As standardized today, LTE does not have built in SMS capabilities. In a recent webinar on VOLGA (Voice over LTE via GAN), Franz Seiser of Deutsche Telekom (formerly T-Mobile International) argued that this might be a significant issue in the future for a number of reasons.
First, he said, there are a lot of systems in the network that rely on SMS such as SIM card provisioning, for updating the roaming operator list and other data on the SIM card for example, SMS subscription to activate/deactivate add-ons, etc.
Second is the EU mandated SMS user interaction while roaming. Introduced during the first wave of roaming regulation, operators are obliged to inform their subscribers by SMS about roaming costs when they start using a network abroad. In the future, notification to prevent "bill shock" (e.g. when using mobile data abroad) might also be based on SMS.
While the roaming tariff SMS announcements for voice and SMS are probably meaningless for LTE networks that do not support voice and SMS, the notification about bill shock might very well apply to LTE as well. Unless of course, the same tariff applies abroad like at home. Unlikely I would say…
So I quite agree with Franz, if a network allows VOLGA roaming in the future, the SMS solution already comes included at no extra price.
Another option is using SMS as part of the CS fallback (CSFB) feature that is already standardized. However, if the roaming country does not support CSFB and the mobile device is mostly data centric, then the SMS can't be delivered. While it's pretty obvious that a USB data dongle is a data centric device, I wonder what an iPhone or an N97 qualifies as.
And then there is SMS over IMS. However, I doubt we will see IMS and mobile IMS clients anytime soon.