[asterisk-users] Asterisk as SMSC to GSM-Phones

[Anselm Martin Hoffmeister]

Am Mittwoch, den 27.02.2008, 16:30 +0100 schrieb Hans-Peter Straub:
> Hello all,
> 
> i today have searched on the internet about a solution to let asterisk act as 
> a SMSC (Short MessageServiceCentre) to deliver SMSes directly to GSM Phones. 
> I only have found some cases with use of an extern SMSC (i.e. by the Mobile 
> Net Provider)
> 
> Is there a possibillity to do that, or ist asterisk only able to send SMS to 
> analog phones?

Hi Hans-Peter,

the asterisk implementation of SMS means the landline type SMS. A short
message is sent to the phone by calling the number in question, giving a
certain caller ID. Phones will usually recognize several caller numbers
as SMSC, for example 0193010 in Germany. Whenever an apparent SMSC
calls, a landline phone will answer the line and have a short chitchat
in 1200 baud modem lingo, exchanging a recognise sequence, the data
per-se and some final status message.

Mobile phone SMS work in q completely different way. AFAIK (and I am
even less an expert there) SMS are sent in frames otherwise unused,
_not_ in the voice channel. I was told to imagine SMS transmission like
UDP packets on a carrier usually running TCP (voice channels), being a
by-product that the phone companuies earn a golden a** with.

Landline SMS service and mobile phone GSM SMS service are completely
different things. The seemless manner in which messages pass to and fro
is in reality a job for gateways that speak both protocols. Germans seem
to be lucky that it works across (nearly?) all fixed and mobile
networks; I remember reading somewhere that most countries have limited
interchange.

You could use one of those landline SMS gateways, call it and hand in
your text message. The downside of course is that you have to pay real
money for it, usually about 19c/message iirc.

An alternative for sending (lots of) SMS may be a web-based service. I
personally use a carrier that relays mails to SMS; mails sent to
mobilephonenumber at example.com with the message as mail subject and my
customer code in the mail body are relayed to a mobile phone. This works
quite well for my purposes; I cannot even tell you the name of the
provider because 'it just works', SMS are usually sent by a script so I
do not ever enter the domainname by hand :-) Depending on the
realiabilty and speed of transportation that you require prices may
vary; I think I pay about 4 cent per message (unreliable, but works 99%
in my experience) up to 9 cent (ultra reliable, less than 5 seconds
usually). I always use the cheap service - works for me.

Contact me off-list if you need a pointer there.

BR
Anselm (leaving for the local Linux User Group meeting :-)