Subject: [manet] Paper announcement

From: "Boleng, Jeffrey L. MAJ" <[email-masked]>
Date: Wed, 4 Jun 2003 19:09:59 +0900

CLASSIFICATION: UNCLASSIFIED

The following paper has been submitted and is available at:
http://toilers.mines.edu/papers/pdf/stationary.pdf

Other papers by our research group are also available at:
http://toilers.mines.edu/papers/

Stationary Distributions for the
Random Waypoint Mobility Model?
William Navidi and Tracy Camp
Department of Mathematical and Computer Sciences
Colorado School of Mines
Golden, Colorado 80401
[email-masked]; [email-masked]
April 12th, 2002
Abstract
In simulations of mobile ad hoc networks, the probability distribution
governing the movement
of the nodes typically varies over time, and converges to a "steady-state"
distribution,
known in the probability literature as the stationary distribution. Some
published simulation
results ignore this initialization discrepancy. For those results that
attempt to account for this
discrepancy, the practice is to discard an initial sequence of observations
from a simulation
in the hope that the remaining values will closely represent the stationary
distribution. This
approach is inefficient and not always reliable. However, if the initial
locations and speeds of
the nodes are chosen from the stationary distribution, convergence is
immediate and no data
need be discarded. We derive the stationary distributions for location,
speed, and pause time
for the random waypoint mobility model. We then show how to implement the
random waypoint
mobility model in order to construct more efficient and reliable simulations
for mobile
ad hoc networks. Simulation results, which verify the correctness of our
method, are included.
In addition, implementation of our method for the NS-2 simulator is
available.

Classification: UNCLASSIFIED

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From: "Tao Lin" <[email-masked]>
Date: Wed, 4 Jun 2003 07:32:52 -0400

William Navidi  and Tracy Camp,

You did a nice job in studying the stationary property of Random Waypoint
model using simulations.

Besides what are studied in your paper, we think another property, link
connectivity changes (link lifetime or link change rate) is also very
important.  Because link connectivity changes are among the fundamental
reasons that cause MANET topology changes and, thus, MANET protocols'
operations, we believe that this kind of study is also very important for
MANET simulations.

We published a paper discussing a simulation study of stationary property of
link stability in Random Waypoint model:

Tao Lin and Scott F. Midkiff, "Mobility Versus Link Stability in Simulation
of Mobile Ad Hoc Networks," in Proceedings of the Communication Networks and
Distributed Systems Modeling and Simulation Conference (CNDS), pp. 3-8, Jan.
2003, Orlando, FL, USA.

We found that at least with the parameters we tested, the warm up time for
link stability is VERY long for the Random Waypoint model, which is usually
much longer than the warm up time and simulation time used in many previous
papers.  Therefore, either we should choose a long enough warm up time or we
should revise/choose the mobility model properly in our simulations.  Hope
this helps.

Thanks,

  Tao Lin
  Ph. D. Candidate
  Laboratory for Advanced Network (LAN)
  ECE Dept.
  Virginia Tech

---

From: bjkwak <[email-masked]>
Date: Wed, 04 Jun 2003 15:37:03 -0400

Hi!

Thank you for the links to the papers.  I haven't read them yet,
but sounds very interesting.

We also have an interesting paper on mobility measure for MANET,
which will appear in IEEE Communications Letters:

http://www.antd.nist.gov/wctg/manet/kwak_CL2003-0133.ps

As Tao pointed out, the link connectivity change is very important
and significantly affects the performance of routing algorithms.
In the performance studies of routing protocols, Random Waypoint 
(RWP) model seems to be one of the more popular mobility models 
used in computer simulations.  One of the reasons for its
popularity is because RWP model is used in many previous studies
available and thus it apeals more to the audience.  However,
RWP model has some weaknesses, including the long warm up time,
and it would be better if the routing protocols are tested
using diverse mobility models.  In our paper, we remedies the 
current situation by providing a mobility measure which can 
standardize different mobility models.  I hope you find it
helpful.

Regards,
Byung-Jae Kwak

Advanced Network Technologies Division
NIST, MD USA

-- 
"Never be afraid to sit awhile and think." -- Lorraine Hansberry
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