Advice on long distance wireless links?
Bruno Lopes F. Cabral
bruno at openline.com.br
Mon Sep 9 12:23:28 EST 2002
Hi there
I did a long distance point to point link here, 45km,
30dBs 1.5meters antennaes on both sides (105m high on
one side, 15m high on the other, no higher obstacles
between the points)
the Link Quality shows 19/92, Signal level: -87 dBm
Noise level:-99 dBm. auto bitrate states 1Mb, but
fixing it at 11Mb also seems to "work" (i.e. pinging
the other side works -- most of the time)
the performance is poor in any case, about 64K/192K
at best. lots of lost packets, very few or none DUP
packets
I dig a bit and found indicattions that long distance
links need increasing ACKs timeouts to prevent "multi-
path" retransmissions, but I could'nt find exactly what
I need to change or any further indications of how to
calculate the parameters involved, so I'm seeking for
advice of you fellows
do I need to increase/decrease one or more of the
following or other parameters? do you have any tables/
formulas indicating the ranges x the distances between
the points?
- Fragmentation threeshold
- Listen interval (or beacon interval)
- RTS threeshold
would be better to use ad-hoc mode instead of managed
mode in this setup?? I'm using linux on the stations,
tried orinoco (orinoco_cs/kernel 2.2) and prism2
(hostap_cs, kernel 2.4) cards (drivers)
any help/FAQ/pointers on this would be greatelly
appreciated :)
Cheers
!3runo
from Brazil
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