Answer the following questions in your own words:
QUES 1 - What do you understand by The Hidden-Node Problem? Give an example of a
three-sender hidden-node problem? Describe 2 different spatial configurations which
exemplify this issue.
ANS - The problem of a node not being able to detect a potential competitor for the medium
because the competitor is too far away is called the hidden node problem.
The three sending nodes can be laid out at the vertices of an equilateral triangle, with the
receiving node in the center.
Alternatively, with impermeable walls the following arrangement works:
sender1
------------
receiver sender2
------------
sender3
QUES 2 - What is the 4B/5B encoding for the 3-byte (ASCII) string “Sun”?
ANS – 0101110101 0111101011 0111011100
QUES 3 - What is the 16-bit Internet checksum for the 3-byte binary message 00110001
00110010 00110011?
ANS – 01100100 00110010 which should have the bits inverted to 10011011 11001101.
Note: both answers should be considered ok for the purposes of the WA assessment.
QUES 4 - Suppose a message is 11011000. What is the CRC checksum using the polynomial
corresponding to 1011 to give a 3-bit answer? (Show the solution steps, not just the answer).
ANS –
Doing modulo-2 division of 11011000 (with 3 0s added at the end) by 1011, as shown below,
yields a remainder of 011. The latter is the CRC checksum.
____________
1011| 11011000000
1011
1101
1011
1100
1011
1110
1011
1010
1011
001000
1011
011
QUES 5 - What is Time Domain Reflectometry?
