Dcs Course File

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&parallel 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

29 1 V Subscriber loop, standard telephone set

30 2 Basic telephone call procedure, call progress tones and signals

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.


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.


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


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.


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---------------------


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.


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.


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


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.


1. Telecommunications uses_______ waves : Sound waves

2. When was the first telephone was manufactured:1920

3. PSTN refers: Public switched telephone network.

4. Which type of keypad used in 2500 type telephone: Touch-tone key pad.

5. Which type of plugs used in telephone cable -RJ-11

6. RJ Stands for: Registered jacks

7. How many conductors used in the RJ-11 :six

8. Switching systems outputs ____voltage: -48vdc

9. The ringer circuit is originally______: electromagnetic bell

10. The STDP is circuit: On/off hook

11. Resistors and capacitors are known as____ : equalizers

12. Speaker converts electric signal into_____: acoustic signal

13. Dialing circuit contain____: touch tone keypad

14. Ring back tone frequency:440hz to 480hz

15. What is the frequency combinations of key 8 in DTMF :852Hz,1336Hz

16. In multi frequency digits travelling speed is: seven bits per second

17. Equipment busy signal sometimes called as: congestion

18. Cordless phones occupied_______ frequency: narrow band

19. When was caller id feature was invented: 1970

20. What is RAM: random access memory

21. Electronic telephone contains: microprocessor and RAM

22. Paging devices are worked on :radio signals

23. Early paging systems are developed by: British post offices

24. Digital modulated carriers are___: FSK,PSK,QAM

.


1.(a) Compare the operation of a cordless telephone and a standard telephone.

(b) What considerations are addressed by facility parameters? Compare phase hits and

phase jitter.

2.(a) What is a paging system? Describe, in detail with a neat block diagram, how a

paging system works.

(b) What is meant by transmission line conditioning? Compare C-type and D-type line

conditioning.

3.(a) What is a telephone set? Describe, in detail with a neat diagram, the various

functional components of a standard telephone set.

(b) What is the difference between dB and dBm? Determine: (i) the power levels in

dBm for signal levels of 10mW and 0.5mW (ii) the difference between the two

power levels in dB.

4.(a) Explain, briefly, how caller ID operates and when it is used. Interpret the following

hex code for a caller ID message(start and stop bits are not included in the hex

codes): 04 12 31 31 32 37 31 35 35 37 33 31 35 37 33 36 31 30 35 33 xx

(b) What is a crosstalk? What are the three types of crosstalk in telephone systems?

Compare near-end crosstalk and far-end crosstalk.

5.(a) Briefly describe the basic functions of standard telephone set.

(b) Briefly describe the steps involved in completing a local telephone call.

6.(a) Describe the basic operation of a cordless telephone and explain how it differs from

a standard telephone.

(b) Describe the transmission characteristics of a local subscriber loop and also explain

about loading coils and bridge taps.

UNIT-VI

CELLULAR TELEPHONE SYSTEMS


The cellular telephone as the advanced mobile telephone system (AMPS) is started in

1983 in U.S.A.

The AMPS cellular telephone system uses narrowband frequency modulation

(NBFM) with a useable audio frequency band of 300 Hz to 3 kHz.

Initially they allotted 825-845MHzfor reverse channels (i.e.) from mobile unit to base

station and 870-890MHz is for forward channels from base station to mobile unit.

It consists of 666channels spacing of 30 KHz each and also 42 control channels.

Transmission from base station to mobile unit is called forward link and from mobile

unit to base station is called reverse link.

The receiver for each channel operating 45 MHz above the transmit frequency.

After few years they allotted additional 10 MHz so that the total channels increases to

832 channels.

Standard telephone subscribers access the AMPS system using a technique called

FDMA.

AMPS use four identification codes those are MIN-mobile identification number,

STD-system identifier, SAT-supervisory audio tone etc.

Control channel uses synchronization bits in order to provide synchronization

between base station and mobile unit.

Personal communication system (PCS) is a combination of cellular telephone

networks and intelligent network

The main difference between PCS and standard cellular system is smaller cell size, all

digital and additional features

It consists of four registers HCR-Home location register, VLR-Visitor location

register and EIR-Equipment identification register.

Additional features are available mode, screen mode, private mode and unavailable

mode.

Second generation telephone system provides better handoffs.

Narrow bands-AMPS (NAMPS) provide more number of channels compared to

AMPS.

USDC is a digitalized cellular system provides fully digital channels.

CDMA-coded division multiple accesses provide better quality signals than N-AMPS

and P-AMPS.

In this the signals transmitted in the form of separate codes. In this each user having

particular frequency allocation.

The main drawback is limited number of users and another main advantage is

maintains constant power throughout the communication.

GSM-Global system for mobile communication has been launched to avoid the

problem for international roaming by providing constant standards.

It uses two frequency bands those are 900 MHz and 1800 MHz bands.

GSM is fully digitalized network.

GSM architecture consists of BTX- BCS-base station control, NSS-

Network switching subsystem and OSS-operational support subsystem.


1. Error detection accomplished with: VRC, LCR, or CRC

2. Error correction is accomplished with: Automatic repeat request(ARQ).

4. SREJ stands for: Service reject

5. GO-back-n frames is easier to implement.

6. STX stands for: start of text

7. ETX stands for: End of Text

8. Character oriented protocols sometimes called as: Byte-oriented protocols

9. Which of these following is character oriented protocol: KERMIT

10. The more efficient protocol is: Bit Oriented protocol

11. SDLC stands for: Synchronous data-link communications.

12. HDLC stands for: High-level data-link Communications.

13. When an operator is not typing, the terminal is in: idle sate

14. The non data characters are: Bell(BEL),CR(carriage return)

15. The assortment of characters transmitted as a group is called as: block of frame of data

16. In a polling environment the which mode of transmission is more appropriate for

multi drop data communications circuit operating: Block mode.

17. The fist file transfer protocol is designed by: Ward Christian

18. In which year the first file transfer protocol is designed?

19. Christiansen’s protocol is now called as: XMODEM

20. The frame format of XMODEM consists of: four fields

LONG ANSWER QUESTIONS:

1.(a) What is N-AMPS cellular telephone system? Explain the operation of NAMPS

cellular telephone system.

(b) List the basic parameters of GSM and describe, briefly, the GSM radio subsystem.

2.(a) What are the three primary subsystems of GSM? Describe, in detail, the GSM

system architecture.

(b) Explain, in detail with neat diagrams, the CDMA traffic channels.

3.(a) Explain the classifications of CDMA radiated power. Determine the transmit power

for a CDMA mobile unit that is receiving a signal from the base station at -

100dBm.

(b) What is a digital cellular system? List the advantages of a digital cellular system.

4.(a) What is a GSM cellular telephone system? Describe the services offered by GSM.

(b) What is meant by false handoff? What are the four types of handoffs possible with

N-AMPS? Compare macro cellular system and digital cellular system.

5.(a) define digital cellular telephone. Describe the advantages and disadvantages of

digital cellular telephone compared to analog cellular telephone.

(b) Briefly describe the EIA/TIA interim standard IS-54

6.(a) List and explain the services offered by GSM

(b) Briefly explain about Iridium satellite System

UNIT-VII

DATA COMMUNICATIONS CODES, ERROR CONTROL


Transmission errors are usually detected at the physical layer of the OSI model.

Transmission errors are usually corrected at the data link layer of the OSI model.

Errors can be categorized as follows:

a. Single-bit: one bit error per data unit.

b. Burst: two or more bit errors per data unit

Redundancy is the concept of sending extra bits for use in error detection.

Four common methods of error detection are the following:

a. Vertical redundancy check(VRC)

b. Longitudinal redundancy check(LRC)

c. Cyclic redundancy check(CRC)

d. Checksum.

In VRC an extra bits (parity bit) is added to the data unit.

VRC can detect only an odd number of errors; it cannot detect an even number of

errors.

In LRC a redundant data unit follows n data units.

CRC, the most powerful of the redundancy checking techniques, is based on binary

division.

Checksum is used by the higher-layer protocols (TCP/IP) for error detection.

To calculate a checksum:

a. Divide the data into sections

b. Add the sections together using one’s complement arithmetic.

At the receiver, when using the checksum method, the data and checksum should add

up to zero if there are no errors present.

The hamming code is a single-bit error correction method using redundant bits. The

number of bits is a function of the length of the data bits.

In the hamming code, for a data units of m bits, use the formula 2r>=m + r + 1 to

determine r, the number of redundant bits needed.


1. Universal Product Code [III-IT-SMCE]is an example of a continuous bar code.

2. The code39 was developed in: 1974

3. Code39 consists of: 36 unique codes representing the 10 digits and 26 upper case

letters.

4. The exclusive start/stop character coded as: Asterisk(*).

5. Each code39 character contains: five bars and four spaces

6. After check characters for * C O D E space 3 9 * is the modified code is “ C O D E

space 39 R*.

7. UPC stands for: Universal Product Code.

8. The National Association of Food Chains officially adopted the upsc code in 1974

9. POSTNET : POSTal Numeric Encoding Technique

10.DBPC: Delivery Point Bar Code

11.The first character code developed in 1840.

12.The Morse code was introduced by Samuel F.B Morse.

13. When was the first mode code is used: 1844

14. The international Morse code for SOS(save our sip) is: . . ._ _

15. The Baudot code is also called as: Telex code.

16. Which of the following are the Baudot code’s special control functions figure shift

left and right.

17. RTTY stands for Radio teletype.

18. ASCII is the extension of: six-bit Trans code

19. IBM PC was developed in: 1981

20. EBCDIC was developed in: 1962

21. The length of EBCDIC is: Eight bit fixed length.

22. Discrete bar has spaces or gaps between characters.

23. Continuous code doesn’t include spaces between characters


1.(a) What is a SYN character? Compare and contrast synchronous and asynchronous

serial data formats. For the following sequence of bits over thetime from left to

right, identify the ASCII- encoded character, the start and stop bits, and the parity

bits (assume an even parity and two stop bits):1 1 1 1 1 1 0 1 0 0 0 0 0 1 0 1 1 1 1 0

0 0 1 0 0 0

(b) What is high speed modem synchronization? What are the purposes of scrambler

and descrambler circuits? Illustrate with an example.

2.(a) What is a Hamming code? For a 12-bit data string of: 101100010010, determine the

number of Hamming bits required, arbitrarily place the Hamming bits into the data

string, determine the logic condition of each Hamming bit, assume an arbitrary

single –bit transmission error, and prove that the Hamming code will successfully

detect the error.

(b) Explain the terms: bits per second (bps), baud, probability of error, bit error rate

with an example each.

3.(a) Compare longitudinal and cyclic redundancy checking. Determine the block check

character (BCC) for the following polynomials:

Data polynomial, G(x) = x8 + x5 + x2 + x0

Generating polynomial, P(x) = x5 + x4 + x1 + x0.

(b) What is modem synchronization? What are its functions? Compare cable modems

and standard voice band modems.

4.(a) What is POSTNET? What is POSTNET bar code? Determine the check character

for the POSTNET nine-digit ZIP + 4 numbers: 13424-7654.

(b) What is a modem? Compare synchronous and asynchronous modems. Explain the

four types of modem operational modes.

5.(a) Explain 3 most common character codes for data communications.

(b) What is the purpose of error detection? Explain any 3 error detection techniques.

6.(a) List and describe the basic blocks of a voice band modem

(b) Describe the characteristics of synchronous voice band modems,

UNIT-VIII

DATA –LINK PROTOCOLS


The second layer in the OSI model,the data link layer, has three main functions: line

discipline ,flow control, and error control.

Line discipline establishes the status of a device (sender or receiver) on a link.

ENQ/ACK is a line discipline method used in point-to-point connections.

The receiving device using ENQ/ACK line discipline responds with an

acknowledgement (ACK) if it is ready to receive data or a negative acknowledgement

(NAK) if it is not ready.

Poll/select is a line discipline method. The primary device always initiates

communication with either a poll or select (SEL) frame.

A poll frame is sent to the secondary device by the primary to determine if the

secondary can has data to send. The secondary can respond by sending a NAK (no .

data to send) or a data frame

A SEL frame is sent to the primary device by the secondary device to tell the

secondary to prepare to receive data. The secondary responds with an ACK or a

NAK.

Flow control is regulation of data transmission so that the receive buffer does not

become overwhelmed by data.

There are two main methods of flow control:

a. stop-and-wait

b. sliding window

In stop-and-wait flow control, each frame must be acknowledged by the

receiver before the next frame can be sent.

In sliding window flow control, the sending of data is constrained by an

imaginary window that expands and contracts according to the acknowledgments

received by the sender. Likewise, the receiving of data is constrained by an imaginary

window that expands and contracts according to the data received.

Error control, or how to handle lost or damaged data or

acknowledgments, is simply the retransmission of data.

Retransmission of data is initiated by automatic repeat request (ARQ).

Three types of errors require ARQ: a damaged frame, a lot frame and a

lost acknowledgment.

The method used to handle error control depends on the method used for

flow control.

For stop-and-wait flow control, stop-and-wait ARQ is used.

For sliding window flow control, go-back-n or selective-reject ARQ is

used.

In stop-and-wait ARQ, the unacknowledged frame is retransmitted.

In go-back-n ARQ, retransmission begin with the last unacknowledged

frame even if subsequent frames have arrived correctly. Duplicate frames are

discarded.

In selective-reject ARQ, only the unacknowledged frame is retransmitted.

A protocol in data communication is a group of specifications used to

implement one or more layers of OSI model.

Data link protocol can be classified as synchronous or asynchronous.

Asynchronous protocol such as XMODEM, YMODEM, ZMODEM,

BLAST, and Kermit are used in file transfer.

Synchronous protocols can be classified into two groups:

a. Character-oriented protocols.

b. Bit-oriented protocol

In character-oriented protocols, the frame is interpreted as a series of

characters.

In Bit-oriented protocols, each bit or group of bits can have meaning.

Binary synchronous communication (BSC) is the most well-known

character-oriented protocol.

BSC operates a half-duplex mode using stop-and-wait ARQ in a point-to-

point or multipoint link configuration.

There are two types of BSC frames:

a. Control frame

b. Data frame

Control frame perform these functions:

a. Make a connection

b. Control flow and error

c. Sever a connection

A bit pattern that resembles a BSC control character in the data field must

not be recognized as a control character; it must be made transparent.

Data transparency in BSC is achieved by a process called byte stuffing.

Byte stuffing involves

a. Demarcation of the transparent region.

b. Addition of DLE (in the transparent region) before every DLE character.

All bit oriented protocols are related to high-level data link

control(HDLC).

HDLC operates in half –or full-duplex mode in point-to-point or

multipoint link configuration.

HDLC stations are categorized as follows: a. primary station-sends

commands. B. secondary station –sends responses c. combined station-sends

commands and responses.

HDLC stations are configured as follows:

a. Unbalanced –one primary, one or more secondaries.

b. symmetric- two physical stations, each capable of switching from primary to

secondary.

c. Balanced –two combined stations , each of equal status.

HDLC stations communicate in one or three modes:

a. Normal response mode(NMR) –the secondary station needs permission to

transmit

b. Asynchronous response mode(ARM) –the secondary station does not need

permission to transmit.

c. Asynchronous balanced mode(ABM) –either combined station may initiate

transmission.

HDLC protocol defines three types of frames:

a. Information frame (I-frame) –for data transmission and control.

b. Supervisory frame(S-frame) –for control.

c. Unnumbered frame(U-frame) –for control and management.

HDLC handles data transparency by adding a 0 whenever there are five consecutive

1s following a 0. This is called bit stuffing.


1. Eliminating echo is called echo suppers

2. the secondary device in a multipoint configuration sends data in response to

------------------

3. In sliding window flow control, if the window size is 63, what is the range of

sequence number

4. In sliding window flow control, the frames to the left of the receiver window are

frames ----------------

5. When the primary device wants to send data to a secondary device, it needs to first

send ----- frame.

6. When a secondary device is ready to send data, it must wait for ----------frame.

7. In a peer-to-peer system, when one device wants to send data to another device, it

first sends ---------------- frame.

8. In go-back-n ARQ, if frames 4, 5, and 6 are received successfully, the receiver may

be send an ACK--------------------to the sender.

9. For a sliding window of size n-1 (n sequence numbers), there can be a maximum of

---------- frames sent but unacknowledged.

10. ARQ stands for ------------------.

11. BSC stands for -----------------

12. A negative response to a poll in BSC is ---------------

13. A negative response to a select in BSC is -------------

14. In BSC, a receiver responds with------------------------ if the frame received is error-

free and even-numbered.

15. BSC protocols uses ----------- mode for data transmission.

16. HDLC is an acronym for ------------

17. The address field of a frame in HDLC protocol contains the address of the

---------------------- station.

18. BSC protocol uses ---------- mode for data transmission.

19. In HDLC protocol, the poll/final bits meaning in an I-frame is independent on

-------------

20. The shortest frame in HDLC protocol is usually the -------


1.(a) What is a line discipline of a data link protocol? Illustrate an

enquiry/acknowledgement (ENQ/ACK) line discipline with an example.

(b) Compare synchronous data link control (SDLC) and high level data link control

(HDLC). Describe the HDLC operational modes.

2.(a) What is the difference between synchronous and asynchronous data link protocols?

Explain, with a neat frame format, how the XMODEM protocol works.

(b) What is an invert-on zero encoding? Obtain the non return-to-zero

inverted (NRZI) encoding to the data stream:

1 0 0 1 1 1 0 0 1 0 1 0 1 0 0 0 1 0 1 1 1 0 0 0 1 1 1

3.(a) What is a synchronous data link control(SDLC)? Describe, in detail, the various

fields of the SDLC frame format.

(b) What is the transparency mechanism used with SDLC? Illustrate with an example.

4.(a) What is a data link protocol? List and describe, in detail, the three data link protocol

functions.

(b) What are the three frame formats used with synchronous data link control (SDLC)?

What the purposes are of: the ns bit sequence, nr bit sequence, P bit and F bit?

5.(a) list and explain the 3 data link protocol functions

(b) Explain two modes of data transmission.

6.(a) What is binary synchronous communication? Explain.

(b) Determine the BSC sequence for the following.

(i) A general poll of station 7

(ii) A specific poll of station 7 at device 3

(iii)A selection of device 12 at station 6.

PROGRAM EDUCATIONAL OBJECTIVES

1. To give a brief history of data communications and introduces the fundamental

concepts of data communications and networking,

2. To give a brief explanation of signal analysis for single frequencies and complex

respective waveforms.

1. To present the fundamental concepts of metallic transmission media, including

the

characteristics of transverse EMW propagation.

2. To compare the advantages and disadvantages between metallic transmission

media and optical fiber transmission media.

1. To introduces the advantages and disadvantages of digital transmission

2. To describe how signals from multiple sources (both analog and digital) can be

multiplexed to improve the capacity of a transmission medium.

To describe the fundamental concepts of wireless communication systems, including

free-space EMW propagation.

1. To introduces the basic concepts of telephone instruments and signals.

2. To give a detailed description of a typical telephone circuit, including local loops

and trunk circuits.

To expands the basic cellular concepts of evolution and fundamental concepts

cellular telephone systems.

1. To cover the fundamental concepts of data communication codes, asynchronous

and synchronous data formats and error control.

2. To expands the coverage of data terminal and data communications equipment.

To give a detailed description of the data link protocol used on private data

communications networks.

PROGRAM OUTCOMES

1. Students got a brief history of data communications and the fundamental concepts of

data communications and networking,

2. Students got a brief explanation of signal analysis for single frequencies and

complex respective waveforms.

1. Students know the fundamental concepts of metallic transmission media,

including

the characteristics of transverse EMW propagation.

2. Students can compare the advantages and disadvantages between metallic

transmission media and optical fiber transmission media.

1. Students learned the advantages and disadvantages of digital transmission.

2. Students can describe how signals from multiple sources (both analog and digital)

can be multiplexed to improve the capacity of a transmission medium.

Students can know the fundamental concepts of wireless communication systems,

including free-space EMW propagation.

1. Students learned sthe basic concepts of telephone instruments and signals.

2. Students know the detailed description of a typical telephone circuit, including

local loops and trunk circuits.

Students came to know the basic cellular concepts of evolution of and fundamental

concepts cellular telephone systems.

1. Students learn how to cover the fundamental concepts of data communication

codes, asynchronous and synchronous data formats and error control.

2. Students learn the coverage of data terminal and data communications equipment.

Students got detailed description of the data link protocol used on private data

communications networks.

Documents

Dcs Course File