[MVMA] MVMA Omnis

[Moe]

The MVMA network was originally deployed as high-gain, omni-directional 
2.4 GHz nodes, mounted as high as possible, designed to neighbor with as 
many like omnis as far away as possible, in order to form a "mesh." 
Focused on the horizon, they have less downward radiation to reach the 
neighborhoods below them, especially as high as many were mounted--170 
to 220 feet. The more of these that were added and saw each other, and 
the more users tried to link to them, the lower the link quality became.

Directional nodes, such as airGrids and NanoStations, were employed to 
try to improve these degrading links between omnis. However, the network 
traffic did not use these better links. Because of the way the routing 
protocol works, traffic will take the lowest cost routes, based on ETX, 
regardless of quality. It won't take a slightly longer route even if 
it's higher quality. See the attached diagram.


We've been assigning these 2.4 GHz omnis different SSIDs to prevent them 
from neighboring. They will then no longer ignore the faster, 
higher-quality nodes and use their faster route.

That doesn't solve the problem of these high-gain, long-range omnis RF 
QRMing each other on the same channel, even far away omnis. We have no 
alternative ham-exclusive channel on 2.4 GHz. Our solutions are either 
to replace the high-gain omni antennas with lower-gain, down-tilts 
(expensive and labor-intensive)

OR... *be good hams and use no more power than is needed for 
"neighborhood" coverage.*  We've lowered transmit power on a number of 
MVMA nodes, the objective being to get their signal at other omnis below 
-90 dBm if possible, but as low as will maintain quality links in "the 
neighborhood" if not.

That may be hard to do with omni antennas chosen and installed to shoot 
over the heads of local users (the "neighborhood") and now QRM as many 
like others as far away as possible in this unique SSID scenario, but 
it's an effort we must make.

-- 
Moe
73 de AB8XA


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