Subject: Scenarios: mobility

From: "Miguel Sanchez" <[email-masked]>
Date: Tue, 29 Sep 1998 09:56:40 -0000

Hi everybody,

As most of you, I've been reading with interest the recent article from CMU
researchers (it is shorter than the five author's names :-).

I really enjoyed it.

I only want to point out a fact that probably most of you have think about.
Mobility models are important to be agreed on if we want to be able to
compare simultation results (not only routing protocols).

In fact, physical and data-link layer offer a variety enough to change
results greatly.

Transport protocol, of course, also imposses some restrictions on wireless
links. BTW, I recomend you an article regarding TCP enhances to be used over
wireless links:

* H. Balakrishnan, V.N. Padmanabhan, S. Seshan, R. H. Katz "A Comparison of
Mechanisms for Improving TCP Performance over Wireless Links" IEEE/ACM
Transactions on networking Vol.5.NO.6 December 1997 Pags 756-769

Regarding to mobility, it is clear for me that the more randomness of
movement is, probably the worst case of motion to the routing protocols.
Therefore, in order to test a routing protocol behavior I would recomend a
random (may I say "pattern"?). The motion model of the CMU article is
similar to the movement of several shopping baskets inside a supermarket
(that's appreciation is mine, the authors may not agree). I think it is OK
due to its high randomness.

However, real world motion scenarios would not present, likely, an excessive
randomness but, more probably, a less caotic motion. This includes motion
restrictions due to the environment, power conservation issues (machine
motion may be expensive in battery comsupmtion), and, of course the
application level (the ultimate purpose of this device). On the other hand,
Autonomus systems (robots) would not exhibit the same kind of motion than
human held devices.

Putting all this short: A common motion model is needed. (I think a highly
random one for protocol stress testing and a second one, less random, for
performance measurements).

Regards,

Miguel Sanchez
Universidad Politecnica de Valencia (SPAIN)

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From: Bora Akyol <[email-masked]>
Date: 29 Sep 1998 09:42:02 -0400

There are a couple of mobility models. The one I am most familiar with
and is highly flexible is SUMATRA from Stanford university.

I believe the most relevant URL is
http://www-db.stanford.edu/pleiades/SUMATRA.html

Even though the Web page says it is connection oriented, the mobility
patterns can be used to model packet data users as well.

This model was developed by Derek Lam et al.

Bora

-- 
Bora Akyol, PhD
BBN Technologies
GTE Internetworking