Download JNTUA M.Tech 1st Sem 2018 Regular Feb 9D06104 Advanced Data Communications Question Paper

Download JNTUA (JNTU Anantapur) M.Tech ( Master of Technology) 1st Semester 2018 Regular Feb 9D06104 Advanced Data Communications Previous Question Paper

Code: 9D06104

M.Tech I Semester Supplementary Examinations February/March 2018
ADVANCED DATA COMMUNICATIONS
(Digital Systems & Computer Electronics)
(For students admitted in 2012, 2013, 2014, 2015 & 2016 only)

Time: 3 hours Max. Marks: 60
Answer any FIVE questions
All questions carry equal marks
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1 (a) Illustrate the amplitude shift keying and frequency shift keying.
(b) Determine the minimum bandwidth, baud and bandwidth efficiency for the following bit rates and
modulation schemes BPSK and QPSK: (i) f
b
= 2400 bps. (ii) f
b
= 4800 bps. (iii) f
b
= 9600 bps.

2 (a) For each of the following 4 networks, discuss the consequence if a connection fails
(i) Seven devices arranged in a mesh topology.
(ii) Seven devices arranged in a star topology.
(iii) Seven devices arranged in a bus topology.
(iv) Seven devices arranged in a ring topology.
(b) What is the maximum number of characters or symbols that can be represented by Unicode?

3 (a) Distinguish between telephone network and internet? What are the similarities? What are the
differences?
(b) When a party makes a local telephone call to another party, is this point-to-point or multipoint
connection? Discuss in detail.

4 For a (7, 4) cyclic code with received vector is 0100110, with generator polynomial g(x) = 1 + x + x
3
.
Draw the syndrome computation circuit and detect and correct the error if any.

5 (a) Byte-stuff the following frame payload in which ?E? is the escape byte, ?F? is the flag byte and ?D? is a
data byte other than an escape or a flag character.
DEDDEDDEFDFD
(b) Assume PPP is in the authentication phase, show payload exchanged between the nodes if PPP is
using: (i) PAP. (ii) CHAP.

6 (a) In a network, datagram and virtual-circuit need a routing or switching table to find the output port from
which the information belonging to a destination should be sent out, but a circuit switched network has
no-need for such table. Give the reason for this difference.
(b) What is the role of the address field in a packet travelling through a virtual-circuit network?

7 In a bus 1-persistance CSMA/CD with T
?
= 50 ?s and T
fr
= 120 ?s, there are 2 stations, A & B. Both
stations start sending frames to reach other at the same time. Since the frames collids, each station
tries to retransmit. Station A comes out with R = 0 and station B with R = 1. Ignore any other delay
including the delay for sending jamming signals. Do the frames collide again? Draw a time line diagram
to prove your claim. Does the generation of a random number help avoid collision in this case?

8 (a) There are only 3 active stations in a slotted ALOHA network A, B and C. Each station generates a
frame in a time slot with the corresponding probabilities ?
A
= 0.2, ?
B
= 0.3 and ?
C
= 0.4 respectively.
(i) What is the throughput of each station?
(ii) What is the throughput of N/W.
(b) Check to see the following set of chips can belonging to an orthogonal systems:
[+1, +1, +1, +1], [+1, -1, -1, +1], [-1, +1, +1, -1], [+1, -1, -1, +1]
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