Download JNTUA (JNTU Anantapur) M.Tech ( Master of Technology) 1st Semester 2018 Aug-Sept 9D06104 Advanced Data Communications Previous Question Paper
M.Tech I Semester Supplementary Examinations August/September 2018
ADVANCED DATA COMMUNICATIONS
(Digital Systems & Computer Electronics)
(For students admitted in 2013, 2014, 2015 & 2016 only)
Time: 3 hours Max. Marks: 60
Answer any FIVE questions
All questions carry equal marks
*****
1 (a) With neat diagram, explain the following modulation schemes: (i) PSK. (ii) QAM.
(b) Find out the minimum bandwidth, baud and bandwidth efficiency for the following bit rates and
modulation schemes are 8-QAM and 16-QAM.
(i) f
b
= 2400 bps. (ii) f
b
= 4800 bps. (iii) f
b
= 9600 bps.
2 (a) In home two computers are connected by an Ethernet hub. In this a LAN or a WAN? Explain the
reason.
(b) Assume 8 devices are arranged in a mesh topology. How many cables are needed? How many
parts are needed for each device?
3 (a) Performance is inversely related to delay. When we use the internet, which of the following are
more sensitive to delay: (i) Sending an e-mail. (ii) Copying a file. (iii) Surfing the internet. Explain in
detail.
(b) How many point-to-point WAN?s are needed to connect ?n? LAN?s, if each LAN should be able to
directly communicate with any other LAN.
4 The parity check bit of (8, 4) block code are generated by C
5
= d
1
+ d
2
+ d
4
, C
6
= d
1
+ d
2
+ d
3
,
C
7
=
d
1
+ d
3
+ d
4
, & C
8
= d
2
+ d
3
+ d
4
, where d
1
, d
2
, d
3
and d
4
are message bits. Find: (i) G and H.
(ii) Minimum weight of code. (iii) Error detecting capacity. (iv) Show that through 2 examples that
the code can detect and correct errors.
5 (a) Compare and contract byte-stuffing and bit stuffing.
(b) Assume the only computer in the residence user PPP to communicate with the ISP. If the user
sends 10 network-layer packets to ISP, how many frames are exchanged in each of the following
cases: (i) Using no authentication. (ii) Using PAP for authentication. (iii) Using CHAP for
authentication.
6 (a) Consider a space division switch with 100 inputs and outputs. What is the total number of cross
points in each of the following cases: (i) Using a single crossbar. (ii) Using a multi-stage switch
based on the Clos criteria.
(b) Consider nXk crossbar switch with ?n? inputs and ?k? outputs.
(i) Can we say that the switch acts as a multiplexer if n>k?
(ii) Can we say that the switch acts as a demultiplexer if n
7 We have defined the parameter ?a? as the number of frames that can fit the medium between two
stations, or a = (T
p
)/(T
fr
). Another way to define the parameter is a = L
b
/F
b
, in which L
b
in the bit
length of the medium and F
b
is the frame length of the medium. Show that two definitions are
equivalent.
8 Alice and Bob are experimenting with CSMA using a W
2
Walsh table. Alice use the code (+1, -1)
and Bob user the code (+1, -1). Assume that they simultaneously send a hexadecimal digit to each
other. Alice sends (6)
16
and Bob sends (B)
16
. Show how they can detect what are other person
has sent.
*****
FirstRanker.com - FirstRanker's Choice
This post was last modified on 30 July 2020