IEEE 802.11

Question

Consider the following statements:

S1  : IEEE 802.11 does not uses sequence number.
S2  : The amount of data send in one time in limited by RTS frame (data = sender’s data + ACK).
S3 : IEEE 802.11 uses CSMA/CA medium access protocol.
S4 : The exponential backoff mechanism reduces the probability of collision on retransmissions in ethernet.

 

Which of the following is true?

This is from topic- wifi. From where should i study this topic ?

Comments

I guesss u can refer this: http://inst.eecs.berkeley.edu/~ee122/sp07/80211.pdf

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S1, S3,S4 correct

https://gateoverflow.in/110450/wifi-madeeasy

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The frame of 802.11 contains a special field called sequence control which contains the sequence number of the frame. Hence s1 is false

Answer 1

- only S3 and S4 are true.

S2 is not true as RTS( request to send ) is used to ask the WAP (wireless access point) whether we can transmit the data or not ( to avoid the chances of collision )

S1 is not true as inside the frame format of 802.11 we've a sequence no. field.

Comments

A starts by sending an RTS (Request To Send) frame to B. This short frame (30 bytes) contains the length of the data frame that will eventually follow. Then B replies with a CTS (Clear To Send) frame. The CTS frame contains the data length (copied from the RTS frame). Upon receipt of the CTS frame, A begins transmission.

This is written in Computer network book by TANENBUM which means S2 is true

 

Answer 2

You can watch the videos from below two links and it'll clarify all your doubts:-

https://www.youtube.com/watch?v=ITAJb3v5VKQ ( for clarification about the sequence number used in first point )

https://www.youtube.com/watch?v=My4VDzviiNg ( for clarification about third point and RTS in second point )

Answer 3

According to me,

only S4 is true.

IEEE 802.11 standard is wireless LAN.

S1- FALSE  wireless LANs use sequence number is transport layer for segments

S2- FALSE  there is no restriction in the amount of payload for transferring

S3- FALSE , CSMA/CD is for the bus topology with wired shared medium

S4- TRUE  This is present in ALOHA where to increase the throughput frames of uniform length is taken and to decrease collision, exponential back-off time is varied.