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

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Code: 9D06104

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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)

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Answer any FIVE questions

All questions carry equal marks

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1. 1. Illustrate the amplitude shift keying and frequency shift keying.
   2. Determine the minimum bandwidth, baud and bandwidth efficiency for the following bit rates and modulation schemes BPSK and QPSK: (i) fb = 2400 bps. (ii) fb = 4800 bps. (iii) fb = 9600 bps.

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2. 1. For each of the following 4 networks, discuss the consequence if a connection fails
      1. Seven devices arranged in a mesh topology.
      2. Seven devices arranged in a star topology.
      3. Seven devices arranged in a bus topology.
      4. Seven devices arranged in a ring topology.

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   2. What is the maximum number of characters or symbols that can be represented by Unicode?
3. 1. Distinguish between telephone network and internet? What are the similarities? What are the differences?
   2. When a party makes a local telephone call to another party, is this point-to-point or multipoint connection? Discuss in detail.

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4. For a (7, 4) cyclic code with received vector is 0100110, with generator polynomial g(x) = 1 + x + x³. Draw the syndrome computation circuit and detect and correct the error if any.
5. 1. 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
   2. Assume PPP is in the authentication phase, show payload exchanged between the nodes if PPP is using: (i) PAP. (ii) CHAP.

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6. 1. 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.
   2. 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 Tß = 50 µs and Tfr = 120 µs, 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?

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8. 1. 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 ? = 0.2, ? = 0.3 and pc = 0.4 respectively.
      1. What is the throughput of each station?
      2. What is the throughput of N/W.
   2. 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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