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Re: Re: [ns] Problem about the implemention of mac802_11
You are right!It's my mistake.
THANKS EVERYBODY FOU YOUR DISCUSSING TO THIS PROBLEM.
--- ��Ӿ <[email protected]> wrote:
> I have just examined the code of mac_802_11.cc and
> find that
> the implementation of ns is somewhat reasonable. I
> have mistaken
> that there are a backoff process after difs.
> Besides, In IEEE802.11
> standard 9.2,it says that "The CSMA/CA protocol is
> designed to
> reduce the collision probably ... Just after the
> medium becomes
> idle following a busy medium...This is the
> situation that
> necessitates a random backoff procedure ...". When
> the medium is
> idle for some time, it's not necessary to backoff.
>
> >A simple example is the "void send(Packet * p,
> Handler
> > *h)" function in Mac-802_11.cc. In this
> >function,there
> >are some statements like:
> >"
> >if(mhBackoff_.busy()==0) {
> > if(is_idle()) {
> > if(mhDefer_.busy()==0)
> > mhDefer_.start(difs_);
> > }
> >else {
> > mhBackoff_.start(cw_.is_idle());
> > }
> >}
> >"
> > From these statements,we can conclude that when
>
> >the media is busy, backoff a random time;else,
> defer
> > difs_ time and send the packet. But the Mac802.11
> > standard requires that even if the media is
> idle,the
> > mac sender must backoff a random time. THIS IS THE
> > FIRST CONFLICT that i can see.
> > The second,we can't find where the physical
> layer's
> >CCA/CA function which the standard requires was
> >implemented in ns-2.
> >
> > --- Jun Zhao <[email protected]> wrote:
> >> Can you give us more detailed info?
> >> ----- Original Message -----
> >> From: "Yun Li" <[email protected]>
> >> To: <[email protected]>
> >> Cc: <[email protected]>
> >> Sent: Tuesday, August 28, 2001 11:25 AM
> >> Subject: [ns] Problem about the implemention of
> >> mac802_11
> >>
> >>
> >> > Dear ns-users:
> >> >
> >> > I have looked into the ns-2.1b8 resources code,
> >> > mAC-802_11.h and Mac-802_11.cc that implement
> the
> >> > MAC802.11 standard. I find that the
> implemention
> >> > doesn't follow the IEEE MAC802.11 standard.
> What's
> >> > your
> >> > opinion about this and am I right?
> >> > Any idea will be appreciated!
> >> >
> >> >
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> >
> >
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> ��
> ��
>
> ��Ӿ
> [email protected]
>
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