[aprssig] Balloon Paths again and again...

Robert Bruninga bruninga at usna.edu
Wed Mar 26 16:18:24 EDT 2008

>>  For BALOONS!
>>  1) Use a path of WIDE2-2.
>>  2) Never use WIDE1-1.
> Blanket statements are always wrong.

But usually involve a lot of thought and are right in most
> We typically fly into rugged terrain and 
> sparsely populated areas.  If it happens 
> that a WIDE1-1 fill-in digi is the only 
> thing in the area, I want to make
> sure that it will digipeat that packet.

Yes, but at what cost?  The cost benefit ratio is very high, on
the order of 1600 to 1.  See the reasoning:

1) FINDU shows only about 30 WIDE1-1 digis in the USA
2) Most of these are not in "rugged terrain"
3) Most WIDE1-1 digis are at home altitudes
4) Coverage area of most WIDE1-1's is less than 10% of a WIDEn-N
5) Cost benefit ratio is extremely high cost, very low benefit.

Assuming a typical WIDE1-1 maybe say 40' high and most decent
WIDEn-N's have HAAT's more than say 160' above average terrain,
then the area coverage ratio of the WIDE1-1 is less than about
8% of the WIDEn-N.  And since there are only 2% as many
WIDE1-1's as WIDEn-N, then the probability of falling into a
WIDE1-1 area is on the order of 0.0016.  Even worse in rugged
terrain.  Combining these probabilities gives us the "benefit"
side of the equation.

Now the "cost" side of the equation is a 100% probablity of
bringing up every WIDE1-1 in say 4 to 20 surrouding states.  Now
WIDE1-1's are particlualrly bad because they do not do DUPE
elimination and when they transmit a packet, the surrounding
WIDEN-N's also do NOT recognize the packet as a DUPE.
Therefore, not only is the balloon bringing up every WIDE1-1 in
an entire multi-state area, but it is also generating N dupes
for EVERY N WIDE1-1,s that it hits, at EVERY WIDEn-N digi that
hears them!  

So, instead of WIDE2-2, which causes each WIDEn-N to transmit
each balloon packet once and ONLY ONCE, the WIDE1-1,WIDE2-1 path
guarantees every digi in the entire area is digipeating EVERY
packet dupe MULTIPLE times.  Even at a minimum, lets just say
there is only one WIDE1-1 in the vicinity of each WIDEn-N in the
country.  By using the WIDE1-1 at altitude, the ballooon
therefore DOUBLEs the load on the entire network.  SO the COST
factor is 200%. 

Computing the COST/BENEFIT ratio to the network is 200%/.16% or
about 1600 to one.  Quite an impact on everyone for such a small
probability of benefit to the balloon.

> smart trackers can change profiles based on a
> variety of factors, including altitude.  We 
> fly opentracker family devices, with a typical 
> (for this area) mobile path of WIDE1-1,WIDE2-2
> or 1-1,2-1 until we get to altitude, where we 
> switch to direct-only.

Agreed, smart devices are very valuable.

Remember, I am not arguing against your chosen path.  I always
defend the originator of any packet to use the packet he thinks
best for his situation.

I am just spelling out the complete rationale as to why WIDE1-1
is so bad anywhere except in the close range neighborhood of a
single fill-in WIDE1-1 on the ground...


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