[ns] 802.11 Carrier sense

[shshah@cairo.cs.uiuc.edu]

On Mon, 15 Apr 2002, Sorav Bansal wrote:

> 
> 
> Hi,
>     The function is_idle() in mac-802_11.cc checks if the medium is idle or
> not (carrier sensing). 

Yes, I am aware of this, but I would like to know which particular call to 
is_idle() is the *first* carrier sense before the *first* RTS is sent. 
is_idle() is checked multiple times in mac-802_11.cc, I am only interested 
in the particular above case. Could you give me this info? Thanks in 
advance.

Regards,
Samarth.

The medium is not idle if a packet is being
> received. And all packets with signal strength above the carrier sense
> threshold are received by the MAC layer (except that the error field is set
> to 1 for packet below the receiving threshold). Hope that answers your
> query.
> --sorav
> 
> 
> 
>                                                                                                 
>                     shshah@cairo.c                                                              
>                     s.uiuc.edu           To:     ns-users@ISI.EDU                               
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>                     ns-users-admin       Subject:     [ns] 802.11 Carrier sense                 
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>                                                                                                 
>                     04/15/02 01:12                                                              
>                     PM                                                                          
>                     Please respond                                                              
>                     to shshah                                                                   
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> 
> 
> 
> 
> Hi,
> 
> I'm unable to discern exactly when (i.e. where in the 802.11 code) the
> first carrier sense before the first RTS for a packet occurs. If the
> carrier is found busy at this carrier sense, I would like to be able to
> modify the backoff interval after the deferral that follows the busy
> carrier sense. Rather than have the station backoff cw_ slot times, I'd
> like to have it backoff some other number of slot times.
> 
> I do not wish to modify the backoff procedure that is followed after a
> collision, however. I want the cw_ doubling, backoff = cw_ number of
> slots, etc. to remain as is, in the case of collision.
> 
> Could anyone kindly provide me some guidance? Thanks in advance.
> 
> Regards,
> Samarth.
> 
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