Question

Question 27 (1 point) Which of the following is not correct for Frequency Division Multiple Access FDMA? Each FDMA user is assigned a sub-channel If the number of users is less than the number of sub-channels, spectrum resource is wasted OFDMA requires synchronization OFDMA requires guard bands Multiple Selection Question 28 (2 points) Select correct statements about CSMA/CA Frame size must be 2 minimum size, which is a property of the network Before transmitting a frame, a station need make sure that the medium is idle A station relies on Acknowledgement to guarantee proper delivery of frames When collision is detected, a short jamming signal is transmitted by sender to make sure that all other stations become aware of the collision

Answer 1

Answer)
Q27.
The following is not correct for Frequency Division Multiple Access FDMA :
FDMA requires synchronization

The synchronization is not needed for the users in FDMA since the users are already having different frequencies for transmitting data. Other facts about FDMA are true that it has guard bits for separating frequencies, users are assigned channels, and also spectrum resources are wasted when a number of users are lesser.

Q28. The correct statements about CSMA/CD are:
Frame size must be >= minimum size, which is a property of the network
Before transmitting a frame, a station needs to make sure that the medium is idle
A station relies on Acknowledgment to guarantee proper delivery of frames
When a collision is detected, a short jamming signal is transmitted by the sender to make sure that all other stations become aware of the collision

All of the above is true since the CSMA/CD frame size should be at least the minimum frame size on Ethernet. Also for CSMA/CD the medium should be checked for being idle and also the acknowledgment would be there for proper delivery of the data, and also jamming signal is sent to alert other stations of collision.

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