[ns] 802.11 MAC timer question (ns2.26)

[Jian Li]

This concern has been raised by Sven et al, and related information can be 
found in their report here:
http://www.tkn.tu-berlin.de/research/802.11e_ns2/

-Jian

On Sun, 30 May 2004, Neeraj Poojary wrote:

> 
> i have a question regarding the backoff timer 
> (ns2.26) ...
> 
> the start() function for the backoff timer does not
> incorporate a DIFS delay if the medium is idle when
> it was called. it sets the timer value as per the
> contention window only. 
> 
> now picture this scenario. at the end of an 
> {RTS-CTS-}-DATA-ACK sequence, on receiving the ACK,
> we set the backoff timer based on the CW. this could
> be a value less than DIFS. before the backoff timer 
> expires, an outgoing packet is received at the MAC. 
> the send() function sees that the backoff timer is 
> active and does not set a defer timer. the packet is 
> transmitted when the backoff timer expires, i.e. less 
> than a DIFS interval after the last ACK was received. 
> isn't this a violation of the standard?
> 
> please let me know if i'm missing something here.
> 
> thanks,
> neeraj
> 
> 
> 	
> 		
> __________________________________
> Do you Yahoo!?
> Friends.  Fun.  Try the all-new Yahoo! Messenger.
> http://messenger.yahoo.com/ 
>