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  • Published on: 7th September 2019
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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.


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



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)


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


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


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.


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.



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.


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.



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


Emergency situations: Emergency responders can

use wi-vi to see through rubble and collapsed


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


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.



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