dheeraj balodia(lnmiit)
TRANSCRIPT
Airport Authority Of India
INDUSTRIAL TRAININGAT
JAIPUR AIRPORT,JAIPURPROJECT REPORT
On Communication , Navigation and
Surveillance
Submitted by:
Dheeraj Balodia
LNMIIT
ACKNOWLEDGEMENT I express my deep gratitude to Ms. Rama Gupta, Jt.G.M.(CNS), Airports Authority of India, Jaipur Airport for providing me this golden opportunity to attend the Industrial/Vocational training.
My sincere thanks to Sh.Rajesh Kumar , Manager (CNS), 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 : 30 / 06 / 2015
TABLE OF CONTENTS
Name Page No.
1. Brief Description of Jaipur 04
2. Airport Authority of India 05
3. Jaipur International Airport 06
4. Brief Description of CNS Department 09
5. Classification of CNS Facilities 10
6. Basic Communication system 13
7. VCCS/Tape recorder/DATIS 19
8. Frequency bands used in communication 22
9. AFTN 23
10. Aeronautical Telecommunication Network 27
11. Air Traffic Control 32
12. Navigation - aids DVOR/DME 34
13. Instrument Landing System (ILS) 41
14 .Security Equipments & PA System 56
12. Automation system 70
13. ADS-B 76
14. Intranet/LAN/WAN 79
15. Networking Devices & Addressing 83
16. Bibliography 90
Brief Description of JaipurJaipur is the capital and largest city of the Indian state of Rajasthan in
Northern India. It was found on 18 November 1727 by Maharaja Sawai
Jai Singh II, the ruler of Amber, after whom the city has been named.
Jaipur is known as the Pink City of India.
Area: 11,152 Sq Km
Population: 6,626,178 (according to 2011 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 Palace: Fabulous museum displays possessions of the
Jaipur Royal family.
(iv) Jantar Mantar: A Unique open air observatory built by the
founder of Jaipur- Sawai Jai singh. It has complex instruments
used for measuring local time, the altitude of stars, meridian etc.
(v) JaiGarh Fort: The victory fort- world’s largest cannon Jaivan.
Perched atop the hill Jaigarh.
Airport Authority of India
The Airports Authority of India (AAI) under the Ministry of Civil Aviation is
responsible for creating, upgrading, maintaining and managing civil
aviation infrastructure in India. It provides Air traffic management (ATM)
services over Indian airspace and adjoining oceanic areas. It also
manages a total of 125 Airports, including 11 International Airports,
8 Customs Airports, 81 Domestic Airports and 25 Civil enclaves at
Military Airfields. AAI also has ground installations at all airports and 25
other locations to ensure safety of aircraft operations. AAI covers all
major air-routes over Indian landmass via 29 Radar installations at 11
locations along with 89VOR/DVOR installations co-located with Distance
Measuring Equipment (DME). 52 runways are provided with Instrument
landing system (ILS) installations with Night Landing Facilities at most of
these airports and Automatic Message Switching System at 15 Airports.
The Government of India constituted the International Airports Authority
of India (IAAI) in 1972 to manage the nation's international airports while
the National Airports Authority (NAA) was constituted in 1986 to look
after domestic airports.The organisations were merged in April 1995 by
an Act of Parliament and was named as Airports Authority of India (AAI).
This new organisation was to be responsible for creating, upgrading,
maintaining and managing civil aviation infrastructure both on the ground
and air space in the country.
Functions
Design, Development, Operation and Maintenance of international
and domestic airports and civil enclaves.
Control and Management of the Indian airspace extending beyond
the territorial limits of the country, as accepted by ICAO.
Construction, Modification and Management of passenger terminals.
Development and Management of cargo terminals at international
and domestic airports.
Provision of passenger facilities and information system at the
passenger terminals at airports.
Expansion and strengthening of operation area, viz. Runways,
Aprons, Taxiway etc.
Provision of visual aids.
Provision of Communication and Navigation aids, viz. ILS, DVOR,
DME, Radar etc.
Jaipur International AirportJaipur airport is the only international airport in the state of Rajasthan. It
was granted the status of international airport on 29 December 2005.
The civil apron can accommodate 14 A320 aircraft and the new terminal
building can handle upto 1000 passengers at a time. There are plans to
extend the runway to 12,000 ft (3,658m) and expand the terminal
building to accommodate 1,000 passengers per hour.
The new domestic terminal building was inaugurated on 1 July 2009.
The new terminal has an area of 22,950 sq m, is made of glass and steel
structure having modern passenger friendly facilities such as central
heating system, central air conditioning, inline x-ray baggage inspection
system, escalators, public address system, car parking, CCTV
surveillance etc. The international terminal building has peak hour
passenger handling capacity of 500 and annual handling capacity of
400,000 passengers.
The Airlines operating at the airport are:
(a)International Airlines: Etihad Airways, Oman Air, Air Arabia, & Air
India Express.
(b)Domestic Airlines: Air Costa, Air India, Go Air, Indigo, Jet Airways,
Jet Konnect & Spice Jet.
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 OF CNS DEPARTMENT1.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 FacilitiesName Of The Equipment
Make Frequency Power
COMMUNICATION EQUIPMENTVHF AM Sets
Transmitters OTEDT-100PARKAIR
125.25 MHz126.6 MHz
50 W
Receivers OTEDT-100PARKAIR
125.25 MHz126.6 MHz
VHF AM Transreceivers
PAE 5610PAE BT6MDS -RadioJORTONI-COM
125.25 MHz
125.25 MHz125.25 MHz125.25 MHz
DVR RETIA 64 Channel
NA
64kbps Line NA NA
FIDS IDDSSOLARI
NA NA
Digital Clock Bihar Communication
NA NA
DSCN VIASAT
LAN/WAN CISCO Tele NA NA
EPABX CoralPanasonic
NANA
NANA
VCCS SCHMID NA NA
Mobile Radio(FM)Communication(Base Station)
Motorola
VERTEX Standard
161.825 MHz for CISF
166.525 MHz for AAI
10 W
Mobile Radio(FM)Communication(Hand Held Sets)
Motorola
SIMCOVERTEX StandardKENWOOD
161.825 MHz166.525 MHz
Automation INDRA NA NA Type B1
ADS-B COMSOFT 1090MHz NA
NAVIGATION EQUIPMENT
DVOR(JJP) THALES 420 112.9 MHz 100 W
HP DME (JJP)(Collocated with DVOR )
THALES Airsys-435
1100 MHz1163 MHz
1 kW
LOCALIZER(IJIP) NORMAC-7013
109.9 MHz 15 W
GLIDE PATH NORMAC-7033
333.8 MHz 5 W
LP DME (IJIP) (Collocated with GP )
THALES Airsys-415
997 MHz1060 MHz
100 W
Locator Outer SAC 100 295 kHz 50 W
SEQURITY EQUIPMENTSX-BIS SYSTEM
Departure Lounge 100100V Heimann(Ger)
Security Hold Area 6040i Heimann(Ger)
Explosive Trace DetectorSmith 500 DT
Smith IONSCAN 500 DT(Singapore)
DFMD METOR-200CEIA
CCTV INFINOVA
PA System BOSCH
Basic Communication System
1.1 Introduction: Transmitter, Receiver & Channel
IntroductionCommunication 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,
CRYSTAL OSC & AMP
MODULATOR & DRIVER PA
RF OUTPUT POWER AMP
AUDIO AMPLIFIER
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
Figure 1.1 Block diagram of typical radio transmitter
ChannelThe acoustic channel (i.e., shouting!) is not used for long-distance
communications and neither was the visual channel until the advent of
Mixer
RF Amplifier
Amplifier
IF Amplifier and Filter
Frequency Amplifier
DemodulatorAudio Voltage and Power amplifiers
the laser. "Communications," in this context, will be restricted to radio,
wire and fibre optic channels. Also, it should be noted that the term
channel is often used to refer to the frequency range allocated to a
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.
ReceiverThere 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
Figure 1.2 Block diagram of AM super heterodyne receiver
Receivers run the whole range of complexity from a very simple crystal
receiver, with headphones, to a far more complex radar receiver, with its
involved antenna arrangements and visual display system. 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 ModulationAnother 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.
Space modulation is a radio amplitude modulation technique used
in instrument landing systems that incorporates the use of multiple
antennas fed with various radio frequency powers and phases to create
different depths of modulation within various volumes of three-
dimensional airspace. This modulation method differs from internal
modulation methods inside most other radio transmitters in that the
phases and powers of the two individual signals mix within airspace,
rather than in a modulator.
An aircraft with an on-board ILS receiver within the capture area of an
ILS, (glideslope and localizer range), will detect varying depths of
modulation according to the aircraft's position within that airspace,
providing accurate positional information about the progress to the
threshold.
The ILS uses two radio frequencies, one for each ground station (about
110 MHz for LOC and 330 MHz for the GP), to transmit two amplitude-
modulated signals (90 Hz and 150 Hz), along the glidepath (GP) and the
localizer (LOC) trajectories into airspace. It is this signal that is projected
up from the runway which an aircraft employing an instrument approach
uses to land.
VOICE COMMUNICATION CONTROL SYSTEM
INTRODUCTION AND NEED OF VCCS AT AIRPORTSThe 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.
VCCS
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 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.
DATIS AND NAV-AIDS
Frequency band and its uses in communicationsTable 1.1 Radio Waves Classification
DIGITAL CLOCK
DIGITAL VOICE AIRPORT TERMINAL
LOW POWER DME REMOTE STATUS
OUTER LOCATER REMOTE STATUS
WALKIE-TALKIE BASE STATION
LLZ & GP REMOTE STATUS
HIGH POWER DME REMOTE
STATUS
DVOR REMOTE STATUS
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
Line/Circuit switching is a methodology of implementing
a telecommunications network in which two network nodes establish a
dedicated communications channel (circuit) through the network before
the nodes may communicate. The circuit guarantees the full bandwidth
of the channel and remains connected for the duration of the
communication session. The circuit functions as if the nodes were
physically connected as with an electrical circuit. 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. The defining example of a
circuit-switched network is the early analog telephone network. When
a call is made from one telephone to another, switches within
the telephone exchanges create a continuous wire circuit between the
two telephones, for as long as the call lasts.
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. Message switching was the precursor of packet
switching, where messages were routed in their entirety, one hop at a
time. It was first built by Collins Radio Company, Newport Beach,
California, during the period 1959–1963 for sale to large airlines, banks
and railroads. Message switching systems are nowadays mostly
implemented over packet-switched or circuit-switched data networks.
Each message is treated as a separate entity. Each message contains
addressing information, and at each switch this information is read and
the transfer path to the next switch is decided. Depending on network
conditions, a conversation of several messages may not be transferred
over the same path. Each message is stored (usually on hard drive due
to RAM limitations) before being transmitted to the next switch.
Because of this it is also known as a 'store-and-forward' network. Email
is a common application for message switching. A delay in delivering
email is allowed, unlike real-time data transfer between two computers.
PACKET SWITCHING
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.
Circuit switching contrasts with packet switching which divides the data
to be transmitted into packets transmitted through the network
independently. In packet switching, instead of being dedicated to one
communication session at a time, network links are shared by packets
from multiple competing communication sessions, resulting in the loss of
the quality of service guarantees that are provided by circuit switching.
In circuit switching, the bit delay is constant during a connection, as
opposed to packet switching, where packet queues may cause varying
and potentially indefinitely long packet transfer delays. No circuit can be
degraded by competing users because it is protected from use by other
callers until the circuit is released and a new connection is set up. Even
if no actual communication is taking place, the channel remains reserved
and protected from competing users.
Virtual circuit switching is a packet switching technology that emulates
circuit switching, in the sense that the connection is established before
any packets are transferred, and packets are delivered in order.
While circuit switching is commonly used for connecting voice circuits,
the concept of a dedicated path persisting between two communicating
parties or nodes can be extended to signal content other than voice. Its
advantage is that it provides for continuous transfer without the overhead
associated with packets making maximal use of available bandwidth for
that communication. Its disadvantage is that it can be relatively inefficient
because unused capacity guaranteed to a connection cannot be used by
other connections on the same network.
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 modes 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 exist 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 AIRNC communication services the AIRNC Data
Network Service. The network provides a communication interface
between airlines, AFTN, Air-route Traffic Control Centre (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
Air Traffic ControlAir traffic control (ATC) is a service provided by ground-
based controllers who direct aircraft on the ground and through
controlled airspace, and can provide advisory services to aircraft in non-
controlled airspace. The primary purpose of ATC worldwide is to prevent
collisions, organize and expedite the flow of traffic, and provide
information and other support for pilots. In some countries, ATC plays a
security or defensive role, or is operated by the military.
To prevent collisions, ATC enforces traffic separation rules, which
ensure each aircraft maintains a minimum amount of empty space
around it at all times. Many aircraft also have collision avoidance
Ground to Air / Air to Ground Voice Communication System with Main and Stand-By VHF Tx /Rx
Equipments
systems, which provide additional safety by warning pilots when other
aircraft get too close.
In many countries, ATC provides services to all private, military, and
commercial aircraft operating within its airspace. Depending on the type
of flight and the class of airspace, ATC may issue instructions that pilots
are required to obey, or advisories (known as flight information in some
countries) that pilots may, at their discretion, disregard. The pilot in
command is the final authority for the safe operation of the aircraft and
may, in an emergency, deviate from ATC instructions to the extent
required to maintain safe operation of their aircraft.
Airport Control
The primary method of controlling the immediate airport environment is
visual observation from the airport control tower (TWR). The tower is a
tall, windowed structure located on the airport grounds. Air traffic
controllers are responsible for the separation and efficient movement of
aircraft and vehicles operating on the taxiways and runways of the
airport itself, and aircraft in the air near the airport, generally 5 to
10 nautical miles (9 to 18 km) depending on the airport procedures.
Surveillance displays are also available to controllers at larger airports to
assist with controlling air traffic. Controllers may use a radar system
called secondary surveillance radar for airborne traffic approaching and
departing. These displays include a map of the area, the position of
various aircraft, and data tags that include aircraft identification, speed,
altitude, and other information described in local procedures. In adverse
weather conditions the tower controllers may also use surface
movement radar (SMR), surface movement guidance and control
systems (SMGCS) or advanced SMGCS to control traffic on the
manoeuvring area (taxiways and runway).
The areas of responsibility for TWR controllers fall into three general
operational disciplines; Local Control or Air Control, Ground Control, and
Flight Data/Clearance Delivery—other categories, such as Apron Control
or Ground Movement Planner, may exist at extremely busy airports.
While each TWR may have unique airport-specific procedures, such as
multiple teams of controllers ('crews') at major or complex airports with
multiple runways, the following provides a general concept of the
delegation of responsibilities within the TWR environment.
NAVIGATIONAL AIDSDoppler VHF Omni Range (D.V.O.R)
DVOR, short for Doppler 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)
Distance measuring equipment (DME) is a transponder-based radio
navigation technology that measures slant range distance by timing
the propagation delay of VHF or UHF radio signals.
Developed in Australia, it was invented by James Gerry Gerrand under
the supervision of Edward George "Taffy" Bowen while employed as
Chief of the Division of Radio physics of the Commonwealth Scientific
and Industrial Research Organisation (CSIRO). Another engineered
version of the system was deployed by Amalgamated Wireless
Australasia Limited in the early 1950s operating in the
200 MHz VHF band. This Australian domestic version was referred to by
the Federal Department of Civil Aviation as DME(D) (or DME Domestic),
and the later international version adopted by ICAO as DME(I).
DME is similar to secondary radar, except in reverse. The system was a
post-war development of the IFF (identification friend or foe) systems
of World War II. To maintain compatibility, DME is functionally identical
to the distance measuring component of TACAN.
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.
PURPOSE AND USE OF DME
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.
Operation
Aircraft use DME to determine their distance from a land-based
transponder by sending and receiving pulse pairs – two pulses of fixed
duration and separation. The ground stations are typically co-located
with VORs. A typical DME ground transponder system for en-route or
terminal navigation will have a 1 kW peak pulse output on the assigned
UHF channel.
A low-power DME can be co-located with an ILS glide slope antenna
installation where it provides an accurate distance to touchdown
function, similar to that otherwise provided by ILS marker beacons.
Association of DME with VORAssociated 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 ILSAssociated 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
DME Antenna
Doppler VHF Omni Directional Range Antenna
As a complement to a VOR to provide more precise
navigation service in localities where there is:
oHigh air traffic density
oProximity 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.
INSTRUMENT LANDING SYSTEM
Purpose and use of ILS:
An instrument landing system (ILS) is a ground-based instrument
approach system that provides precision lateral and vertical guidance to
an aircraft approaching and landing on a runway, using a combination of
radio signals and, in many cases, high-intensity lighting arrays to enable
a safe landing during instrument meteorological conditions (IMC), such
as low ceilings or reduced visibility due to fog, rain, or blowing snow.
An instrument approach procedure chart (or 'approach plate') is
published for each ILS approach to provide the information needed to fly
an ILS approach during instrument flight rules (IFR) operations. A chart
includes the radio frequencies used by the ILS components or
navaids and the prescribed minimum visibility requirements. 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.
Radio-navigation aids must provide a certain accuracy (set by
international standards of CAST/ICAO); to ensure this is the case, flight
inspection organizations periodically check critical parameters with
properly equipped aircraft to calibrate and certify ILS precision.
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:
A localizer is an antenna array normally located beyond the approach
end of the runway and generally consists of several pairs of directional
antennas. Two signals are transmitted on one of 40 ILS channels. One
is modulated at 90 Hz, the other at 150 Hz. These are transmitted from
co-located antennas. Each antenna transmits a narrow beam, one
slightly to the left of the runway centreline, the other slightly to the right.
The localizer receiver on the aircraft measures the difference in the
depth of modulation (DDM) of the 90 Hz and 150 Hz signals. The depth
of modulation for each of the modulating frequencies is 20 percent when
the receiver is on the centreline. The difference between the two signals
varies depending on the deviation of the approaching aircraft from the
centreline.
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.
LOCALIZER
Glide Path Unit:
A glide slope station uses an antenna array sited to one side of the
runway touchdown zone. The GS signal is transmitted on a carrier
frequency using a technique similar to that for the localizer. The centre of
the glide slope signal is arranged to define a glide path of approximately
3° above horizontal (ground level). The beam is 1.4° deep (0.7° below
the glide-path centre and 0.7° above).
The pilot controls the aircraft so that the glide slope indicator remains
centered on the display to ensure the aircraft is following the glide path
to remain above obstructions and reach the runway at the proper
touchdown point (i.e., it provides vertical guidance).
LOCALIZER LOG PERIODIC ARRAY ANTENNA
SWITCH MODE POWER SUPPLY WITH EXTERNAL BATTERIES
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.
Figure2 Typical Locations Of ILS Component
GLIDEPATH LOW POWER DISTANCE MEASURING EQUIPMENT
DME ANTENNA
GLIDEPATH ANTENNA
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 7miles in front of
the 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 3500feet 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 1.000feet
from the approach end of the runway, so the pattern intersects the
glide angle at 100feet. The transmitter is modulated by a tone of
3000 Hz keyed by continuous dots.
Distance Measuring Equipment (DME):
Distance measuring equipment (DME) is a transponder-based radio
navigation technology that measures slant range distance by timing
the propagation delay of VHF or UHF radio signals.
Developed in Australia, it was invented by James Gerry Gerrand under
the supervision of Edward George "Taffy" Bowen while employed as
Chief of the Division of Radiophysics of the Commonwealth Scientific
and Industrial Research Organisation (CSIRO). Another engineered
version of the system was deployed by Amalgamated Wireless
Australasia Limited in the early 1950s operating in the
200 MHz VHF band. This Australian domestic version was referred to by
the Federal Department of Civil Aviation as DME(D) (or DME Domestic),
and the later international version adopted by ICAO as DME(I).
DME is similar to secondary radar, except in reverse. The system was a
post-war development of the IFF (identification friend or foe) systems
of World War II. To maintain compatibility, DME is functionally identical
to the distance measuring component of TACAN.
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.
Process of Operation
Aircraft use DME to determine their distance from a land-based
transponder by sending and receiving pulse pairs – two pulses of fixed
duration and separation. The ground stations are typically co-located
with VORs. A typical DME ground transponder system for en-route or
terminal navigation will have a 1 kW peak pulse output on the assigned
UHF channel.
A low-power DME can be co-located with an ILS glide slope antenna
installation where it provides an accurate distance to touchdown
function, similar to that otherwise provided by ILS marker beacons.
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 indication 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:
In aviation, a localizer (LOC) is the lateral component of the instrument
landing system (ILS) for the runway centreline when combined with the
vertical glide slope, not to be confused with a locator, although both are
parts of aviation navigation systems.
A localizer (like a glideslope) works as a cooperation between the
transmitting airport runway and the receiving cockpit instruments. An
older aircraft without ILS receiver cannot take advantage of any ILS
facilities at any runway, and much more important, the most modern
aircraft have no use of their ILS instruments at runways which lack ILS
facilities. In parts of Africa and Asia large airports may lack any kind of
transmitting ILS system. Some runways have ILS only in one direction,
this can however still be used (with a lower precision) known as back
beam.
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 incline 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 touchdown 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
continuous distance information from the touchdown 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 model used in AAI:
Different model 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 .Nowadays 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 in
modernization programme. One of the ILS model at Delhi is a CAT
III ILS.
GENERAL CONCEPTS OF SECURITY EQUIPMENTS & PUBLIC ADDRESSING 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 coloured 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.
SECURITY EQUIPMENTSLarge numbers of people pass through airports every day. This presents
potential targets for terrorism and other forms of crime because of the
number of people located in a particular location. Similarly, the high
concentration of people on large airliners, the potential high death rate
with attacks on aircraft, and the ability to use a hijacked airplane as a
lethal weapon may provide an alluring target for terrorism, whether or not
they succeed due their high profile nature following the various attacks
and attempts around the globe in recent years.
Airport security attempts to prevent any threats or potentially dangerous
situations from arising or entering the country. If airport security does
succeed in this, then the chances of any dangerous situations, illegal
items or threats entering into both aircraft, country or airport are greatly
reduced. As such, airport security serves several purposes: To protect
the airport and country from any threatening events, to reassure the
travelling public that they are safe and to protect the country and their
people.
Monte R. Belger of the U.S. Federal Aviation Administration notes "The
goal of aviation security is to prevent harm to aircraft, passengers, and
crew, as well as support national security and counter-terrorism policy.”
DOOR FRAME METAL DETECTOR X RAY BAGGAGE SYSTEM
EXPLOSIVE TEST DETECTION SYSTEM
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 DETECTORS2. DOOR FRAME METAL DETECTORS
HAND HELD METAL DETECTOR
1. MELU 5087M28 ELECTRONICS UNIT
2. METOR COIL SET
3. 8 BUTTON M28
4. CARRING STRAP
5. BUTTON SLIDE
6. BATTERY/CHARGE CABLE
7. CLAMPING SCREW
OPERATIONThe 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 DETECTORSAlmost 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
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 is
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.
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.
PUBLIC ADDRESSING SYSTEM
A public address system (PA system) is an electronic sound
amplification and distribution system with a microphone, amplifier and
loudspeakers, used to allow a person to address a large public, for
example for announcements of movements at large and noisy air and
rail terminals or at a sports stadium. The term is also used for systems
which may additionally have a mixing console, and amplifiers and
loudspeakers suitable for music as well as speech, used to reinforce a
sound source, such as recorded music or a person giving a speech or
distributing the sound throughout a venue or building.
ATS AUTOMATION SYSTEM
General System DescriptionOne 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
PERSONAL ANNOUNCEMENT BOOTH
FLIGHT INFORMATION DISPLAY SYSTEM
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 4000The 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 its own state vector
and other information without knowing what other entities might be
receiving it, and without expectation of an acknowledgment or
reply. ADS-B aircraft transmissions received by a network of
ground stations can provide surveillance over a wider area.
Referred to as ADS-B OUT, this provides ATC with the ability to
accurately track participating aircraft.
ADS-B is automatic because no external stimulus is required; it is
dependent because it relies on on-board position sources and on-
board broadcast transmission systems to provide surveillance
information to other parties. Finally, the data is broadcast, the
originating source has no knowledge of who receives and uses the
data and there is no two-way contract or interrogation.
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 kilometres.
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: WANIn 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.
Metropolitan Area Network (MAN)
A metropolitan area network (MAN) is a computer network larger than
a local area network, covering an area of a few city blocks to the area of
an entire city, possibly also including the surrounding areas.
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
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.
Networking Devices Hubs
An Ethernet hub, active hub, network hub, repeater hub, multiport
repeater or hub is a device for connecting multiple
Ethernet devices together and making them act as a
single network segment. It has multiple input/output (I/O) ports, in
which a signal introduced at the input of any port appears at the
output of every port except the original incoming. A hub works at
the physical layer (layer 1) of the OSI model. Repeater hubs also
participate in collision detection, forwarding a jam signal to all ports
if it detects a collision. In addition to standard 8P8C ("RJ45") ports,
some hubs may also come with a BNC and/or Attachment Unit
Interface (AUI) connector to allow connection to
legacy 10BASE2 or 10BASE5 network segments.
Hubs are now largely obsolete, having been replaced by network
switches except in very old installations or specialized applications.
Uses
Historically, the main reason for purchasing hubs rather than
switches was their price. This motivator has largely been eliminated by
reductions in the price of switches, but hubs can still be useful in special
circumstances:
For inserting a protocol analyzer into a network connection, a hub is
an alternative to a network tap or port mirroring.[7]
When a switch is accessible for end users to make connections, for
example, in a conference room, an inexperienced or careless user
(or saboteur) can bring down the network by connecting two ports
together, causing a switching loop. This can be prevented by using a
hub, where a loop will break other users on the hub, but not the rest
of the network (more precisely, it will break the current collision
domain up to the next switch/bridge port). This hazard can also be
avoided by using switches that can detect and deal with loops, for
example by implementing the spanning tree protocol.
A hub with a 10BASE2 port can be used to connect devices that only
support 10BASE2 to a modern network.
A hub with an AUI port can be used to connect to a 10BASE5
network.
Switches
A network switch (also called switching hub, bridging hub, officially MAC
bridge) is a computer networking device that connects devices together
on a computer network, by using packet switching to receive, process
and forward data to the destination device. Unlike less
advanced network hubs, a network switch forwards data only to one or
multiple devices that need to receive it, rather than broadcasting the
same data out of each of its ports.
A network switch is a multiport network bridge that uses hardware
addresses to process and forward data at the data link layer (layer 2) of
the OSI model. Switches can also process data at the network
layer (layer 3) by additionally incorporating routing functionality that most
commonly uses IP addresses to perform packet forwarding; such
switches are commonly known as layer-3 switches or multilayer
switches. Beside most commonly used Ethernet switches, they exist for
various types of networks, including Fibre Channel, Asynchronous
Transfer Mode, and InfiniBand. The first Ethernet switch was introduced
by Kalpana in 1990.
Uses
Switches may operate at one or more layers of the OSI model, including
the data link and network layers. A device that operates simultaneously
at more than one of these layers is known as a multilayer switch.
In switches intended for commercial use, built-in or modular interfaces
make it possible to connect different types of networks,
including Ethernet, Fibre Channel, RapidIO , ATM, ITU-
T G.hn and 802.11. This connectivity can be at any of the layers
mentioned. While layer-2 functionality is adequate for bandwidth-shifting
within one technology, interconnecting technologies such
as Ethernet and token ring is easier at layer 3.
Devices that interconnect at layer 3 are traditionally called routers, so
layer-3 switches can also be regarded as (relatively primitive) routers.
Where there is a need for a great deal of analysis of network
performance and security, switches may be connected between WAN
routers as places for analytic modules. Some vendors
provide firewall, network intrusion detection,and performance analysis
modules that can plug into switch ports. Some of these functions may be
on combined modules
In other cases, the switch is used to create a mirror image of data that
can go to an external device. Since most switch port mirroring provides
only one mirrored stream, network hubs can be useful for fanning out
data to several read-only analyzers, such as intrusion detection
systems and packet sniffers.
Routers
A router is a networking device that forwards data
packets between computer networks. A router is connected to two or
more data lines from different networks (as opposed to a network switch,
which connects data lines from one single network). When a data packet
comes in on one of the lines, the router reads the address information in
the packet to determine its ultimate destination. Then, using information
in its routing table or routing policy, it directs the packet to the next
network on its journey. This creates an overlay internetwork. Routers
perform the "traffic directing" functions on the Internet. A data packet is
typically forwarded from one router to another through the networks that
constitute the internetwork until it reaches its destination node.
The most familiar type of routers are home and small office routers that
simply pass data, such as web pages, email, IM, and videos between
the home computers and the Internet. An example of a router would be
the owner's cable or DSL router, which connects to the Internet through
an ISP. More sophisticated routers, such as enterprise routers, connect
large business or ISP networks up to the powerful core routers that
forward data at high speed along the optical fiber lines of the Internet
backbone. Though routers are typically dedicated hardware devices, use
of software-based routers has grown increasingly common
Uses
Routers intended for ISP and major enterprise connectivity usually
exchange routing information using the Border Gateway
Protocol (BGP). RFC 4098 standard defines the types of BGP routers
according to their functions:
Edge router: Also called a Provider Edge router, is placed at the edge
of an ISP network. The router uses External BGP to EBGP routers in
other ISPs, or a large enterprise Autonomous System.
Subscriber edge router: Also called a Customer Edge router, is
located at the edge of the subscriber's network, it also uses EBGP to
its provider's Autonomous System. It is typically used in an
(enterprise) organization.
Inter-provider border router: Interconnecting ISPs, is a BGP router
that maintains BGP sessions with other BGP routers in ISP
Autonomous Systems.
Core router: A core router resides within an Autonomous System as a
back bone to carry traffic between edge routers.
Within an ISP: In the ISP's Autonomous System, a router uses
internal BGP to communicate with other ISP edge routers,
other intranet core routers, or the ISP's intranet provider border
routers.
"Internet backbone:" The Internet no longer has a clearly identifiable
backbone, unlike its predecessor networks. See default-free
zone (DFZ). The major ISPs' system routers make up what could be
considered to be the current Internet backbone core. ISPs operate all
four types of the BGP routers described here. An ISP "core" router is
used to interconnect its edge and border routers. Core routers may
also have specialized functions in virtual private networks based on a
combination of BGP and Multi-Protocol Label Switching protocols.
Port forwarding: Routers are also used for port forwarding between
private Internet connected servers
Voice/Data/Fax/Video Processing Routers: Commonly referred to
as access servers or gateways, these devices are used to route and
process voice, data, video and fax traffic on the Internet. Since 2005,
most long-distance phone calls have been processed as IP traffic
(VOIP) through a voice gateway. Use of access server type routers
expanded with the advent of the Internet, first with dial-up access and
another resurgence with voice phone service.
Binary NotationIn binary notation, the IP address is displayed as 32 bits. To make the
address l I l (J readable, one or more spaces is usually inserted between
each octet (8 bits). Each <XII 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 NotationTo 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 AddressingIP addresses, when started a few decades ago, used the concept of
classes. This architecture 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.
Net id And Host idIn classful addressing, an IP address in classes A, B, and C is divided
into net id and host id. These parts 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
Bibliography1. Jaipur Airport , Jaipur2. https://en.wikipedia.org 3. http://www.aai.aero
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