.Abstract
During sleep ,we can detect human vital signs
and heart rate which is very important as it can
access the general physical health of a person
and thus it will give us the details of that
individual and with that details we can come to
a conclusion.By determing respiration rate,we
can detect our heart rate and he can detect
many diseases such as sleep apnea and chronic
obstructive pulmonary disease.
In this paper we present heart rate detection
and as well as detection of human body
movements, using wireless signals through
walls of a room. Here we discussed about two
main technologies, both implemented using
WiFi router at home,namely WiVi and Vital
Radio.WiVi is used for tracking human body
movements and Vital Radio developed using
WiVi is used to track human heart rate and
breathing pattern.
Introduction
Wifi is a technology that allows electronic
devices to connect to a wireless LAN, mainly
using the 2.4 gigahetz(12 cm)UHF and 5
gigahertz(6 cm)SHF ISM radio bands.
Basically WiFi signals transfer information
carriers between a transmitter and a receiver.
Radio waves is being used by wi-fi to locate
four people in a room (with in few
centimeters) .WiFi signals can also be used as
a sort of x-ray vision to track a person’s
movement by sending out a pair of inverse
wireless signals as pings.. This paper is mainly
investigating about the WiFi signals with the
advanced MIMO communications by
capturing the motions of humans behind the
walls. In this technology, the most challenging
part is the reflections from the wall itself rather
than reflections from the object. Reflections
are difficult because the signal power after
traversing the wall twice is reduced.Due to
this, minute variations coming through the
object are not tracked.Wifi signals is
transmitted at a wall, a portion of the signal
enter through it, and reflecting off any human
.A fraction of a signal goes to other room as it
spread out and rest is reflected through the
walls. Due to this reflections from the wall, we
are not able to track the minute variations of
an human. Thus, to detect the variation of a
human , we need to track the minute variations
of a human.
The two main innovationsin this paper
includes a)how signals are nullified when they
hit something stationary. The receiver is then
focussed on a moving target whichcreates an
offset between the signals that can be processed
to determine themovement of the
target. Thisis called the MimoInterference.
WiVi uses these methods to track a person’s
body movement through walls.
b) The Vital-Radio is a new input device for
tracking breathing and heartbeats without any
instrument or device being attached to the
person’s body It also works in the presence of
multiple users in the environment and can
track the vital signs of the present users
simultaneously which was previously not
possible.
WORKS:-
Wall radar imaging.
This technology is used to detect the human
and other objects.In this system ,the reflected
signal off the wall from the objects are
isolated.By doing wall sensing we can detect
the room layouts and classify the object in the
buildings.we can decomposed the body
detection and localisation into zero (0‐D), one
(1‐D), two (2‐D), or three‐dimensional (3‐D)
systems.
1)By using 0-D we detect if the room is
occupied or not.
2)By using 1-Dimensional whether a detection
is in the adjacent room.
3) 2-D provides us the best location of the
living object.
Occurrence of incorrect position of the object
is that if the object is outside the room or
building is being removed by the reflection off
the first wall and subsequently creating an
ambiguous image .
Heart-rate detection and tracking human body-movements through walls at
home.
Gesture-based Interface.
We can determine the gestures of human either
by using cameras or by using sensors i.e placing
the sensors on the human body.We get the
gestures by some body movement.The
technology is embedded in a wifi device and it can
detect the motion of human body as their motion
affect the wifi network.Wifi sends the array of
straight signals and this signals bounce into the
things into our home. The waves with the
frequency range of 2.4ghz or 5ghz band ,one will
see that ripple effect is produced from the
movement.But normally,it is noticed that this
ripples are very small to detect. Microdoppler
effect created by a gesture is distributing a wifi
network.It can translate the difference in to one of
nine gestures and it will be giving us with an
accuracy rate of 94 percent.
Vital signs using radar
As wireless signal traverse through the static
object and they could be used to sense the
chest movements of a victim by using rubble
OVERVIEW
As a WiFi signals are transmitted through a
wall, a portion of the signal enter through it,
and reflects off any human body. A few
signals goes to another room as it spreads out
and rest is reflected through the walls. Due to
the reflections from the wall,we are not able to
track the minute variations of a human
perfectly.So,to detect the minute variations of
a human, a new technology is invented and it
is known as “WiVi”.It can be done even if the
human is in a closed room or hiding behind the
wall. WiVi is a wireless device that captures
moving objects behind a wall. It leverages the
ubiquity of WiFi chipsets to make through
wall imaging .It is relatively low-power, lowcost,
low-bandwidth device and uses its
reflections to track moving humans and it is
accessible to average users as well. WiVi uses
WiFi OFDM signals in the ISM band (at 2.4
GHz) and typical WiFi hardware.WiVi is
basically a 3-antenna MIMO device in which
two antennas are used for transmitting and one
is used for receiving. This also includes
directional antennas to focus the energy
towards the wall or room of interest.
The Vital-Radio is a new input device for
tracking breathing rates and heartbeats without
any instrument or device being attached to a
person’s body. It also works in the presence of
multiple users in the environment and can
track the vital signs of the present users
simultaneously which was previously not
possible. Vital-Radio does not require the
user's awareness. Vital-Radio accurately tracks
a user’s breathing and heart rate even from 8
meters away or even from a different room.
Vital-Radio works by using wireless signals to
detect the minute movements due to inhaling,
exhaling, and heartbeats. The wireless system
transmits a low-power wireless signal and
measures the time it takes for the signal to
reflect back to the device. The reflection time
depends on the distance of the reflector from
the device, and changes as the reflector moves.
Wi-Vi :-
Eliminating the Flash Effect
The signal reflected from the wall is much
stronger i.e the flash of it is stronger.This is
because of the attenuation which
electromagnetic signals suffer while traversing
the obstacles. As reflected signal depends on
both the reflection coefficient as well as the
cross-section of object due to which the actual
reflected signal becomes weaker .Hence, WiVi
increases the sensitivity to the reflection of
interest by using the phenomenon of
interference nulling.As the reflected rays from
the wall prevents to detect the minute variation
of the object.Such activity of a object is called
Flash effect.
Nulling.
Wi-Vi do not use an antenna array for two
reasons. First, to obtain a narrow beam and to
get a good resolution, one needs a large
antenna array.And due to having a large
antenna array with large number of antenna
elements, naturally it would results in to bulky
device. Secondly, Wi-Vi removes the flash
effect using MIMO nulling, adding multiple
receive antennas would require nulling the
signal at each of them by using nulling
algorithm.This algorithm can be done with
Manchester coding .They require more transit
antennas to capture the reflections from the
object by using Wi-vi technology.
Nulling is used to remove the reflections from
the wall i.e the non-living items. As wireless
signal takes those reflections that moves
between two stages. Nulling allows to
remove the weak and bad signals so to get a
better resolution.
.HOW TO TRACK A SINGLE
PERSON?
They move the array beam to determine the
direction of maximum energy. The position
where we get the maximum energy, we can
predict that at that position a moving object is
present.The direction gives us an angle of
arrival. And by tracking that spatial angle of
arrival we can determine how the object
moves . Infact, we can determine the exact
movement by capturing gestures. As we have
discussed how the gesture interface works.
How to track a multiple persons?
Each and every individual human will produce
a diffierent antenna of array. As we know WiVi
has a single antennae, and they avoid
multiple array of antennas because it would
make it heavy and expensive and it would
make it complicated.
To detect multiple of humans, the noise also
increases .The received signal will be a
superposition of the antenna arrays of the
moving humans.Instead of having one curved
line, there will be as many curved lines as
moving humans at that point in time.Each
human is not just one object because of
different body parts moving in a loosely
coupled way. On the other hand, the signal
reflected off all of these humans is correlated
in time, since they all reflect the transmitted
signal.The lack ofindependence between the
reflected signals is important.
Vital – Radio:-
Vital-Radio transmits a low-power wireless signal
and monitors its reflections off the human body. It
identifies the signals and differentiates the periodic
and non-periodic movements like breathing and
limb movements.
To develop Vital-Radio, we used a WiVi, which
provides accurate motion tracking using wireless
signals reflected off from a human body. WiVi
eliminates signals reflected off from static objects
like furnitures and walls. Vital-Radio is built on
WiVi which mainly operates in three steps. Firstly,
Vital-Radio uses WiVi to eliminate reflections
from static objects (e.g., walls and furniture) and
sort reflections from moving objects (i.e., people)
into bins based on their distances from the device.
Secondly, Vital-Radio identifies changes in the
signal due to body motion as opposed to breathing
motion. Vital-Radio detects the body movements
and isolates the signals.Once it detects large motion
it eliminates them and focuses on the time intervals
which have no major limb motion.
It mainly focuses on the phase of the reflected
signal. Phase variations are used to track subtle
centimetre oscillations in a reflector (e.g., chest
breathing motion) even when the reflector itself
does not change its overall distance from the
device. The distance varies at every instance with
inhaling and exhaling , hence the distance and
phase difference varies with every corresponding
reflection. The main challenge is any other motion
in the environment is also detected which interferes
with the phase of breathing signals .These
interferences creates noise in the phase signals. By
isolating a user’s reflection, Vital-Radio also
eliminates other sources of interference including
noise which may otherwise mask the minute
variations due to the user’s vital signs. This enables
Vital-Radio to monitor multiple users’ breathing
and heart rates, and to operate at distances up to 8
m from the user or even from behind a wall.
Advantages
WiVi requires only few MHZ of bandwidth and
operates in the same range of WiFi . It transmits
very low power signal which is 1000 times smaller
than what cell phone can transmit. WiVi works
similar to radar .But in radar, it uses microwaves
(300mhz to 300ghz) which is of bulky and
restricted frequencies .A radar system consists of a
transmitter producing electromagnetic waves in the
radio or microwaves domain , an emitting antennae
and a receiving antennae. While in WiVi , it
disposes the large antenna array, and instead uses
a smaller 3-antenna MIMO radio.
Vital Radio developed using WiVi doesn’t requires
any biosensors to be attached to the body. It can
beused as a smart home technology.It helps to track
health status of multiple users without any
interference in the recorded signal.
.
Applications
There are some of the applications of WiVi
technology described here.
Law enforcement: Law enforcement personal can
use the device to avoid walking into an ambush,
and minimize causalities in hostage and standoffs
situations.
Emergency situations: Emergency responders can
use wi-vi to see through rubble and collapsed
structures.
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. Personal Security:
Common users can use it for intrusion detection
and when stepping into dark alleys and unknown
places. Entertainment: It enables a new dimension
for input-output devices in gaming which does not
affect on occlusion and works in non-line-of-sight.
User Interface Design: This technology may also
be leveraged in the future to enable the controlling
household appliances via gestures, and noninvasive
monitoring of children and elderly
Conclusion
As we discussed WiVi, a wireless technology that
uses WiFi signals to detect moving humans behind
walls or doors and also in closed rooms and
compared to previous systems, which are targeted
for the military, WiVi enables the small cheap seethrough-wall
devices which operate in the ISM
band, rendering them feasible to the general public.
. We believe that WiVi has a set of functionality
that future wireless networks will provide. Future
WiFi networks will likely expand beyond
communications and deliver facilities such as
indoor localization, sensing as well as control.
WiVi gives evidence of advanced form of WiFi
based sensing and localization by using Wi-Fi to
track humans behind wall without carrying any
wireless device, Vital-Radio being one of its major
application. The same device which was used to
develop WiVi can be used to track vital signs of
human behind the wall . It doesn’t require users to
be aware of its presence, and hence doesn’t
interfere with user experience. Additionally, VitalRadio
enables new interface and interaction
capabilities. Thus we draw the conclusion that our
system can not only track human movements
behind the wall using WiVi technology but also
detect vital signs of human such as breathing rate
and heart rate using Vital Radio which is
developed by using WiVi.
References
1.iBabyGuard. http://www.ibabyguard.com/.
2. Kai Medical. http://www.kaimedical.com/.
3. Aardal, O., Paichard, Y., Brovoll, S.,
Berger, T., Lande, T. S., and
Hamran, S.-E. Physical working principles of
medical radar.
Biomedical Engineering, IEEE Trans. on
(2013).
4. Adib, F., Kabelac, Z., Katabi, D., and
Miller, R. C. 3D Tracking via
Body Radio Reflections. In Usenix NSDI
(2014).
5. Anitori, L., de Jong, A., and Nennie, F.
Fmcw radar for life-sign
detection. In IEEE Radar Conference (2009).
6. Balakrishnan, G., Durand, F., and Guttag, J.
Detecting pulse from head
motions in video. In IEEE CVPR (2013).
7. Bargas-Avila, J. A., and Hornbæk, K. Old
wine in new bottles or novel
challenges: a critical analysis of empirical
studies of user experience.
In ACM CHI (2011).
8. Callahan, J., Cox, D., Hoffman, K., O’shea,
D., Pollatsek, H., and
Senechal, L. Calculus in context: the five
college calculus project,
Chapter 7 (Periodicity). WH Freeman, 1995.
9. Chi, Y., Jung, T.-P., and Cauwenberghs, G.
Dry-contact and noncontact
biopotential electrodes: Methodological
review. Biomedical
Engineering, IEEE Reviews in (2010).
10. CNET. Do wristband heart trackers
actually work? A checkup.
http://www.cnet.com/news/how-accurate-arewristband-heart-ratemonitors/.
11. How Signal is affected.
www.ci.cumberland.md.us/. City of
Cumberland Report
12 G. Char vat, L. Keppel, E. Roth well, C.
Coleman, and E. Mohole. A through-dielectric
radar imaging system IEEE Trans. Antennas
and Propagation, 2010