[ns] Strange results in wireless3.tcl

[gmc50 <gmc50@student.canterbury.ac.nz>]

Hi,

I am trying to simulate a mobile node going from one cell to another and
I am getting some strange results. I am using Mobile IP with the
wireless3.tcl example in ns-2.1b7 with the following modification to the
position of FA:

FA at (x = 501.0, y = 2.0, z = 0.0): no space between cells since HA is
at (x = 1.0, y = 2.0, z = 0.0)

MH starts to move at 100.0s towards (640.0, 2.0, 0.0) at 2.67m/s.

I record the values of cwnd_ and current simulation time each 0.01s.
Since the default beacon period is 1.0s, I would expect that my cwnd_
would be reduced to 1 for approximately 1 to 2 seconds as the mobile
moves from HA to FA coverage areas.

Also, since the mobile always moves with the same speed, I would expect
the disconnection duration to be approximately the same, independently
of where within the HA coverage area my mobile starts its movement.

However, I am getting the following results as I start my mobile
movement from various places:

MH start point (x, y, z):   Period that Cwnd_ = 1 (s)
(2.0, 2.0, 0.0)    2.4

(25.0, 2.0, 0.0)    24.82

(50.0, 2.0, 0.0)    12.03

(75.0, 2.0, 0.0)    5.62

(100.0, 2.0, 0.0)   15.03

(125.0, 2.0, 0.0)   12.03

(150.0, 2.0, 0.0)   3.63

(175.0, 2.0, 0.0)   24.82

(200.0, 2.0, 0.0)   12.03

(225.0, 2.0, 0.0)   8.42

Does anybody have any idea as to why I get these widely varying and
rather long periods when cwnd_ = 1? Am I missing something?

Any ideas would be very appreciated. Thank you in advance,

Gustavo.