91. A slotted ALOHA network transmits 200 bits frames using a shared channel with 200 kbps bandwidth. If the system (all stations put together) produces 1000 frames per second, then the throughput of the system is .................
a. 0.268
b. 0.468
c. 0.368
d. 0.568
Answer: (c).0.368

92. An analog signal has a bit rate of 8000 bps and a baud rate of 1000.
Then analog signal has .............. signal elements and carry ............ data elements in each signal.
a. 256, 8 bits
b. 128, 4 bits
c. 256, 4 bits
d. 128, 8 bits
Answer: (a).256, 8 bits

93. The plain text message BAHI encrypted with RSA algorithm using e=3, d=7 and n=33 and the characters of the message are encoded using the values 00 to 25 for letters A to Z. Suppose character by character encryption was implemented. Then, the Cipher Text message is ............
Answer: (b).HAQC

94. If link transmits 4000 frames per second and each slot has 8 bits, the transmission rate of circuit of this TDM is ...............
a. 64 Kbps
b. 32 Mbps
c. 32 Kbps
d. 64 Mbps
Answer: (c).32 Kbps

95. Given the following statements:

(a) Frequency Division Multiplexing is a technique that can be applied when the bandwidth of a link is greater than combined bandwidth of signals to be transmitted.
(b) Wavelength Division Multiplexing (WDM) is an analog multiplexing Technique to combine optical signals.
(c) WDM is a Digital Multiplexing Technique.
(d) TDM is a Digital Multiplexing Technique.

Which of the following is correct?
a. (a), (b), (c) and (d) are true
b. (a), (b), (c) and (d) are false
c. (a), (b) and (d) are false; (c) is true
d. (a), (b) and (d) are true; (c) is false
Answer: (d).(a), (b) and (d) are true; (c) is false

96. A pure ALOHA Network transmit 200 bit frames using a shared channel with 200 Kbps bandwidth. If the system (all stations put together) produces 500 frames per second, then the throughput of the system is ..............
a. 0.384
b. 0.184
c. 0.286
d. 0.586
Answer: (b).0.184

97. Match the following:

(a) Line coding                         (i) A technique to change analog signal to digital data.
(b) Block coding                       (ii) Provides synchronization without increasing
number of bits
(c) Scrambling                          (iii) Process of converting digital data to digital signal.
(d) Pulse code modulation    (iv) Provides redundancy to ensure synchronization
and inherits error detection.

      (a)   (b)   (c)   (d)
a. (iv)  (iii)   (ii)   (i)
b. (iii)  (iv)   (ii)   (i)
c. (i)    (iii)   (ii)   (iv)
d. (ii)   (i)    (iv)   (iii)
Answer: (b).(iii)  (iv)   (ii)   (i)

98. Assume that we need to download text documents at the rate of 100 pages per minute. A page is an average of 24 lines with 80 characters in each line and each character requires 8 bits. Then the required bit rate of the channel is ................
a. 1.636 Kbps
b. 1.636 Mbps
c. 2.272 Mbps
d. None of the above
Answer: (d).None of the above

99. Encrypt the plain text Message “EXTRANET” using Transposition cipher technique with the following key. Using ‘Z’ as bogus character.
Answer: (a).TAXERTZENZ

100. Suppose that the time to do a null remote procedure call (RPC) (i.e, 0 data bytes) is 1.0 msec, with an additional 1.5 msec for every 1K of data. How long does it take to read 32 K from the file server as 32 1K RPCs?
a. 49 msec
b. 80 msec
c. 48 msec
d. 100 msec
Answer: (b).80 msec