Re: [RFC] b43: multiple MAC addresses support

[Kalle Valo <Kalle.Valo@nokia.com>]

Jouni Malinen <j@w1.fi> writes:

> On Fri, Nov 09, 2007 at 11:52:30AM +0100, Johannes Berg wrote:
>
>> Something I'm not clear on right now is the timing of it all. If there
>> are say two BSSes, the driver can simply program the hardware to half
>> the beacon period and then the beacons will alternate. But if there are
>> seven BSSes, the beacon period might not be divisible by seven so timing
>> errors will happen and, worse yet, accumulate. Does hostapd somehow
>> account for this? Or should the beaconing work completely differently,
>> for example with all N beacons sent in a burst?
>
> You could always modify the beacon period to a suitable number that
> would be divisible by whatever number of BSSes there are and/or add
> empty slot to move from, say, 7 to 8, and just not send a beacon at some
> of the slots. Sending a burst of all beacons at the same time is also a
> valid option up to a certain limit on how long a time would be allocated
> for this. However, this may have some timing issues when there are
> multiple power save buffered broadcast/multicast frames waiting to be
> sent out. In general, it would be good to try to send the beacon frames
> as close to their correct time as possible to allow power saving
> stations to remain asleep most of the time.

Exactly, it is important for small mobile devices that beacons are
sent at the correct time. For example, I have seen broken APs which
Target Beacon Transmission Time fluctuates and Nokia N800 has high
power consumption because of that.

-- 
Kalle Valo