22-05-2012, 10:19 AM
Wireless Sensor Network for Wearable Physiological Monitoring
[attachment=22644]
Abstract
Wearable physiological monitoring system
consists of an array of sensors embedded into the fabric of
the wearer to continuously monitor the physiological
parameters and transmit wireless to a remote monitoring
station. At the remote monitoring station the data is
correlated to study the overall health status of the wearer.
In the conventional wearable physiological monitoring
system, the sensors are integrated at specific locations on the
vest and are interconnected to the wearable data acquisition
hardware by wires woven into the fabric. The drawbacks
associated with these systems are the cables woven in the
fabric pickup noise such as power line interference and
signals from nearby radiating sources and thereby
corrupting the physiological signals. Also repositioning the
sensors in the fabric is difficult once integrated. The
problems can be overcome by the use of physiological
sensors with miniaturized electronics to condition, process,
digitize and wireless transmission integrated into the single
module. These sensors are strategically placed at various
locations on the vest. Number of sensors integrated into the
fabric form a network (Personal Area Network) and
interacts with the human system to acquire and transmit the
physiological data to a wearable data acquisition system.
The wearable data acquisition hardware collects the data
from various sensors and transmits the processed data to
the remote monitoring station. The paper discusses wireless
sensor network and its application to wearable physiological
monitoring and its applications. Also the problems
associated with conventional wearable physiological
monitoring are discussed.
Index Terms— Wearable monitor, physiological parameters,
data acquisition hardware, remote monitoring station,
wireless sensor network
I. INTRODUCTION
Wearable physiological monitoring systems uses an array
of sensors integrated into the fabric of the wearer to
continuously acquire and transmit the physiological data
to a remote monitoring station. The data acquired at the
remote monitoring station is correlated to study the
overall health status of the wearer. The wearable
monitoring systems allow an individual to monitor his/her
vital signs remotely and receive feedback to maintain a
good health status. These systems alert medical personnel
when abnormalities are detected. The conventional
physiological monitoring system used in hospitals cannot
be used for wearable physiological monitoring
applications due to the following reasons [1-2].
• The conventional physiological monitoring systems
are bulky to be used for wearable monitoring.
• The gels used in the electrodes dry out when used
over a period of time, which lead to increase in the
contact resistance and thereby degrading the signal
quality.
• The gels used in the electrodes cause irritations and
rashes when used for longer durations.
• There are number of hampering wires from the
sensors to the data acquisition system.
• The signals acquired are affected with motion
artifact and baseline wander as the electrodes float
on the layer of gel.
• The sensors used in conventional monitoring
systems are bulky and are not comfortable to wear
for longer durations.
To overcome the above problems associated with the
conventional physiological monitoring there is a need to
develop sensors for wearable monitoring and integrate
them into the fabric of wearer and continuously monitor
the physiological parameters. A wearable data
acquisition, processing and transmission hardware, which
is portable, comfortable to wear for longer durations, and
having sustainable battery power and a remote
monitoring station is to be developed. The wearable
physiological monitoring systems consists of three
systems namely (a) vest with the sensors integrated (b)
wearable data acquisition and processing hardware and
© remote monitoring station. In the vest sensors for
acquiring the physiological parameters are integrated.
The sensors outputs and power cables are interconnected *Corresponding Author
Phone: +91-80-25058407; Fax: +91-80-25282011
JOURNAL OF NETWORKS, VOL. 3, NO. 5, MAY 2008 21
© 2008 ACADEMY PUBLISHER
to the data acquisition and processing hardware by means
of wires routed through the wires woven in the vest. In
the wearable data acquisition and processing hardware,
the circuits for amplification, filtering and digitization are
housed. The digitized and processed data is transmitted
wireless to a remote monitoring station. In the remote
monitoring station the data is received and displayed in a
form suitable for diagnosis. Fig. 1 illustrates the overall
architecture of the wearable physiological monitoring
system, consisting of a vest with sensors integrated,
wearable data acquisition and processing hardware and a
remote monitoring station.
A number of wearable physiological monitoring
systems have been developed to monitor the health status
of the individual wearer. A wearable physiological
monitoring system called ‘Smart Vest’ to monitor various
physiological parameters such as ECG, PPG, heart rate,
blood pressure, body temperature and GSR is developed.
The acquired physiological parameters are transmitted
wireless to a remote monitoring station along with the
geo-location of the wearer [3]. A wrist worn wearable
medical monitoring and alert system (AMON) targeting
high-risk cardiac/respiratory patients has been developed
to monitor physiological parameters such as ECG, heart
rate, blood pressure, skin temperature [4]. Vivometrics
has developed a wearable physiological monitoring
system called ‘Life Shirt’ to monitor various cardiorespiratory
parameters [5].
A wearable physiological monitoring system for space
and terrestrial applications named ‘Life Guard’ to
monitor the health status of the astronauts in space is
developed [6]. The Georgia Tech, Smart Shirt
characterized as a “wearable motherboard” allows for a
variety of vital parameters to be incorporated into the
vest, which can be easily and comfortably worn by the
soldiers [7]. A textile based wearable system, called
MagIC (Maglietta Interattiva Computerizzata) for the
unobtrusive recording of cardiorespiratory and motion
signals during daily life and in a clinical environment on
cardiac patients [8].
The Armband SenseWear (BodyMedia Inc, Pittsburgh,
PA, USA) wearable body monitor has been used to study
bodily movement and energy expenditure in normal
subjects and Chronic Obstructive Pulmonary Disease
(COPD) subjects [9]. The WEALTHY (Wearable Health
Care System) involves wearable textile interfaces
integrating sensors, electrodes and connections realized
with conductive and piezoresistive yarns. The WEALTHY
system is made up of a sensorized cotton or lycra shirt
that integrates carbon-loaded elastomer strain sensors and
fabric bio-electrodes, enabling the monitoring of
respiration, ECG, EMG, body posture and movement
[10]. MyHeart wearable monitoring system focuses on
integration of unobtrusive sensors into everyday garments
and miniaturized on-body electronic modules for data
processing and storage with dedicated software for data
analysis like ECG preprocessing and motion artifact
detection, computation of heart rate and heart rate
variability parameters [11].
A number of wearable physiological monitoring
systems have been put into practical use for health
monitoring of the wearer in hospital and real life
situations and their performances have been reported [12-
17]. Varying degrees of success have been reported and
the percentage failures in the outdoor use are high. The
drawbacks associated with the conventional wearable
physiological systems are
• The cables woven into the fabric to interconnect the
sensors to the wearable data acquisition hardware
pick up interfering noises (e.g. 50 Hz power line
interference). The wires integrated into fabric act
like antennas and can easily pick up the noises from
nearby radiating sources.
• The sensors once integrated into the fabric, its
location cannot be changed or altered easily.
• The power required for the sensors to operate is to
be drawn from the common battery housed in the
wearable data acquisition hardware and are routed
through wires woven in the fabric.
• Typically these systems consist of a centralized
processing unit to digitize, process and transmit the
data to a remote monitoring system. The processor
is loaded heavily to perform multi-channel data
acquisition, processing and transmission of data.
• The cables from the vest interconnecting the sensors
can get damaged very easily due to twisting and
turning of the cables, while the wearer is
performing his routine activity.
To overcome the above issues related to wearable
physiological monitoring, the individual sensors
integrated into the vest can be housed with electronics
and wireless communication system to acquire and
transmit the physiological data. The recent advances in
the sensors (MEMS and Nanotechnology), low-power
microelectronics and miniaturization and wireless
networking enable Wireless Sensor Networks (WSN) for
human health monitoring. A number of tiny wireless
sensors, strategically placed on the human body create a
wireless body area network that can monitor various vital
signs, providing real-time feedback to the user and
medical personnel [18-22]. A multi-channel, bidirectional
and implantable bio-telemetric platform for real time invivo
monitoring of several physiological monitoring
systems have been developed [23].
Remote Monitori
Station
Wearable Data
Acquisition System
Wireless
Communication
Woven wires
Physiological
sensors
Figure 1. Overall architecture of the wearable physiological monitoring
system
22 JOURNAL OF NETWORKS, VOL. 3, NO. 5, MAY 2008
© 2008 ACADEMY PUBLISHER
Fig. 2 illustrates the architecture of a WSN based
wearable physiological monitoring system. Wireless
Sensor Networks (WSN) consists of a large number of
small nodes, which have built-in computing, power,
sensors to acquire physiological data from the wearer and
wireless transmission and reception capability. A wireless
sensor network for smart electronics shirt has been
developed which allows the monitoring of individual
biomedical data and is transmitted wireless for further
processing using a wireless link [24]. A number of
wireless ECG monitoring systems based on conventional
electrodes have been developed [25-28], a two lead
wireless ECG and oxygen saturation in blood monitoring
systems is developed [29]. A wireless body sensor
network with embedded intelligent motion sensors for
computer assisted physical rehabilitation is developed to
give feedback to the user and generate warnings based on
the users state, level of activity and environmental
conditions with data transmission capability to medical
servers via internet [30]. A personal health monitor
based on a wireless body area network (BAN) integrated
with intelligent sensors for psychophysiological
evaluation of military members undergoing intense
training by measuring heart-rate variability (HRV) to
quantify stress level prior to and during training as well
as to predict stress resistance is developed [31]. The
project CodeBlue describes the wireless medical sensor
network hardware and software platform to medical
monitoring of individuals [32]. Patient monitoring over
the wireless infrastructure oriented ad-hoc network has
been investigated [33-34]. These systems are useful in
transmitting the medical over larger distances and do not
discuss about the applications of wearable physiological
monitoring.
DEBEL has gained sufficient expertise during the
development of a wearable physiological monitoring
system named as Smart Vest [3]. The development has
culminated in the form of Smart Vest with sensors
integrated to sense, process, store and transmit the
physiological data. The developed system made use of
sensors integrated into the fabric interconnected by
woven wires, and interfaced to a wearable data
acquisition and processing hardware. To address the
various issues and problems encountered during the
development of the Smart Vest, the development of
wireless sensor network for wearable physiological
monitoring has been initiated.
The objective of this paper is to discuss a conceptual
design of a wearable physiological monitoring system
based on wireless sensor network to monitor a number of
physiological parameters. The physiological parameters
to be monitored are Electrocardiogram (ECG),
Electromyogram (EMG), Electroencephalogram (EEG),
Oxygen Saturation in blood (SaO2), body temperature,
systolic and diastolic blood pressure, respiratory rate,
Galvanic Skin Response (GSR) and movement of the
wearer recorded by an accelerometer. The acquired
physiological signals are preprocessed at each node and
transmitted to the wearable data acquisition hardware
(sink node) for further processing and transmitted
wireless to a remote monitoring station. The paper also
discusses the architecture of the WSN for wearable
physiological monitoring, protocols, security issues and
power requirements.
[attachment=22644]
Abstract
Wearable physiological monitoring system
consists of an array of sensors embedded into the fabric of
the wearer to continuously monitor the physiological
parameters and transmit wireless to a remote monitoring
station. At the remote monitoring station the data is
correlated to study the overall health status of the wearer.
In the conventional wearable physiological monitoring
system, the sensors are integrated at specific locations on the
vest and are interconnected to the wearable data acquisition
hardware by wires woven into the fabric. The drawbacks
associated with these systems are the cables woven in the
fabric pickup noise such as power line interference and
signals from nearby radiating sources and thereby
corrupting the physiological signals. Also repositioning the
sensors in the fabric is difficult once integrated. The
problems can be overcome by the use of physiological
sensors with miniaturized electronics to condition, process,
digitize and wireless transmission integrated into the single
module. These sensors are strategically placed at various
locations on the vest. Number of sensors integrated into the
fabric form a network (Personal Area Network) and
interacts with the human system to acquire and transmit the
physiological data to a wearable data acquisition system.
The wearable data acquisition hardware collects the data
from various sensors and transmits the processed data to
the remote monitoring station. The paper discusses wireless
sensor network and its application to wearable physiological
monitoring and its applications. Also the problems
associated with conventional wearable physiological
monitoring are discussed.
Index Terms— Wearable monitor, physiological parameters,
data acquisition hardware, remote monitoring station,
wireless sensor network
I. INTRODUCTION
Wearable physiological monitoring systems uses an array
of sensors integrated into the fabric of the wearer to
continuously acquire and transmit the physiological data
to a remote monitoring station. The data acquired at the
remote monitoring station is correlated to study the
overall health status of the wearer. The wearable
monitoring systems allow an individual to monitor his/her
vital signs remotely and receive feedback to maintain a
good health status. These systems alert medical personnel
when abnormalities are detected. The conventional
physiological monitoring system used in hospitals cannot
be used for wearable physiological monitoring
applications due to the following reasons [1-2].
• The conventional physiological monitoring systems
are bulky to be used for wearable monitoring.
• The gels used in the electrodes dry out when used
over a period of time, which lead to increase in the
contact resistance and thereby degrading the signal
quality.
• The gels used in the electrodes cause irritations and
rashes when used for longer durations.
• There are number of hampering wires from the
sensors to the data acquisition system.
• The signals acquired are affected with motion
artifact and baseline wander as the electrodes float
on the layer of gel.
• The sensors used in conventional monitoring
systems are bulky and are not comfortable to wear
for longer durations.
To overcome the above problems associated with the
conventional physiological monitoring there is a need to
develop sensors for wearable monitoring and integrate
them into the fabric of wearer and continuously monitor
the physiological parameters. A wearable data
acquisition, processing and transmission hardware, which
is portable, comfortable to wear for longer durations, and
having sustainable battery power and a remote
monitoring station is to be developed. The wearable
physiological monitoring systems consists of three
systems namely (a) vest with the sensors integrated (b)
wearable data acquisition and processing hardware and
© remote monitoring station. In the vest sensors for
acquiring the physiological parameters are integrated.
The sensors outputs and power cables are interconnected *Corresponding Author
Phone: +91-80-25058407; Fax: +91-80-25282011
JOURNAL OF NETWORKS, VOL. 3, NO. 5, MAY 2008 21
© 2008 ACADEMY PUBLISHER
to the data acquisition and processing hardware by means
of wires routed through the wires woven in the vest. In
the wearable data acquisition and processing hardware,
the circuits for amplification, filtering and digitization are
housed. The digitized and processed data is transmitted
wireless to a remote monitoring station. In the remote
monitoring station the data is received and displayed in a
form suitable for diagnosis. Fig. 1 illustrates the overall
architecture of the wearable physiological monitoring
system, consisting of a vest with sensors integrated,
wearable data acquisition and processing hardware and a
remote monitoring station.
A number of wearable physiological monitoring
systems have been developed to monitor the health status
of the individual wearer. A wearable physiological
monitoring system called ‘Smart Vest’ to monitor various
physiological parameters such as ECG, PPG, heart rate,
blood pressure, body temperature and GSR is developed.
The acquired physiological parameters are transmitted
wireless to a remote monitoring station along with the
geo-location of the wearer [3]. A wrist worn wearable
medical monitoring and alert system (AMON) targeting
high-risk cardiac/respiratory patients has been developed
to monitor physiological parameters such as ECG, heart
rate, blood pressure, skin temperature [4]. Vivometrics
has developed a wearable physiological monitoring
system called ‘Life Shirt’ to monitor various cardiorespiratory
parameters [5].
A wearable physiological monitoring system for space
and terrestrial applications named ‘Life Guard’ to
monitor the health status of the astronauts in space is
developed [6]. The Georgia Tech, Smart Shirt
characterized as a “wearable motherboard” allows for a
variety of vital parameters to be incorporated into the
vest, which can be easily and comfortably worn by the
soldiers [7]. A textile based wearable system, called
MagIC (Maglietta Interattiva Computerizzata) for the
unobtrusive recording of cardiorespiratory and motion
signals during daily life and in a clinical environment on
cardiac patients [8].
The Armband SenseWear (BodyMedia Inc, Pittsburgh,
PA, USA) wearable body monitor has been used to study
bodily movement and energy expenditure in normal
subjects and Chronic Obstructive Pulmonary Disease
(COPD) subjects [9]. The WEALTHY (Wearable Health
Care System) involves wearable textile interfaces
integrating sensors, electrodes and connections realized
with conductive and piezoresistive yarns. The WEALTHY
system is made up of a sensorized cotton or lycra shirt
that integrates carbon-loaded elastomer strain sensors and
fabric bio-electrodes, enabling the monitoring of
respiration, ECG, EMG, body posture and movement
[10]. MyHeart wearable monitoring system focuses on
integration of unobtrusive sensors into everyday garments
and miniaturized on-body electronic modules for data
processing and storage with dedicated software for data
analysis like ECG preprocessing and motion artifact
detection, computation of heart rate and heart rate
variability parameters [11].
A number of wearable physiological monitoring
systems have been put into practical use for health
monitoring of the wearer in hospital and real life
situations and their performances have been reported [12-
17]. Varying degrees of success have been reported and
the percentage failures in the outdoor use are high. The
drawbacks associated with the conventional wearable
physiological systems are
• The cables woven into the fabric to interconnect the
sensors to the wearable data acquisition hardware
pick up interfering noises (e.g. 50 Hz power line
interference). The wires integrated into fabric act
like antennas and can easily pick up the noises from
nearby radiating sources.
• The sensors once integrated into the fabric, its
location cannot be changed or altered easily.
• The power required for the sensors to operate is to
be drawn from the common battery housed in the
wearable data acquisition hardware and are routed
through wires woven in the fabric.
• Typically these systems consist of a centralized
processing unit to digitize, process and transmit the
data to a remote monitoring system. The processor
is loaded heavily to perform multi-channel data
acquisition, processing and transmission of data.
• The cables from the vest interconnecting the sensors
can get damaged very easily due to twisting and
turning of the cables, while the wearer is
performing his routine activity.
To overcome the above issues related to wearable
physiological monitoring, the individual sensors
integrated into the vest can be housed with electronics
and wireless communication system to acquire and
transmit the physiological data. The recent advances in
the sensors (MEMS and Nanotechnology), low-power
microelectronics and miniaturization and wireless
networking enable Wireless Sensor Networks (WSN) for
human health monitoring. A number of tiny wireless
sensors, strategically placed on the human body create a
wireless body area network that can monitor various vital
signs, providing real-time feedback to the user and
medical personnel [18-22]. A multi-channel, bidirectional
and implantable bio-telemetric platform for real time invivo
monitoring of several physiological monitoring
systems have been developed [23].
Remote Monitori
Station
Wearable Data
Acquisition System
Wireless
Communication
Woven wires
Physiological
sensors
Figure 1. Overall architecture of the wearable physiological monitoring
system
22 JOURNAL OF NETWORKS, VOL. 3, NO. 5, MAY 2008
© 2008 ACADEMY PUBLISHER
Fig. 2 illustrates the architecture of a WSN based
wearable physiological monitoring system. Wireless
Sensor Networks (WSN) consists of a large number of
small nodes, which have built-in computing, power,
sensors to acquire physiological data from the wearer and
wireless transmission and reception capability. A wireless
sensor network for smart electronics shirt has been
developed which allows the monitoring of individual
biomedical data and is transmitted wireless for further
processing using a wireless link [24]. A number of
wireless ECG monitoring systems based on conventional
electrodes have been developed [25-28], a two lead
wireless ECG and oxygen saturation in blood monitoring
systems is developed [29]. A wireless body sensor
network with embedded intelligent motion sensors for
computer assisted physical rehabilitation is developed to
give feedback to the user and generate warnings based on
the users state, level of activity and environmental
conditions with data transmission capability to medical
servers via internet [30]. A personal health monitor
based on a wireless body area network (BAN) integrated
with intelligent sensors for psychophysiological
evaluation of military members undergoing intense
training by measuring heart-rate variability (HRV) to
quantify stress level prior to and during training as well
as to predict stress resistance is developed [31]. The
project CodeBlue describes the wireless medical sensor
network hardware and software platform to medical
monitoring of individuals [32]. Patient monitoring over
the wireless infrastructure oriented ad-hoc network has
been investigated [33-34]. These systems are useful in
transmitting the medical over larger distances and do not
discuss about the applications of wearable physiological
monitoring.
DEBEL has gained sufficient expertise during the
development of a wearable physiological monitoring
system named as Smart Vest [3]. The development has
culminated in the form of Smart Vest with sensors
integrated to sense, process, store and transmit the
physiological data. The developed system made use of
sensors integrated into the fabric interconnected by
woven wires, and interfaced to a wearable data
acquisition and processing hardware. To address the
various issues and problems encountered during the
development of the Smart Vest, the development of
wireless sensor network for wearable physiological
monitoring has been initiated.
The objective of this paper is to discuss a conceptual
design of a wearable physiological monitoring system
based on wireless sensor network to monitor a number of
physiological parameters. The physiological parameters
to be monitored are Electrocardiogram (ECG),
Electromyogram (EMG), Electroencephalogram (EEG),
Oxygen Saturation in blood (SaO2), body temperature,
systolic and diastolic blood pressure, respiratory rate,
Galvanic Skin Response (GSR) and movement of the
wearer recorded by an accelerometer. The acquired
physiological signals are preprocessed at each node and
transmitted to the wearable data acquisition hardware
(sink node) for further processing and transmitted
wireless to a remote monitoring station. The paper also
discusses the architecture of the WSN for wearable
physiological monitoring, protocols, security issues and
power requirements.