Multiple SMS, or Concatenated SMS?

What are the pros & cons to be considered when you need to send more stuff than will fit into a sinlge SMS?


  • Might there be a tariff advantage to Concatenated SMS?
  • Is it any more or less likely that the complete Concatenated set will be delivered, as opposed to multiple individual messages?


Do you have an API to send concatenated SMS?
Concatenated SMS is better suited for mobile phones as it is read as a single large SMS.


But using multiple individual SMS would mean that I’d have to invent my own protocol to be able to re-assemble the data when it’s received!
So that would be a certain amount of wheel-reinvention - as Concatenated SMS already handles that!

Also, implementing my own protocol would mean using-up some of the payload space for the multi-message overhead. Does Concatenated SMS also eat into the payload?
(I haven’t got into that level of detail yet)

See above!

What a reason to discuss concatenated SMS if you don’t have API to send it?

You don’t need an API - you can code it “manually” from first principles!

Just as, of course, inventing one’s own proprietary scheme based on multiple SMS would require coding “manually” from first principles!

However, using something standards-based like concatenated SMS does increase the chance of finding an API…


It looks as though the format for concatenated SMS’s are handset dependent - which may not be an issue for you if you are sending between wavecom devices.

There is a wikipedia article on Concatenated SMS - briefly it looks as though the messages are sent in PDU mode, rather than text mode; and a few bytes are used as a user data header (UDH) at the begining of each message. There’s a couple of links at the bottom of the page…

Here’s a link to a message on decoding the UDH - and this message implies that Concatenated SMS messages are documented in GSM 0340.

I don’t know what the SMS tarifs are like where you are - but for me it’s far cheaper to shift the data (even small amounts of data) via GPRS. Of course, if you need to initiate a connection to a mobile device if you can’t get a routable IP for your device there are a few issues (which aren’t insurmountable).

However, the big issue for SMS is that they are not ‘time delivery guaranteed’ - my best personal experience with an SMS is over 4 days between sending and receiving - and have a look at the year 2010/2016 bug that popped up in some Windows Mobile based smartphones over the new-year period.

ciao, Dave

Yes, that’s my understanding.

I wasn’t sure if that used-up some of the “payload” space, or was independent of it.

It seems that it comes out of the “payload” - so there’s no advantage there over inventing one’s own scheme.

From other enquiries, it seems that the networks can’t distinguish concatenated SMS from any other SMS - so there is no cost advantage.

But the inquiry seemed to think that GPRS was either not available, or not usable in (all of) the target areas.

Tell me about it! :open_mouth:

In fact, delivery isn’t even guaranteed at all!


It’s my understanding that here in Oz, a concatenated SMS is sent as a number of single SMS’s and re-assembled by the receiver. This means that the network charges standard SMS rates for EACH SMS. Sending a couple of hundred bytes of data gets expensive, quickly.

Maybe you could look at using MMS rather than SMS. I believe that the data payload is greater (although MMS cost more than SMS) - and if you are wrapping your own protocol then you won’t need to worry about compatability with other operator handsets…

ciao, Dave

But doesn’t that rely on GPRS?


Apparently so - I’ve never used the MMS service so didn’t realise that :blush: .

Counts it out for your application, doesn’t it…

ciao, Dave

I used Wavecom MMS API. It is definitely based on GPRS. And even on HTTP protocol.

Sounds like there’s no real reason to use Concatenated SMS, then.

So I might as well just use multiple “normal” SMS.

As an update, in case anyone’s interested, the requirement went away - so I didn’t pursue this.

However, I have just spotted that Skype will automatically send a “Concatenated” SMS if you enter >160 characters for a message - so that could be useful for testing if I (or anyone else) ever needs to…