As well as the discussion about voice, re-use of existing circuit cores vs. IMS and so on, there was a fascinating comment by the speaker (from T-Mobile) about the "under the hood" use of SMS in mobile broadband dongles.
It's used for a wide range of functions - most visibly in enabling texts to be sent by the user from the operator dashboard connection sooftware. But beyond that, it's used for things like roaming notifications, internal configuration of roaming lists and other settings, and assorted others. There are apparently "many more than 10" systems at T-Mobile that rely on SMS in the context of a mobile broadband computing service - and which would need to be changed if SMS was not supported easily.
This all represents a huge issue for early releases of LTE-based mobile broadband. Despite the argument by 3GPP that "IMS will eventually get deployed, and phones will take a while to develop, so voice on LTE can wait a while", it seems likely that SMS will be needed from Day 1 .
In any case, I completely disagree with the 3GPP representative that every LTE network will inevitably feature an IMS back-end. If it becomes almost mandatory (and some of the "hooks" in the radio and EPC bits of the standard are heading that way), it's a good way to ensure that it won't get deployed universally. Many operators are implacably set against IMS, as it still has huge limitations. (For example: would an MVNO on an LTE network need its own IMS, or be forced to use wholesales apps via the host operator's IMS?)
There was also a comment from 3GPP that LTE could use CS-fallback for SMS. How that would work in the context of a 3G dongle and PC I'm not sure - presumably this would mean that an incoming text (or system message) would force the connection to degrade. Fine for an occasional message - but not for a teenager sending & recieving 200 SMS's per day from their laptop. Can you imagine any other type of broadband link having to drop speed each time an email or IM arrived?
I don't think VoLGA is perfect - once again, it will need extra software in the device protocol stacks. But given the complete abdication by the vendor and standards bodies in sorting out voice/SMS over LTE in timely fashion (ie 3 years ago), it's currently the best workaround I've seen. The fact that it's not even been included in 3GPP's release 9 workplan is ludicrous.
[Sidenote for the "voice on LTE can wait" believers: pretty much every laptop user connected via LTE, especially where it's used a fixed broadband substitute, will want some sort of voice capability. Right now, the only options are Skype or various Internet SIP alternatives. Are you really happy to give them an open goal?]
NEW Mobile Broadband Traffic Management Paper
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