TRIBHUVAN LTNIVERSITY

INSTITUTE OF ENGINEERING
lnffi.*---*ffi
iLtygl BE Full Marks 80
Examination Control Division P-ryq"lyyg ecr Pass Marks 32
i .
2081 Bhadra i Year lPart III / I Time 3 hrs. 1

Subjeet: - DataCornmunication Gf 602)

Candidates are required to give their answers in their ou,n words as far as practicable,
Attempt Atl questions.
The_figures in ihe ntctrgin indicate Futt frlarks,
Assume stdtable data i{ ne c:e s,t arv"

1. a) Prepare a generic block diagram of a digital communication system representing

oommunications between an air traffic controller and an in flight pilot in a cockpit.
i5]
b) Explain the basic causes of transmission impairm€r1ts in conrmunication systern. 13]
2. Define a linear system and a time invariant system. Evaluate the odd anci even colnponent
of a signal defined as: x(r) = e-ztu(t). [2*61
a
-). Clonsidering the combinations o1'at Ieast se\ren rnathernatical operations in an equation"
prepare a signal florv diagram of any system.
t,8]
4. Compare and contrast Fourier series ancl Fourier transfbrm. Iv{ention the conclitions and
properties of Fourier transformation. l2-2+4i
a) Explain the different modes of data transmission in optical fiber. List out and menticn
the protocois of different categories of twisted pair cables. i3r-31
b) ;l
A bandlimited signal u,ith marimum frequency KHz is sampled at the rate of
Nyquist freqr"rency. It is quantized into 128 levels and encoded. Calculate:
Bandwidth of the channel required to transmit the clata through a channel with SNR of
0 dB. 121
6. Encode the given bit sequence 1100000000010'l using an1'sr-ritable iu,o olpolar and two
of bipolar encodsrs. r,,2
'2'2-21
7, Prepare Code Tree. State Space ancl Trellis diagrams of i,t2 rate convolutional channei
coding for a message bit of 1101; and demonstrate how Viterbi Deooding corrects a
singlc bit error. l2=Z-2-a)
8. Encode "SaReGaMaPaDhaNiSa" using Fluffmam Encoding and calculate its
transmission efficiency. What would be the code sequence if the recipient has lvlongly
received the message like "SaReSaR.ePaDhaNiSa"? t,4.'1r tI
i- L *J
9. Write short notes on: (Any Three) [3xa]
a) CDMA
b) Packet switching
c) CR.C-4
d) 16-QAM
e) E1 Hierarchy
* ,k ii. ,ii
 TRIBHUVAN T]NIVERSITY Exam.
INSTITUTE OF ENGINEERING i Level BE Full Marks 80 t

Examination Control Division Programme BCT

LPtog" Pass l\{arks 32
I
1
I

2081 Baishakh Year I P;"t- iiil"i^^-*-

i,ea;i
iL-------------. Time 3 hrs. i

s_y11!ie.9!;
i Data Communication (CT 6A2)

,/ Candidates are required to give their answers in their own words ^- f-- ^^ *-^^+j^^Ll^
r' Attempt All questions.
{ Thefigures in the margin indicate Full Marks.
:rucffi
/ Assume suitable ilata dnecessary.

1" Expiain the digital data communication system r+,orking in fuil duplex mode using a block
diagram. Define the transmission performance parameters in a data communication
system. 14;-41
2. Define energy and power signal with examples. Check whether the following system is
linear, causal and time invariant or not. [4+6]
y(t): logx(t)
3. State the properties of Fourier Transforrn. Convolve the following signals graphically. 12+61

x2i:i n

4. a) Expiain the importance of Scrambling in the digital data encoding process. Encode
the binary pattern 101000011101 using polar R7-, NRZ-I, AN4I and Manchester line
coding techniques. [2*4]
b) Explain 16-QAM with constellation diagram. 14l
5. Compress "Ghurnne Mech Mathi Andho N{anche" Lrsing Huffman coding to determine
efficiency redundancy and cornpare it with entropv. i10l
6. Write down the applications of multiplexing. Describe FHSS and DSSS with necessarl'
diagrams. L2+4*41
7. Expiain CRC-4 generator and decoder with example lbr both no-error and rvith-error
CASES,
l8l
8. With suitable example demonstrate how convolutional code corrects enors. t6l
9. Write short notes on: (Any Two) 12x5l
a) Difltrence between circuit sivitching and packet srvitching
b) Code division Multipie Access (CDMA)
c) Shannon's charurel capacity theorem.
 TRIBHUVAN UNIVERSITY
INSTIT.UTE OF ENGINEERING Level BE F'ull Marlc 80
Examination Control Division f-----------------
iProgramme BCT
2080 Bhadra i Year lPart III i I

Subject: -Data Communication {CT 602)

'/ Candidates are required to give their ans',vers in their

,/ Attempt.,4,ll. qwestions.
'/ The figures in the margin inclicaie Full Marks.
d Asswme suitable data if'necessat)).

1. Define transmission performance paralneters in data communication system. Expiain

digital communication system with appropriate generic block diagram. [4+4]
2. Define a carisal system and a stable system with example . Evaluate por,ver and energy of
al+t
a signal'given as x(t) - e-zrtr . Justifv whether it is energy signal or po\ /er signal. 14+61
J. Define LTI system. Convolve the follou,ing signals graphicall1,. {2+61
/'.
-1
x2(t) i
I
I
I

i
4t. a'; Explain dilI-erent types of pulse modulation techniques with necessary diagrams" t6]
b) Explain brietly about 8-QAM with consteilation diagram. t4l
5. a) Detennine the CDlvfA encoded transmitting message for four users using Walsh
Hadamard codes, where user A, B" C and D are transrnitting 1,0, silent, I respectively. t5]
b) What is rnultip)exing? Why statisticai TDM is prefferred than synchronous TDM? i2+31
6, Define Hamming distance and Minimum hamming distance with an example. What are
the error detection and error correction capabilities of block codes? Explain. [2+41
1
Obtain all code words for a (6, 3) biock ccde fiorn the s-v*stematic generator matrir given
below. t8l
1-r

i' 0 0:1 11i

G -10 1 0:l f 0l

L0 0 0:1 0ll
I

L Using a sui table example, explain state, tree and trellis diagrams 1-or l,L code rate and 4
states. [10]
9. Write short notes on : (Any Two) [2x5]
a) Datagram packet switching vs Virtual cjrcuit packet srvitching
b) E1 and T1 Hierarchies
c) Ir{odes of operation of optical fiber
*rk*
 TRIBHUVAN UNIVERSITY i Exarn.
i..................,....,...............,........ ............
llite li,
INSTITUTE OF ENGINEERING Full Markr 80
Examination Control Division i Programme BCT Pars Mark 32
I Year / Part III / I
Io,-,,r,,,..,,.,,,...-,,,.i .,-.i..,i,,..i.,

2080 Baishakh Tlme 3 hrs,

Subjgct: -Data Communication gf 602)

,/ Candidates are required to give their answers in their own

r' Anempt All questians.
'/
y'
Thefigures in the margin indicate Full Marks.
Assurne suitable data iJ'necessary.

1. Define data and signal. Elaborate the advantages of digital communication system as
compared to analog communications system. Explain the basic causes of transmission
impairments in communication system.
l2+2+41
) a) Determine whether or not the lollowing CT signai is periodic. If the signal is periodic,
determine its fundamental period, x(t):3cos (4t*n/3).
l2l
b) Test the linearity of the systems. y(r) = x21t; ancl y(t) : 3x(t) i-5 141
c) Test the systems staric or dynamic. :,'(t) = 2>r(t) and y(t) : 2x(t) -3x(t-3) t4l
3. a) Find the output response of an L'fl system u,hen input x(t) : e-, u(t) and impulse
response h(tt= e-2' u1t;.
t4)
b) Find magnitude and phase spectrum of x(t) = 4-rZ"or31. * 4sinllt
33 .
t41

c) Discuss an,v four properlies of Fourier Transflorm. etr

4. Compare coaxial cabie r,vith oplical fibre. Evaluate the iaaximuni capaeity of a channel
through which a signal with power of 10 dBW is transmitted. (Assume that the noise
power spectral densitl, is given as 5 m W/Hz).
[4_+4]
5. a) Consider AM signal as m(t) : 5i1+2cos lLx *1000Q1 cos(2n*101). Determine
modulation index, total power delir.ered.
t4]
b) Define PCIvI technique used to convefi anaiog signal into cligital data. In a pCM
system. a bandlimited signal with maximum frequency 4 kHz is sampled at the rate of
Nyquist frequency. lt is quantized into 256 levels and encoded" Calculate:
[2+4]
(i) Minimum data rate avilabie at the output of the encoder.
(ii) Bandwdth of the channel required to transmit the data through a charurei of l5 dB
SNR.
c) What are the basic factors to be considered while line coding? Encode the binary
pattern 100000000100001 using B8ZS and HDB3 encoding.
l2ral
6. Explain the major bandwidth utilization techniques used in data communication. Explain
flequency Hopped Multiple Access (FHMA) technique using its transmitter and receiver
blocks. g+6j
7. Differentiate between circuit su'itching and Packet switching usecl in computer networks
with an example.
t6l
8' a) Explain error detection and cr:rection mechanism with trellis diagram.
[101
1r) Differentiate convolutional code and block code.
12)
**{<
 TRIBHUVAN LINIVERSITY Exam.
INSTITUTE OF ENGINEERING Level BE Full Marks 80
Examination Control Division
2078 Bhadra
Programme
Year / Part
BCT
m/I Time
F* 32
3 hrs.

,Sg pj-ec!_;
_ ppta Communication (CT 602)
Candidates,are required to give their answers in their own wgr4qis@s practicable.
AttemptAil questions.
Thefigures in the margin indicate fa$ Mafks.
Assume surtabk data dnecessary. Wrucp
..1

1' cit'ierentiate hetween ensrgY ;rnd power signals with examples. Determine
if the
iollowing sy.srirm staiil* ntr
is v!s{/rv
ar^ ru I"'i'i,
'{' [5+5]
Y{t) : *G';

2' List *trd describe all data communication parameters that describe
the perfonnanee of the
sys1.em.
t8l
3' Explain how r'le plot line spectrurns of a continious time signal and
illustrate an example, L{il
4. Encode 111000000000000011 using Bgzs and HDI]3 en'oders.
Ir0l
5' I-'temonostrate how checksum is used to detect errors nhile sending a eiata rruor<l of lZ,15,
15, la, 5,2. tgl
6. .li Expl*.in the u,arking principle of FF{SS technique.
ISJ
b) Explain how CDMA wcrks w,itl: exarnple.
tsl
7 ' trVhat are linear block codes? Iiesigri a code word of a C(8, 4) block code with any
suitable generation matrix. tgl
I' Flncode "Jasta lai tastai dhido lai nistai" using rrysighted Huffman
encoder. Also
dernonstrate holr, it is decoded.
tl0l
9. Dcscribe with shon notes c*: (Ar:"v Two!
[zxl.l
aJ Doubie-i*ee AM
b) "F{ar::.lning codes
c) Packet switching versus message switching
d) X.25 protocol
*(**
 I i{ r il; t i ivAN uNi\/l1I{si.fY
i}iSTI'iUTE OF ENGINEERNG
Examination Control Division
2078 Kartik Year/Part lIfi lI

Subject: - Data Communication Qr 602)

Candidates are required to givc their ansrvers in their orvn words as far as practicable.
Attempt AII questions.
The Jigm'es in the margin indicate Full Morks.
Assume suitable data if necessary.
#nsce
1. a) Differentiate data and signal *,ith two examples of each.
tIffiRARY
t5l
b) Explai, the procedure of con,crling an analog signal to digital. Also, briefly explain
each steps involved.
t5l
2. Define periodic and non-periodic signals with examples.
12+1+41
a) Test the stabitity of the system lr(t) : eat.u(t)
b) Test the given function y(0 : t.x(t) for causality, non causality and anti causality.
3 ' Hor'v Nyquist theorem applied for a noiseless channel? Calculate number
of disciete
signal content in the channel if a chamel has a spectrum of 3 to 4 MHz
with signal to
ncise ratio of 24 dB.
[s+5]
4. Explain the operation of cRC-4 lith exampic oieiior cietection. oj
i1
5' .:.ding Exi-''12i* pclar r\.2 and bipolar AMI line coding scheme wirh example
9:"|||.]t-:
anci compare them.
'
6. a) Ifow is source coding different from
[4+3+3]
channel coding?
l2l
b) Under rvhat conditions does a linear code become a cyclic code? Explain r,vith the
help of an example.
t3l
c) Explain the couoept of convolr-rtional code rvith the help of a state-transition diagram. tsl
7 ' Write dou'n the Huffinan Algoritlm 'clearly and find an efficient code word
anci
efficiency that can be assign to the symbols rxing Huffman Algorithm
for ,,Kun Manciir
.L,r.
Ma Janchhau Yattd".
[10]
I' a) Explain the mechanism of fi'equenc1. Hopping spread spectrum (I,'HSS). Also,
compare FDM and FHSS using s,itable tirne_frequerr.y grupt
.
[4+3]
b) Explain the "near-far problem" in GDMA. How can it be solved?
L2+11
 TRIBHUVAhI UNIVERSITY Exam. Redular '', '':1'
INSTITUTE OF ENGINEERING Level BE Full Marks 80

Examination Control Division Programme BCT Pass Marks J/

2076 Chaitra Year / Part m/I :Time 3 hrs.

Subie,r:I, ; Data C_ommunication (c7- 642)

d Canclidates are required to give their ansrverrs in tireir cwr words
,/ All questions.
.Atlemytt
,/ fhe.figures in tlte margin indiaate Fu$:V{r{!f.
'/ Asswme .strilable duta if necessary.

1. Drar.v a generic irtrock diagram of a digital comrnunicati*n system used ir mobile

telephi-rny and explain each block. Compare analog and eligital eommunication system
with examples, [6+2]
2. example.
Erplain the propecies ot'causal. non-criusal and anticairsal sy'stems rvith [10]
3 " Expiain wh;r \1,,e nee<i Fourier
'fransform. Plot the line spectrums of
X(t) = 12 + Ssin (140rt t 30') - 9cos(B0at - 70")" [5+5]
4" Why lve need kloduiation? lilusirate an example of a 4-bit FCNrt with AIvfI encodes. [2-6]
5. Demonostrate horv Cltc-s norks 1o detect effors in data communication. 18]

6. What is muitipiexing? Compare synchronous and statist,ical TDM. Describe Frequency

hcpping sprerad speotrum ard direct sequence spread spectrum with its bli;ck diagram. i71-4+4)
7 " Construct a (7, 4j Flamrning code using a 4x.4 generaticn inatrix for any arbr.itery
message. t8l
L Encode "Phool ko aanl,;"hama phoolai sansala" using HulTrnan encocler and tind the
transmission ethcienc;,. [10]
q. \furite shcrt notes on: lAny tr.t'o) {ax2)
a) STP versris UTP
b) Frame relay
o) 16-Quadrai.irre arnplitude nrodulation
d) Multi rnode optical fiver:
 TRIBHUVAN UI,IIVERSITY Exam. ::. ir;i,:l;" r,:l :i,;Baep,r=ar:ti.l-i.,.,1]1i,:.
IN STITUTE OF ENGINEERING Level BE Ii'ull Marks 80

BCT Marks )/.

Examinatiou Control Division Programme Pass

2076 Ashwin Year / Part ru/I Time 3 hrs.

fY-rjY:g:!;-: P-S"*
Communisation (Cf 602)

Candidates are required to give their answers in their own words as far as practicable.
At t enzpt 4!! qu es ti o ns.
The fi.gures in the margin indicate Fy"ll.4[utks.
As surne suitable data if necess ary.

1. pniirt the advantages and disadvantages of digital communication system over analog
communication system. Discuss the transmission impairments of data communication
system with suitable diagrams and suggest the methods in overcoming [3+5] attenualion.
2. What are properties Fourier transform? Plot the magnitude and phase spectra of
x(t; = 5 + sin(l 2t + 20') - cos(161 - 60") + cos(201 + 40o) [4+41 .
3. Sketch the output of LTI systern having impulse response h(t1- e-utu(t) (a>0) aud
h(t) = eutu(-t) (,,o)' t10l
,,]L,.
':,,

4i:i' List differentiitypes of digital.to-arlalog line encoding techniques. Give an example of.
QAM-32 in its constelletion diagram. v2+61

5. Explain with example how cRC-s lvork to detect 3 burst elrors. t10l

6. Define Fr"qu"rr.y division Multiplexing. Explain the FDM Multiplexing ard

. ' demultiplexing process with rleat diagrarus. t81
and
7. Design a suitable generation makix for a convolution code using c(3,1,3) architecture
encode input data sfream of (001 10). 110l

g. Design a Binary Shannon-Fano code with a six symbol sotlrce with probabiiity
assifrment as p(s11=9.94, P(s2):0.1, P(s3)=0.1, P(s4)=0.4, P(s5)=0.06, P(s6)=6.3. Tost its
transmission efficiencY [7+3]

9. Write short notes cin: (AnY Two) [4x2]

a) Analog versus digital mux hierarchy
b) DSSSH versus FSSH
c) Optical fiber versus STP
d. ,lr t
 TRIBHUVAN UNIVERSITY
INSTITME OF ENGINEERING
Full Marks
Examination Control Division
2075 Chaitra

.. _--._:-. . . Subject; _ Data Communication rcT 602) .

'H"--',

'/ candidates are required to give their answers in their own

words as far *
/ Attempt All questions. '.i! orr"rt""ble.
,/ The figures in the margin indicote Fult M-arks.
/ Assume suitable data if necessary.

1' a generic block diagram of digital data communication systern

for tull duplex
::ff:
t8l
2. Distinguish between power and energy signars with exampres,
.t8I
3. state the condition g.ft" of LTI system. Test the stability of the system
-..lu!ltiry whose
impulse rqsponse is h(t)=e-3tu(t)
t8l
4' List digital- to-digital line encoding techniques and explain in detail
Bipolar
substitution 8-zero
and High-Density 3-zero iubstituti,on techniques.
[2+4+4]
5. with suitable mathematicar expression, explain double-tone AM technique.
t8j
6. Demonstrate how cRC-4 works to trace two burst errors.
[10]
7. Differentiate between digital and analog spread
spectrum techniques using examples.
t8l
8. entropy in information theory. Find the efficient code word
rT"
Hoffrnan algorithm using probabilities p(xl):0.6, p(x2):0.2,
and efficiency using
-pix+l=0.05,
p(x3):0.i,
p(x5)=0.05.
t8l
9. Exglain why channel codingis required in data
communication. Generate a convolution
code for ainput trit streams of (l r tbr i; using a c1:,t,iy
arctritecture.
[2+10]
,f*{.
 fi
1f
1l
,l
1

35 TRIBHUVAN UNIVERSITY
INSTITUTE OF ENGINEERING
Examination Control Division
2075 Ashwin Year / Part

Subject: - Data Communication Gf602)

Candidates are required to give their answers in their own words as far as practicable.
Attempt AII questions.
The figures in the margin indicate Full Marks.
Assume suitable data if necessary.

1. Describe the transmission impairments of data communication system with suitable

example. t6l
2. Define periodic and non-periodic signals with examples. Determine whether the
following signals are periodic or not.
a) X(t): sinl5nt b) x(t): sin{2nt 12+3+31
3. What are Recursive and Nonrecursive system? Test the stability of the CTI system r,r&ose
impulse response is given as: h(t) = e-tsin(t)u(t) [3+5]
/l
State and explain Shannon-.Hartley channel capacity theorem with example. Briefly
discuss about the measures that are used to characterize the performance of a channel. 14+41

5. a) An audio frequency signal i0 sin1000nt is used for a single tone amplitude

rnodulation with a carrier of 50 sih2n x 10st. Calculate :
(i) Modulation index
(ii) Bandwidth requirement
(iii)Total power delivered if load: 60f) t)x?1
L- "J

b) Encode the bit stream 10010110001 using the following encoding schemes:
(i) Polar NRZ-L .
(ii) Polar NRZ-I
(iii)Differential Manchester 12x3l
6. a) Explain, how splead spectrum techniques like FHSS and DSSS work? t6l
b) Explain the operation of packet switching system. t4l
ai
1

7. Considering rate,4-state convolutional code, correct 3 bits effors using the help of its
z
trellis diagram. [10]
8. Explain QAM with its transmitter circuit and draw any one constellation diagram for 3?-
QAM. L6+2)
9. The source of information s).'rnbols {A0, Al, A2, ,{3 and ,A.4} have corresponding
probabilities {0.4, 0.3, 0.15, 0.1 and 0.5}. Encode the source symbols using most efficient
coding scheme and calculate the corresponding efficiency. [10]
{<*{<
 35 TRIBHUVAN LJNIVERSITY
INSTITUTE OF ENGINEERING
Examination Control Division
2074 Chaitrz Year / Part

S ubject : - Data Communication (CT602)

'/ Candidates are required to give their answers in their own words as far as practicable.
,/ Attempt All questions.
'/ Thefigures in the margin indicate Full Marks.
/ Assume suitable data if necessary.

1. Draw a generic block diagram of digital communication system for fulI duplex mode and
briefly explain the function of each block. t8l
2. Derive an expression to find even and odd part of signal x(t). Find even and odd part of a
signal x(t) : 0.5(t+1) for -1 < t < 1. L4+41
3. State the properties of continuous time Fourier series. t6l
4. Define LIT system. Determine the range of vallres of "t' and"b" for the stability of LTI
: eut u(t) + e-btu(t)
system with impulse response. h(t) [3+5]
5. A single tone FM is represented by the voltage equation as
v(t) : 1 2cos(5x I 08t+5 sinl 2501). Determine following: t8l
a) Carrier frequency
b) Modulatingfrequency
c) Modulation index
d) Maximum frequency deviation
1
6. Applying a -z rate, 4-state convolutional code correct errors of two bits with the help of
its trellis diagram. iSl
7. What is multiplexing and why we need it? Explain FDM hierarchy in telephone system. [3+5]
8. What is CRC? Explain 3 bit CRC generator and decoder with example of no error case. 12+61
9. Write douar the Huffrnan Algorithm clearly. Find an efficient code word and calculate
efficiency that can be assign to the s5mbols using Hufftnan Algorithm using probabilities
p(xl) :0.5, p(x2):0.25, p(x3) :0.125, p(x4) :0.125. 14+41
10. Write short notes on: (Any two) [2xs]
a) Means of Band width utilization
b) Data comrhunication impairments
c) BSZS
*tF*
',*

TRIBHUVAN LNIVERSIT'Y
INSTITUTE OF ENGINEERING
Examination Control Division
' Z}T4Ashwin

Subject: - Data Communication Pr602)

Candidates are required to give their answen in their own words as far as practicable.
Attempt All questions.
The Jigures in the margin indicate Full Marlr.$.
Assume suitable data if necesssrv.

1.Define transmission Impairment. Compare analog communication system with digital

communication system with appropriate block diagram for half-duplex mode. [4+6]
2. Explain the linearity and time invariance property of a system with example. Check
whether the following system is linear, time invariant and causal or not. [5+3J
y(t)=x(t-2)+x(2-t)
J. Find the output of LTI system having impulse response h(t; = e-2';t > 0 to the input" t8]

s O for tc0
x(t)= t I
1 for Ost<1
I
I
L_ O far 3.<t

4. a) What are the advantages of optical fibers over coaxial cable and twisted pair cable? t3]
b) State Nyquist's and Shannon's channel capacity formula. Find the Capacity of a
channel for a signal with a bandwidth of 3.1 KHz and Signal to Noise ratio of O dB
and comment on it. [2+3+3]
5. Encode the bit stream 10i0011001 using NRZ-L, NRZ-I, RZ, Manchester, Bipolar AMI
encoding technique. [2x5]
6. a) Define multiplexing with exarnple. Compare synchronous and asynchronous TDM. [3+3]
b) . Generate a CRC-3 transmission code and analyze its error detection performance with
example.
,|
Explain the rate of switching and compair circuit switching with packet switching. I?+51
8. Consider a symbol source with probability assignment as P(X, ) = 0.2, P(Xz ) = 0.35
{Ve
P(Xr)=0.1,P(X+)=0.2,P(Xs)=0.15. By using Huffman algorithm, find the sourc.e
code for these symbols and determine efficiency of the code. F0l
9. Describe with short notes: (any two) [2x51
i) HD3S coding
ii) Packet switching
iii) Designing a codeword of a c(6,3) block code with any suitable generation matrix
.t$ tr rf
.*
TzuBHUVAN TINIVERSITY
INSTITUTE OF ENGINEERING Full Marks : 80
Examination Control Division BCT Pass Marks i 32 *--a

2073 Shrawan i Year lPart u/r Time

"*i'*

:3hrs.
--
i

S ubject: - Data Communication (Cf602)

./ Candidates are required to give their answers in their own words as far as practicable.
{ Attempt All questions.
'/ Thefigures in the margin indicqte FaA Marks'
/ Assume suitable dato if necessary.

l. Draw generic block diagram of digital communication duplex system and explain each
block. Write down the advantages and disadvantages of digital communication over
analog communication system [5+3]
2. Define LTI system. Compute convolution between two signals x(t; : e-"t.u(t) (a > 0) and

h(t; = e"'.u(-t)(a > 0) and plot the resulting signal. [3+6+1]

3. Check linearity, causality, stability and time invariance characteristics of system
y(t):2x(t+l) t6l
4. Identify and discuss different data transmission channels. How synchronous kansmission
differs from asynchronous transmission? l4+4]
5. What is Frequency modulation (FM)? Explain with suitable equations and waveforms. [2+4]
6. Define multiplexing. Compare the merits and demerits of synchronous TDM and
statistical TDM method. L2+61

7. What is Data Switching? Clari$' the differences between datagram switching and virtual
packet switching. 12+6)

8. Where convolution codes are used? Describe a convolution codes wtthYzrate. 12+61

9. What do you mean by entropy? Describe linear block codirg method with a suitable
example for detection of an effor. [2+6]
10. Explain the general working principle of Binary Hufftnan Coding Algorithm. Design a
Binary Huffman code with a six symbol source with probability assignment
as: P(s1):0.0P(sr)=0.1,P(sr)=0.1,P(so)=0.4,P(sr)=0.06andP(su)=0.3. [4+6]
o'o!. {< *,1.

q
.,

45 TRIBHUVAN UNIVERSITY mffi:--

INSTITUTE OF ENGINEERING
Examination Control Division
2072 Chaitra

S ubject : - Data Communication (CT602)

,/ Candidates are required to give their answers in their own words as far as practicable.
{ Attempt All questions.
{ Thefigures in the margin indicate {ull Marks.
{ Assume suitable data if necessary.

1. Describe the Transmission Impairments of Data Communication system with suitable

examples. t6l
2. Define stable and unstable systems. Test the stability of the LTI systems whose impulse
responses are given as (i) h(t) = eYtu(t) (ii) h(t) = e-Y'u(t) [2+3+3]
3. Distinguish between energy and power signal with an example. Justify whether a signal

x(t) = e-ultl.u(tXa > 0) is energy or power signal. 14+41

4. State and explain Shannon-Hartley channel capacity theorem. Briefly discuss about the
channel.
measures that are used to characterize the performance of a [4+4]
5. Encode the Bit Stream 10110001110 using the following scheme. t10l
a) RZ
b) NRZ-I
c) NRZ-L
d) AMr
e) Manchester
6. What do you mean by multiplexing? Explain about working mechanism of FDM and
TDM. [2+3+3]
7. Differentiate between circuit switching and packet switching with suitable diagram. t6]
8. What are block codes? The generator matrix for a (6,3) block code is shown below.
Obtain all code words. [2+8]
[too:1ttl
tl
G=10 1 0 : I 1 0l
L0 0 ,1 : I 0 ll
9. What are Hamming codes? Write the properties of Hamming codes. Visualize a 3-bit
code words as code vector. 12+4+41
10. A message source generates I symbols with the following probabilities: t6l
P(X') =1 2, P(Xr) =114, P(Xr) =118, P(Xo) =ll16, P(Xr) =1132, P(Xu) =1164
P(X') =ll128and P(X*) =l/128
Encode the message using Huffrnan
"oO*.***
 45 TRIBHUVAN I"'NIVERSITY Exem. Ite gu Iir l'
INSTITUTE OF ENGINEERING Level BE Full Marks 80

Examination Control Division Programme BCT PassMarks 32

2072 Chritrt Year /Part m/I Time 3 hrs.

Suhject: - Data Communication (c1602)

{ Candidates are required to give their answers in their own words as far as practicable.
{ Aaempt All questions.
{ Thefigures in the margin indicate Full Marks.
{ Assume suitable data tf necessary.

1. Describe the Transmission Impairments of Data Commturication system with suitable

examples. t6I
2. Define stable and unstable systems. Test the stability of the LTI systerns whose impulse
responses are given as (i) h(t) = eftu(t) (ii) h(t) = e-Ytu(t) [2+3+3]
3. Distinguish between energy and power signal with an example. Justiff whether a signal

x(t) - e-'l'l.u(t)(a > 0) is energy or power signal. 14+41

4. 'State and explain Shannon-Hartley channel capacity theorem. Briefly discuss about the
measures that are used to characterize the performance of a channel. [4+4]

-r: - -- 'j,.==H{p tr E1$relgl9]]999t-Up usjge$!.&llsryElscheme' ll0L";_

a) PZ
b) NRZ-I
c) NRZ-L
d) AMI
e) Manchester
6. What do you mean by multiplexing? Explain about working mechanism of FDM and
TDM. t2+3+37
7. Differentiate between circuit switching and packet switching with suitable diagram. t6]
8. What are block codes? The generator matrix for a (6,3) block code is shown below.
Obtain all code words. [2+8]
lr 00 :1111
c=lo 10 : I I 0l
lo 0l :10Ij
9. What are Hamming codes? Write the properties of Hamming codes. Visualize a 3-bit
code words as code vector. t2+4+47
10. A message source generates 8 symbols with the following probabilities: t6l
P(Xt) =ll2, P(Xr) =114, P(Xr) = 1/8, P(Xo) =ll16, P(Xr) =1132, P(X.) =1164
P(Xr) =lll2Band P(Xs) =lll28
Encode the message using Huffnran
"o0".***

,*n! --"-
I

Level BE ij FuIIM:trI<s ll
Prgg5:rmm. q BCT ,Pass lYlarlcs ,.#
ear Time

,I q 'a
F'

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 Exam.
Level

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 : :,

i]\is TITUTE OF ENGI\IEERING Lerrel

Examinat'ion Conti'ol Diyision
etr I, 3'hrs::

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l-*oo'.' !-
,5

-J- 11
 45 TRIBITWAI{T'NTVERSITY Eram. Ite gtr llr r'
i INSTIruTE OF ENGINEERING Level BE FulI Marks 80

Ilivision Programme BCT PasslUarla 32

lPart
Yeer m/r Time 3 hs.
Data Communication
r' Candidates are required to give their answers in their own word5 re far as practicable.
r' Anempt All qtesfCIw.
{ Thefigtres in tlrc margtn indicate Full Marhs.
/ Assume suitoble dota if necessary.

l. Define noise. Briefly discuss the tlpes of noise. Defme thermal noise power density;
calculate the thermal noise power density in Watts/Hz at a iernperature of l7oC, the
Boltzmann's constant is 1.38x l0-" J/K. What is delay distortion and how can it be corrected?
Why is digital transmission pr-eferred over analog transmission? [4+2+27
2. Define energy and power signal. Check the signal x(t) : u(t) and x (t) = 6(t) is Energy or
Powertlpe. [l+4J
3. Define Linear, Stable, Time Invariant and Causal system wlth suitable t4l
"*"-plr..
4. Find the Fourierseries representatiorof the half-wave rectified Sineu,ave. I4I

a ra
t
4n -ht -2n -n It

5. Find the Fourier transform of the signal x(t) : r-"ltl, where (0 < a < o) is real-valued and ltl
denotes the absolute value of (t). Define the terms linear time-innuiant (LTI) systems and
impulse response. 14+21

6. Compare the transrnission characteristics and performance (frequency range, bandwidtlr,

security, flexibility, interference, connectivity) of
Optical fiber cable and Satellite
transmission. t6I
7. Given a channel with an intended capacity of 40 Mbps. The bandruidth of the channel is 6
MHz. What signal-to-noise ratio is required in order to achieve dris capacity? Also find
nrmber of bits/sample if channel becomes noiseless. 13+21

8. rExplain the working of Pulse Code Modulation (PCM).Draw AMI md Manchester encoding
forthesequence[0 I101000U. t4+3+31
9. Define multiplexing. Explain the working mechanism of WDM. Differentiate between
synchronous and statisticil mU. How is spread spectmm utilized in CDMA? What are the
advantages and disadvantages of CDMA? [2+2+2+2+21
10. How does ATM differ from frame rclay? What are the advantages and disadvantages of
ATM compared to franre relay? 12+31

ll.Why is source coding necessary? Differentiate between fixed length codbs and variable
- length codes. What is the purpose of Huffinan's coding algorithm? Explain the general
working principle of the Huffinan coding algorithm. [+l+l+3]
12. Define Dataword and Codeword with suitable example. List the error detection and
correction coding techniques with their application case. 12+41

13. Discuss the concept of redundancy in error detection and conection. Define Hamming
distance? Differentiate between linear block codes and cyclic codes. [+l+3]
rl**