Wireless vision is a device which operates wirelessly and captures the moving objects behind the wall. WiFi or Wireless Fidelity signals are information carriers between a transmitter and a receiver. Through Wireless Vision, WiFi can be extended to our senses thereby allowing visualizing moving objects through closed doors and walls. These signals are helpful in identifying the people number and their locations while they are in a closed room. It can also help in identifying gestures behind the wall and also it combines gestures to communicate the messages to the wireless receiver without carrying any transmitting device.

1. WI-VI TECHNOLOGY
PRESENTED BY,
ALAN SHIJO
180021098213

2. WHAT IS WI-VI ?
• WI-Vi is one of the most modern technology which
modifies the Wi-Fi technology to make the concept of
wireless vision possible.
• The main logic or idea is the tracking and manipulation of
reflected Wi-Fi signals.
• It can hence be called as an adaption of sonar or radar.

3. HISTORY
• Developed by Professor Dina Katabi and her graduate student Fadel
Adib.
• Developed in science and AI laboratory of MIT by the faculty and
student of electrical engineering and computer science
department.

4. WHAT WI-VI CAN DO ?
• Detect the Number of Moving Humans in a Closed Room
Wi-Vi allows us to detect presence of a moving human in a closed room. It can also determine
with high accuracy up to multiple moving objects.
• Enable Communication through a Wall without Carrying a Wireless Device:
Wi-Vi is both a transmitter and a receiver. A human can communicate with it using simple
gestures without carrying or wearing any wireless device.
• Identify Simple Gestures from Behind a Wall:
Wi-Vi can detect very simple gestures made through a wall, making it the first through-wall
gesture-based interface.

5. KEY IDEA

6. OLD v/s NEW
• An array of special antennas are required in earlier technology to
map over obstacles.
• Each of them capture the signals for mapping.
• Hence it becomes more expensive.
• Wi-Vi uses simpler device receiver.

7. PRINCIPLE
• Doppler effect is used in Wi-Vi similar to SONAR and RADAR.
• But less frequency is used compared to above two.
• Doppler effect :- an increase (or decrease) in the frequency of sound,
light or other waves as the source and observer move towards (or
away from) each other.
• Depends on its own transmitted signal.

8. WORKING
• Two antennas transmit identical signals where the second antenna
signal is the inverse if the first.
• This causes interference for imaging.
• Wi-Vi relies on a simple 2.4 GHz Wi-Fi hardware radio.
• Simply this can be decoded on handheld devices.

9. • During the motion of the target, the distance of it changes with
respect to receiver.
• It changes the time that reflected signal takes to get back to
receiver.
• Only those reflections that changes between the two signals such
as those from the moving object arrive back at the receiver.

10. For example, here all the signals from other obstacles are
cancelled out and the only target is moving human.

11. Tracking reflections
• Reflection from human behaves like it is the source.
• Antennas are used to trace a radio frequency source.
• We can find the direction of the signal movement by steering the
beam of antennas.
• Finally using this method, when the person moves, the change in
direction can be tracked.

13. Extend of resolution
• It delivers a basic perspective of the moving object.
• Simple gestures can be traced using Wi-Fi.
• The imaging clarity grades lower to that of a camera quality due to
RF signals used rather than direct light.

14. Challenges faced in designing Wi-Vi
• Due to the obstructions and intermediate object it is essential to
generate more sharper output rays.
• The major challenges faced are:
1) Flash effect 2) Identifying and tracking humans

15. Flash effect
• In this technology, the most challenging part is the reflections for
the wall itself rather than reflections from the object. Due to
reflection off the wall, minute variations coming through the
object are prevented from being tracked. This behaviour is
known as flash effect.
• To cancel both wall reflections and direct signal from
transmitting and receiving antenna, Wi-Vi uses interference
nulling.
• This increases the sensitivity of the reflections.
• Multi Input Multi Output (MIMO) antennas are used to nullify
the flash effect.

16. Nullification
• Wi-Vi, however, avoids using an antenna array for two reasons:
 In order to achieve a good resolution, one needs a large antenna array
with many antenna elements. This would result in a bulky and
expensive device.
 Since Wi-Vi eliminates the flash effect using MIMO nulling, adding
multiple receive antennas would require nulling the signal at each of
them. This would require adding more transmit antenna, thereby
enabling the Wi-Vi to capture the reflections from objects.
• To eliminate the flash effect we have to remove reflected signal
received from stationary objects both in front off and behind the wall
and direct signals from transmitting antenna to receiving antenna.

17. • Wi-vi’s uses nulling algorithm which provides a 42dB mean reduction in signal power
which is enough to remove the flash effect.
• Nulling can be performed in the presence of objects moving behind the wall and front of the
wall.
• Nulling involves steps:
 Initial nulling
Initial output signals are nullified.
 Power nulling
MIMO radars and antennas boost the power of signal to increase the sharpness.
 Iterative nulling
Nulling is done continuously on final signals.

18. Transmit
Antennas
αx
x
ELIMINATING THE WALL’S REFLECTION
Receive Antenna:

19. y = h1 x + h2αx
0
Receive Antenna:
h2
h1
αx
x
ELIMINATING THE WALL’S REFLECTION

20. ELIMINATING ALL STATIC REFLECTIONS
y = h1 x + h2αx
0
People move, therefore their
channels change
y = h1
’ x + h2
’(- h1/ h2)x
Not Zero
h2
h1
αx
x
y = h1 x + h2(- h1/ h2)x
Static objects (wall, furniture, etc.)
have constant channels

21. TRACK HUMAN MOVEMENTS
• Reflections include every objects behind the wall.
• But it is possible to clear out the human reflected rays and to
trace their movement.
• So one of the important challenges faced are those to track the
human movements only.
• Antenna array can eliminate by movement of target by using
ISAR (Inverse Synthetic Aperture Radar).
• There is only one receiver antenna in ISAR, so at any point in
time we capture a single measurement.

22. • Since the target is moving consecutive measurements in time
eliminate an inverse antenna array that is as if the moving human
is imaging the Wi-Vi device.
• By processing such consecutive measurements using standard
antenna array beam steering. Wi-Vi can identify the spatial
direction of the human.

23. COMPARISON WITH WITH ANTENNA ARRAY – A GRAPHICAL VIEW
θ
Antenna Array
Direction of motion
At any point in time, we have
a single measurement
WI-VI
DEVICE

24. COMPARISON WITH WITH ANTENNA ARRAY – A GRAPHICAL VIEW
Direction
of
motion
θ
Antenna Array
Direction of motion
θ
WI-VI
DEVICE

25. THROUGH - WALL GESTURE - BASED COMMUNICATION
• For a human to transmit a message to a computer wirelessly, they
typically has to carry a wireless device.
• Wi-Vi can enable a human who does not carry any wireless
device to communicate commands or short messages to a
receiver using simple gestures.
• Wi-Vi designates a pair of gestures as a ‘0’ bit and a ‘1’ bit.
• At this stage, Wi-Vi’s interface is still very basic, yet we believe
that future advances in through-wall technology can render this
interface more expressive.

26. GESTURE ENCODING
Bit ‘0’ : step forward followed by step backward
Bit ‘1’ : step backward followed by step forward
Step Forward
Step Backward

27. GESTURE DECODING
Output of matched filter: Decoded bits:
Accuracy of Gesture Decoding as a Function of Distance

28.  Wi-Vi is relatively a low-power, low-cost, low-
bandwidth, and accessible to average users.
 Display has very low resolution.
 Wi-Vi requires only few MHz of bandwidth and
operates in the same range as Wi-Fi. It operates
in ISM band.
 We cannot detect humans behind concrete walls
thicker than 8".
 Wi-Vi can perform through-wall imaging
without access to any device the other side of the
wall.
 To achieve a narrow beam the human needs to
move by about 4 wavelengths (i.e., about 50
cm).
 Wi-Vi employs signals whose wavelengths are
12.5 cm.
 Extend human vision beyond the visible
electromagnetic range, allowing us to detect
objects in the dark or in smoke.

29. APPLICATIONS OF WI-VI TECHNOLOGY
• Emergency Situation
Emergency responders can use Wi-Vi see through rubble and collapsed structure. Wi-Vi
invents the technology could one day we use for range of application including search in
rescue operation and disaster areas.

30. • Law Enforcement
Law Enforcement personal can use the device to avoid walking into an
ambush and minimize causalities in hostage and standoffs situations,
and the police to identify number of suspects in building before the
ride.

31. • Personal Security
Common users can use it for intrusion detection and when
stepping into dark alleys and unknown places.
• Smart Sensing
This Wi-Vi technology can be extended to sense motion in
different parts of a building and allow automated control of
heating or cooling and lighting systems.
• Entertainment
It enables a new dimension for input output devices in gaming
which does not effect on occlusion and works in non-line-of-sight.

32. FUTURE SCOPE
 Wi-Vi could be built into a Smartphone or a special handheld device.
 Evolution of seeing humans through denser building material and
with a longer range.
 High quality images.
 Possibly the next generation RADAR.

33. CONCLUSION
Wi-Vi, a wireless technology that uses Wi-Fi signals to
detect moving humans behind walls and in closed rooms. In
contrast to previous systems, which are targeted for the
military, Wi-Vi enables small cheap see-through-wall devices
that operate in the ISM band, rendering them feasible to the
general public, without carrying any transmitting device.

34. REFERENCES
[1] Adib, Fadel, and Dina Katabi, “See through Walls with WiFi,” Proceedings of the ACM SIGCOMM
Conference, 2013.
[2] Prerna Garg, Shikha, “Wi-Vi Technology”, International Journal of Advance Research In Science And
Engineering, Vol. No.2, Issue No.9, September 2013.
[3] Seeing through walls - MIT’s Lincoln Laboratory. - http://www.youtube.com/watch?v=H5xmo7iJ7
[4] Sudarshan Adeppa, “Detection of Objects across the Walls with Wi-Fi Technology”, International
Journal on Emerging Technologies, 2015.

35. Thanks