Re: [Madwifi-users] Stats and 11g

[Greg C. <ma...@at...>]

Tom,

Let me suggest the following:

1. keep running stats with the per-node structure for each node you're 
exchanging
      packets with.   This would go in wlan.o as Sam points out.
2. this method works for AP mode, client mode, and ad hoc mode.
3. the values need to be available to the rate adaptation algorithm 
which is not in wlan,
     but in the driver.
4. But roaming decisions will be made in wlan, so the results are needed 
there as well.

The node struct is common to everything.
So, do the averaging where the descriptors are processed.
Keep the results in the node.

The SNR offsets per modulation type are also chip dependent.
I'll have to think some more about how to and if we need to add that 
complexity.
I think we should avoid it for now because the differences are small and 
it is changes
in the relative rssi that are more important for adaptive algorithms 
(rate, roaming, and power).

g


Sam Leffler wrote:
>>I'll volunteer to work on this.
>>
>> * From the above, it looks like rssi is a SNR calculation and you've
>>   provided enough info to get all three values into the stats.
True enough.   But all the adaptive algorithms can operate nicely with 
just average rssi
and the 1st derivative of rssi.
>>
>> * Averaging should be a piece of cake: just keep a running array.  Looks
>>   like the stats are updated on packet rx, not by time, so perhaps a
>>fixed    size array entries with timestamps would be good -- keep up to N
>>entries    and remove entries older than some small time threshold, say 1
>>sec.
dead on.

>>
>> * I'm unclear on what these values would represent in AP mode (average
>>   across clients?)  I wonder what the Linux HostAP driver does.
nooo..  must be per client.
> 
> 
> You want to keep per-client information for non-station mode.  Note that
> you want to do this in the wlan layer.  In fact the wlan code is sorely
> lacking in statistics, especially per-client ones that a real AP would
> keep.  
yah.
> 
> As to what to report through the wireless extensions, that's unclear and
> probably doesn't matter.  Not sure it's worth keeping a running value over
> all clients.
agreed.
> 
> 	Sam
>