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<center>
<h1>Mobile Wireless Testbed Reference</h1>
</center>

<h2>Contents</h2>
<ul>
<li> <a href="#INTRO">Introduction</a>
<li> <a href="#HARDWARE">Hardware</a>
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<li> <a href="#BATTERY">Battery Life</a>
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<li> <a href="#VISION">Tracking Cameras</a>
<li> <a href="#NAVIGATION">Robot Navigation</a>
</ul>

<hr>

<ul>
<li> <a NAME="INTRO"></a>
     <h3>Introduction</h3>

The mobile wireless testbed integrates robots and motes into the standard
Emulab testbed.  If you want to know how to create experiments utilizing these
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resources, check out the detailed <a href="/tutorial/mobilewireless.php3">tutorial</a>.
This document you're reading is intended to (eventually) provide a more
in-depth description of what makes up this part of Emulab.
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<p>
<li> <a NAME="HARDWARE"></a>
     <h3>Hardware</h3>

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This one is small; it will grow large, but in a different location.
The hardware in the current mobile wireless testbed is:
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<ul>
<li>Four Acroname <a
href="http://www.acroname.com/garcia/garcia.html">Garcia</a> robots.
<li><a href="http://www.xbow.com/Products/XScale.htm">Intel Stargate</a> single
board computers for each robot.
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<li>Two statically-placed
<a href="http://www.xbow.com/Products/productsdetails.aspx?sid=90">E-Mote</a>
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Ethernet gateways for Berkeley Motes.
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<li><a href="http://www.xbow.com/Products/productsdetails.aspx?sid=72">Mica2 
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motes</a> with 900MHz radios attached to each stargate and E-Mote.
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<li>Four overhead cameras for <a href="#VISION">vision-based tracking</a> of the
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robots.
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<li>Two <a href="/webcam.php3">webcams</a> for viewing the robots in their
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habitat.
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<li>Habitat: open office area about 8 x 3.5 meters.
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</ul>

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<p>
<li> <a NAME="BATTERY"></a>
     <h3>Battery Life</h3>

We are still collecting data on the expected battery life for these robots, for
the moment though, you can expect about two and half to three hours of usage
before the batteries will need to be changed.

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<p>
<li> <a NAME="VISION"></a>
     <h3>Tracking Cameras</h3>

Tracking the robots in physical space is done by identifying colored circles on
top of each robot using four video cameras mounted overhead.  Because of the
reliance on visual tracking, the robots must stay within the cameras view of
the world.  The viewable area for each camera can be seen on the <a
href="/robotmap.php3">robot map</a> by selecting the "Show Tracking Camera
Bounds" display option.

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<p>
Currently the accuracy of the vision system with respect to the real world
coordinates is around 10cm, but is usually closer to 5cm.  We are working to
improve this wherever possible, but it may take some time.

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<p>
<li> <a NAME="NAVIGATION"></a>
     <h3>Robot Navigation</h3>

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Due to obstacles in the area and the size and maneuverability of the robots,
there are limitations on where the robots can go and how they can get there.
For example, the "tail" of the robot sticks out further from the center axis of
the wheels than its "head", so there needs to be a fair amount of clearance for
the robot to be able to pivot correctly.  Therefore, we enforce a 0.25 meter
exclusion zone around obstacles to ensure the robots can maneuver freely.
These exclusion zones can be seen on the <a href="/robotmap.php3">robot map</a>
by selecting the "Show Exclusion Zones" display option.
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</ul>