Topics

ISP plans, VOIP and NTP/GPS

Gordon Haverland
 

I've been trying to pay my yearly ISP bill for a few weeks. Any time I
stop by, nobody is there. Today it got done.

The recommendations I had seen as far as "simple" VOIP to a small
business, is that the connection to the Internet should be a T1 link
(or better). Which is nominally 1.5 Mbps (I think). When I download
updates (like all the TeX packages), I see rates approaching 400 or
so. I thought it was 400 kbps, but talking to my ISP today it is
likely it is 400 kB/s (or 400 kBps).

Which is about twice a T1 link.

Most small business and house LANs are running on 100 Mbps or 1000
Mbps. The Ubiquiti Unifi Security Gateway (USG) I am going to be
installing, can do QOS on the basis of deep packet inspection. The UGS
will do most things at 1GbE (1000 kb/s on Ethernet), but it will not do
QOS with deep packet inspection at that speed. But, since my
connection to the Internet is only about 3 Mbps; I shouldn't have
problems.

I didn't know, but my ISP has a VOIP package, which works out to about
$25 per month. Something to keep in mind.

At some point, I hope to have a GPS chip meant for base station use
hooked up and working (and producing a 1 MHz precision pulser). The
biggest part of the GPS set up, is to produce corrections (the base
station isn't moving). And this could be computation intensive.

Another part of having a GPS base station, is that it becomes a Stratum
1 NTP source (because it is slaved to many atomic clocks in GPS
satellites). And so, I could adverise my LAN as a place to get NTP
from. It turns out, that the way my ISP is wired, all packets go to
Kelowna (or somewhere further south) before coming back up here. So,
there are going to be a lot of hops even for local people to get NTP
from my LAN. There are going to be a fair number of hops just within
my LAN (which includes the other end of the PTP at my ISP). And those
are probably going to be mostly deterministic (I seldom do thing on my
LAN which take up much bandwidth). And NTP can easily work with that.

The bounce to Kelowna and then bounce back to Dawson Creek is likely to
introduce the largest random delay. And it could be large enough that
people syncing to Dawson Creek would see no improvement over Vancouver,
Calgary (maybe Edmonton) and Fairbanks, Alaska. But for NTP to work, I
think you need to sync to at least 3 NTP servers.

Maybe my ISP's provider, is willing to put in a shortcut to keep NTP
from doing this long trip? They might want to charge for this, I was
wanting to provide this free of charge.


When I first got involved in GPS, differentials were what we were
using. If we put a "base" station over top of an Alberta survey marker
(at a known distance) and broadcast differential corrections (radio
modem at 9600 baud) we got distances to 20cm (this is mid 1990s with
Novatel GPS equipment). Later on, we started using differentials from
a ground station (in Kansas?) that got returned via geosynchronous
satellites. This was typically to 1.5m. Which was still better than
the 10m with no corrections.

I believe the hotrod R-Pi I want to use for GPS, will be able to do
RTKlib type corrections. Which should be quite a bit better than
20cm. How good corrections are, depends on how far away you are. For
the farm itself, no part is far away. A base station can also store
information to allow post-processing, which can usually improve
precisions.

Back in the mid 1990s, I suspect these corrections were broadcast in
plain text as regular RTCM (I think that is the term) messages. So,
anyone who was running GPS in the area could have used them.

I have not gone around trying to sell a service which doesn't exist
yet. But if at some point I can provide corrections (there are many
different kinds); I am not going to do so carte blanche. If a local
farmer wants corrections, they will either be free of charge, or nearly
so. If the oil patch or some commercial company wants corrections,
there will be a healthy charge. And if they want access to stored
phase information for post-processing, the charge will be more.

And I will probably inflate prices at significantly over the inflation
rate into the future. At some point I will be beyond what the market
will bear, and they will go away. What I hope is that by that time, I
can get a better radio tower put in a better place, to help more
farmers at zero or low cost.

But, in my plans is also to set up a lower power FM radio-station that
is all run by computer. For me, mostly written in Perl. Written in a
manner such that it mostly presents weather information, some news
snippets of a weather oriented nature (in a strange way) and public
domain music. For instance, at some point my program picks a
direction, and constructs the great circle around the Earth on that
bearing. Part of the "news" is to report on some things from locations
near that "great circle" (including weather information).

My inspiration in this, is "Wall Drug" of South Dakota. Which I do
not believe has any radio stations.


In terms of distributing corrections; they will be via VPN. If farmers
want access, they need to use a particular key to decode the data.
After that, it is free to them. I need to find a way to watermark the
data, to keep farmers from passing this on to others.

If farmers can save their raw GPS data, and I have phase information
stored; it is possible that they could post-process. I would like to
be able to do that for free, but I don't have enough experience on
post-processing to keep commercial outfits from taking advantage of
things.

--

Gord