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From: motcid!linneweh@uunet.uu.net (Louis Linneweh)
Newsgroups: comp.dcom.telecom
Subject: Re: Answer Supervision on Cellular Roam Ports
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Date: 10 Jan 91 23:47:46 GMT
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X-Telecom-Digest: Volume 11, Issue 24, Message 2 of 9


forrette@cory.berkeley.edu (Steve Forrette) writes:

>automatically find me.  Someone has to dial into the roamer port, then
>enter my 10 digit number to reach me.  The problem is that if they are
>calling long distance, they must pay a toll charge for each attempt,
>whether or not I'm on the air, since the call supervises at the point
>the secondary dialtone is provided.

Some suppliers of cellular switches do allow the system operator to
configure the ROAM trunk group to delay answer supervision until the
called party (or the voice message system or the party to which the
call was transfered) answers.  However, if the call is delivered by an
Inter-Lata carrier, the carrier may not cut through the forward audio
path (from caller to called) until answer supervision is received as a
method of fraud prevention.  

This would prevent the End-to-End DTMF from being received by the
cellular system.  Therefore, the cellular operator must configure most
incoming trunk groups for immediate answer supervision since the
source of the call is normally not known.  When the cellular system
operator has a sufficiently sophisticated (read "large") operation,
they may be able to separate the incoming traffic on unique trunk
groups (such as with direct connections to the offending IC) so that
only those networks that require immediate answer supervision get it.

 From the carrier's point of view the caller reached the destination
that was requested (the ROAM port) and they feel justified in getting
paid.  Certainly, business arrangements could be reached between a
cellular operator and the carriers to avoid this problem if it was of
sufficient importance.

>Since cellular is provided through DID or some other method whereby
>the cellular switch appears as the "end office," why can't the
>supervision be done based on when the call is actually answered?  US
>Sprint manages to do precisely this with their FONcard system,
>overcoming any technical or legal hurdles.  You enter the called
>number and your FONcard number, all without supervision taking place.

Cellular service providers are at the wrong end of the connection,
i.e.  after the IC has done its thing, in the situation that causes
concern.  In the case of a FONcard, the cost of the call to the
carrier will be paid for by the carrier as soon as the carrier
connects.

>I guess part of the answer is that the people affected by this problem
>are not the cellular carrier's home customers, but only associates of
>roamers from other systems.  But whatever happened to just wanting to
>do it right for the sake of it?  It seems that especially cellular
>carriers are not apt to do anything that doesn't increase airtime
>revenues.

I'm sure something would be worked out if the cellular operator's
customers thought it was important enough to take their business
elsewhere.  The real "right thing" will only happen when the carrier
enters the process of finding the mobile (instead of being done when
the ROAM port is reached).