WiFi 10Mhz Channel

[Ramon Bauza]

Hello,

I would like to model a Wifi 10Mhz channel in ns-3. As far as I know,
the current Wifi model corresponds to a 20Mhz channel with data rates
from 6Mbps to 54Mbps. In order to simulate a Wifi channel with a
different spacing, some parameters would have to be changed. Here
below, I mention the different values of the parameters for both
channels and where in ns-3 these parameters are considered. I would
like you to tell me if there is any missing parameter I would also
have to change to completely model a 10Mhz channel.

In the PHY Layer, the data rates offered: 6, 9, 12, 18, 24, 36, 48 and
54Mbps for the 20Mhz channel and 3, 4.5, 6, 9, 18, 24 and 27Mbps for
the 10Mhz channel. Below, the modifications needed in ns-3 to model a
10Mhz channels are shown:

* A new function similar to void YansWifiPhy::Configure80211a is
needed in order to configure the new set of data rates.
* Also, a new function similar to void
ns3::InterferenceHelper::Configure80211aParameters should be
implemented taking into account that in a 10Mhz channel the value of
the parameters ns3::InterferenceHelper::m_plcpLongPreambleDelayUs,
ns3::InterferenceHelper::m_plcpShortPreambleDelayUs,
ns3::InterferenceHelper::m_longPlcpHeaderMode,
ns3::InterferenceHelper::m_shortPlcpHeaderMode and
ns3::InterferenceHelper::m_maxPacketDuration are different.
* New Wifi modes corresponding to the data rates of the 10 Mhz channel
have to be defined. New functions similar to WifiMode
ns3::WifiPhy::Get6mba should be implemented for the new modes.

In the MAC layer, there is no need to modify or implement new
functions since the parameters to be changed can be modified through
the attribute system. Below, I show the parameters that will take a
different value in a 10 Mhz channel.

* The slot time used in the MAC layer: 9us for the 20Mhz channel and
13us for the 10Mhz channel.
* The SIFS time used in the MAC layer: 16us for the 20Mhz channel and
32us for the 10Mhz channel.
* Other parameters such as CtsTimeout, AckTimeout and EifsNoDifs
employed in the MAC layer. The values of these parameters should be
recalculated for the 10Mhz channel. All the MAC parameters could be
modified through the ns3::NqosWifiMacHelper and the
ns3::QosWifiMacHelper and thus no modification in the ns-3 MAC
implementation would be needed.

I would appreciate that you provide me your comments on these
modifications I intend to introduce into the simulator in order to
make sure that they are consistent with the current wifi code.

Thank you very much,
Ramon Bauza.

[Mathieu Lacage]

hi ramon,

On Tue, 2009-05-12 at 04:45 -0700, Ramon Bauza wrote:

> I would like to model a Wifi 10Mhz channel in ns-3. As far as I know,
> the current Wifi model corresponds to a 20Mhz channel with data rates
> from 6Mbps to 54Mbps. In order to simulate a Wifi channel with a
> different spacing, some parameters would have to be changed. Here
> below, I mention the different values of the parameters for both
> channels and where in ns-3 these parameters are considered. I would
> like you to tell me if there is any missing parameter I would also
> have to change to completely model a 10Mhz channel.

I can't think of any missing item. Maybe timo or nicola can comment on
that if they know more about this kind of thing.

Mathieu