[maemo-users] Power consumption and WLAN APs

From: Andrew Daviel advax at triumf.ca
Date: Tue Jul 22 23:45:47 EEST 2008
On Mon, 21 Jul 2008, Andrew Daviel wrote:

> Is there anything for the tablets that can log wireless traffic in enough
> detail to show whether PSM is working ? airodump-ng ??

Should have tried before posting. I have a couple of capture files made
with airodump-ng --beacons, which I can view in wireshark.

Lots of detail I don't understand. I can see the beacon interval on the 
Proxim APs is 100ms (same as the Linksys default), and see the DTIM info 
(whether data is being held).

IEEE 802.11 Beacon frame, Flags: ........
     Type/Subtype: Beacon frame (0x08)
     Frame Control: 0x0080 (Normal)
         Flags: 0x0
             ...0 .... = PWR MGT: STA will stay up
IEEE 802.11 wireless LAN management frame
     Fixed parameters (12 bytes)
         Beacon Interval: 0.102400 [Seconds]
         Capability Information: 0x0421
             .... .... .... ...1 = ESS capabilities: Transmitter is an AP
             .... 0... .... .... = Automatic Power Save Delivery: apsd not implemented

home and work have the same flags, except at home
short preample is allowed. I.e. PWR MGT is 0 at home, too.

We have multiple APs at work; I assume that in normal operation the
tablet is registered with only one and will ignore beacons from
the others.

All the packets from home, and most from work, show as "malformed packet" 
for some reason. airodump didn't offer a capture length and the packets 
are fairly small (85 bytes) so I don't think truncated

Andrew Daviel, TRIUMF, Canada

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