Gujarat University
MCA Semester IV
Networking Technologies I
Networking Technologies I
Date: August 1, 1994 Marks: 50
Note:
1. Write the Two sections in Separate answer-books.
2. Q.No. 1 and 4 carry 9 marks each. Other questions carry 8 marks each.
3. Make suitable assumptions wherever necessary and state them clearly.
Section I
Q-1 (a) How does CRC provide error detection? How is the CRC checksum generated in theory?
(b) A simple 4-bit register had feedback taps at locations 2 and 4. The register is set to all 0s initially. The
data bits entered serially are 1010 (rightmost bit first). Show the contents of the shift register for each
bit entered. What is the CRC checksum?
Q-2 (a) Compare the operation of command/response, interrupt-driven, token passing and CSMA/CD access,
with respect to efficiency, reliability, predictability and cost.
(b) Compare the number of links needed in each of the following three topologies for five users:
STAR, BUS, and RING.
How many new links are needed in networks with each of the three topologies when a sixth user is
added to the system.
OR
Q-2 (a) A data communication system, which follows RS 232C standard is sending characters, by using
hardware handshake lines RTS and CTS, at 10 characters/s. After 5 characters, the receiver sends a
signal which intimates that the sender must stop for the 1-a time that it takes to process these 5
characters. Sketch the timing diagram for 15 characters.
(b) Compare RS-232, RS-422, RS-423 & RS-465 in terms of bit rate, distance, single-ended versus
differential signals, signal voltage levels and decision points.
Q-3 (a) Where is SDLC used? What are some of its key characteristics?
(b) A designer must choose between differential input with CMRR of 120 dB and an opto-isolator with
CMRR of 150 dB. The system requires that the CMV of 100v be reduced to less than 0.0001V. Which
of the two inputs meets the design needs? Give reasons for your answer.
OR
Q-3 (a) What is the purpose of jamming? Explain how the techniques used to overcome it may also be used for
recovering extremely weak signals, such as those from space vehicles?
(b) What is Manchester encoding? Compare the bandwidth it uses to that of NRZ. What are the advantages
of Manchester encoding?
Section II
Q-4 (a) State and explain the Nyquist Sampling Theorem?
(b) A system can transmit 500 kbits/s. The users who are multiplexed into this system have 5-khz
bandwidth each. They are each sampled at twice the Nyquist rate, and digitized to 10 bits.
(i) How many users can be handled by the system?
(ii) How many users can be handled if the sampling is performed at three times the Nyquist rate?
Q-5 (a) A System is being designed to handle five pairs of users. Sketch the system using block diagrams, for
implementation with:
(i) SDM (ii) FDM (iii) TDM
(b) What are ASK, FSK and PSK? Why are they so named?
OR
Q-5 (a) A satellite is located in a stationary orbit 22,300 miles above the earth. A speaker in New York is
talking to a person in London, 4000 miles way using the satellite connection. How much time is lost
from wave travel when a question is asked and as answer received?
Compare it with the time that would be lost if the medium used were a cable between New York and
London? (Assume that the velocity of prorogation in the cable is 50% of the speed of ,light in free space.)
(b) What is channel capacity for signal power of 50 W, noise power of 3 W, and bandwidth of 15 KHz?
Q-6 Write Notes on any three of the following:
1. 7-layer OSI Reference Model
2. standard dial telephone
3. MODEMs
4. IEEE 488 Standard
5. INTEL 8251 UART
