Configuring the multicast data rate with iw/nl80211

Configuring the multicast data rate with iw/nl80211

[jpo]

Hello all,
I know that it is now possible to configure the data rate bitmask that the RC
algorithm uses to select data rates for individual peer nodes. However, I could
not figure out, how to specifically assign a broadcast/multicast data rate. Is
this supported? If so, how?

The scenario I'm facing is that I'm perfectly happy to let the RC figure out the
best data rate for the peer nodes up to the supported maximum. However, I need
to multicast video streams as well. For this I have to balance the required data
rate with the distance I can achieve. 

Kind regards
  Joerg

AW: Configuring the multicast data rate with iw/nl80211

[Joerg Pommnitz]

>Not a good idea... I tried it too, but as soon as a STA goes into PSM [or does 
a
>background scan], it'll affect the stream badly [So, you'll probably need a
>dedicated AP just for your video clients]. The reason is that the AP
>[in my case it was mac80211] will now buffer the transmissions, so you only get
>about 128 frames every 300ms until the STA comes back or disappears.

An interesting and good point. However, I'm in full control of the clients
so I can actually disable PS-Mode. So, while your note of caution is 
appreciated,
it doesn't get me off the hook. As I wrote earlier I'm evaluating a transition
from Madwifi to ath5k. Madwifi with net80211 had an iwpriv call to configure the 

multicast data rate. I'm looking for an equivalent solution with ath5k/mac80211.

>As an alternative, It's worth a try to look into multicast-to-unicast proxies
>such as http://sourceforge.net/projects/udpxy/ .

But then you duplicate the multicast traffic for every STA, no?

Regards
  Joerg

Re: AW: Configuring the multicast data rate with iw/nl80211

[Christian Lamparter]

On Friday 24 June 2011 14:34:55 Joerg Pommnitz wrote:
> >As an alternative, It's worth a try to look into multicast-to-unicast proxies
> >such as http://sourceforge.net/projects/udpxy/ .
> 
> But then you duplicate the multicast traffic for every STA, no?
Not every STA, only those which subscribed to udpxy at the time.

But there's more, I found it very difficult to "fine-tune" the multicast
setup properly, since there's no automatic feedback for
multicast link quality. Either the rate I picked was too low, or the
signal was too weak, in both cases the video stream as pretty
pretty poor at best.

So I went with the proxy, which as it turns out is a much better
option once you go for 11n. However, the decision is truly yours :D

Re: Configuring the multicast data rate with iw/nl80211

[Joerg Pommnitz]

----- Original Mail ----

> From: Christian Lamparter <chunkeey@googlemail.com>
>
> But there's more, I found it very  difficult to "fine-tune" the multicast
> setup properly, since there's no  automatic feedback for
> multicast link quality. 

Just how did you do this "fine-tuning"?

Regards
  Joerg