- SEEING THROUGH WALLS USING WI-FI

Presented by:

P.Elakkiya

Agenda

HistoryWI-VI IntroductionWhat WI-VI can do?Basic PrincipleWorkingResultApplicationsRelated workConclusion

Its research has been done prominently at MIT’s(Massachusetts Institute of Technology) Computer Science and Intelligence Laboratory.

By Dina Kitabi ,a professor in MIT’s Department of Electrical engineering and computer science ,and her graduate student Fadel Adib.

History

WI-VI

WI-VI is a wireless device that captures moving objects behind a wall using WI-FI signal.

WI-VI stands for Wi-Fi Vision. It is relatively a low power , low cost , low-bandwidth and accessible to average users.

This tech uses reflected WI-FI signal to track movements of people behind wall.

WI-VI is small enough to be portably used and can be integrated in hand held devices.

Cont…

WI-VI is essentially a 3-antenna MIMO device: two of the antennas are used for transmitting and one is used for receiving.

Limits itself to a 20 MHz wide Wi-Fi channel and avoids ultra-wide band solutions used today to address the “Flash Effects”.

WI-VI uses Wi-Fi OFDM signals in the ISM band (at 2.4 GHz) and typical Wi-Fi hardware.

What WI-VI can do ?

• Detect the Number of Moving Humans in a Closed

Room.

• Determine the Relative Locations of Moving

Humans.

• Eliminate the reflections from static objects.

• Identify Simple Gestures from Behind a Wall.

Basic Principle

WI-VI is Based on the principle of RADAR and SONAR imaging(doppler effect).

RADAR is an object detection system which uses radio waves to determine the range, altitude, direction, or speed of objects.

It’s similar to the way radar and sonar work but without the expensive ,bulky gear and restricted frequencies that radar requires.

Depends on its own transmitting signal.

Working

Cont…

WI-VI uses two transmitting antennas and a single receiver.

Transmitting signals are low power Wi-Fi signals.

The two antennas transmit almost identical signals, except the second antenna's signal is the inverse of the first, resulting in interference.

Cont…

Cont…

These 2 transmitted waves are going to reflect off the wall and come back to the receive antenna. Let us call their corresponding channels h1 and h2.

So, the receive antenna gets y=h1x + h2.alha.x

And here is how we structure our signals. we set alpha to be equal to –h1/h2. As a result, y becomes zero, which means that the reflection from the wall disappears.

Of course, this implies that we need to estimate the channels h1 and h2 in real-time.

Cont…

Cont…

Any static objects that the signals hit including the wall create identical reflections, they too are cancelled out by this nulling effect.

Only those reflections that change between the two signals, such as those from a moving object, arrive back at the reciever.

Result

a.) two humans

b.)three humans

Applications

Cont…

Possible use in smart phones as a hand held device.

Monitoring situations in hospitals,malls,hotels, etc.

Disaster recovery

Gaming

Military purpose

Related Work

Conclusion

WI-VI a Smart hand held device which gives an insight vision through walls.

Could prove to be very powerful and effective device for defence purposes.

Possibly the next generation RADAR.

THANK YOU!!!