[Ns-developers] SIFS is not handled in yans-wifi-phy

[Mathieu Lacage]

On Thu, 2009-06-11 at 12:45 +0400, kirillano wrote:
> Hi all!
> 
>   Running different wifi-scanarios with hidden stations in NS-3, I
> have observed a strange thing: inside SIFS interval PHY starts to
> receive packet and tells about about it to DcfManager. A bit later PHY
> starts to send ACK (which was sheduled by MacLow) and cancells EndSync
> method of YansWifiPhy without notifying DcfManager about this (and
> DcfManager does not reset m_rxing flag). So, DcfManager thinks that
> the medium is busy (IsBusy () says true), but actually that is not
> right.

That sounds like a bug. A testcase to reproduce it would help to
understand what is going on better.

>   Also chapter 9.2.10 DCF timing relations says, that inside SIFS we
> can not know the state of the medium (that is a time to switch from TX
> to RX), and can not start to receive any packet. But YansWifiPhy goes
>  to IDLE (or CCA_BUSY) state and can start receiving a packet inside
> SIFS (see picture in attachment)

SIFS is purely a MAC concept. The PHY has no idea of what it is so, if
you want to implement more logic, you need to do it at the MAC layer.

Mathieu