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

[Gabriel Rossetti]

Grant wrote:
>>>>> 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?
>>>
>> I still don't understand what you're asking.  Unless you're
>> 800MHz AMPS service, it's all digital.  There is no analog
>> signalling on the network.
>>
>> If you're using an 800MHz AMPS service, then the "voice"
>> channel is an analog FM link band-limited to 300-3KHz with C
>> message weighting (just like a landline phone connection).  You
>> can push an analog modem signal through that voice channel, but
>> the channel quality varies a lot and you need a really
>> bullet-proof error-correction scheme like MNP5.
>>
>
> What I'm trying to determine is, if AT&T or T-Mobile have the type of
> service you're describing:
>
> 1. will it work in both "analog" and "digital" service areas
> 2. does the phone need to support anything in particular to use it
>
>
>>> Are you saying it depends on whether or not the phone is
>>> capable of 800MHz AMPS service?
>>>
>> I guess so.  The carriers are going to shut down AMPS service
>> soon anyway.
>>
>>
>>>> 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?
>>>
>> If you're using analog service, you can use any carrier that
>> allows normal phone calls to access a dial-up modem.  You just
>> need a phone with a phone jack into which you can plug an
>> analog modem.  Motorol "bag" style phones used to have a
>> accessor that plugged between the handset and the radio which
>> provided a modem jack.  I don't think you're going to find too
>> many current phones that provide an analog modem jack.
>>
>
> I don't think I'll have any luck finding a cell phone with an analog
> modem jack.  Were you using an analog modem plugged into your cell
> phone with the service you were first describing?
>
>
>> Sprint also apparently has a free low-speed Internet access
>> service similar to Verizon's "QNC" service.  I don't know if
>> Sprint's free low-speed service allows you dial up a
>> landline-modem or not.
>>
>> FWIW, I just plugged my VX4400 into my laptop, and Verizons
>> low-speed QNC service is still working.  There are rumors
>> that Verizon is about to pull the plug on QNC, but those rumors
>> have been around for years.
>>
>
> I've got to go with GSM.  If both Sprint and Verizon offer it, there
> is probably a good chance that AT&T and/or T-Mobile do too.
>
Neither Sprint nor Verizon offer GSM, they use CDMA, thus you can't
travel anywhere (that I know of) with those phones. If you are looking
for a "world phone", get a quad-band GSM phone, Cingular/AT&T or
T-Mobile carries them in the US, in Europe everyone carries them.

-Gabriel
> - Grant
>

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