Subject: Re: [MOBILE-IP] Applicability of IP Mobility to CDMA Soft Handoff

From: James Kempf <[email-masked]>
Date: Thu, 4 May 2000 16:03:50 -0700

Andras,

Thanx for the long email.

>James: Do you think that IP is still a non-feasible solution,
>if we consider that even the curcuit switched model may be
>redesigned based on IP principles?
>
>

These are my own opinions, my co-authors may have others.

The design of the CDMA RAN has little or nothing to do with circuit
switched/non-circuit switched. I don't claim to be a radio engineer, but
those I've talked to claim it is primarily governed by the physics
of radio propagation to a mobile terminal over a larger area, and how best to
maintain signal quality given that. Therefore, I think moving
to an overall packet-switched solution will have little effect. In
fact, if you look at the 3GPP UTRAN network architecture, the design
calls for ATM w. AAL5 for signalling and AAL2 for voice in the RAN.
ATM is already packet (well, cell) switched. There is a potential opportunity
for replacing ATM with IP, provided the stringent timing and jitter
constraints can be met, but I don't think that existing IP mobility solutions
will have a role to play in CDMA RAN networks for soft handoff purposes.
There is a remote possibility that new routing algorithms could
change this situation, though none of the proposals I've seen so
far are look very convincing.

That said, I agree with Amanda's comments that other solutions are
possible, though they have some significant competition in CDMA, based, as
it is, on the physics of radio propagation.

                jak

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From: Arthur Ross <[email-masked]>
Date: Thu, 4 May 2000 16:28:33 -0700

>it is, on the physics of radio propagation.
Indeed, the solutions are very much dependent on that ugly mobile radio
propagation environment - "multipath" propagation, which may or may not be
characterizable as "fading" depending on the physical circumstances and
bandwidth of the signal, and many tens of dB variation in path loss.

But, that said, I think there ARE alternative solutions. Whether they are
"optimal" in any sense will depend very much on the nature, distribution,
mobility, and intensity of the traffic ... to say nothing of the
business/service model. IP packets for non-speech applications may have
VERY different statistics and QoS requirements than speech. The existing
standards, which are nicely fine-tuned for speech, may not be so optimal if
the traffic is bursty, intermittent, and very asymmetric.

   -- A

   Dr. Arthur H. M. Ross
   2325 East Orangewood Avenue
   Phoenix, AZ 85020-4730
   Tel: 602-371-9708
   Fax: 602-336-7074
   Portable (CDMA, of course!): 602-677-1021

---

From: Andras Veres <[email-masked]>
Date: Fri, 5 May 2000 10:41:51 -0500

James,

> will have a role to play in CDMA RAN networks for soft handoff purposes.

You claim that IP is not able to guarantee delay and jitter
requirements, while ATM is able to do it. This is not proven. If this
is the central point of the draft, you will have to back it with data,
otherwise we are not on solid ground. Personally I would be very
interested in arguments in favor of ATM regarding QoS guarantees, and
for a complete and satifying draft, you should probably consider
extending the draft in this direction.

If it is not QoS which differentiates an ATM based RAN and an IP based
RAN, then it the mobility protocol which is used. I think THIS FITS
the charter of this WG, and we should focus on whether MIP and
the micomobility proposals (CIP, RMIP, HAWAII) are able to support
the needs of ANY radio technology. The MIP in its current form
is not able to "penetrate" the WCDMA RAN, it has to stop at the
edges.

Regards,
Andras

--
Andras Veres

http://comet.ctr.columbia.edu/~veres
Columbia University
Dept. of Electrical Engineering mc 4712
500 West 120th Street, H1
New York, NY 10027

Office phone:   (212) 854-3117
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