[Ns-developers] 802.11 10Mhz Channel

[Mathieu Lacage]

1) you can't add a SetCwMin method on WifiMac because there can be more
than one DcaTxop per WifiMac and they should not have the same CwMin.

2) The DcaTxop parameters are initialized in the associated helpers in
src/helper. See QosWifiMacHelper::Default for example.

I don't have any bright idea right now of how this should be dealt with
and what we could do to make this both 'automatic' and flexible to do
something different. Ideas welcome.

Mathieu

On Thu, 2009-07-16 at 16:59 -0700, Pei, Guangyu wrote:
> Hi,
> Here is what I see in DcaTxop:
>  
>  98 TypeId
>  99 DcaTxop::GetTypeId (void)
> 100 {
> 101   static TypeId tid = TypeId ("ns3::DcaTxop")
> 102     .SetParent<Object> ()
> 103     .AddConstructor<DcaTxop> ()
> 104     .AddAttribute ("MinCw", "The minimum value of the contention
> window.",
> 105                    UintegerValue (15),
> 106                    MakeUintegerAccessor (&DcaTxop::SetMinCw,
> 107                                          &DcaTxop::GetMinCw),
> 108                    MakeUintegerChecker<uint32_t> ())
> 109     .AddAttribute ("MaxCw", "The maximum value of the contention
> window.",
> 110                    UintegerValue (1023),
> 111                    MakeUintegerAccessor (&DcaTxop::SetMaxCw,
> 112                                          &DcaTxop::GetMaxCw),
> 113                    MakeUintegerChecker<uint32_t> ())
> 114     .AddAttribute ("Aifsn", "The AIFSN: the default value conforms
> to simple DCA.",
> 115                    UintegerValue (2),
> 116                    MakeUintegerAccessor (&DcaTxop::SetAifsn,
> 117                                          &DcaTxop::GetAifsn),
> 118                    MakeUintegerChecker<uint32_t> ())
> 119     ;
> 120   return tid;
> 121 }
> 122 
> 
> The default value of 15 was set at line 105. Why do you think that CwWin
> has nothing to do with DcaTxop?
>  
> Gary
> 
>  
> 
> 
> ________________________________
> 
> 	From: Basim Javed [mailto:basimjaved at gmail.com] 
> 	Sent: Thursday, July 16, 2009 3:17 PM
> 	To: Pei, Guangyu
> 	Cc: Nicola Baldo; ns-developers
> 	Subject: Re: [Ns-developers] 802.11 10Mhz Channel
> 	
> 	
> 	hi all
> 	
> 	CwMin parameter has to do nothing with DcaTxop. In QoS enabled
> MAC, each queue handles its own DcaTxop independently. 
> 	
> 	regards
> 	B
> 	
> 	
> 	On Thu, Jul 16, 2009 at 11:23 PM, Pei, Guangyu
> <Guangyu.Pei at boeing.com> wrote:
> 	
> 
> 		It seems to me that CwMin parameter is controlled by
> DcaTxop. Each MAC
> 		handles its own DcaTxop.  Should we add a virtual
> function SetCwMin may
> 		be added in WifiMac class? For non-QoS MACs, it seems
> that each mac has
> 		only one DcaTxop and it is straightforward to add one.
> For QoS  MAC, it
> 		seems that only beacon Dca needs to be set. Does this
> sound ok?
> 		
> 		Gary
> 		
> 
> 
> 		> -----Original Message-----
> 		> From: Nicola Baldo [mailto:nbaldo at cttc.es]
> 		> Sent: Thursday, July 16, 2009 9:03 AM
> 		> To: ns-developers
> 		> Subject: Re: [Ns-developers] 802.11 10Mhz Channel
> 		>
> 		> Also CwMin should be set to 31 (instead of 15) when
> using 802.11b.
> 		> See IEEE Std. 802.11-2007, section 15.3.3 "DS PHY
> characteristics".
> 		>
> 		> Nicola
> 		>
> 		> Pei, Guangyu wrote:
> 		> > Hi,
> 		> >
> 		> > I double-checked the standard. I believe the
> following
> 		> settings are correct.
> 		> >
> 		> > +WifiMac::Configure80211b (void)
> 		> > +{
> 		> > +  SetSifs(MicroSeconds(10));
> 		> > +  SetSlot(MicroSeconds(20));
> 		> > +  SetEifsNoDifs(MicroSeconds(10+304));
> 		> > +  SetPifs(MicroSeconds(10+20));
> 		> > +
> 		> >
> 		>
> +SetCtsTimeout(MicroSeconds(10+304+20+GetDefaultMaxPropagationDelay().
> 		> > +GetMicroSeconds ()*2));
> 		> > +
> 		> >
> 		>
> +SetAckTimeout(MicroSeconds(10+304+20+GetDefaultMaxPropagationDelay().
> 		> > +GetMicroSeconds ()*2)); }
> 		> >
> 		> > In particular, I believe 304 is the Ack Tx time =
> AckSize + PLCP
> 		> > Preamble + PCLP Header = 8*14 + 144 + 48 = 304
> 		> >
> 		> > Thanks,
> 		> >
> 		> > Gary
> 		> >
> 		> >> -----Original Message-----
> 		> >> From: Ramon Bauza [mailto:monbauza at gmail.com]
> 		> >> Sent: Monday, July 13, 2009 3:22 AM
> 		> >> To: Mathieu Lacage
> 		> >> Cc: ns-developers at ISI.EDU
> 		> >> Subject: Re: [Ns-developers] 802.11 10Mhz Channel
> 		> >>
> 		> >> Hi,
> 		> >>
> 		> >> Thank you for your comments. Please find the new
> patch modified
> 		> >> accordingly to your suggestions. Now,
> WifiMacHelpers
> 		> remain the same
> 		> >> way as in ns-3-dev.
> 		> >> I have also added the Configure80211b method to
> configure MAC
> 		> >> parameters.
> 		> >> However, I would like someone to review the
> parameters, since I am
> 		> >> not very familiar with the 802.11b specification.
> As Std
> 		> 802.11-2007
> 		> >> states (page 654), I have considered:
> 		> >>
> 		> >> - SlotTime = 20us
> 		> >> - SIFS = 10us
> 		> >>
> 		> >> Ramon.
> 		> >>
> 		>
> 		
> 		
> 
>