Visvesvaraya Technological University (VTU) 2006 B.E Fifth Semester , uary/ruary , Computer Science/Information Science and Engineering - Question Paper

Fifth Semester B.E. Degree Examination, January/February 2006
Computer Science/Information Science and Engineering
Data Communications
Time: three hrs. Max.Marks: 100
Note: 1. ans any 5 full ques..
2. All ques. carry equal marks.
1. (a) Briefly define any 5 essential elements of network architecture. (10 Marks)
(b) presume that n computers are connected in the subsequent topologies:
2. (a) A host computer is connected to a connectionoriented
packetswitching
network
to a server through a pointtopoint
link. Show the sequence of layered services
that take place ranging from layer (n+1) of the host and that of the server through the
respective lower layers (n) and deploying the needed PDU’s and SDU’s.
(10 Marks)
(b) A scanner has a resolution of 600 * 600 pixels/square inch. How many bits are
produced by on 8inch
* 10 – inch image. If scanning uses eight bits/pixel? If this
image is compressed at a ratio of 12. How long will it take to transmit this
compressed image over a 56 Kbps transmission medium?
3. (a) Draw the Manchester encoding of the subsequent binary sequence:
1 0 one 0 one 1 one 0
Why is Manchester encoding called as IB2 code? (10 Marks)
(b) Derive the expression for the band width of a Frequency Shift Keying (FSK)
signal and hence determine the maximum bit rate of transmission, if the
bandwidth of the medium is 12,000 Hz and the difference ranging from the two
carriers is 2000 Hz. presume that the transmission is in full – duplex mode.
(10 Marks)
4. (a) Draw the diagram of a typical QAM – modulator and prove that its output y(t) is
provided by:
( ) ( ) two cos [2 tan one ( ) ]
1
2 2
k k c k k y t = A + B p f t + B A where
Ak is in – phase component, Bk is quadrature component and fc is centre
frequency.
(b) Draw the QAM – constellation diagrams of the subsequent
i) eight – QAM represented by two – amplitudes and four phases
ii) 16QAM
represented by 3ampliltudes
and 12 phases. (10 Marks)
5. (a) Draw the structure of SONET frame STS1
at the line level and briefly define
the segments in it. Prove that the overall bit rate of STS – one is 51.84 (10 Marks)
(b) In a TDM system, 4 channels of 1Kbps every are multiplexed together.
every time slot, called as a unit, carries one bit of info. Data from every time
slot is transmitted as a frame. Find:
i) Transmission rate of the output link of the multiplexer
ii) The duration of a frame (10 Marks)
6. (a) In the selective repeat ARQ, discuss the meanings of:
Slast, Srercent, Rnext, Ws&WR. (10 Marks)
(b) In HDLC protocol explain the functions executed by the control frame.
(10 Marks)
7. (a) Derive the expression connecting the throughput S and the total arrival rate G in
A slotted ALOHA system and hence derive the maximum value of the
throughput. (10 Marks)
(b) Suppose a radio system uses 9600 bps channel for sending call setup request
messages to a base station. Suppose that frames are 120 bits long. What is the
maximum throughput possible with ALOHA and with slotted ALOHA.
(10 Marks)
8. provide a brief description of the following:
a) Repeaters
b) Loop issue in connecting LAN’s using bridges
c) Cyclic Redunddancy Check(CRC) in fault detection
d) CSMA/CD

Earning:   Approval pending.