[maemo-users] Power consumption and WLAN APs

[From: Kalle Valo]

"ext Andrew Daviel" <advax at triumf.ca> writes:

> 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.

Beacons (and all other frames originating from the AP) will always
have the PWR MGT bit zeroed, because AP will never sleep.

> 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.

Correct.

> 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

Usually missing FCS causes this. There's a setting in Wireshark under
IEEE 802.11 to enable and disable FCS calculation. Try reverting that
option.

-- 
Kalle Valo