mesh link experience
David Rowe
Over the past few days I have been working with some local guys (Mathew,
John, and Chris) on setting up a local mesh network using MP01s. Today
we installed a MP01 on the chimney of John & Chris's place. We have it
sort of connected to the mesh at my house, about 500m away. We don't
have line of sight or a free Fresnel zone, some trees and roofs in the
way.
"iwlist ath0 scan" shows about 15 APs at either end.
A few data points:
1/ Ping tests showed that larger packets can't get thru:
sudo ping 10.130.1.56 -c 1000 -i 0.01 -q -s 1400
1000 packets transmitted, 3 received, 99% packet loss, time 15988ms
but small ones are ok:
sudo ping 10.130.1.56 -c 1000 -i 0.01 -q
1000 packets transmitted, 956 received, +1 duplicates, 4% packet loss,
I used a full function ping from my laptop, routed to the mesh
network.
2/ Phone call quality is fair. Usable but lots of packet loss. John
sounded like a "Dalek" for those of you familiar with Dr. Who.
3/ The signal strengths are low-ish and not quite symmetrical:
on 10.130.1.36:
# wlanconfig ath0 list
ADDR AID CHAN RATE RSSI DBM
00:09:45:57:a7:d0 0 10 36M 11 -84
on 10.130.1.36:
# wlanconfig ath0 list
ADDR AID CHAN RATE RSSI DBM
00:09:45:56:ac:90 0 10 36M 7 -88
The rate is reported incorrectly by wlanconfig, you can check rate
information here:
# cat /proc/net/madwifi/ath0/rate_info
4/ The batman scores jump about in the range 0 to 230 , occasionally the
link gets completely nailed and nothing can get thru. The whole link
seems to vary over time. Packet loss numbers from ping vary from a few
% to 30%.
5/ We found we could get ssh between MPs to work reliably if we reduced
the MTU:
# ifconfig ath0 mtu 200
Otherwise ssh would freeze all of the time.
6/ I experimented with /proc/sys/dev/wifi0/rxantenna and found:
rxantenna 0 & 1: external antenna (N-type rubber antenna for betas)
rxantenna 2....: PCB diversity antenna
Probably best to stick with 1 for outdoor applications.
Cheers,
David
elektra
> 5/ We found we could get ssh between MPs to work reliably if we reduced
> the MTU:
>
> # ifconfig ath0 mtu 200
>
> Otherwise ssh would freeze all of the time.
this indicates clearly that the link way on a very tight budget! If you can
still make phone calls it is amazing. You might also try to use the
fragmentation feature of Madwifi:
iwconfig ath0 frag 256
Fragmentation was broken for a long time, but is working since the last Madwifi
update in the VT firmware.
Cheers,
Elektra