operators are trained to look for suspicious items -- and not just o also anything that could be a
component of an improvised explosive device (IED). Since there is no such thing as a commercially available bomb, IEDs are the way most terrorists and
hijackers gain control. An IED can be made in an astounding variety of ways,
from basic pipe bombs to sophisticated, electronically-controlled component bombs.
While the colors used to signify "inorganic" and "metal" may vary between
manufacturers, all X-ray systems use shades of orange to represent "organic." This is because most explosives are organic. Machine operators are trained to
look for suspicious items -- and not just obviously suspicious items like guns or knives, but also anything that could be a component of an improvised explosive
device (IED). Since there is no such thing as a commercially available bomb, IEDs are the way most terrorists and hijackers gain control. An IED can be
made in an astounding variety of ways, from basic pipe bombs to sophisticated, electronically-controlled component bombs.
WORKING PRINCIPLE
Nature of X-rays X-rays are electromagnetic waves whose wavelengths
range from about (0.1 to 100)x 10-10 m. They are produced when
rapidly moving electrons strike a solid target and their kinetic energy
is converted into radiation. The wavelength of the emitted radiation
depends on the energy of the electrons.
Production of X-Rays There are two principal mechanisms by which x-rays are
produced. The first mechanism involves the rapid deceleration of a
high-speed electron as it enters the electrical field of a nucleus.
During this process the electron is deflected and emits a photon of x-
radiation. This type of x-ray is often referred to as bremsstrahlung or
"braking radiation". For a given source of electrons, a continuous
spectrum of bremsstrahlung will be produced up to the maximum
energy of the electrons.
The second mechanism by which x-rays are produced is through
transitions of electrons between atomic orbits. Such transitions
involve the movement of electrons from outer orbits to vacancies
within inner orbits. In making such transitions, electrons emit
photons of x-radiation with discrete energies given by the differences
in energy states at the beginning and the end of the transition.
Because such x-rays are distinctive for the particular element and
transition, they are called characteristic x-rays.
Both of these basic mechanisms are involved in the production of x-
rays in an x-ray tube. Figure 1 is a schematic diagram of a standard x-
ray tube. A tungsten filament is heated to 20000C to emit electrons.
A very high voltage is placed across the electrodes in the two ends of
the tube and the tube is evacuated to a low pressure, about 1/1 000
mm of mercury. These electrons are accelerated in an electric field
toward a target, which could be tungsten also (or more likely copper
or molybdenum for analytical systems). The interaction of electrons
in the target results in the emission of a continuous bremsstrahlung
spectrum along with characteristic x-rays from the particular target
material. Unlike diagnostic x-ray equipment, which primarily utilize
the bremsstrahlung x-rays, analytical x-ray systems make use of the
characteristic x-rays.
INTRODUCTION TO AIRPORT METAL DETECTORS
Old metal detectors worked on energy absorption principle used two coils as search coils, these were forming two loops of a blocking oscillator. When any person carrying a metallic object or a weapon stepped through the door carrying
coils, some energy was absorbed and the equilibrium of the blocking oscillator got disrupted. This change was converted into audio and visual indications. Size
and weight of the metallic object was determined by proper sensitivity settings.
The hand held metal detectors used the same technique. These type of metal detectors carried various shortcomings and they have been superseded by new
generation multi zone equipments working on PI technology
TYPES- The metal detectors, used in aviation sector are generally of two types.
1. HAND HELD METAL DETECTORS
2. DOOR FRAME METAL DETECTORS
1.MELU 5087 M28
Electronics unit
2.METOR coil set
3. 8.Button M28
4.Carring strap
5.Button slide
6. Battery/ charger cable
7.Clamping screw
8.Frame M28
9.Button extender hose
10 Cover M28
11. Battery cover
HAND HELD METAL DETECTOR
(HHMD)
4 Detailed block diagram description
OPERATION
The coil is part of the oscillating circuit which operation frequency is 23.5
kHz. When a metal object is inside the sensing area of the coil, it will
effect to amplitude of the oscillating signal. After a while the integrating
control will set the amplitude a constant value.
Output of oscillator is rectified and it is connected through the filter
section to comparator. When the signal is lower than the adjusted
reference level (sensitivity setting) comparator generates alarm signal.
It activates the alarm oscillator and the audible alarm / the red alarm
light.
Battery voltage is controlled with a low voltage circuit and constant
alarm is activated when the battery voltage is under 7V.
The connector in the rear of the unit operates as headphone and
charger connections. The charger idle voltage is between 14 and 24
VDC. During charging operation the green light is plinking and with full
battery it lights constantly. If headphone is connected, audible alarm is
not operational.
DOOR FRAME METAL DETECTORS
Almost all airport metal detectors are based on pulse induction (PI). Typical PI systems use a coil of wire on one side of the arch as the transmitter and receiver.
This technology sends powerful, short bursts (pulses) of current through the coil of wire. Each pulse generates a brief magnetic field. When the pulse ends, the
magnetic field reverses polarity and collapses very suddenly, resulting in a sharp electrical spike. This spike lasts a few microseconds (millionths of a second) and causes another current to run through the coil. This subsequent current is called the reflected pulse and lasts only about 30 microseconds.
Another pulse is then sent and the process repeats. A typical PI-based metal detector sends about 100 pulses per second, but the number can vary greatly
based on the manufacturer and model, ranging from about 25 pulses per second to over 1,000 If a metal object passes through the metal detector, the pulse
creates an opposite magnetic field in the object. When the pulse's magnetic field collapses, causing the reflected pulse, the magnetic field of the object makes it
take longer for the reflected pulse to completely disappear. This process works something like echoes: If you yell in a room with only a few hard surfaces, you
probably hear only a very brief echo, or you may not hear one at all. But if you yell into a room with a lot of hard surfaces, the echo lasts longer. In a PI metal
detector, the magnetic fields from target objects add their "echo" to the reflected pulse, making it last a fraction longer than it would without them.
A sampling circuit in the metal detector is set to monitor the length of the
reflected pulse. By comparing it to the expected length, the circuit can determine if another magnetic field has caused the reflected pulse to take longer
to decay. If the decay of the reflected pulse takes more than a few microseconds longer than normal, there is probably a metal object interfering with it.
The sampling circuit sends the tiny, weak signals that it monitors to a device
call an integrator. The integrator reads the signals from the sampling circuit, amplifying and converting them to direct current (DC).The DC's voltage is
connected to an audio circuit, where it is changed into a tone that the metal detector uses to indicate that a target object has been found. If an item is found, you are asked to remove any metal objects from your person and step through
again. If the metal detector continues to indicate the presence of metal, the attendant uses a handheld detector, based on the same PI technology, to isolate
the cause.
Many of the newer metal detectors on the market are multi-zone. This means that they have multiple transmit and receive coils, each one at a different height.
Basically, it's like having several metal detectors in a single unit.
METOR 200 (PRINCIPLE OF OPERATION)
The transmitter coils generate a pulsed magnetic field around them. Metal
objects taken through the detector generate a secondary magnetic field, which
is converted into a voltage level by the receiver coils. Metor 200 consists of
eight separate overlapping transmitter and receiver coil pairs. The signal
received from each receiver coil are processed individually thus the transmitter
and receiver coil pairs form eight individual metal detectors. The operation is
based on electromagnetic pulsed field technology as below in addition to the
above explanation.
Transmitter pulses cause decaying eddy currents in metal objects inside the sensing area of the WTMD
The signal induced to the receiver by the eddy currents is sampled and
processed in the electronics unit.
Moving metal objects are detected when the signal exceeds the alarm
threshold.
METOR 200
Eight overlapping detection zones
METOR 200 is a multi-channel metal detector with eight overlapping detection zones. The zones create a sequential pulsating magnetic field within the
detection area of the WTMD.
With overlapping construction, sensitivity differences are minimised when metal objects of different shape pass through the WTMD in various orientations
Metal objects at different heights are detected separately by the individual
detection zones producing superior discrimination.
Advanced microprocessor technology is used for digital signal processing and internal controls. This provides reliable functioning of the metal detector,
versatile features and user friendly operations.
The electronics unit processes the signals received from the receiver coils. It indicates the result of the signal processing through an alphanumerical display, alarm LEDs and Buzzer. The zone display unit, which is mounted on transmitter
coil panel, points out the position where a weapon was taken through the gate. The user controls the functions of the metal detector with a remote control
unit. It sends to the electronics unit an IR signal corresponding to the pressed keyboard code.
The traffic counter counts the number of persons walking through the gate and the amount of alarms generated.
ATS AUTOMATION SYSTEM
General System Description One of the main characteristics of the system is its availability, due to the employment of redundant elements on a distributed scenario, and to the use of tested and highly reliable commercial equipment. The software architecture of the system is determined by its modularity and distribution and has been organized using distributed discrete processes for the different subsystems. At the same time, the system makes use of communication by messages, both for intercommunications between tasks and for its synchronicity. In order to assure a maximum level of maintenance, communications and application tasks have been isolated. The Operating System used is RED HAT ENTERPRISE LINUX 5. This system includes all the necessary functionality required in a modern ATC system. Its main elements are following described: The integration of all its subsystems is performed via:
Local Area Network (LAN). A redundant five (5) category with a 1-Gigabyte bandwidth capacity LAN is used and, therefore, future updates of the system can be easily implemented making use of standard communication protocols.
Main components:
Flight Data Processing (FDP). It is based on INTEL redundant computers. It manages the flight plans generated within the System or coming from external sources, including the Repetitive Flight Plans (RPLs). It confirms all flight data inputs, calculates the flights’ progression and keeps all controllers inform by means of screen displays and flight plan strips printing. The System is designed in redundant configuration, having an FDP as operative and another one as reserve, with the possibility to switch them.
Surveillance Data Processor (SDP). It is based on INTEL redundant computers. It receives and processes data (primary, secondary and meteorological) coming from the radar sites. Next, it performs the merge all the received information to create a coherent airspace picture for controllers’ (SDD) presentation. It also performs surveillance tasks (STCA, MTCD) between aircraft and integrates the radar information and the flight plan information in order to get a precise tracking. The System is duplicated (operative/reserve) being possible to switch them. Attempting to the Tower type the system shall provide or not the SDP servers.
Radar Communications Processor (RDCU). It centralizes the System radar communications to interpret and convert the received radar formats to join them. The System is composed of two RDCU units working parallel. It is possible to carry out the received radar data reproduction during an established period.
Controlling positions:-
Situation Data Display (SDD). It receive data processed by FDP. Later on, it manages all these information for a coherent displaying at the controllers screens (SDD). At the same time, it displays additional relevant information such as geographic maps, meteorological data, radar data, and flight plans presentations shown on the controller screens and it can show additional information like geographical maps, airways, meteorological data, etc.
Flight Data Display (FDD). It displays information concerning flight plans not supplying data display of data on air situation. It allows controllers to perform adjustments on flight plans and other significant data.Its aim is to provide a work environment to the operational personnel of the Air Traffic Control Centre for flight plans handling. This environment consists
of an HMI computer (screen, mouse and keyboard) connected to the subsystem that manages Flight Plans so that the entire flight plan related information is easily reachable by the operator. The FDD Position allows the controller mainly to handle flight plans during the strategic planning phase. That is, the controller of this position manages future flight plans (Flight plans received trough AFTN and Repetitive Flight Plans (RPL)).
Control and Monitoring Display (CMD). The Control and Monitoring Display Position (CMD) is one of the components of the Tower and Approach Integrated System. Its main aim is to offer help to technical staff in the Traffic Control Centre, providing a work environment able to monitor the whole system in an easy but precise way in real time. For that reason, the position is connected to the other subsystems. Its main element is a computer with screen, mouse and keyboard.It continuously monitors the whole system and shows its status in real time. When a components fails or is not working correctly, an operator can take the appropriate actions on the CMD console. Some system parameters can be changed trough the CMD to adequate the system configuration to the actual working conditions, as they can be the VSP parameters or active sectorization.
Auxiliary equipment:
Common Timing Facility (CTF). It receives the GPS time, which is spread to all the subsystem (via LAN) and all clocks (via Terminals) with NTP protocol.
Data Recording Facilities (DRF). The Data Recording and Playback Position (DRF) is one of the elements of the Tower and Approach Integrated Control System. The main duties of this position are the recording of all relevant data in a convenient order and their subsequent recognition and playback. The DRFs is a utility for recording and playbacking. The information of SDDs is saved on tapes. The process is: 1. SDDs record all data in local files. The data are: Events, monitoring, etc. This data files are sent to the DRFs each hour automatically. 2. When the DRFs receive the files from the SDDs, these ones are recorded on tapes. 3. The DRFs displays to technical staff all files received from the SDDs on a screen as well all files save on tapes. Also, the DRFs allow monitoring the tapes states, the recorder files, used capacity tapes.
This component records continuously all the data related to the tracks data, flight plans data, and the controller actions to allow later playback and analysis. To reproduce information stored in tape it would be enough with: 1st: To gather the necessary files stored in tape. This operation is carried out by means of an intuitive graphic interface. 2nd: The DRF will take charge loading the above mentioned information in the SDD specified by the technician for his later reproduction.
Data Base Management (DBM). It provides the necessary facilities the creation and modification of the adaptation databases to supply the system with the precise knowledge of its geographical environment to achieve the required efficiency. From this database, all necessary data to define the control centre characteristics are defined (fixpoints, aerodromes, airways, sectorization, adjacent control centres, QNH zones, etc.)
Multichannel Signal Recorder / Neptuno 4000 The Neptuno 4000 is a multi-channel signal recording. Neptuno 4000 performs the sampling of multiple analogue and/or digital channels, with variable bandwidth and quality requirements. The sampled signals are stored digitally, and can be replayed, transmitted, routed or edited.
ADS-B
Definition
A means by which aircraft, aerodrome vehicles and otherobjects can
automatically transmit and /or receive data such as
identification,position and additional data , as appropriate, in a
broadcast mode via datalink.
Theory Of Operation
The ADS-B system enables the automatic broadcast of an aircraft’s
identity,position, altitude, speed, and other parameters at half-second
intervals usinginputs such as a barometric encoder and GNSS equipment
The result is afunctionality similar to SSR. Under ADS-B, a target
periodically broadcasts itsown state vector and other information
without knowing what other entitiesmight be receiving it, and without
expectation of an acknowledgment or reply.ADS-B aircraft transmissions
received by a network of ground stations canprovide surveillance over a
wider area. Referred to as ADS-B OUT, this providesATC with the ability
to accurately track participating aircraft.
ADS-B is automatic because no external stimulus is required; it
isdependent because it relies on on-board position sources and on-
boardbroadcast transmission systems to provide surveillance
information to otherparties. Finally, the data is broadcast, the
originating source has no knowledgeof who receives and uses the data
and there is no two-way contract orinterrogation.
Categories of Networks
Today when we speak of networks, we are generally referring to three primary categories:
local area networks, metropolitan area networks, and wide area networks. In which category
a network falls is determined by its size. its ownership, the distance it covers, and its
physical architecture (see Figure below).
Figure: Categories of network
Local Area Network (LAN)
A local area network (LAN) is usually privately owned and links the devices in a single office,
building, or campus (see Figure below).
Depending on the needs of an organization and the type of technology used, a LAN can be
as simple as two PCs and a printer in someone's home office; or it can extend throughout a
company and include audio and video peripherals. Currently, LAN size is limited to a few
kilometers.
LANs are designed to allow resources to be shared between personal computers or
workstations. The resources to be shared can include hardware (e.g., a printer), software
(e.g., an application program), or data. One of the computers may be given a large capacity
disk drive and may become a server to the other clients. Software can be stored on this
central server and used as needed by the whole group. In this example, the size of the LAN
may be determined by licensing restrictions on the number of users per copy of software, or
by restrictions on the number of users licensed to access the operating system.
In addition to size, LANs are distinguished from other types of networks by their
transmission media and topology. In general, a given LAN will use only one type of
transmission medium. The most common LAN topologies are bus, ring, and star.
Traditionally, LANs have data rates in the 4 to 16 megabits per second (Mbps) range.
Today, however, speeds are increasing and can reach 100 Mbps with gigabit systems in
development. The local area networks can also be subdivided according to their media
access methods. The well-known media access methods are: Ethernet or CSMA/CD, Token
Ring and Token Bus. The Ethernet LAN used in ECIL AMSS is discussed in detail later in
this Chapter.
Wide Area Network (WAN)
A wide area network (WAN) provides long-distance transmission of data, voice, image, and video
information over large geographic areas that may comprise a country, a continent, or even the
whole world (see figure below).
Figure: WAN
In contrast to LANs (which depend on their own hardware for transmission), WANs may
utilize public, leased, or private communication equipment, usually in combinations, and can
therefore span an unlimited number of miles.
A WAN that is wholly owned and used by a single company is often referred to as an
enterprise network
The Internet is built on the foundation of TCP/IP suite. The dramatic growth of the
Internet and especially the World Wide Web has cemented the victory of TCP/IP over OSI.
TCP/IP comprises of five layers:
Application Layer
Transport/TCP Layer
IP/Network layer
Network Access/Link Layer
Physical Layer. Internet Address
The identifier used in the network layer of the Internet model to identify each device
connected to the Internet is called the Internet address or IP address. An IP address, in the
current version of the protocol (IP Version 4) is a 32-bit binary address that uniquely and
universally defines the connection of a host or a router to the Internet.
IP addresses are unique. They are unique in the sense that each address defines
one, and only one, connection to the Internet. Two devices on the Internet can never have
the same address at the same time. However, if a device has two connections to the
Internet, via two networks, it has two IP addresses.
The IP addresses are universal in the sense that the addressing system must be
accepted by any host that wants to be connected to the Internet.
There are two common notations to show an IP address: binary notation and dotted decimal
notation.
Binary Notation
In binary notation, the IP address is displayed as 32 bits. To make the address lIl(J readable,
one or more spaces is usually inserted between each octet (8 bits). Each <XI! is often
referred to as a byte. So it is common to hear an IP address referred to as 32-bit address, a
4-octet address, or a 4-byte address. The following is an example an IP address in binary
notation:
01110101 10010101 00011101 11101010
Dotted-Decimal Notation
To make the IP address more compact and easier to read, Internet addresses are usually
written in decimal form with a decimal point (dot) separating the bytes. Figure below shows
an IP address in dotted-decimal notation. Note that because each byte (octet) only 8 bits,
each number in the dotted-decimal notation is between 0 and 255.
Figure: Dotted-decimal notation
Classful Addressing
IP addresses, when started a few decades ago, used the concept of classes. This archi-
tecture is called classful addressing. In the mid-1990s, a new architecture, called classless
addressing, was introduced which will eventually supersede the original architecture.
However, most of the Internet is still using classful addressing, and the migration is slow.
In classful addressing, the IP address space is divided into five classes: classes A, B,
C, D, and E. Each class occupies some part of the whole address space. The following
figure shows the address ranges of these five classes of network.
Addresses in classes A, B, and C are for unicast communication, from one source to one
destination. A host needs to have at least one unicast address to be able to send or receive
packets.
Addresses in class D are for multicast communication, from one source to a group of
destinations. If a host belongs to a group or groups, it may have one or more multicast
addresses. A multicast address can be used only as a destination address, but never as a
source address.
Addresses in class E are reserved. The original idea was to use them for special
purposes. They have been used only in a few cases.
Netid and Hostid
In classful addressing, an IP address in classes A, B, and C is divided into netid and hostid. These p arts
are of varying lengths, depending on the class of the address. The following figure shows the netid
and hostid bytes.
The numbers 0,127,255 have some special meaning in TCP/IP.
Every network itself has an address. For example if a computer in a network has an
address of 191.56.56.13 the network address is 191.56.0.0.
Every network needs a separate broadcast address. Network access layer uses it
to broadcast an ARP request to determine the destination’s MAC address. For
191.56.56.13 the broadcast address is 191.56.255.255.
A separate address is for local loop back that is 127.0.0.1. PING command uses
this for local connectivity.
SUBNET MASK
Subnet mask defines network address part and host/computer address part of an
IP address. For the subnet address scheme to work, every machine on the
network must know which part of the host address will be used as the subnet
address. This is accomplished by assigning a subnet mask to each machine. A
subnet mask is a 32-bit value that allows the recipient of IP packets to distinguish
the network ID portion of the IP address from the host ID portion of the IP
address. The network administrator creates a 32-bit subnet mask composed of
1s and 0s. The 1s in the subnet mask represent the positions that refer to the
network or subnet addresses. Not all networks need subnets, meaning they use
the default subnet mask. This is basically the same as saying that a network
doesn't have a subnet address. Table below shows the default subnet masks for
Classes A, B, and C.
CLASS A
255.0.0.0
CLASS B 255.255.0.0
CLASS C 255.255.255.0
Figure: TCP/IP Protocol Suite