fixed TX rates for broadcast messages

Markus Jakob (EEI) Markus.Jakob at
Thu Jan 10 03:49:55 EST 2002

it's me once more. I did some more testing on the
problem I posted last week. It seems to be more a 
problem of fixed bit rates for broadcast messages for 
the ELSA MC-11 card why the ranges differ.

I measured available bit rates between two nodes 
for broadcast and unicast messages.

I run a simple application on one node which sends packets 
of a selected bitrate out to specified IP-address.
On a second node, placed directly beside, an application 
checked the amount of received packets.

For the Elsa Airlancer MC11 card I could see that independant of 
the TX bitrate set via iwconfig the broadcast messages 
(sending to IP-address are sent out with the 
same bit rate. (I could never record more than around 1600kb/s
on the second node.)
If I have sent directly to the address of node 2 the transmission rate
could be increased according to the rate set with iwconfig.
(1600kb/s for 2Mb/s, 3200kb/s for 5Mb/s,...)

Could  this explain why I got different ranges for broadcast and unicast 
messages, because I had set the card to 11Mb/s but the broadcast 
messages were always transmitted with lower rate and therefore 
better coded?

With a netgear MA401 card the rates are the same for broadcast and unicast 
using the same driver.

Is it possible to influence this behaviour in the driver or is it a pure firmware 
or hardware problem for the ELSA cards?



> -----Original Message-----
> From:	Markus Jakob (EEI) 
> Sent:	Friday, January 04, 2002 5:05 PM
> To:	'wireless at'
> Subject:	range differencies
> Hi all,
> I try to get routing protocols on an adhoc network running, 
> using ELSA airlancer cards and the orinoco driver
> (kernel version 2.4.9, driver version 0.06f).
> I experienced that broadcast messages have 
> bigger ranges than unicast messages sent to a 
> particular IP and MAC address, e.g at certain distances
> between two nodes it is possible to receive a broadcast 
> messages from the other node but ping doesn't work 
> anymore between the nodes.
> Is this a normal behaviour or is it somehow possible 
> to influence it to get the same ranges for all types of 
> messages?
> Thanks 
> Markus

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