CST All 5 Units 2 Marks

8/12/2019 CST All 5 Units 2 Marks

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(III YEAR/B.Tech-IT)

SUBJECT: COMMUNICATION SWITCHING TECHNIQUES

UNIT-I

COMPONENTS AND PRINCIPLES

1. What is meant by telecommunication?

Telecommunication network carry information signals among entities. Entitiesmay be computers, a human being and data terminals. The process of information

transfer may be file transfer, message transfer in between terminals, etc.

2. Define calling and called subscriber.

alling subscriber!

"n telephone con#ersation, the one who initiates the cal.alled subscriber! The one for whom the call is destined.

$. Define switching system?

The subscribers are not connected directly with others% instead, they are connectedto switching system. When a subscriber wants to communicate with another, a connectionis establishing b&w the two switching system.

'witching system also called as switching office (or) E*change.

+. Define control function?

The function performed by a 'witching system in establishing andreleasing connections

. What are the types of switching system?

-anual 'witching system

utomatic 'witching system

/. What are the types of utomatic 'witching system?Electromechanical switching systemElectronic switching system

0. What are the types of Electromechanical and Electronic switching system?

Electromechanical! Electronic!

'trowger switching 'pace di#ision switching

rossbar switching Time di#ision switching


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. What is meant by 'trowger switching?

The control functions are performed by circuits associated with switchingsystem.

. What is meant by Electronic switching?

The control functions are performed by the 3rocessor (or) a computer."t also called as 'tored 3rogram ontrol ('3).

14. Define 'pace di#ision and Time di#ision switching.'pace di#ision!

dedicated path is established b&w the calling and called subscriber for theentire duration of the call.Time di#ision!

The sampled #alues of speech signals are transmitted at fi*ed inter#als.

11. Define Trunk?The 5inks that run between switching system are called trunks

12. Define Transducer?

Transducers perform the energy con#ersion. Whether optical signal to #oicesignals (or) Electrical signal to 6oice signals

1$. What are the telecommunication networks?Telegraph networks

Tele* networks

Telephone networks

Data networks

1+. 7asic components of switching system?

"nlets, outlets and switching network

1. Define symmetric network?"nlets and outlets are e8ual in a switching (9:-)

1/.Define blocking and non;blocking network?7locking network!

There is a path free in the n&w.9on;blocking network!

There is no path free in the network

10. What is meant by "nterdigit gap?

Two successi#e trains are distinguished from one another by a pause in betweenthem.


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1. What are the different types of signaling tones?Dial tonerigin based routing

9o dialing calls

22. What is the procedure for establishing a connection in crossbar switching?

Energi=e hori=ontal bar Energi=e #ertical barEnergi=e #ertical bar (or) energi=e hori=ontal bar

De;energi=e hori=ontal bar De;energi=e #ertical bar

2$. What is the principle of crossbar switching?

To pro#ide a matri* oh nm sets of contact with only n@m acti#ators (or) less toselect one of the nm sets of contacts.


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UNIT-II

SPACE DIISION AND TIME DIISION SWITCHING

1. Define stored program control('3)?

A 3rogram or a set of instruction to a computer is stored in its memoryand e*ecuted automatically one by one by the processor.

2. What are the electronic space di#ision switching systems?

Electromechanical switchingElectronic switching

$. What are two approaches to organi=ing '3?entrali=ed '3Distributed '3

+. Define centrali=ed '3?

ll the control e8uipment is controlled by a single processor. "t must be capableof processing 14;144 calls per second.

. What are the modes of dual processor'tandby mode

'ynchronous duple* mode

5oad sharing mode

/. Define standby mode?

>ne processor is acti#e and the other is on standby, both hardware and software.

"t is used to determine which of the subscribers and trunks are busy (or) free.

0. Define 'ynchronous duple* mode?

The hardware coupling is pro#ided between the two processors which e*ecute thesame set of instructions and compare the results continuously.

. Define a#ailability and una#ailability of the processor?

A :MTB!/(MTB! " MTTR)

: a#ailability-T7A:-ean time b&w failure

-TT


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14. Define Distributed '3?

The control functions are shared by many processors within the e*change itself.This offers better a#ailability and reliability.

11. Difference between micro programmed control and hard;wired control?

-icro programmed control Card;wired control1. Ale*ible not fle*ible

2. 'lower faster $. -ore e*pensi#e for processing functions less e*pensi#e

+. Easier to implement comple* processing functions difficult to implement

12. Difference between single and multistage networks?i) "nlet to outlet is through a "nlet to outlet is through a

'ingle cross point multiple cross point

ii) Bse of a single cross point per Bse of a multiple cross point mayonnection results in better 8uality link degrade the 8uality of a connection

iii) Time for establishing a call is less Time for establishing a call is

morei#) The network is none blocking The network is blocking

1$. Define full a#ailability?

There are k alternati#e paths for any inlets&outlets pair connection. Thenetwork is said to be full connecti#ity (or) full a#ailability

1+. Define baseline networks?

9etworks that support 9 simultaneous connections but under restrictedtraffic distribution conditions

1. When a network is called as analog and digital time di#ision switching?When 3- samples are switched in a time di#ision manner, the switch is

called as analog time di#ision switching.

When 3- samples are switched in a time di#ision manner, the switch iscalled as digital time di#ision switching.

1/. Define time di#ision space switching?

A 'ingle switching element (bus) is being time shared by 9 connection, all ofwhich can be acti#e simultaneously and a physical connection is establishing b&winlet and outlet duration of time sample transfer is called time di#ision spaceswitching.

10. What is the controlling in a time di#ision time switching?'e8uential write & random read


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The inlets and outlets are trunks which carry time di#ision multiple*ed data

streams. 'uch a switches called a time multiple*ed switch.

24. Define combination switching?

"t can be built by using a number of stages of time and space switches accordingto time space (T') and space time ('T).


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UNIT-III

TRA!!IC ENGINEERING

1. Why we are going for traffic engineering?

The load (or) traffic pattern on the network #aries during the day with hea#ytraffic at certain times and low traffic at other times. 'uch a bisis are pro#ides a trafficengineering.

2. What is meant by busy hour?

"n a day, the /4 minute inter#al in which the traffic is highest is called busy hour(7C).

$. What are the basic busy hours7usy hour3eak busy hourTime consistent busy hour

+. Define busy hour calling rate and day;to;busy hour traffic ratio?

7usy hour calling rate : a#erage busy hour calls & total number of subscriberDay;to;busy hour traffic ratio: busy hour calling rate&a#erage calling rate

. Define traffic intensity (4)?4: period for which a ser#er is occupied&total period ofobser#ation Traffic intensity is called e%&' (E).

/. Define traffic carried per ser#er?

Traffic carried per ser#er:occupied duration&total duration

0. Define centum call second?

Traffic intensity is also called as ce*+, c'&& ec.

This represents a call;time product. >ne ' may mean one call for 144

seconds duration (or) 144 calls for one second duration each or any other

combination.

. Cow can the o#erload traffic may be handled?

The o#erload traffic may be reected without being ser#iced (or)Celd in a 8ueue until network becomes a#ailable.

.Define loss and delay system? 5oss system!

Bnder o#erload traffic condition a user call is blocked and is not ser#iced unlessthe user makes retry. Delay system!

good operator registers the user re8uest and establishes connection as soon as

network becomes a#ailability without the user ha#ing to make another re8uest.


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14. What are traffic models in loss system and delaysystem? 5oss system

7locking models

ongestion

models

Delay systemueuing models

11. Define Frade of ser#ice (F>')?

The amount of traffic reected by the network is an inde* of the 8uality ofthe ser#ice offered by the network. This is termed as Frade of ser#ice.G%'e 0 e%12ce#L* *%'002c/00e%e *%'002c.

12. What is meant by random or stochastic process?

>ne or more 8uantities #ary with time in such a way that the instantaneous#alues of the 8uantities are not determinable precisely but are predictable with certainprobabilities.

1$. What are the stochastic processes?ontinuous time ontinuous

state ontinuous time discrete

state Discrete time ontinuous

state Discrete time discrete

state

1+. Define stationary processes?


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< is defined as the ratio of the number of successful calls to thenumber of call attempts. The number of call attempts in the busy hour is calledbusy hour call attempts (7C).

24.Define busy hour calling rate.

"t is defined as the a#erage number of calls originated by a subscriber duringthe busy hour.

21. n e*change ser#es 2444 subscribers. "f the a#erage 7C is 14,444 and the


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2. 'tate random process.

random process or a stochastic process is one in which one or more

8uantities #ary with time in such a way that the instantaneous #alues of the

8uantities are not determinable precisely but are predictable with certain

probability. The 8uantities are called


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when all the ser#ers are busy no traffic is accepted by the network. 'uch a traffic onthe network is known as Erlang traffic or pure chance traffic of type 1.

"n this case, we ha#ei: H for 4 I i I


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144 L14

F>' : 4.10

The F>' is lower in the case of 5 model with finite sources.

++. T'" system has 14 channels and 24 sources connected to it. What isthe probability of clipping if the acti#ity factor for each source is 4.+?

'olution!#erage number of busy ser#ers : 4.+ 24 :

lipping occurs if 14 or more sources are in the acti#ity phasesimultaneously. Therefore,

the probability that 14 or more sources are acti#e gi#es the clipping probability.This is determined from the poison e8uation as!

N

3rob (clipping) : O3 (t:)

D:14

: 1; O3 (t : )

:4

2

: 1; eL(1 @ @ @ PP @ )2

3rob (clipping) : 4.2+

+. 5ist out the analysis assumptions in lost calls returned system1) 9o new call is generated when a blocked call is being retried.

2) number of retry attempts may be in#ol#ed before a call e#entuallygets ser#iced.

$)


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T'" 'ystem.

+. 5ist out the important


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1. Write down the 3oisson 3rocess E8uation.

"f we assume a constant birth rate H which is independent of the state ofthe system, then we get 3oisson process. The go#erning e8uations of a 3oissonprocess are

d3J(t)for k T 1

: 3kL1(t) L3k(t)dt

d34(t)

for k : 4

: L34(t)dt

2. -ention some of the real life e*amples for 3oisson 3rocess.a) 9umber of telephone calls arri#ing at an e*change.b) 9umber of coughs generated in a medical ward by the patients.

c) 9umber of rainy days in a year.d) 9umber of typing errors in a manuscript.e) 9umber of bit errors occurring in a data communication system.

2. Describe the 3oisson 3rocess according to 6enn Diagram.a) 3ure 7irth process with constant birth rate.b) 7irth;Death process with =ero death rate and a constant birth rate.

c) -arko# process with state transitions limited to the ne*t higher state or to

thesame state, and ha#ing a constant transition rate.

/. What is meant by 3ure Death 3rocess.

The system is said to be pure death process in a 7;D 3rocess, is setting the 7irth rate e8ual to =ero. Thus the e8uation of pure death process is gi#en by,

d3J(t)

: 3k@1(t)k@1Lk3k(t)for k T 1

dt

d34(t)

:131(t)for k : 4

dt

0. Write down the necessary condition for stable operation of delay system forinfinite 8ueue apacity.

p1

Where,H; -ean rri#al


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UNIT-I DIGITAL SUBCRIBER ACCESS

1. What is the main obecti#e of "'D9?

The main obecti#e of "'D9 is to offer new digital transmissions ser#ices to'ubscribers.


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2. Define "'D9

n integrated ser#ices digital network in which the same digital switches anddigital paths are used to establish different ser#ices, for e*amples, telephony anddata.

2. What are the bearer ser#ices of "'D9?

The main bearer ser#ices are the transport of audio and digiti=ed #oice, circuit'witched digital channels at rate that are multiples of /+ Jbps, 3acket switched #irtual

ircuits and connectionless ser#ice.

$. What are the principles of "'D9?1. 'upport #oice and non;#oice communication

2. 'upport switched and non switched application.

$.


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c) 'er#ice rate distributions are identical.

14. Define 7earer 'er#ice functions

"n "'D9 protocol architecture, the lower three layer functions are known asbearer ser#ice functions.11. Define Teleser#ices

'er#ices offered by ser#ice pro#iders are known as teleser#ices. Aunctionalitiesof layers 1;0 are re8uired to offer teleser#ices which are built o#er bearer ser#ice

functions.

12. list out the three fundamental channels in "'D9.

There are $ types of fundamental channels in "'D9 around which the entire

information transmission is organi=ed. These area) 7asic information channel 7 channel, /+ kbps

b) 'ignaling channel D channel, 1/ or /+ kbps

c) Cigh speed channel C channels

C4 hannels, $+ kbpsC1 hannels, 1$/ kbpsC2 hannels, 124 kbps

1$. Write down the frame si=e and frame rate e8uations in the case of transmissionchannels.

" :


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1. Fi#e the signalling categories of "'D9.

a) Bser le#el signalling

b) 9etwork le#el signalling

24. Define functional terminal

-essage based signalling is employed when the user end e8uipment is anintelligent terminal. "n "'D9 parlance, an intelligent terminal is known as functional

terminal.

21.write the functions of addressing

1. ddressing scheme is easy to understand by the user

2. "t adapt the e*isting one$. "t should allow the e*pansion of si=ing bit

+. 9umber should be a decimal one.

22. 5ist out the messages groups.1) all establishment messages

2) all control messages

$) all disconnect messages+) -iscellaneous messages

2$. What are the mandatory fields for all the messages?

1) 3rotocol discriminator

2) all reference$) -essage type

2+. What are the si* fieldUs present messages formats of "'D9?

a) ptional part.

g)2. What are the features of physical

layer.

1. Encoding of bit stream2. Aull duple*ing

$. -ultiple*ing

+ cti#ation and deacti#ation of physical circuit

. Terminal identification.

2/. What are the three types of traffics in collisiona#oidance.1. 7 channel traffic2. "ncoming 7 channel traffic

$. >utgoing 7 channel traffic.

20. What are the methods used for the control of supplementaryser#ices.1. Jey pad control2. Aeature key management protocol

$. Aunctional protocol.


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2. What are the three types of "'D9 ser#ices?

7earer ser#ices (layer three function), teleser#ices (+ to 0 layer), supplementaryser#ices (conunction b&w bearer and teleser#ices).

2. 5ist out the some of the important new ser#ices pro#ided by "'D9.a) 6ideote*t

b) Electronic mail

c) Digital facsimiled) Telefa*e) Database access

f) Electronic fund transfer

g) "mage and graphics e*changeh) Document storage and transfer

i) Document storage and transfer

) utomatic alarm ser#ices, e.g., smoke,fire,police,and medical

k) audio and #ideo conferencing.

$4. What are the ser#ices of 53D?

1. cknowledgement information transfer ser#ice

2. Bnacknowledgement information transfer ser#ice

$1. What is the purpose of ''0

''0 is used to generali=e the common channel signalling.

$2. 5ist out the characteristics of ''01. >ptimi=ing digital communication

2. Designed reliability$. 'uitable for point to point terrestrial link

$$. 5ist out the interacti#e ser#ices

1. on#ersational2. -essaging

$.


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a) "nteracti#e ser#ices

i) on#ersational ser#icesii) -essaging ser#ices

iii)


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+2. What is the transmission technologies used in pro#iding local digitalloop.opper wire pairs

Aiber

oa*ial

cables

Wireless

+$. What are the two le#els of digital access in "'D9?

7asic rate access (27@D interface)

3rimary rate access(2$7@D

interface)

++. Aeatures of "'D9 7 channels?1. End;to;end four;wire digital circuits! no loss or echoes for #oice

circuits using digital instruments2. 'hared network access for #oice, data and leased lines

$. Cigh bandwidth (/+ kbps)+. 5ower error rates than #oice band modems+. Aeatures of "'D9 D channels?

1. 'ignaling simultaneously with acti#e connections2. alling number identification

$. Aar;end super#ision

+. Bser;to;user message transfer. ccess to packet switching network

+/. Define "'D9 basic rate access?

"t is a standard copper pair that has been specially conditioned to support a

bidirectional 1/4kbps data rate. This is also referred as Digital subscriber loop(D'5).

+0. Define '&T interfaces?

"t is defined as in "TB;T recommendation 1.+$4 to be supplied bynetwork termination e8uipment.

+. Define T-?

"t is a time compression multiple*. "t pro#ides full duple* transmission on asingle pair of wires by alternately transmitting bursts of data in each direction. "t is alsoreferred as 3ing;3ong

+. Define "'D9 D channel protocol?"t is defined in two separate series of "TB;T! the " series and the series

4. Define Cigh data rate digital subscriber loops?

This techni8ue allows larger bandwidths on copper wire pairs for thea#ailability of low cost, high performance digital signal processing.

1. Define D'5?

ADSL-A4,,e*%2c 22*'& +6c%26e% &2e


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D'5 is allows high data rates to subscriber and moderate to low data rates

from the subscriber to the network. "t deli#ered switched digital #ideo o#er a copper

loop.

2. 6ersions of digital subscriberlines.

D'5D'5

CD'5

'D'56D'5

$. What are the two #ersions of D'5 transmission.

arrier less amplitude and phase modulation

(3)

Discrete multi tone modulation (D-T)

+. Define D-T implementation?

"t utili=e an in#erse AAT as a modulator as the corresponding demodulator.

. What is the use of 3T splitter!

"t used in both ends of transmission to separate the analog #oice from the data.

/. Define 6D'5?

6D'5;6ersion of D'5 to achie#e e#en higher bandwidths on particularly

short lines as would be a#ailable from remote terminals of fiber to the curb system

0. Define uni#ersal digital loop carrier loop system?

The BD5 can be interfaced to any other system like analog and digital. Theinterface b&w local switching system of the public network and the central officeterminal in#ol#es indi#idual circuits.

. Define A"T5?

A"T5;Aiber in the loop is refers to one of three more specific descriptions ofthe use of fiber for local distribution.

The 2ndcategory of A"T5 is a fiber;to;the;curb(ATT). These systemsare designed to reach within 1444feet of a subscriber residence.

. What is the use of #oice band modem?

1. The a#ailability of economical D'3 technology for e8uali=ation&echocanceling

2. The impro#ed 8uality of the network in terms of lower noise and distortionresulting.

/4. Define 3- modem?


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The principal source of noise in the end;to;end connection is the 8uanti=ationnoise of the &D con#erters leads to alternati#e modem implementations thatdirectly utili=e the digital /+;kbps channel and eliminate 8uanti=ation noise. Thesemodems are referred as 3- modems.

UNIT-

CELLULAR WIRELESS NETWOR9S

1. What is the use of cellular network?

"t is de#eloped to increase the capacity a#ailable for mobile ratiotelephone ser#ice. "t pro#ides high power transmitter&recei#er.

2. Define base station?

Each cell is allocated a band of fre8uencies and ser#ed by a basestation, consisting of transmitter, recei#er and control unit.

$. Define rosstalk?

dacent cells are assigned same fre8uencies. "t can be a#oided byassigning different fre8uencies.

+. Define fre8uency reuse?

"n cellular system, each cell has a base transcei#er. The obecti#e is to use

same fre8uency band in multiple cells at some distance from another. This allows the

same fre8uency band to be used for multiple con#ersations in different cells.

. Define fre8uency borrowing?

Are8uencies are taken adacent cells by congested cells. The fre8uencies canalso be assigned to cells dynamically.

/. Define cell splitting?

ells in areas of high usage can be split into smaller cells. The original cellsare about /. to 1$km in si=e.

0. Define cell sectoring?

A cell is di#ided into a number of wedge shaped sectors, within own setof channels, $ (or) / sectors per cell.

. Define handoff?

"t is the procedure for changing the assignment of the mobile unit from one 7'

to another as the mobile unit mo#es one cell to another.

.What are the handoff

strategies.


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14. What is the use of cordless systems?

"t pro#ides user with mobility within a residence or small office by separating

the handset from the rest of the telephone and pro#iding a simple analog wireless link.

11. Define TDD?

TDD- T2,e 2122 D+&e;."t also known as time compression multiple*ing, data are transmitted in one

direction at a time.

12. Define TD-&TDD?

"t is used in wired subscriber system but TDD in#ol#es transmitter andrecei#er on the same carrier fre8uency but at different time.

1$. What is meant by differential 8uanti=ation?

"t is based on the speech signals tend not to change much b&w two signals.Thus with original 3-, the 8uanti=ed #alues of adacent samples.

1+. Define adapti#e differential 3-?

The predictor and difference 8uanti=e adapt to the changing characteristics of

the speech being coded.

1. What is meant by W55?

WLL- 32%e&e &c'& & (%) 02;e 32%e&e 'cce.

W55 alternati#es narrow band, which offer a replacement for e*isting

telephony ser#ices and broadband. "t pro#ide high speed two;way #oice and data

ser#icing

1/. What is the use of mobile "3?

The network portion of an "3> address is used by routers to mo#e datagram

from the source computer to network to which target computer is attached

10. What the basic capabilities of mobile"3. Disco#ery


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CST All 5 Units 2 Marks