Cell as analog modem?

Is it possible to get an adapter to go from a phone plug to a headset
adapter/plug for a cell and use it like a regular phone line modem? I
seem to remember hearing it wasn't for some reason, but I don't see why.
Is the freq. range to small on cells compared to landline?
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› See More: Cell as analog modem?

<[email protected]> wrote in message
news:[email protected]...
> Is it possible to get an adapter to go from a phone plug to a headset
> adapter/plug for a cell and use it like a regular phone line modem? I
> seem to remember hearing it wasn't for some reason, but I don't see why.
> Is the freq. range to small on cells compared to landline?
> --


You can use your cellular phone as a "regular" modem but what you need is
for your service provider to provision your account with CSD (Circuit
Switched Data). CSD basically turns your cellular connection into an analog
modem so you can dial up your ISP, for example, and make a connection. I am
not certain that all handsets support this feature but many do. You'll need
a way to connect the phone to a computer such as a cable or a Bluetooth
connection.

Good luck.

TC

[POSTED TO alt.cellular.cingular - REPLY ON USENET PLEASE]

In <[email protected]> on Sat, 15 Oct 2005 07:36:16
-0700, [email protected]lid wrote:

>Is it possible to get an adapter to go from a phone plug to a headset
>adapter/plug for a cell and use it like a regular phone line modem? I
>seem to remember hearing it wasn't for some reason, but I don't see why.
>Is the freq. range to small on cells compared to landline?

A GSM phone has no real dialup modem, just a sort of virtual modem which
makes a connection to a carrier's IWU (Inter Working Unit), located in some
service center. The IWU has the actual modem that can make analog data calls
and/or fax calls over the PSTN (public switched telephone network). If the
carrier doesn't provide an IWU, or if your account isn't provisioned for CSD
(Circuit Switched Data), then a GSM phone cannot make data and/or fax calls.
If your account is provisioned for CSD, then all you need is to install the
phone as a modem with Windows Dial-Up Networking.

A regular dialup modem cannot be made to work over a GSM voice channel because
of the audio compression used in the GSM voice channel.

--
Best regards, HELP FOR CINGULAR GSM & SONY ERICSSON PHONES:
John Navas <http://navasgrp.home.att.net/#Cingular>

[POSTED TO alt.cellular.gsm - REPLY ON USENET PLEASE]

In <[email protected]> on Sat, 15 Oct 2005 07:36:16
-0700, [email protected]lid wrote:

>Is it possible to get an adapter to go from a phone plug to a headset
>adapter/plug for a cell and use it like a regular phone line modem? I
>seem to remember hearing it wasn't for some reason, but I don't see why.
>Is the freq. range to small on cells compared to landline?

A GSM phone has no real dialup modem, just a sort of virtual modem which
makes a connection to a carrier's IWU (Inter Working Unit), located in some
service center. The IWU has the actual modem that can make analog data calls
and/or fax calls over the PSTN (public switched telephone network). If the
carrier doesn't provide an IWU, or if your account isn't provisioned for CSD
(Circuit Switched Data), then a GSM phone cannot make data and/or fax calls.
If your account is provisioned for CSD, then all you need is to install the
phone as a modem with Windows Dial-Up Networking.

A regular dialup modem cannot be made to work over a GSM voice channel because
of the audio compression used in the GSM voice channel.

--
Best regards, HELP FOR CINGULAR GSM & SONY ERICSSON PHONES:
John Navas <http://navasgrp.home.att.net/#Cingular>

<[email protected]> wrote in message
news:[email protected]...
> Is it possible to get an adapter to go from a phone plug to a headset
> adapter/plug for a cell and use it like a regular phone line modem? I
> seem to remember hearing it wasn't for some reason, but I don't see why.
> Is the freq. range to small on cells compared to landline?

Yes and no. You need to understand that a GSM phone has no analog signal and
will not pass analog modem tones. However, there is a GSM service called
"CSD" in which the phone acts like a modem to connect your computer over the
air to the network where there is a real modem that then will do the dial-up
(at 9600 baud). Your phone can carrier both have to support CSD and you may
have to subscribe to the option. CSD is fairly slow and most users prefer to
connect to the net via GPRS, which gives speeds about like a modern dial-up
connection.

--
Donald R. Newcomb
DRNewcomb (at) attglobal (dot) net

On Sun, 16 Oct 2005 08:03:51 -0500, "Donald Newcomb"
<[email protected]> wrote:

>
><[email protected]> wrote in message
>news:[email protected]...
>> Is it possible to get an adapter to go from a phone plug to a headset
>> adapter/plug for a cell and use it like a regular phone line modem? I
>> seem to remember hearing it wasn't for some reason, but I don't see why.
>> Is the freq. range to small on cells compared to landline?
>
>Yes and no. You need to understand that a GSM phone has no analog signal and
>will not pass analog modem tones. However, there is a GSM service called
>"CSD" in which the phone acts like a modem to connect your computer over the
>air to the network where there is a real modem that then will do the dial-up
>(at 9600 baud). Your phone can carrier both have to support CSD and you may
>have to subscribe to the option. CSD is fairly slow and most users prefer to
>connect to the net via GPRS, which gives speeds about like a modern dial-up
>connection.

CSD is a compromise solution to allow circuit-switched data over GSM.
However, it is definitely falling out of use with the widespread
deployment of GPRS, which is superior to CSD. Using any of the CSD
variants, the amount of timeslots used for carrying data stays the
same during the connection, which is a great waste of radio resources,
while GPRS dynamically allocates the timeslots for the data
connection, and also allows you to be "always connected" without being
more expensive. These days, all GSM handsets also support most GPRS
variants, and in practice all operators have support for GPRS.

CSD works if your operator supports it, but both performance and cost
means that it is probably no longer worth it. In principle, CSD can be
seen as working in a very similar way to how analog modems work, and
it can also support different data speeds depending on how many
timeslots are allocated to CSD (typically not very many in most
networks).

Data over the regular voice timeslots in GSM is impossible, since
voice is not carried over the air in the same way it is done in PSTN.
In PSTN, voice is carried over 64kbit/s PCM links, which is
transformed into different voice codecs over GSM (typically today
encoded to an "enhanced full-rate" 12.2kbit/s channel, which
conveniently fits into one GSM timeslot for each carrier) -- this
transformation really means that "voice codec filter parameters" are
sent over the air rather than the actual voice samples, and this codec
is very unsuitable for lossless data traffic. So, use GPRS/EDGE for
your data transfers (or even better, any 3G technology).

--
Joakim Persson
M.Sc student, CS/E @ LTH

Donald Newcomb wrote:
> Yes and no. You need to understand that a GSM phone has no analog signal and
> will not pass analog modem tones.

Or more specifically, it will pass along any analog siganl from the
headest jack like its supposed to, but the necessay analog modem tones
will get hacked to pieces by the compression in the phones voice circutry.

We tried it once LONG time ago with a 150 baud modem and it worked, but
prolly not now as there is so much more compression.

"DecTxCowboy" <[email protected]> wrote in message
news:[email protected]...
> Or more specifically, it will pass along any analog siganl from the
> headest jack like its supposed to, but the necessay analog modem tones
> will get hacked to pieces by the compression in the phones voice circutry.

I figured that the OP didn't need to know the details of how the GSM CODEC
works. But on Usenet whenever you simplify an explanation someone is sure to
step in an swamp you with the details.
--
Donald R. Newcomb
DRNewcomb (at) attglobal (dot) net

On Mon, 17 Oct 2005 22:42:57 GMT, DecTxCowboy
<[email protected]> wrote:

>Donald Newcomb wrote:
>> Yes and no. You need to understand that a GSM phone has no analog signal and
>> will not pass analog modem tones.
>
>Or more specifically, it will pass along any analog siganl from the
>headest jack like its supposed to, but the necessay analog modem tones
>will get hacked to pieces by the compression in the phones voice circutry.
It will pass the tones, and there is the bind. Information on analog
modem is carried by phase relationships rather than the tones
themselves. At 300 or 600 bits per second, you use Frequency Shift
Keying (FSK) , and there the information is conveyed by the tone, the
phase relationships carry no information. Go past 600 bits per
seconds, like 9600bps, and well, it is carried on one or more phase
modulated carriers, Phase Shift Keying (PSK)

(Yes, in addition to AM, and FM, there REALLY IS PM).

In human speech the phase relations carry no information. In any modem
more complex than FSK (read: faster than 1200 bits per second), the
data is all carried by phase modulating one or more carriers. The
failure to preserve the phase relationships in the GSM transmission
scheme means nothing to voice, but precludes phase modulated carriers
as a method of data transmission.
>
>We tried it once LONG time ago with a 150 baud modem and it worked, but
>prolly not now as there is so much more compression.

AS I pointed out, any of the FSK signaling schemes like Bell 103/113,
will work using the voice channel. None of the PSK signaling schemes
will work however.

Donald Newcomb wrote:
> "DecTxCowboy" <[email protected]> wrote in message
> news:[email protected]...
>
>>Or more specifically, it will pass along any analog siganl from the
>>headest jack like its supposed to, but the necessay analog modem tones
>>will get hacked to pieces by the compression in the phones voice circutry.
>
>
> I figured that the OP didn't need to know the details of how the GSM CODEC
> works. But on Usenet whenever you simplify an explanation someone is sure to
> step in an swamp you with the details.

I stepped in with a correction when you said that .. oh nevermind.