Wi vi- wifi that see through walls

  • View

  • Download

Embed Size (px)

Text of Wi vi- wifi that see through walls

  • 1.Wi-Vi: See Through Walls With Wi-Fi

2. Outline Introduction What can Wi-Vi do?Applications Design Methodology Results Advantages LimitationsConclusion Bibliography 3. Through Wall RADAR Eliminate Flash Effect by isolating signals reflected off the wall from the signals reflected off the objects behind the wall. Isolation can be achieved in Time or Frequency domain which requires UWB (Ultra-Wideband Widths) of the order of 2GHz. Difficult to capture the reflections. Narrowband RADARs use Doppler Shift to detect moving objects behind the wall but can be done only in free space with no obstruction or with low attenuation standing wall 4. Wi-Vi Wi-Vi stands for Wi-Fi Vision. Demonstrated by Dina Katabi, a professor in MITs Department of Electrical Engineering and Computer Science, and her graduate student Fadel Adib. Wi-Vi uses Wi-Fi OFDM signals in the ISM band (at 2.4 GHz) and typical Wi-Fi hardware. Wi-Vi limits itself to a 20 MHz-wide Wi-Fi channel, and avoids ultra-wide band solutions used today to address the ash effect. 5. Contd Wi-Vi is essentially a 3-antenna MIMO device: two of the antennas are used for transmitting and one is used for receiving. It also employs directional antennas to focus the energy toward the wall or room of interest. It is relatively a low-power, low-cost, low-bandwidth, andaccessible to average users. 6. What can Wi-Vi Do? Detect the Number of Moving Humans in a Closed Room. Determine the Relative Locations of Moving Humans. Enable Communication through a Wall without Carrying a Wireless Device. Identify Simple Gestures from Behind a Wall. 7. Contd Transmit two waves that cancel each other when they reflectoff the Static object but not the Moving object. Wall is StaticDisappearsPeople tend to moveDetactable 8. Wi-Vi Setup 9. Applications Police avoids ambushPersonal SecurityFirefighters check for humansGesture Interface from behind a wall 10. MIMO Nulling 11. Contd Xh1 y = h1 x + h2x = -h1 / h2xh2Static objects( wall, furniture, Etc.) have constant channels.People move, therefore their Channel change.y = h1 x + h2(- h1/ h2)x = 0y = h1 x + h2(- h1/ h2)x =0 12. ISARDirection of reflectionDirection of motion 13. Results A prototype of Wi-Vi using USRP N210 radios software was implemented and evaluated in two office buildings byFadel Adib and Dina Katabi, Massachusetts Institute of Technology (MIT), Results are as follows: Wi-Vi can detect objects and humans moving behind opaque structural obstructions. This applies to 8" concrete walls, 6" hollow walls, and 1.75" solid wooden doors. 14. Contd Wi-Vi depends on the amount of movement. To achieve a narrow beam the human needs to move by about 4wavelengths (i.e., about 50 cm).Table. Accuracy of Automatic Detection of Humans 15. Detection Accuracy of Wi-Vi for Different Types of Obstructions 16. Advantages Wi-Vi requires only few MHz of bandwidth and operates in the same range as Wi-Fi. It operates in ISM band. Wi-Vi can perform through-wall imaging without access to any device on the other side of the wall. 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. 17. 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 4 wavelengths (i.e., about 50 cm). 18. Future Scope Wi-Vi could be built into a Smartphone or a special handheld device. Can be used in search-and-rescue missions and law enforcement 19. Conclusion Wi-Vi, a wireless technology that uses Wi-Fi signals to detectmoving 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. 20. Bibliography http://people.csail.mit.edu/fadel/wivi/ Fadel Adib and Dina Katabi, See Through Walls with Wi-Fi, ACM SIGCOMM'13, Hong Kong August 2013. 21. THANK YOU