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This video describes a device that
can capture the human figure through walls using RF signals.
We place our device behind a wall,
and it can see the silhouette of a person who
walks in an adjacent room.
The device works correctly even if the room
is completely closed.
For example, if a person stands behind the wall,
the device's output looks like this.
In particular, the output on the right
shows the background in navy blue
and the various human body parts in red, orange, and yellow.
Here, we can see the person's head, chest, arms, and feet.
How does this work?
The device operates by transmitting wireless signals
that traverse the wall, reflect off the human body,
and come back.
At every point in time, only a subset of human body parts
reflect the signal back to the device.
Here, we show the output of a device as the person walks.
At different points in time, different parts
of the human body reflect the signal,
and the device captures multiple snapshots
at various points in time.
It then combines the snapshots through a reconstruction
algorithm that allows the device to recover the human silhouette
through the wall.
Here, we can see the person's head, chest, arms, and feet.
The device can distinguish between different people
behind the wall.
So for example over here, we asked two different people
to stand behind the wall.
And this is the output of our device.
By training on different subjects,
we can use a classifier to distinguish between them.
The device can also distinguish between certain human postures.
If the person stands straight, the output looks like this.
Well, when someone stands in other postures,
the device's output reflects his postures.
The device can also track human limbs from behind the wall.
Here, we show a scenario where a person draws a shape in the air
and we show the output of our device to the right.
The device can trace the person's hand
with high accuracy.
We compared the device's output to that
of a Kinect placed directly in front of the person,
and show that connects up with red.
In comparison to Kinect, our immediate error
is around 2 centimeters.
For more information on how the device works,
check out our Project web page.