Subject: [manet] Carrier Sensing in 802.11 DCF

From: Jas C <[email-masked]>
Date: Wed, 4 Feb 2004 07:47:42 -0800 (PST)

Hi all,
 
As per the IEEE 802.11 Specifications, the Short Inter Frame Space (SIFS) has the following functions in DCF:
 
1. Allow stations that have seized the medium to retain it for the duration of their frame exchange sequence.
 
2. Prevent other nodes from accessing the medium when there is an on-going transmission 
 
3.  To seperate transmissions belonging to the same conversation
 
4. Allow nodes to reverse roles from Transmit to Receive mode and vice-versa
 
Pertaining to point 3, does every node perform physical carrier sensing for SIFS beore it actually transmits CTS, DATA or ACK frames for the same conversation? 
 
According to me, physical carrier sensing is performed only once for DIFS before initiating an RTS for any new transaction.
 
Please help in clarifying this doubt.
 
Thanks in advance,
Jasmina Chauhan

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