Progress on the GSM network at FreeCalypso HQ

[Mychaela Falconia]

Das Signal wrote:

> Thank you for this update. Have you considered the use of an indoor
> directional antenna (such as a couple cheap yagis)? It could provide
> the necessary boost required to reach the meeting place you mention.

Thank you for the great idea!  I knew about directional antennas, but
my original line of thinking was to do the most with omnidirectional
first, i.e., deploy a combo of amplifier+omnidirectional first and see
how it performs, and then possibly go directional.  But thanks to your
suggestion, I now see that it would make more sense to try the
directional antenna approach first, before going for the amplifier -
if nothing else, for cost reasons: the amplifier would be a hefty
investment at $2600, whereas directional antennas are way more
affordable.

Onward to specific directional antenna types - here are two that I
found:

https://excel-wireless.com/product/1850-1990-mhz-yagi-antenna-17-dbi/
https://excel-wireless.com/product/1850-1990-mhz-grid-parabolic-antenna-20-dbi/

Yesterday I spoke to an RF engineer at my day job, and he told me that
the parabolic antenna would probably work better than the Yagi for my
application.  What do you think?

Note that if I go with any kind of "big" antenna (like either of the
above, as opposed to little antennas that screw directly onto SMA
connectors on the back of sysmoBTS 1002), I will have just one antenna
for both DL and UL.  I already have a Sysmocom cavity duplexer for PCS
band (the one they sell in their webshop, the indoor version with SMA
connectors), and I know that I will need to keep all 3 coax cables
(two between the BTS and the duplexer, and one between the duplexer
and the antenna) as short as possible.

Denver wrote:

> There are some carriers that will let you send SMS PDUs, if I understand what
> you mean.  Normally this is done via SMPP.  The carrier that we at JMP use
> (Bandwidth) has given us SMPP access, and we could setup a test environment
> for you if you're interested in seeing if it does what you want.

I am interested - but not right this moment.  Would it be possible to
revisit this discussion a little later - say, maybe a few weeks from
now?  There is some significant homework which I will need to do on my
own before I get back into all this SMPP etc discussion and test
setups:

1) In my worldview, voice calls come first and SMS is an addition to
voice telephony, not a replacement - voice first, SMS second, in this
order.  For this reason, I would like to get voice calls working
properly first, including outside connectivity, beyond just the minimal
internal-switch-only MNCC built into OsmoMSC.  Here the main homework
for me will be getting Asterisk installed and running on my Slackware
server (I decided to try Asterisk first, before others), getting it to
work with BulkVS SIP trunks (their service is so cheap that it will
cost me next-to-nothing to use them for this test bed, and I figure it
will be a good learning exercise even if I end up going with someone
else in the end), and then connecting my GSM network to this beast via
osmo-sip-connector.

2) Once I get voice calls working to my satisfaction and I am ready to
move on to SMS, I will start with some tests on the extant T-Mobile
GSM network, to see if SMS transfer from one T-Mobile GSM subscriber
line to another really is as transparent as I imagine, or not quite -
seeking a reference point here.

3) I will need to study the existing implementation of SMPP in OsmoMSC
(yay for FOSS with study-able source code!), to get a better idea of
how GSM-to-SMPP SMS interfacing has already been done by people with
more experience than me.

Only after I do all of the homework listed above, only then I will be
in the right shape to continue this SMS discussion on an intelligent
level, and only then I will be ready to accept your offer of a test
setup.

M~