[Ns-developers] Adding Wifi Phy models

[Mathieu Lacage]

On Sun, 2009-03-22 at 17:14 +0100, Nicola Baldo wrote:

> Such a hardware is for instance Calradio:
> http://calradio.calit2.net/calradio1a.htm
> 
> For those who are not familiar with it, Calradio is an experimental 
> platform with a 802.11b PHY and a fully customizable MAC layer written 
> in C code which runs on a DSP. The PHY in particular is based on two 
> components: the baseband module (the Intersil HFA3863 chipset I 
> mentioned earlier) and the RF module (based on the Maxim MAX2820 chipset).

Not that I don't care about this kind of hardware but, really, the goal
of the ns-3 PHY module is to modelize real hardware :) (more on this
below)

> In Calradio, the setting of the PHY mode belongs to the baseband module, 
> whereas the setting of the frequency to be used belongs to the RF 
> module. Both these settings are performed by writing to appropriate 
> configuration registers when desired. As a consequence, per-packet 
> frequency selection can be implemented by setting a new frequency just 
> prior to transmission.

I would be curious to know how much time it takes to make the RF
baseband actually perform the frequency switch. I suspect that this
delay is sufficiently long that frequency switches on a per-packet basis
are not practical and I suspect that this is also the case in real
hardware and I also suspect that the cost of building hardware which can
do this for 802.11 is sufficiently high that it would prohibit any real
deployment.

But, well, the real issue here is that the goal of the current codebase
is to modelize real 802.11 systems where per-packet frequency switches
are simply not feasible so, I would tend to happily ignore this
possibility for now.

Mathieu