Hidden node question...

Jeff Meden blade
Tue Sep 16 07:39:30 PDT 2003

The 'hidden node issue' is something thats addressed by the nature of 
managed 802.11b.  When in managed mode, nodes cant send if they know 
someone else is talking (coordinated by the AP) and they have to CTS/RTS 
with the AP before they will start up with data.  Hostap's shortcoming 
is that it makes it difficult to tune the managed timing properly.  Ive 
yet to confirm that any of the advanced features like adjustable DTIM, 
RTS, and Frag levels actually work.  As a more forward thinking 
solution, the best bet is to size down the individual cells, either with 
sector antennas, or shorter, lower power ones.  This not only reduces 
the exponential contention issue (the problem youre probably seeing) but 
it allows more total bandwidth per customer.  Karlnet is a very nice 
product, but their oppressive licensing tactics forced our company away 
from them a long time ago, we had to almost double the TCO for our 
system after the hardware was bought, just to keep up with them.  Hope 
this helps!


Curtis V. Schleich wrote:

>Is there any way to determine if a problem I'm dealing with is related to
>the hidden node issue?  Any debug information or something that can help me
>identify a station or stations exhibiting this problem?
>I've had great service from HostAP, it is an incredible project.  Until the
>last few weeks, my WAN was running smoothly.   Now for the last few weeks
>I've had slow service and laggy ping times.  Is Karlnet my best answer if I
>am dealing with the hidden node issue?  I've also looked at frottle and
>WiCCP.  Anyone have strong opinions?
>Thanks for your time!
>Curtis V. Schleich,
>CCA and CCAonline,
>cvslist (at) ccaonline (dot) com
>HostAP mailing list
>HostAP at shmoo.com

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