ABSTRACT:
A new technology known as Wi-Vi is bouncing up with a good progress.It is similar Radar and Sonar imaging..it depends on radio signals of wifi.I monitor movements of people in closed rooms or behind a wall. Wi-Vi was created by Dina Katabi ,a professor in MIT,and her graduate student Fadel Adib.
Wi-Vi technology can detect number of humans in a closed room. Enable communication through a wall without carrying a wireless device.Identify simple gestures from behind a wall.
This Wi-Vi signals uses Wi-Fi signals,as Wi-Fi signals can penetrate through walls. Wi-Vi relies on a simple hardware of 2.GHz Wi-Fi radios small enough to be portably used.Integrated in hand held devices.Low power Wi-Fi signals are used.
A Wi-Vi system constitutes-
1.Two transmitting antennas
2.single receiver.
This technology is based on principle of Rada and Sonar.Radar and Sonar works on Doppler effect. This technology uses reflected Wi-Fi signals to track the movement of people behind walls.
It 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.
Any static objects that the signals hit including the wall create identical reflections and they get cancelled out.
As the person moves through the room, his or her distance from, receiver changes and remains detectable.
— Flash Effect:
— When you take a device, point it at a wall, and transmit Wi-Fi signals, a huge amount of reflection is going to come from the wall itself.This reflection is 10000* of the beyond wall object’s reflection.
How to track using reflections?
1.Human reflects the signal, it’s as if he is the source of that signal.
2.We know that if you want to track an RF source, you can do that using an antenna array. We don’t use antenna array as it is expensive and bulky. Instead the moving object simulates as array.
3.By steering the beam of the array we can find the direction of from which the signal is coming.
4.Now when a person moves, that direction would change, and we are able to track him.
5.All reflections from static objects are cancelled out, and the only thing registered by the device is the moving humans.
Advantages:
— Wi-vi require same bandwidth & operates in the same range as Wi-Fi.
— Wi-vi can perform, through wall imaging without access to any device on the other side of the wall.
— Wi-vi employs signals whose wavelength are 12.5 cm.
— Extend human vision beyond the visible electromagnetic range, allowing us to detect objects in the dark or in smoke.
Limitations:
— Display has very low resolution.
— We cannot detect humans behind concrete walls thicker than 8”.
— To achieve a narrow beam the human needs to move by about 50 cm.
Applications:
— Law enforcement:
— Law enforcement personnel can use the device to avoid walking into an ambush, and minimize casualties in standoffs and hostage situations.
Emergency situations:
— Emergency responders can use it to see through rubble and collapsed structures.
— Personal Security:
— Common users can use it for intrusion detection, or when stepping into dark alleys and unknown places.
Conclusion:
— The possibilities are numerous and can be explored further.
— If this technology can be put into practical use, It can be used in a variety of applications.
— We will proceed toward the cleaner, greener, safer and brighter future.
— Wi-Vi technology can change our world before we realize it.
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