JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITY KAKINADA III Year B.Tech. IT I-Sem T P C 4+1* 0 4 DATA COMMUNICATION SYSTEMS Unit I: INTRODUCTION TO DATA COMMUNICATIONS AND NETWORKING: Standards Organizations for Data Communications, Layered Network Architecture, Open Systems Interconnection, Data Communications Circuits, Serial and parallel Data Transmission, Data communications Circuit Arrangements, Data communications Networks, Alternate Protocol Suites. SIGNALS, NOISE, MODULATION, AND DEMODULATION: Signal Analysis, Electrical Noise and Signal-to-Noise Ratio, Analog Modulation Systems, Information Capacity, Bits, Bit Rate, Baud, and M-ary Encoding, Digital Modulation. Unit II: METALLIC CABLE TRANSMISSION MEDIA: Metallic Transmission Lines, Transverse Electromagnetic Waves, Characteristics of Electromagnetic Waves, Transmission Line Classifications, Metallic Transmission Line Types, Metallic Transmission Line Equivalent Circuit, Wave Propagation on Metallic Transmission Lines, Metallic Transmission Line Losses. OPTICAL FIBER TRANSMISSION MEDIA: Advantages of Optical Fiber Cables, Disadvantages of Optical Fiber Cables, Electromagnetic spectrum, Optical Fiber Communications System Block Diagram, Optical Fiber construction, The Physics of Light, Velocity of Propagation, Propagation of Light Through an Optical fiber Cable, Optical Fiber Modes and Classifications, Optical Fiber Comparison, Losses in Optical Fiber Cables, Light sources, Light Detectors, Lasers. Unit III:
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JAWAHARLAL NEHRU TECHNOLOGICAL UNIVERSITYKAKINADA
III Year B.Tech. IT I-Sem T P C 4+1* 0 4
DATA COMMUNICATION SYSTEMS
Unit I:INTRODUCTION TO DATA COMMUNICATIONS AND NETWORKING: Standards Organizations for Data Communications, Layered Network Architecture, Open Systems Interconnection, Data Communications Circuits, Serial and parallel Data Transmission, Data communications Circuit Arrangements, Data communications Networks, Alternate Protocol Suites.SIGNALS, NOISE, MODULATION, AND DEMODULATION:Signal Analysis, Electrical Noise and Signal-to-Noise Ratio, Analog Modulation Systems, Information Capacity, Bits, Bit Rate, Baud, and M-ary Encoding, Digital Modulation.
Unit II:METALLIC CABLE TRANSMISSION MEDIA:Metallic Transmission Lines, Transverse Electromagnetic Waves, Characteristics of Electromagnetic Waves, Transmission Line Classifications, Metallic Transmission Line Types, Metallic Transmission Line Equivalent Circuit, Wave Propagation on Metallic Transmission Lines, Metallic Transmission Line Losses.OPTICAL FIBER TRANSMISSION MEDIA:Advantages of Optical Fiber Cables, Disadvantages of Optical Fiber Cables, Electromagnetic spectrum, Optical Fiber Communications System Block Diagram, Optical Fiber construction, The Physics of Light, Velocity of Propagation, Propagation of Light Through an Optical fiber Cable, Optical Fiber Modes and Classifications, Optical Fiber Comparison, Losses in Optical Fiber Cables, Light sources, Light Detectors, Lasers.
Unit III:DIGITAL TRANSMISSION:Pulse Modulation, Pulse code Modulation, Dynamic Range, Signal Voltage –to-Quantization Noise Voltage Ration, Linear Versus Nonlinear PCM Codes, Companding, PCM Line Speed, Delta Modulation PCM and Differential PCM.MULTIPLEXING AND T CARRIERS:Time- Division Multiplexing, T1 Digital Carrier System, North American Digital Multiplexing Hierarchy, Digital Line Encoding, T Carrier systems, European Time- Division Multiplexing, Statistical Time – Division Multiplexing, Frame Synchronization, Frequency- Division Multiplexing, Wavelength- Division Multiplexing, Synchronous Optical Network
Unit IV:WIRLESS COMMUNICATIONS SYSTEMS:
Electromagnetic Polarization, Rays and Wavefronts, Electromagnetic Radiation, Spherical Wavefront and the Inverse Square Law, wave Attenuation and Absorption, Optical Properties of Radio Waves, Terrestrial Propagation of Electromagnetic Waves, Skip Distance, Free-Space Path Loss, Microwave Communications Systems, Satellite Communications Systems.
Unit V:TELEPHONE INSTRUMENTS AND SIGNALS:The Subscriber Loop, Standard Telephone Set, Basic Telephone Call Procedures, Call Progress Tones and Signals, Cordless Telephones, Caller ID, Electronic Telephones, Paging systems.THE TELEPHONE CIRCUIT:The Local Subscriber Loop, Telephone Message- Channel Noise and Noise Weighting, Units of Powers Measurement, Transmission Parameters and Private-Line Circuits, Voice-Frequency Circuit Arrangements, Crosstalk.
Unit VI:CELLULAR TELEPHONE SYSTEMS:First- Generation Analog Cellular Telephone, Personal Communications system, Second-Generation Cellular Telephone Systems, N-AMPS, Digital Cellular Telephone, Interim Standard, North American Cellular and PCS Summary, Global system for Mobile Communications, Personal Communications Satellite System.
Unit VII:DATA COMMUNICATIONS CODES, ERROR CONTROL, AND DATA FORMATS:Data Communications Character Codes, Bar Codes, Error Control, Error Detection, Error Correction, Character Synchronization.DATA COMMUNICATIONS EQUIPMENT:Digital Service Unit and Channel Service Unit, Voice- Band Data Communication Modems, Bell Systems- Compatible Voice- Band Modems, Voice- Band Modern Block Diagram, Voice- Band Modem Classifications, Asynchronous Voice-Band Modems, Synchronous Voice-Band Modems, Modem Synchronization, ITU-T Voice- Band Modem Specifications, 56K Modems, Modem Control: The AT Command Set, Cable Modems, Probability of Error and Bit Error Rate.
Unit VIII:DATA –LINK PROTOCOLS:Data –Link Protocol Functions, Character –and Bit- Oriented Protocols, Data Transmission Modes, Asynchronous Data – Link Protocols, Synchronous Data – Link Protocols, Synchronous Data – Link Control, High – Level Data – Link Control.
LECTURE SCHEDULE
Sl.No No. of Hrs
Unit Topic Remarks
1 1 I INTRODUCTION TO DATA COMMUNICATIONS AND NETWORKING
2 1 Layered Architecture Networks,3 2 OSI Layers4 1 Data communication circuits, serial¶llel data
transmission5 2 Data communication n/ws, TCP-IP Protocol6 1 Signal Analysis 7 1 Electrical noise and S/N ratio8 2 Analog Modulation S/Ms, information capacity, bits, baud
rate 9 1 M-ray encoding , Digital Modulation
10 1 II Introduction to Metallic Tx lines11 1 TE&TM waves, characteristics of EM waves12 1 Transmission line classification, metallic Tx line
equivalent ckt13 1 Advantages&disadvantages of optical fiber14 1 EM spectrum,optica5l fiber communications block
diagram15 1 Construction of optical fiber, physics of light, velocity
propagation16 1 Modes of propagation, light sources, detectors, LASERs
17 2 III Pulse Modulation, PCM, dynamic range18 1 Signal voltage to quantization noise, linear vs non linear
PCM19 1 TDM, T1 Digital carrier system20 2 North American digital multiplexing, digital line
encoding21 1 T carrier system, European TDM22 1 Frame synchronization, FDM
23 1 IV EM radiation, spherical wave front24 1 Inverse square law, wave attenuation , absorption25 2 Terrestrial propagation of EM waves
26 1 Skip distance ,free space path loss27 1 Microwave communication28 1 Satellite communication
31 1 Card less telephones and caller ID32 1 Electronic telephone, paging system33 1 Local subscriber loop, telephone msg-channel noise34 2 Noise weighting Tx parameters and private line ckts, voice
frequency ckt arrangements
35 2 VI First generation AMPS, PCS36 2 Second generation cellular telephone system37 1 N-AMPS38 1 Digital cellular telephone, interim standard39 1 North American cellular and PCS summary40 1 GSM41 1 DCSS
42 2 VII Digital communication character codes, bar codes43 1 Error control, error detection, error correction44 1 Digital service unit and channel service unit45 1 Voice band data communication, modem classification
45 1 VIII Asynchronous voice band modems, synchronous voice band modems
47 1 Modem synchronization, ITU-T voice band48 1 Modem specification, 56k modems49 1 Modem control, point and bit error rate50 1 Data link protocol functions, character & bit oriented
protocols51 1 Transmission modes52 1 Asynchronous data link protocol53 1 Synchronous data link protocol54 1 High level data link protocol
UNIT-I
INTRODUCTION TO DATA COMMUNICATIONS &NETWORKING
ESSENCE OF THE UNIT:
Data communication is the transfer of data from one device to another via some form
of transmission medium.
Data communication ckt consists five basic elements those are the message, the
sender, the receiver, the medium and the protocol.
Networks allow shared access to information devices and uses distributed processing,
in which a task is divided among multiple computers.
A protocol is a set of rules and regulations that govern communication
Standards are necessary to ensure that products from different manufacturers can
work together as expected.
The ISO,ITU-T,ANSI,IEEE, and EIA are some of the organizations involved in
standards creation.
A line configuration defines the relationship of communication devices to a
communication pathway.
In point-to-point line configuration, two and only two devices are connected by
dedicated link .
In multipoint line configuration three or more devices share a link.
Topology refers to the physical or logical arrangement of a network. Devices may be
arranged in a mesh, star, tree, bus, ring, or hybrid topology.
Communication between two devices can occur in one of three transmission modes:
simplex, half duplex, or full duplex.
A network can configured as a local area network (LAN), me tropolitan area network
(MAN), a wide area network (WAN).
An internetwork is a network of networks.
An International Standards Organization (ISO) created a model called the Open
System Interconnection (OSI), which allows diverse systems to communicate.
OSI system consists of seven layers those are physical layer, data link layer, network
layer, transport layer, session layer, presentation layer and application layer.
The physical layer coordinates the functions required to transmit a bit stream over a
physical medium.
The data link layer is responsible for delivering data units from one station to the next
without errors.
The network layer is responsible for the source to destination delivery of a packet
across multiple networks.
The transport layer is responsible for the source to destination of the entire message.
The session layer establishes, maintains, and synchronizes the interactions between
communicating devices.
The application layer enables the users to access the network.
The TCP/IP, a five layer hierarchical protocol suite developed before the OSI model,
is the protocol suite used in the internet.
Information must be transformed into electromagnetic signals prior to transmission
across the network.
A signal is periodic or aperiodic in nature.
We can represent a signal in time domain as well as frequency domain.
A time domain graph plots amplitude as a function of time.
A frequency domain graph plots each sine wave’s peak amplitude again its frequency.
Information can be transformed into electromagnetic signals prior to transmission
across a network.
A digital signal can be decomposed into an infinite number of sine waves.
Modulation is the process varying any one of the parameters of the carrier is made
proportional to instantaneous amplitude of the modulating signal.
In AM the amplitude of the carrier wave varies with the amplitude of the modulating
wave.
In FM the frequency of the carrier is varied with the instantaneous amplitude of the
modulating signal.
In AM radio, the bandwidth of the modulated signal must be the amplitude of the
modulating signal.
In QAM i.e quadrature amplitude modulation both the phase and amplitude of the
carrier is vary.
SHORT ANSWER QUESTIONS
1. Which of the following gives minimum probability of error. PSK.
2. In ASK the transmission bandwidth is equivalent to Twice the base band bandwidth.
3. In ASK the threshold level is Function of AC.
4. The QAM is the combination of ASK and PSK.
5. In FSK the threshold level is independent on :-> Carrier Amplitude.
6. ISO started in :-> 1952.
7. One of the characteristics of WAN is :-> inter connects computers with in and around
an entire country.
8. Example of mainframe connectivity is :-> E-mail.
9. Data link layer is responsible for :-> providing error free communication.
10. Which is the fourth layers of ISO layers :-> Transport layer.
11. The process of impressing relatively low frequency information signals onto a high
frequency carrier signal is called :-> Modulation.
12. Which of the following is fully connected topology :-> mesh topology.
13. The layer in which the protocols provide the logical connection entities at the
application layer is called :-> transport layer.
14. Which layer translates between different data formats and protocols :-> presentation
network layer.
15. Which layer is also called as the work group layer :-> distribution layer.
16. ___________ typically operate at bit rates from 1.5mbps to 2.4gbps and cover at a
distance of 100 to 1000miles is :-> MAN.
17. _______ topology describes how the network is actually laid out :-> physical layer.
18. Each computer in a network has a special expansion card called :-.> network interface
card.
19. In______ mode transmissions are possible in direction simultaneously but they must
be between the same two stations. :-> full duplex.
20. Signal to noise power ratio in dBm is :-> 10log Ps/Pn.
LONG ANSWER QUESTIONS
1.(a) Name and briefly describe the differences between the two kinds of data
communication standards
(b) What are the various types of network topologies? What are the implications of
having different topology?
2.(a) Define analog and digital signals. Describe the difference between them.
(b) Define digital modulation? Give a brief description of ASK, FSK, PSK and QAM.
3.(a) What is an open system? Explain, in detail, about open systems interconnection.
(b) Explain in detail, about quadrature amplitude modulation and trellis code
modulation.
4.(a) What is meant by a layered protocol? Why are protocol layered? Explain.
(b) What is meant by M-ary encoding? Explain higher-than-binary encoding with an
example.
5.(a) What is the difference between the communication of data and
communication of information?
(b) What is the difference between electrical noise and thermal noise? For an electronic
device operating at 17oC with a bandwidth of 10 kHz, determine the thermal noise
power in watts and dBm.
6.(a) Compare peer-to-peer client/server network and dedicated client/server network
(b) What is a signal-to-noise power ratio? For a circuit with a signal power of 100W
and a noise power of 0.002mW, determine the signal-to-noise power ratio in
absolute and dB values.
UNIT-II
METALLIC CABLES & OPTICAL FIBER TRANSMISSION MEDIA
ESSENCE OF THE UNIT: Signals are travel from transmitter to receiver via a path. This path is called as
medium can be guided or unguided.
A guided medium is contained within physical boundaries, while an unguided
medium is boundless.
The most popular types of guided media are twisted-pair cable(metallic), coaxial
cable(metallic), optical fiber(glass or fiber).
Twisted pair consists of two insulated copper wires twisted together. Twisting allows
each wire to have approximately the same noise environment.
Shielded twisted pairs consists of insulated twisted pairs encased in a metal foil or
braided covering.
Both twisted pair cable snd coaxial cable transmit data in the form of an electric
current.
Fiber-optic cables are composed of a glass or plastic inner core surrounded by
cladding encased in an outside jacket.
Fiber optic cables carry data signals in the form of light. The signal propagated along
the inner core by reflection.
Fiber optic transmission is becoming increasingly popular due to its noise resistance,
low attenuation, and high bandwidth capabilities.
In fiber optics signal propagation can be multimode (multiple beams from a light
source) or single mode (essentially from one source).
In multimode graded index cable the core density decreases from the center.
In multi mode step index propagation the core density is constant and light wave
direction changes suddenly at the core cladding interface.
SHORT ANSWER QUESTIONS
1. Transmission media are usually categorized as -----------------.
2. In fiber optics, the signal source is ---------------- waves.
3. --------------- are the highest frequency electromagnetic waves in use for data
communications.
4. Which of the following primarily uses guided media?
5. Which of the following is not a guided medium?
6. In an environment with many high-voltage devices, the best transmission medium
would be ---------------
7. What is the major factor is that makes coaxial cable less susceptible to noise than
twisted-pair cable?
8. The RG number gives us information about --------------------
9. In an optical fiber, the inner core is -------------- the cladding.
10. When making connections in fiber optics, which of the following could contribute to
signal distortion?
11. Radio communication frequencies range from ------------------
12. The radio communication spectrum is divided into bands based on ---------------
13. In --------------------propagation, low-frequency radio waves hug earth.
14. The type of propagation used in radio communication is highly dependent on the
---------------------of the signal.
15. VLF propagation occurs in ------------------
16. If a satellite is in geosynchronous orbit, it completes one orbit in -------------
17. If a satellite is in geosynchronous orbit, its distance from the sending station------------
18. When a beam of light travels through media of two different densities, if the angle of
incidence is greater than the critical angle, ---------occurs.
19. ----------has the units of bits/second.
20. The wavelength of green light in air is ----------- the wavelength of green light in
fiber-optic cable.
LONG ANSWER QUESTIONS
1. (a) What is a metallic transmission line? Explain the five types of metallic transmission
line losses.
(b) State Snell’s law for refraction and outline its significance for optical fiber cables.
2. (a) What is a transverse electromagnetic wave? Explain with a neat diagram.
(b) What is an optical fiber mode? Explain the three practical types of
optical fiber modes.
3. (a) What is a transmission line? Compare balanced and unbalanced transmission lines.
(b) What is an optical communication system? Explain an optical fiber
communication system with a neat block diagram.
4. (a) What is a plenum cable? Compare plenum and non-plenum cables.
(b) What is a laser? Explain, in detail, the four types of lasers.
5. (a) Define the terms:
(i) Guided and unguided transmission lines
(ii) Metallic transmission lines.
What are the different types of metallic transmission lines?
(b) What are the advantages and disadvantages of optical fibers.
6. (a) Describe the block diagram of optical fiber communication system.
(b) Briefly describe the construction of an optical fiber cable.
7. (a) List and describe the types of losses associated with metallic transmission lines
(b) Describe the three types of optical fiber configurations.
(i) Single mode step index
(ii) multimode step index
(iii) Multimode graded index
UNIT-III
DIGITAL TRANSMISSION
ESSENCE OF THE UNIT:
Digital transmission is the transmittal of digital signals between two or more points in
a communication system. The signals can be binary or any other form of discrete
level digital pulses.
The primary advantage of digital transmission over analog transmission is noise
immunity and also they are more suitable for processing and combining by
multiplexing.
The main drawbacks are they require more bandwidth than analog signals and also it
is costly. They need additional circuitry for encoding and decoding.
Pulse modulation consists of essentially of sampling analog information signals and
then converting those samples into discrete pulses and then transporting the pulses
from source to a destination over a physical transmission medium.
There are four types of pulse modulation techniques those are PAM, PWM, PPM and
PCM.
Pulse Code Modulation is the only one of the digitally encoded modulation technique
that is commonly used for digital transmission.
With PCM the pulses are fixed amplitude and fixed width. In PCM technique first
signal is sampled and then quantized that means the values are rounded to its nearest
values and then encoded into digital form by means of binary codes.
In order to get exact signal at the receiver the sampling rate should be twice the
highest frequency of the modulating signal. This is called nyquist rate.
Quantization is the process of converting infinite number of values into finite number
of conditions.
The number of PCM bits transmitted is determined by several variables which include
maximum allowable input amplitude, resolution, and dynamic range.
For representation of PCM we have two types of codes those are linear codes and non
linear codes.
Companding is the process of compressing and expanding. With the companding
systems the higher amplitude signals are compressed prior to transmission and then
expanded at the receiver.
Multiplexing is the transmission of information in any form from more than one
source to more than one destination over the same transmission medium.
There are several domains in which multiplexing can be accomplished, including
space, phase, time, frequency, and wave length. The most predominant methods are
time division multiplexing (TDM), frequency division multiplexing (FDM), and wave
length division multiplexing (WDM).
With TDM the transmission from multiple sources occur on the same facility not at
the same time. Transmission from various sources is interleaved in the time domain.
PCM is the most prevalent encoding technique used for TDM digital signals.
A digitally carrier system is a communication system that uses digital pulses rather
than analog signals to encode information. A T1 carrier system time division
multiplexes PCM encoded samples from 24 voice-band channels for transmission
over a metallic pair or optical fiber transmission line.
SHORT ANSWER QUESTIONS
1. ---------------------- is the transmittal of digital signals between two or more points in a
communications system.
2. pulse width modulation is also called as ------------- or ------------------
3. ---------------------- is the only one of the digitally encoded modulation techniques that
is commonly used for digital transmission.
4. --------------- is the simply the data rate at which serial PCM bits are clocked out of
the PCM encoder onto the transmission line.
5. ----------------- uses a single-bit PCM code to achieve digital transmission of analog
signals.
6. Digital companding involves compression in the transmitter after the input sample
has been converted to a --------------------and then expanding in the receiver prior to
PCM decoding.
7. What are the two methods of analog companding ?
8. ----------- is the process of converting an infinite number of possibilities to a finite
number of conditions.
9. The ---------- establishes the minimum sampling rate (fs) that can be used for a given
PCM system.
10. --------------------- is the transmission of information from more than one source to
more than one destination over the same transmission medium.
11. What are the predominant methods of multiplexing?
12. A ---------------------- system is a communications system that uses digital pulse rather
than analog signals to encode information.
13. The -------- of a binary pulse can be used to categorize the type of transmission.
14. ----------------------- is the popular type of line encoding that produces a strong timing
component for clock recovery.
15. T-carrier are used for the transmission of ----------encoded time division multiplexed
digital signals.
16. -------------------- framing is the same as added-digit framing except that digits are
added in groups or words instead of as individual bits.
17. ------------------waves are comprised of many frequencies and each frequency
corresponds to a different color.
18. The --------------------- is a multiplexing system similar to conventional time division
multiplexing.
19. ------------------------ is the second level of SONET multiplexing.
20. Digital biphase is also called as---------------------
LONG ANSWER QUESTIONS
1.(a) What do you understand by companding? Compare analog companding and
Digital companding.
(b) A PCM-TDM system multiplexes 24 voice-band channels. Each sample is
encoded into 7-bits., and a framing bit is added to each frame. The sampling rate is
9000 samples per second. Determine the line speed in bps.
2.(a) What is the relationship between dynamic range and the number of bits in a pulse
code modulation (PCM) code? For a PCM system with the minimum dynamic
range: 46dB, determine minimum number of bits used in the PCM code.
(b) What is superframe and extended superframe time division multiplexing (TDM)
format? Explain each with an example.
3.(a) What is pulse code modulation (PCM) line speed? For single-channel PCM system
with a sample rate, fs = 6000 samples per second and a 7-bit compressed PCM code
determine the line speed.
(b) What is a T carrier system? What is a fractional T carrier? Describe, in detail, the
various T carrier systems.
4.(a) What do you understand by signal voltage-to-quantization noise voltage ratio? Give
its relationship to resolution, dynamic range, and the maximum number of bits in a
pulse code modulation (PCM).
(b) Compare wavelength division multiplexing (WDM) and dense wave division
multiplexing (D-WDM); and also list the advantages and disadvantages of WDM.
5.(a) Define digital transmission. Contrast the advantages and disadvantages of digital
transmission.
(b) What is a transmission line and explain five types of metallic transmission loss
6.(a) Describe the North American Digital Multiplexing Hierarchy.
(b) Describe the basics concepts of wavelength division multiplexing. List the
advantages of WDM.
7.(a) Contrast Delta modulation PCM and standard PCM.
(b) Draw and explain about PCM.
8.(a) Write a short notes on time division multiplexing.
(b) Describe T1 carrier System.
UNIT-IV
WIRLESS COMMUNICATIONS SYSTEMS
Radio waves can be used to transmit data. These waves use unguided media and are
usually propagated through the air.
Regulatory authorities have divided up and defined the users for the electromagnetic
spectrum dealing with radio communication.
Radio wave propagation is dependent on frequency. There are five propagation types.
Surface wave propagation.
Tropospheric propagation.
Ionospheric propagation.
Line of sight propagation.
Space wave propagation
VLF and LF waves use surface wave propagation. These waves follow the contour of
the earth.
MF waves are propagated in the troposphere either through direct line of sight
propagation from transmitter to receiver or through reflection with the ionosphere as
the upper bound.
In earths atmosphere ray propagation may be altered from free space behavior by
optical effects such as reflection, refraction, diffraction and interference.
Ground waves are EM waves that travel long the surface of the earth. They must be
vertically polarized to avoid the signal loss.
Ground waves propagated over salt water with less attenuation and the maximum
frequency which supports ground wave propagation is below 2MHz only.
Space wave propagation of em waves done at the lower miles of earths atmosphere
i.e. at troposphere. Space wave contains both direct wave and reflected waves.
This propagation is limited by the curvature of the earth.
Electromagnetic waves that are directed above the horizon level are called sky waves
and the propagation is called sky wave propagation or ionospheric propagation.
In ionosphere it is having four layers those are D, E, F1 and F2 layers. D and E layers
appear only at day time and F1 and F2 appear at both day and night time.
Skip distance is the minimum distance from a transmitting antenna that a sky wave of
given frequency will be returned to earth.
Free space path loss is the loss occurred by an EM wave as it propagates in a straight
line through a vacuum with no absorption or reflection of energy from nearby objects.
Microwaves are generally described as EM waves with frequencies that range from
500MHz to 300GHz.
Microwave repeaters are used to amplify the signal in between microwave transmitter
and receiver to avoid the looses that are caused by atmosphere.
Satellite is a celestial body that orbits around a planet. However a satellite is a space
vehicle launched by humans that orbits earth.
Communication satellite is a microwave repeater in sky and they uses same frequency
as microwave systems.
A satellite repeater is called a transponder and a satellite may have many
transponders.
Satellites may rotate in different orbital paths, and also in different orbits like
elliptical inclined or circular.
Geosynchronous satellites are those which rotates in the same direction as earth and
also with same velocity. That means it will took 24 hours for completion of one
revolution.
All communication satellites are geosynchronous satellites only.
The main drawbacks will be placing a geosynchronous satellite is difficult and also
costly.
SHORT ANSWER QUESTIONS
1. PSLV-C12 is also called:> Rasat & Anusat
2. Foot print also called as:-> Foot print map
3. In RADAR which frequency bands are used:-> L-band.
4. In microwave S-band frequency range is:-> 2GHz to 4GHzs.
5. In microwave L-band frequency range is:-> 1GHz to 2GHzs.
6. Sky wave propagation is also called as:-> ionosperic propagation
7. Duct propagation occurs when density of the :-> lower atmosphere
8. Space wave propagation is also called as :-> Line of sight propagation.
9. Ground waves are some times called as :-> Horizontal waves.
10. The following is the first India’s operational satellite:-> INSAT.
11. Microwave frequency range extends from :-> 500Mhz to 300GHz.
12. Satellites used for international communication is called as :-> INTEL SAT.
13. Which layers are present at night time in sky wave propagation;-> Both F1 and F2.
14. Ground wave propagation allows frequencies up to :-> 2MHz.
15. Geo synchronous satellites are placed at the height of :-> 36,000KMs or 22,000
Miles.
LONG ANSWER QUESTIONS
1.(a) What is a radio wave? What are the optical properties of radio waves? Explain all
the details of how they relate to radio wave propagation?
(b) What are the three modes of terrestrial propagation of electromagnetic waves?
Explain.
2.(a) What is meant by a free space path loss of an electromagnetic wave? Give the
mathematical equation in decibel form. Determine, in dB, the free space path loss
for a frequency of 6 GHz traveling a distance of 50km.
(b) What is a satellite multiple accessing arrangement? List and describe, in detail with
neat diagrams, the three forms of satellite multiple accessing arrangements.
3.(a) What is a radio wave? What are the optical properties of radio waves? Explain all
the details of how they relate to radio wave propagation?
(b) What is meant by a free space path loss of an electromagnetic wave? Give the
mathematical equation in decibel form. Determine, in dB, the free space path loss
for a frequency of 6 GHz traveling a distance of 50km.
4.(a) What are the three modes of terrestrial propagation of electromagnetic waves?
Explain.
(b) What is a satellite multiple accessing arrangement? List and describe, in detail with
neat diagrams, the three forms of satellite multiple accessing arrangements.
5.(a) Describe a geosynchronous satellite contrast the advantages and disadvantages of
geo synchronous satellites
(b) Explain the components that make up a microwave radio link
6.(a) Describe the electro magnetic polarization?
(b) Explain Wave attenuation, wave absorption and give relation between them?
UNIT-V
TELEPHONE INSTRUMENTS AND SIGNALS
ESSENCE OF THE UNIT:
Public telephone network is a part of global communication network which uses
telephone or a data modem on a telephone network.
The subscriber loop means to connect a telephone set at a subscriber’s location to the
closest telephone office, which is commonly called an end office, local exchange
office, or central office.
Electronic switching system (ESS) enables the subscribers to access the public
telephone network.
Tip is one wire on the local loop. Ring is another wire on the local loop. Ring come
from the ¼-inch-diameter two conductor phone plug and patch cords used at
telephone company switch-board to interconnect and test circuits.
RJ stands for registered jacks and is sometimes called as RJ-XX, a series of telephone
connection interface s (receptacle and plug) that are registered with the U.S. FCC.
-48Vdc voltage is selected to minimize electrolytic corrosion on the loop wires; used
for supervisory signaling and to provide talk battery for the microphone in the
telephone set.
Call progress tones and signals are acknowledgement and status signals that ensure
the processes necessary to set up and terminate a telephone call are completed in an
orderly and timely manner.
Cordless telephones are simply tones that operate cords attached to the handset; a full
duplex, battery-operated, portable radio transceiver that communicates directly with a
stationary transceiver located somewhere in the subscriber’s office.
Caller Id enables the destination of a telephone call to display the name and telephone
number of the calling party before the telephone is answered; allows subscribers to
screen incoming calls and decide whether they want to answer the telephone; a
simplex transmission sent from the central office switch over the local loop to a caller
ID display unit at the destination.
Paging systems are simplex wireless communications system deigned to alert
subscribers of awaiting messages; relay radio signals and messages from wire-line
and cellular telephones to subscribers carrying portable receivers.
Local subscriber loop is only facility required by all voice-band circuits, as it is the
means by which subscriber locations are connected to the local telephone company.
Psophometric noise weighting used primarily in Europe, assume a perfect receiver,
therefore, its weighting curve corresponds to the frequency response of the human ear
only.
Decibel (DB) is the basic yardstick used for making power measurements in
communications.
A transmission characteristic depends on the wire diameter, conductor spacing,
dielectric constant of the insulator separating the wires and the conductivity of the
wire.
Transmission parameters, apply to dedicated private –line data circuits that utilize the
private sector of the public telephone network-circuits with bandwidths comparable to
those of standard voice-grade telephone channels that do not utilize the public
switched telephone network.
Private-line circuits are direct connections between two or more locations.
Line conditioning is the process used to improve a basic telephone channel; improves
the high frequency response of a message channel and reduces power loss
C-type conditioning specifies the maximum limits for attenuation and envelope delay
distortion, pertains to line impairments for which compensation can be made with
filters and equalizers.
D-type conditioning is neither reduces the noise on a circuit nor improves the signal-
to-noise ratio; a requirement and does not add anything to the circuit and it cannot be
used to improve a circuit; it simply places higher requirements on circuits used for
high-speed data transmission.
Crosstalk can be defined as any disturbance created in a communications channel by
signals in other communications channels; a potential problem whenever two metallic
conductors varying different signals are located in close proximity to each other; was
originally coined to indicate the presence of unwanted speech sounds in a telephone
receiver caused by conversations on another telephone circuit.