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cdcox parent
Could you achieve a more high throughput version over voice? I wonder, after compression what the data rate ends up being. I'm reading gzip can get 2:1-4:1 with text. So about a kb/s?
bcohen5055
I may be wrong but aren't we going backwards here... data over voice=dialup right? 56kb/s ideal? Still possibly useful but this just reminds me of the wep browser days on my old nokia
vidarh
56kbps over landlines. That works because the landline network, when it is trunked, is compressed into 56kbps or 64kbps channels using methods the 56kbps modems were explicitly designed to take maximal advantage of.

Over a cell phone connection you will get much less. GSM data modems gets to bypass the voice codec, and are still limited to 9600 bps. An acoustic modem over a GSM connection will get less than that, if it will connect at all: A full data rate GSM code is compressing the audio down to about 12.2kbps using codecs geared towards reproducing voice as well as possible, which is going to be brutal to a regular modem and far more wasteful than GSM data.

icebraining
data over voice=dialup

Yeap, except voice is now carried over a digital channel, so it'd be digital-over-voice-over-digital :)

anubiann00b
It's unfortunately pretty slow. I mean, when you factor in the overhead for text messages, it adds up. We haven't tested it enough but it definitely won't match 4g. We also are planning to switch to a better compression algorithm.
vidarh
It won't even match GPRS.

I'm guesstimating you'll find an upper bound, assuming "friendly" telcos that don't start rate limiting, or dropping SMSs, at no more than about 6kbps. Quite likely less.

GSM data (which is normally possible anywhere where you can get a GSM voice connection) is 9600bps and uses the full, raw GSM data/voice channel. You'd not be able to exceed the channel bandwidth. Then you have the SMS overhead. And you're unlikely to manage to max out the channel.

virjog
May I suggest Pied Piper?
vertex-four
> Could you achieve a more high throughput version over voice?

The issue is that it quickly ends up costing about the same amount as a data connection would in the first place.

rikkus
Except that many contracts now have 'unlimited' voice minutes.

Unfortunately, voice calling uses lossy compression, so your data rate would be somewhat limited as you struggle to be 'heard' over that.

kalleboo
Before this fancy GPRS thing, we used to have something called CSD (circuit-switched data), where your phone could use a raw GSM voice circuit to send data instead of digital audio.

I think we lost that feature in the transition to 3G.

vidarh
GSM data still only gave you 9600bps, though.
kalleboo
The later versions let you bundle multiple channels (at n times the cost) to reach 57 kbps http://en.wikipedia.org/wiki/High-Speed_Circuit-Switched_Dat...
nknighthb
Has anyone tried transmitting a QPSK-125 signal over a cell phone call? I wouldn't be surprised if it worked.

That by itself could get you up to about 0.5kbps for text with decent compression, with no other effort.

marvy
that's what error correcting codes are for :) If you design things to play nicely with the compression algorithm that's used by trying to stay within normal human vocal range and stuff, might be okay.
cdcox OP
True, but if you were somewhere where data was unavailable or you didn't want to use a local data connection, it might be a nice way to force a map app to update to your current location, get an email, send your location to somebody, or answer a chat message.

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