Re: [gentoo-user] Re: Cell phone as modem

[Grant]

> >> Yes. My Verizon LG VX4400 works fine as a modem.  When plugged
> >> into a USB port, it shows up as /dev/ttyUSBn.  You can dial up
> >> any landline modem you like using "AT" commands, or you can
> >> dial up Verizon's internal ISP number.  The connection looks
> >> exactly like any other PPP connection via a serial modem.
> >> Verizon provides low-speed (14.4Kbps) internet access for
> >> "free" (doesn't cost you anything but normall calling
> >> minutes). The free low-speed access isn't officially
> >> supported: you won't find it listed in your contract. But,
> >> it's always worked for me when I've needed it (I haven't tried
> >> it for a few months, so YMMV). Higher speed access requires a
> >> data plan.
> >
> > Nice, I'm very glad to hear it works so well.  I guess
> > something like that would work even over an analog connection.
>
> On a true analog (800MHz AMPS service) cell phone, I've had
> pretty decent success using MNP5 modems up to about 2400 baud.
> The standard CCITT error dectection/correction schemes used on
> landline modems isn't resilient enough for RF links. Good luck
> finding MNP5 analog modems. ;) Multitech in St. Paul was the
> last vendor I knew about that sold them, and that was 10+ years
> ago.
>
> If you're talking about an analog connection to a digital
> phone, it just won't work. The Codecs that digital phones use
> are optimized for human speech and won't pass QPSK (or even
> FSK) modem signals in a usable manner.

What I meant there was that I should be able to dial up in this manner
even if the signal is reported to be analog instead of digital.  Is
that true?  Are you saying it depends on whether or not the phone is
capable of 800MHz AMPS service?

> >> AFAIK, most of the Verizon phones can work as modems.  At least
> >> that was true back when I was reading up on the subject (about
> >> 4-5 years ago).  AFAICT, all the other US carriers required you
> >> to pay for a data plan if you want to use your phone for
> >> tethered internet access.
> >
> > Unless you just dial another ISP right?
>
> I don't think so.  According to what information I could
> gather, I don't think the other carriers provide data
> connections to dial-up landline numbers without a data plan.
> I'm not sure they even provide that _with_ a data plan. If you
> find out otherwise, post a followup.  I'd be particularly
> interested in Sprint and QWest (which uses Sprint's network).
>
> The problem is that you can't send modem carrier over a digital
> cell phone.  The phone implements "AT" commands in order to
> pretend it's a modem for the convenience of user software.
> It's not, however, a modem at all.
>
> It's just passing on digital data that's carried by the
> wireless protocol in use (GSM/TDMA or 1xRTT/CDMA).  When you
> "dial up a landline" with a digital cell phone, the wireless
> carrier actually has to connect a modem to a landline at the
> carriers switch and dial the number.  The digital data from the
> cellphone is then routed to that modem.
>
> If you're using the wireless carrier as the ISP, then there are
> no modems involved at all: the digital data from the modem is
> simply routed onto the Internet.

I see.  So the only ways you know of to get a laptop online with a
cell phone are with a data plan in a digital service area, or with any
Verizon plan in either an analog or digital service area?

- Grant
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