Path: utzoo!attcan!uunet!virtech!cpcahil
From: cpcahil@virtech.uucp (Conor P. Cahill)
Newsgroups: comp.dcom.modems
Subject: Re: Modems with cellular telephones
Message-ID: <1990Oct27.123851.13301@virtech.uucp>
Date: 27 Oct 90 12:38:51 GMT
References: <9010262354.AA04244@alw.nih.gov>
Reply-To: cpcahil@virtech.UUCP (Conor P. Cahill)
Organization: Virtual Technologies Inc., Sterling VA
Lines: 36

In article <9010262354.AA04244@alw.nih.gov> RAF@CU.NIH.GOV ("Roger Fajman") writes:
>Some people here would like to use a laptop PC and modem with a celluar
>telephone for the purpose of giving demonstrations in various locations
>where a modular jack may not be available.  Can anyone recommend
>cellular telephones and adapters for this purpose?  We don't have a
>particular cellular telephone yet -- it would be purchased specifically
>for this.  The phone would be stationary, of course, while the
>demonstration is going on, but would be inside various buildings.

Just make sure that you get a telephone that transmits at the maximum
wattage (I think this is something like 3 watts).  Most hand-helds will
only transmit at .3 watts and this will have a hard time getting out 
of interior rooms of buildings.  The other thing you might want to 
get is a good antenna that can be plugged into the phone.

>A related question is how well various modem technologies work over
>cellular telephones.  We are mainly interested in v.22bis (2400 bps)
>and V.32 (9600 bps) so that so special modem would be needed at the
>other end.  Is it important to have MNP or V.42 error correction?

To work with cellular systems you have to have an extremely good error
correction algorithm that is hardened for very bad lines.  Telebit PEP
modems would probably do OK.  V.32 modems would probably die and drop
the line very often (this often happen on standard phone lines). V.22bis
would probably do OK.

For the error correction protocol, MNP-10 sounds like the one you 
need, but this is only available on Microcom modems at this time.
I don't know how well v.42 performs on bad lines, but MNP-7 and below
do not handle it very well. 


-- 
Conor P. Cahill            (703)430-9247        Virtual Technologies, Inc.,
uunet!virtech!cpcahil                           46030 Manekin Plaza, Suite 160
                                                Sterling, VA 22170