atcomsystems.ca/forum Forums VOIP Phones & IP PBX VoIP & Cloud Phones, Hosted PBX, General IP Phones Analog modem over VoIP

To add to my post above, some modems with onboard controllers/DSPs:

Multitech Multimodems (I think all of them have onboard controllers and/or DSPs).

USR Courier Business (I've used the "V.Everything" model)

Hayes Optima (I think some of the Accura models are controller-based too)

Some of the old async Paradyne models, though they never made it to the latest standards.

If you don't want to pay $$$ for analog dial-up (though some of them work over 2 and 4 wire sync/leased lines as well) there's always ebay.

It really depends on the type of compression that the VoIP carrier is using. If they are using something like CELP (code excited linear prediction) for example it will pretty much destroy your data since a lot of codecs were designed around the principle of the majority of a conversation is silence. Nyquist's rule states that your sampling rate must be twice the highest frequency in your data in order to accurately reproduce it and compression codecs don't follow that.

Works great for voice because our ears are crappy in the great scheme of things, but data suffers because it is not comprised of mostly silence. There is a heck of a lot of difference between voice audio and a QAM stream.

If the VoIP carrier uses Mu-law (G.711) it's usually going to be alright because it follows Nyquist. That can be somewhat rare to find because it's a whole heck of a lot of bandwidth to use when they can usually squeeze a lot more on to their carrier groups with compression and with 99.99% of your usage being for voice they don't worry much about data (and faxes transmitting at slow speeds doesn't matter so much as long as they successfully transmit).

The other challenge is that most VoIP providers have a very, VERY limited understanding of voice which causes an uphill battle for most anything.

The problem is not with the standard, Modem-Over-IP has been in force since the turn of the millenium. It's with the fact that for most providers there is no pressing business reason to offer the service - the demand for this is just not there for most users (home or/and small business users). If the ISPs/CLECS do offer this, it is often sloppily implemented with inferior equipment, oversold nodes, non-specialist personnel (=bad configurations) etc.

The major, business-oriented providers, do offer Moip (V. 150.1) either a la carte or as part of their IP bundles, and they implement it properly to the point where it is transparent. Their customers usually have (still) big investments in dialup communications of all kinds (don't forget that the first application for end-user DSL was "always-on ISDN" - IDSL). The big boys' offerings ofcourse are considerably more expensive across the board.