Path: utzoo!attcan!uunet!aplcen!samsung!cs.utexas.edu!mailrus!accuvax.nwu.edu!nucsrl!telecom-request
From: covert@covert.enet.dec.com (John R. Covert  12-Jun-1990 0939)
Newsgroups: comp.dcom.telecom
Subject: Re: Two Cellular Phones, Same Number
Message-ID: <8916@accuvax.nwu.edu>
Date: 12 Jun 90 13:45:31 GMT
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X-Telecom-Digest: Volume 10, Issue 431, Message 1 of 11


>What I envision is a smart-card that contains your ESN, phone number, ...

For those of you who have read the description of the German C-Netz
system which I translated and posted to the Digest a year ago, this is
already known.  That system provides exactly what you're suggesting.

Unfortunately, the AMPS protocol can't do what it really takes to make
this secure.  The German system has two serial numbers -- one for the
smart card and one for the phone itself.  If either the phone or the
card is stolen, it can be blocked from making further calls.

With the single ESN built into the AMPS protocol, if the smart card
contained the ESN, a stolen phone would have full market value.  If
the phone contained the ESN, you would have to change your phone
number (and never reuse it, using up numbers permanently) if the card
were lost, stolen, or damaged.

Since the U.S. seems to be firmly wedded to the AMPS protocol, so much
so that we'll not be adopting the CCITT standard Group Special Mobile,
which would have allowed U.S. <-> Europe roaming, you won't see any
changes that would require protocol changes.

But _hopefully_ our system will continue to get cheaper, both in the
cost of phones, calls, and cell-site construction, such that smaller
and smaller pocket portables can be expected to operate well enough
that the smart-card idea won't ever be necessary.  Why have a heavy 3
Watt phone when there's always a cell close enough to reach it with
600 mW or less?


/john