From: Lyman Hazelton <lrh@crl.com>
Date: Thu, 11 Aug 94 13:33:52 PDT
To: cypherpunks@toad.com
Subject: Re: Satellite Cellphones
In-Reply-To: <9408100627.AA17861@pig.jjm.com>
Message-ID: <Pine.3.87.9408111315.A417-0100000@crl.crl.com>
MIME-Version: 1.0
Content-Type: text/plain


On Wed, 10 Aug 1994, Dave Emery wrote:

> 	My understanding of both IRIDIUM and the Loral effort are that
> the satellite will be used to directly connect a remote user to a ground
> based MTSO (switch) which will actually route the call out over land
> lines or another satellite link.  This implies that the satellite is not
> being used as a classical bent-pipe repeater linking the transmitter of
> one satellite phone to the receiver of another, but rather as a space
> born cell-site linked to the MTSO via a separate radio system on a
> completely different frequency band not unlike the terrestrial microwave
> links that link most cell sites to the current MTSOs. 
> 
> 	This means that there is no way for a mobile satellite user to
> bypass the switch and use the satellite directly to relay his
> communications to another satellite phone, just as there is no way in
> the current analog AMPS/NAMPS cellphone system for a user on one
> cellphone to talk directly to another cellphone without going through a
> cell site relay and the MTSO switch.  Thus the switch can always serve
> as a gateway authenticating users, and providing billing and access
> control services.
> 							Dave Emery

  Your understanding of how IRIDIUM(r) will work is incorrect.  It most 
certainly WILL be the NORMAL operating mode for a subscriber unit (cell 
phone, if you will) to talk to another subscriber unit by only going 
through satellite links.  The caller will be authenticated via a "home" 
equivalent to the MTSO switch, but the call itself will NOT go through 
the switch (or any other) unless it is to a phone number which is not a 
subscriber unit. ONLY in that case will the call be routed through the 
MTSO equivalent.

  Your thoughts about caller authentication are correct.  I don't know if 
IRIDIUM is planning to do this correctly or not.
						Lyman

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