GATE | GATE-CS-2016 (Set 2) | Question 64

For the IEEE 802.11 MAC protocol for wireless communication, which of the following statements is/are TRUE?

I. At least three non-overlapping channels are
   available for transmissions.
II. The RTS-CTS mechanism is used for collision detection.
III. Unicast frames are ACKed.

(A) All I, II, and III
(B) I and III only
(C) II and III only
(D) II only


Answer: (B)

Explanation: 802.11 uses 5 GHz Radio Band(High Frequency) which has 23 overlapping channels rather than the 2.4 GHz frequency band which has only three non-overlapping channels.

RTS(Request To Send) and CTS(Clear To Send) are control frames, which facilitate the exchange between stations and help in collision reduction and not DETECTION. As Station 1 would send data frame to Station 2, only when it receives a CTS frame.



First Station 1 sends a RTS to Station 2, in response Station 2 sends back CTS. After data is received by Station 2, it send Acknowledgement frame(ACKed). As Station 2 sends a Acknowledgement to a single recipient on a network, Unicast Frames are acknowledged.


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