[aprssig] Re: [ui-view] RE: APRS low-power-local ALT input channel>>144.34 ?
Robert Bruninga
bruninga at usna.edu
Sat Sep 25 13:35:01 EDT 2004
APRS on 144.99 if available for local coordination:
I think what many people may not understand about this
proposal is how an alt-channel is different than 144.39.
On 144.39 in a busy area, each DIGI hears the following:
1) A few packets per minute from a *few* Local users
2) 20 to 40 packets per minute from surrounding DIGIs
3) 40 to 20 seconds of DIGI QRM (distant digis that hold off TX)
4) Lots and LOTS of collisions with no successful throughput
On an alt-input channel, however, the listen-only digi hears:
1) A few packets per minute from a *few* local users
It doesnt take much to conclude that the *few* local users
are better off on the alternate channel, and furthermore, that
there is absolutely no difference in their ability to hear
each other for collision avoidance on one or the other. That
is only a function of their geometry, NOT of which channel
they are on.
It is a WIN-WIN situation all around. This splitting of ALOHA
users among multiple input channels has been the primary
improvement mechanism for ANY Aloha network since they
were first defined in the 1960's. It is fundamental to ALOHA
network design Its time for APRS to consider it...
de Wb4APR, Bob
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