[OLSR-users] LQ Routing and 802.11b Link Speed

[aaron]

On Wed, Jun 15, 2005 at 12:16:16PM +0200, Holger Mauermann wrote:
> Bruno Randolf wrote:
> >to get the expected transmission times we would have to send unicast
> >packets to each neighbor (the current HELLO packets are broadcast
> >with the lowest basic rate) which can result in a lot of additionally
> >used bandwidth.
> 
> yes, but the link speed usually doesn't change very often (with fixed 
> stations), e.g. the link to one of my neighbors changes 5 to 10 times 
> per hour between 18, 24 and 36 Mbps and a bad 1 Mbps link always stays 
> at 1 Mbps. So I think it's adequate if the packet-pair to measure the 
> bandwidth is sent at intervals of several minutes.
> 
hm, here (lots of WLAN equipment, everything is a bit more dense than 
in Berlin, streets are more narrow etc) we experience frequent changes
in bandwidth rate. I guess that depends very much on the physical topology
and RF interference.

cheers,
aaron.

> >another option may be to read the current rate (physical link speed)
> >from the wlan driver and multiply the ETX with that value.
> 
> This is very OS and driver dependent. I've recently seen an USB adapter
> with ndiswrapper that always reports 54 Mbps...
> 
> >could you send a link to the ETT paper?
> 
> Yes, of course [1]. However, it's from Micro$oft ;-)
> 
> I found another interesting paper about Medium Time Metric MTM [2]. Its 
> idea ("minimize the usage of a shared medium to maximize its capacity") 
> is similar to ETT and the authors measured up to 17 times more 
> throughput compared to min hop and ETX routing...
> 
> [1]-http://research.microsoft.com/mesh/papers/multiradio.pdf
> [2]-http://www.cnds.jhu.edu/research/networks/archipelago/publications/AHR-MediumTimeMetric-TechnicalReport.pdf
> 
> -- 
> \-- Holger Mauermann
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