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For the $\text{IEEE 802.11 MAC}$ protocol for wireless communication, which of the following statements is/are TRUE?

  1. At least three non-overlapping channels are available for transmissions.
  2. The RTS-CTS mechanism is used for collision detection.
  3. Unicast frames are ACKed.

 

  1. All I, II, and III
  2. I and III only
  3. II and III only
  4. II only
  • 🚩 Edit necessary | 👮 priyansh_1705 | 💬 “Out of syllabus”
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$802.11$ $\text{MAC}$ = Wifi

  1. This is true, maximum $3$ overlapping channels are possible in Wifi !
  2. This is false. Collision detection is not really possible in Wireless, because signal strength of sending & receiving signal need not be same ! So Wifi uses collision Avoidance instead ! In this $\text{RTS-CTS}$ are used to announce to all nodes, that for which node wireless channel is reserved for communication. So this is collision avoidance, not detection
  3. This is true. Every frame in Wifi is acked, because Wifi station do not use collision detection, in Ethernet we use collision detection, in which it is possible for us to listen channel for collision & use exponential back off in case of collision detection. As in case of wifi, due to more error rate and not using collision detection strategy , we instead use $\text{ACK}$ frame, in case of not getting $\text{ACK}$ Host will retransmit after Random back off period

Answer is (B).

Source: Kurose & Ross Top down approach to internet

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Option (b). 802.11 uses collision avoidance, not collision detection.
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IEEE 802.11 MAC is wifi

(1) True - Max three overlapping channel is possible in wifi

(2) False -RTS (Request to send) and CTS(clear to send) are control frames which is used for collison avoidence not in collison detection

(3) True - Every frame in Wifi is acked, because Wifi station do not use collision detection, in Ethernet we use collision detection, in which it is possible for us to listen channel for collision & use exponential back off in case of collision detection. As in case of wifi, due to more error rate and not using collision detection strategy , we instead use ACK frame, in case of not getting ACK Host will retransmit after Random back off period
Answer:

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