Subject: [manet] APEView Functionality of APE Testbed

From: "Siva Sivavakeesar" <[email-masked]>
Date: Wed, 16 May 2007 16:57:03 +0100

Hello there,

I am wondering whether somebody can shed me some light on how the
"APEView" functionality of APE testbed is implemented. I have been
involved with MANET testbed experiments, where I need to make sure
that in successive test runs participating nodes take the same
trajectories. This is important because I am comparing the
performances of two high-level routing protocols.

As far as I understood, the APEview makes use of some log files (e.g.,
RSSI measurement) to provide movement instructions to
test-participants during the actual testruns. My question is whether
this signal quality information is logged in real-time and it is
mearely this information being used for navigating purposes. In othere
words, what information is used to provide such movement instructions
to the users ? Please shed some light as much as possible.

Thanks in advance for taking your invaluable time to answer my question.

Best Regards,

Dr. Siva

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From: "Henrik Lundgren" <[email-masked]>
Date: Fri, 18 May 2007 13:09:12 +0200

Siva,

The APEview tool can display node/link information and position
nodes relative to each other based on the information you feed into it.
It can be done to replay testruns in terms of the information you
choose to provide to the tool. It can also be used in real-time as long
as you have implemented the means to provide the information to
the tool in real-time, for example, through a backhaul network.

However, the positioning of nodes in the APEview tool is not used
to drive movement instructions. Instead this movement choreography
is typicially based on pre-determined (carefully designed, timed, and
rehearsed) to provide the highest level of repeatability possible.
This movement choreography is provided in a separate global configuration
file in which the movement including timing is provided for each node.

hope this helps,

-- Henrik

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From: "Siva Sivavakeesar" <[email-masked]>
Date: Fri, 18 May 2007 12:31:48 +0100

Henrik,

Thanks - this is exactly what I wanted. From your mail, I can now
understand that the virtual-mobility functionality does not make use
of any data being logged in real-time to give instructions about
future movements. Initially, I was suspecting how can SNR information
be used to give such movement instructions. Despite this, this is
what, however, one of your README files (ape-testbed.tex) says:

"APE introduce a new mobility metric for real world tests called
``virtual mobility'' (vM), which is based on SNR changes in links
between nodes. SNR is mapped to a ``virtual distance'', then vM is
calculated as the changes in ``virtual distance'' between two
consecutive time intervals. vM is mainly used for two purposes: one is
to estimate the degree of similarity between two testruns (in a
mobility and movement sense, but also in a connectivity sense, since
vM is dependent on inter-node connectivity), and to provide a way to
evaluate how it affects other metrics, for example packet loss".

I am sure that VM is different from APEview - the latter being
responsible for displaying the instantaneous topological
configurations of nodes during each test run. Hence, it is reasonable
to expect that for the APEview to work, it needs to rely on SNR data
being logged in real-time. On the other hand, as far as I understood
from reading the APE documents, I have the impression that it is the
VM functionality that gives the users the movement instructions. If it
the case, it should not rely on any SNR inofmration - but the previous
paragraph says that it makes use of SNR - is this correct ? If you
have time, please clarify my ambiquity.

Thanks in advance for taking your invaluable time to answer my questions.

Best Regards,

Siva

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From: "Henrik Lundgren" <[email-masked]>
Date: Mon, 21 May 2007 11:33:54 +0200

Dear Siva,

see my comments inlined.

> what, however, one of your README files (ape-testbed.tex) says:

No, you have misinterpreted the text. There is nothing that
states that SNR is used to give movement instructions. The text
very briefly explains what the virtual mobility metric is, and that
you can use it when comparing the similarity between testruns
(in terms of "virtual" mobility, i.e., snr fluctucations, and
connectivity).

> evaluate how it affects other metrics, for example packet loss".

I hope it is clear now :)

> configurations of nodes during each test run. Hence, it is reasonable

vM is a metric, typically used when post-processing a testrun.
APEview is a graphical tool that displays node connectivity and the
distance between nodes is based on the quality of the links between
them (e.g., based on SNR).

> being logged in real-time. On the other hand, as far as I understood

As I have said in reply to one of your other recent emails, you can use
APEview either in real-time or you can use it to replay a scenario based
on stored log files. (to run it in real-time you must collect the needed
information and send it to APEview in real-time, typically through a
backhaul network).

> have time, please clarify my ambiquity.

No, neither vM nor SNR information is used to drive movement instructions!
The movement choreography is separate from this. See what I said in my
previous email (below):
<SNIP>
> > Instead this movement choreography
<SNIP>

I hope it is clear(er) for you now. If not, please download the source code and
have a look at the testrun configuration files and this will become
clear to you :)

I hope this helped,

Henrik

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From: "Siva Sivavakeesar" <[email-masked]>
Date: Mon, 21 May 2007 11:35:31 +0100

Henrik,

Thanks for making an effort to answer my questions.

Cheers

Siva