Re: Connecting 2 Wifi Networks Via Cantenna

John Navas <spamfilter1@xxxxxxxxxxxxxx> hath wroth:

The rule of thumb used to be 10:1 (overselling bandwidth by 10x), but
all it takes is one bandwidth hog (e.g., file sharer) to invalidate
that.

Chuckle. I think you'll find that the satellite uplink path is far
more oversubscribed than just 10:1. If you want, I'll dig out the
number of transponders, their aggregate bandwidth, and divide it into
the number of satellite users (all of which have essentially full time
connections). Actually, I'm not familiar enough with the modulation
methods to make an accurate guess, but a ballpark guess might be
possible. DW has 260,000 subs
<http://www.isp-planet.com/research/rankings/usa.html>
scattered over who knows how many birds and transponders. Upload
bandwidth is 50Kbits/sec on a 6MHz wide transponder.

The number of transponders is a bit messy. See:
<http://www.dslreports.com/faq/2058>
I went to the PDF list of transponders and simply added up all the
bandwidth available on all "broadcast (downlink)" transponders. I get
1,784Gbits/sec download available on 11 birds.

If every customer started downloading simultaneously, each would get:
1.8Gbits/sec / 260,000 customers = 7Kbits/sec
which isn't going to work very well.

If every customer were guaranteed 500Kbits/sec, then the system could
theoretically handle:
1.8Gbits/sec / 0.5Mbits/sec = 3600 customers
which is also not very good.

The oversubscription rate would therefore be:
260,000 customers / 3600 customers = 72:1 oversubscription

I'm too lazy to do the upload numbers, but I suspect they're in the
same ballpark (or worse).

--
Jeff Liebermann jeffl@xxxxxxxxxxxxxxxxxxxxxx
150 Felker St #D http://www.LearnByDestroying.com
Santa Cruz CA 95060 http://802.11junk.com
Skype: JeffLiebermann AE6KS 831-336-2558
.