Int. J. Communications, Network and System Sciences, 2009, 2, 797-803
doi:10.4236/ ijcns.2009.28093 ublished Online November 2009 (
Copyright © 2009 SciRes. IJCNS
A Review of Wireless Body Area Networks for Medical
Sana ULLAH1, Pervez KHAN1, Niamat ULLAH1, Shahnaz SALEEM2,
Henry HIGGINS3, Kyung Sup KWAK1
1Graduate School of Telecommunication Engineering, Inha University Incheon, Nam-Gu, South Korea
2Graduate School of Computer Engineering, Inha University Incheon, Nam-Gu, South Korea
3Zarlink Semiconductor Company, Portskewett, Caldicot, United Kingdom
Email: {sanajcs, pervaizkanju, roshnee13},,,
Received March 8, 2009; revised May 16, 2009; accepted July 27, 2009
Recent advances in Micro-Electro-Mechanical Systems (MEMS) technology, integrated circuits, and wire-
less communication have allowed the realization of Wireless Body Area Networks (WBANs). WBANs
promise unobtrusive ambulatory health monitoring for a long period of time, and provide real-time updates
of the patient’s status to the physician. They are widely used for ubiquitous healthcare, entertainment, and
military applications. This paper reviews the key aspects of WBANs for numerous applications. We present
a WBAN infrastructure that provides solutions to on-demand, emergency, and normal traffic. We further
discuss in-body antenna design and low-power MAC protocol for a WBAN. In addition, we briefly outline
some of the WBAN applications with examples. Our discussion realizes a need for new power-efficient solu-
tions towards in-body and on-body sensor networks.
Keywords: Wireless Body Area Networks, Low Power MAC, Body Sensor Networks, BSN, WBAN
1. Introduction
Cardiovascular disease is the foremost cause of death in
the United States (US) and Europe since 1900. More
than ten million people are affected in Europe, one mil-
lion in the US, and twenty two million people in the
world [1–3]. The number is projected to be triple by
2020. The ratio is 17% in South Korea and 39% in UK
[4–5]. The healthcare expenditure in the US is expected
to increase from $2.9 trillion in 2009 to $4 trillion in
2015 [6]. The impending health crisis attracts researchers,
industrialists, and economists towards optimal and quick
health solutions. The non-intrusive and ambulatory
health monitoring of patient’s vital signs with real time
updates of medical records via internet provides eco-
nomical solutions to the health care systems.
A WBAN contains a number of portable, miniaturised,
and autonomous sensor nodes that monitors the body
function for sporting, health, entertainment, and emer-
gency applications. It provides long term health moni-
toring of patients under natural physiological states
without constraining their normal activities. In-body
sensor networks allow communication between im-
planted devices and remote monitoring equipments. They
are used to collect information from Implantable Car-
dioverter Defibrillators (ICDs) in order to detect and
treat ventricular tachyarrhythmia1 and to prevent Sudden
Cardiac Death (SCD) [7].
A number of ongoing projects such as CodeBlue,
MobiHealth, and iSIM have contributed to establish a
proactive WBAN system [8–10]. A system architecture
presented in [11] performs real-time analysis of sen-
sor’s data, provides real-time feedback to the user, and
forwards the user’s information to a telemedicine
server. UbiMon aims to develop a smart and affordable
health care system [12]. MIT Media Lab is developing
MIThril that gives a complete insight of human-ma-
chine interface [13] HIT lab focuses on quality inter-
faces and innovative wearable computers [14]. NASA
is developing a wearable physiological monitoring
system for astronauts called LifeGuard system [15].
IEEE 802.15.6 aims to provide low-power in-body and
1Ventricular tachyarrhythmia are abnormal patterns of electrical activ-
ity originating withinventricular tissue.
ISO Model IEEE 1073
Data link
Medical device data
Figure 1. Model ISO and IEEE 1073.
on-body wireless communication standards for medical
and non-medical applications [16]. IEEE 1073 is work-
ing towards a seven layers solution for wireless commu-
nication in a WBAN [17]. Figure 1 shows IEEE 1073
The rest of the paper is organized into five sections.
Section 2 presents a WBAN infrastructure for medical
and non-medical applications. Section 3 and 4 discuss
in-body antenna design and low-power MAC protocol
for a WBAN. Section 5 outlines some of the WBAN
applications. The final section concludes our work.
2. WBAN Infrastructure
A WBAN consists of in-body and on-body nodes that
continuously monitor patient’s vital information for di-
agnosis and prescription. Some on-body nodes are used
for multimedia and gaming applications.
A WBAN uses Wireless Medical Telemetry Services
(WMTS), unlicensed Industrial, Scientific, and Medical
(ISM), Ultra-wideband (UWB), and Medical Implant
Communications Service (MICS) bands for data trans-
mission. WMTS is a licensed band used for medical te-
lemetry system. Federal Communication Commission
(FCC) urges the use of WMTS for medical applications
due to fewer interfering sources. However, only author-
ized users such as physicians and trained technicians are
eligible to use this band. Furthermore, the restricted
WMTS (14 MHz) bandwidth cannot support video and
voice transmissions. The alternative spectrum for medi-
cal applications is to use 2.4 GHz ISM band that includes
guard bands to protect adjacent channel interference. A
licensed MICS band (402-405 MHz) is dedicated to the
implant communication.
Figure 2 shows the proposed WBAN infrastructure for
medical and non-medical applications.
The WBAN traffic is categorized into On-demand,
Emergency, and Normal traffic. On-demand traffic is
initiated by the coordinator or doctor to acquire certain
On-demand Traffic
Emergency Traffic
Normal Traffic
Image 1Image 2
Data Interface
To integrate in-body and on-body
nodes in a WBAN
Used to wakeup the in-body
and on-body nodes in case of
on-demand and emergency
Used for data
transfer including
normal traffic
Server Ambulance NurseTelemedicine
Game Server
Comm. Tower
Internet Portable
Server Game ServerMedical/
E me rgenc y
Ambulance Nurse
Coo rdinator
Implantable Vision System
Figure 2. A WBAN infrastructure for medical and non-medical applications.
Copyright © 2009 SciRes. IJCNS
information, mostly for the purpose of diagnostic rec-
ommendations. This is further divided into continuous
(in case of surgical events) and discontinuous (when oc-
casional information is required). Emergency traffic is
initiated by the nodes when they exceed a predefined
threshold and should be accommodated in less than one
second. This kind of traffic is not generated on regular
intervals and is totally unpredictable. Normal traffic is
the data traffic in a normal condition with no time critical
and on-demand events. This includes unobtrusive and
routine health monitoring of a patient and treatment of
many diseases such as gastrointestinal tract, neurological
disorders, cancer detection, handicap rehabilitation, and
the most threatening heart disease. The normal data is
collected and processed by the coordinator. The coordi-
nator contains a wakeup circuit, a main radio, and a
bridging function, all of them connected to a data inter-
face. The wakeup circuit is used to accommodate on-
demand and emergency traffic. The Bridging function is
used to establish a logical connection between different
nodes working on different frequency bands. The coor-
dinator is further connected to telemedicine, game, and
medical servers for relevant recommendations.
3. In-Body Antenna Design
The band designated for in-body communication is
MICS and is around 403MHz. The wavelength of this
frequency in space is 744mm so a half wave dipole will
be 372mm. Clearly, it is not possible to include an an-
tenna of such dimensions in a body [19]. These con-
straints make the available size much smaller than the
The electrical properties of a body affect the propaga-
tion in several ways. First, the high dielectric constant
increases the “electrical length” of E-field antennas such
as a dipole. Second, body tissue such as muscle is partly
conductive and will absorb some of the signal but it can
also act as a parasitic radiator. This is significant when
the physical antenna is much smaller than the optimum.
Typical dielectric constant (r
), conductivity (
) and
characteristic impedance properties of muscle
and fat are shown in Table 1.
1) Dipole Antenna: For a dipole of length 10mm, at
403MHz, the radiation resistance is 45m. in air. The
electrical length of the dipole is increased when sur-
rounded by material of a high dielectric constant such as
the body.
2) Loop Antenna: For a loop of 10mm diameter the
area is 78.5mm2, this gives the radiation resistance of
626μΩ. However, the loop acts, as a “magnetic dipole”
producing a more intense magnetic field than a dipole.
The loop is of use within the body as the magnetic field
is less affected by the body tissue compared to a dipole
or a patch and it can be readily integrated into existing
3) Patch Antenna: A patch antenna can be integrated
into the surface of an implant. Without requiring much
additional volume, the ideal patch will have dimensions
as shown in Figure 3 and acts as a λ/2 parallel-plate
transmission line with an impedance inversely propor-
tional to the width.
The radiation occurs at the edges of the patch, as
Table 1. Body electrical properties [19].
Muscle Fat
Frequency (r
(S.m-1) 0()Z
100 66.2 0.73 31.6 12.7 0.07 92.4
400 58 0.82 43.7 11.6 0.08 108
900 56 0.97 48.2 11.3 0.11 111
Feed Point
(Position Affects
L< λ/2
Figure 3. Patch antenna plan view, λ in the surrounding
Shorting Pin
Patch Propagation
from Edge
Air or Other
Figure 4. Patch antenna side view.
opyright © 2009 SciRes. WSN
shown in Figure 4. For in-body use a full size patch is
not an option. However, as it is immersed in a body tis-
sue that has a dielectric constant in the order of 50, the
electrical size of the patch becomes larger than would be
in air. An electrically small patch will have low real im-
pedance and therefore impaired performance compared
to the ideal one. There are several other options for an-
tenna such as Planar Inverted-F Antenna (PIFA), loaded
PIFA, the bow tie, spiral and trailing wire. These anten-
nas may have properties that may make them better
suited for some applications.
4) Impedance Measurement: The impedance of the
patch and dipole will be affected considerably by being
surrounded by the body tissue. The doctor who fits it
determines the position of an implant within a body. It
may move within the body after fitting. Each body has a
different shape with different proportions of fat and
muscle that may change with time. This means that a
definitive measurement of antenna impedance is of little
value. Measuring it immersed in a body phantom can
make an approximation of impedance liquid [20]. Using
this impedance, the antenna-matching network can be
designed with the provision of software controlled trim-
ming as can be done with variable capacitors integrated
into the transceiver. The trimming routine should be run
on each power up or at regular intervals to maintain op-
timum performance.
4. MAC Protocol
The design and implementation of a low-power MAC
protocol for a WBAN is currently a hot research topic.
The most challenging task is to accommodate the in-
body nodes in a power-efficient manner. Unlike on-body
nodes, the in-body nodes are implanted under human
skin where the electrical properties of the body affect the
signal propagations. The human body is a medium that
poses many wireless transmission challenges. The body
is composed of several components that are unpredict-
able and subjected to change.
Li et al. proposed a novel TDMA protocol for an
on-body sensor network that exploits the biosignal fea-
tures to perform TDMA synchronization and improves
the energy efficiency [21]. Other protocols like WASP,
CICADA, and BSN-MAC are proposed in [22–24]. The
performance of a non-beacon IEEE 802.15.4 is investi-
gated in [25], where the authors considered low up-
load/download rates, mostly per hour. Furthermore, the
data transmission is based on periodic intervals that limit
the performance to certain applications. There is no reli-
able support for on-demand and emergency traffic.
The WBAN traffic requires sophisticated low-power
techniques to ensure safe and reliable operations. Exist-
ormal traffic
Emergency traffic
On-demand traffic
Gather information
Mapping Send
Figure 5. WBAN MAC mapping.
ing MAC protocols such as SMAC [26], TMAC [27],
IEEE 802.15.4 [28], and WiseMAC [29] give limited
answers to the heterogeneous traffic. The in-body nodes
do not urge synchronized wakeup periods due to spo-
radic medical events. Medical data usually needs high
priority and reliability than non-medical data. In case of
emergency events, the nodes should access the channel
in less than one second [30]. IEEE 802.15.4 Guaranteed
Time Slots (GTS) can be utilized to handle time critical
events but they expire in case of a low traffic. Further-
more, some in-body nodes have high data transmission
frequency than others. Figure 5 shows the required MAC
mapping of the WBAN traffic.
The IEEE 802.15.4 can be considered for certain
on-body sensor network applications but this does not
achieve the required power level of in-body nodes. For
critical and non-critical medical traffic, the IEEE
802.15.4 has several power consumption and QoS issues
[31–34]. Also, this standard operates in 2.4 GHz band,
which allows the possibilities of interference from other
devices such as IEEE 802.11 and microwave. Dave et al.
studied the energy efficiency and QoS performance of
IEEE 802.15.4 and IEEE 802.11e [35] MAC protocols
under two generic applications: a wave-form real time
stream and a real-time parameter measurement stream
[36]. Table 2 shows the Packet Delivery Ratio and the
Power (in mW) for both applications. The AC_BE and
AC_VO represent the access categories voice and
best-effort in the IEEE 802.11e.
IEEE 802.15.4 uses CSMA/CA mechanism that does
not provide reliable solutions in the in-body sensor net-
works. The path loss inside human body results in im-
proper Clear Channel Assessment (CCA). For a thresh-
Table 2. Packet delivery ratio and power (in mW).
Sensor Nodes IEEE
Wave-form100% 100% 100%
Ratio Parameter 99.77% 100% 100%
Wave-form1.82 4.01 3.57
(mW) Parameter 0.26 2.88 2.77
Copyright © 2009 SciRes. IJCNS
Copyright © 2009 SciRes. WSN
Table 3 shows some of the in-body and on-body ap-
plications [40]. In-body applications include, monitoring
and program changes for pacemakers and implantable
cardiac defibrillators, control of bladder function, and
restoration of limb movement [41]. On-body medical
applications include monitoring ECG, blood pressure,
temperature, and respiration. Furthermore, on-body non-
medical applications include monitoring forgotten things,
establishing a social network, and assessing soldier fa-
tigue and battle readiness.
The following part discusses some of the WBAN ap-
1) Cardiovascular Diseases: Traditionally, holter
monitors were used to collect cardio rhythm disturbances
for offline processing without real-time feedback. How-
ever, transient abnormalities are sometimes hard to cap-
ture. For instance, many cardiac diseases are associated
with episodic rather than continuous abnormalities, such
as transient surges in blood pressure, paroxysmal ar-
rhythmias or induced episodes of myocardial ischemia
and their time cannot be accurately predicated [42]. A
WBAN is a key technology to prevent the occurrence of
myocardial infarction, monitor episodic events or any
other abnormal condition and can be used for ambulatory
health monitoring.
Figure 6. Residual emergency at on-body nodes.
old of -85dBm and -95dBm, the on-body nodes cannot
see the activity of in-body nodes when they are away at 3
meters distance from the body surface [37]. An alterna-
tive solution is to use TDMA-based protocols for a
WBAN. Therefore, we analyze the performance of a
preamble-based TDMA [38] protocol for an on-body
sensor network. We use ns-2 [39] for extensive simula-
tions. Figure 6 shows the residual energy at the on-body
nodes and the coordinator. After the nodes finish their
transmissions, they go into sleep mode. The ECG node
sleeps after 150 seconds. When the EEG node finishes its
transmission at 300 seconds, the coordinator consumes
less energy as indicated by the slight change in the curve.
2) Cancer Detection: Cancer remains one of the big-
gest threats to the human life. According to National
Center for Health Statistics, about 9 million people had
cancer diagnosis in 1999 [43]. A set of miniaturised sen-
sors capable of monitoring cancer cells can be seam-
lessly integrated in a WBAN. This allows physician to
diagnose tumors without biopsy.
5. WBAN Applications
WBANs have great potential for several applications
including remote medical diagnosis, interactive gaming,
and military applications.
3) Asthma: A WBAN can help millions of patients
suffering from asthma by monitoring allergic agents in the
Table 3. In-body and on-body sensor networks applications.
Type Sensor Node Date Rate
Duty Cycle
(per device)%
per time
(Sensitive to Latency) Privacy
Glucose Sensor Few Kbps <1% Extremely Low Yes High
Pacemaker Few Kbps <1% Low Yes High
Endoscope Capsule >2Mbps <50% Low Yes Medium
ECG 3kbps <10% Low Yes High
SpO2 32bps <1% Low Yes High
Blood Pressure <10bps <1% High Yes High
Music for Headsets 1.4Mbps High Relatively High Yes Low
Forgotten Things
Monitor 256kbps Medium Low No Low
Social Networking <200kbps <1% Low Low High
Vid e o
conf erence
Panel of Doctors
Doctor Hom
Ca rdiolody
Coordi nator
Figure 7. A real-time telemedicine infrastructure for patient rehabilitation.
air and providing real-time feedback to the physician.
Chu et al proposed a GPS-based device that monitors
environmental factors and triggers an alarm in case of
detecting information allergic to the patient [44].
4) Telemedicine Systems: Existing telemedicine sys-
tems either use dedicated wireless channels to transfer
information to the remote stations, or power demanding
protocols such Bluetooth that are open to interference by
other devices working in the same frequency band. These
characteristics limit prolonged health monitoring. A
WBAN can be integrated into a telemedicine system that
supports unobtrusive ambulatory health monitoring for
long period of time. Figure 7 shows a real-time tele-
medicine infrastructure for patient rehabilitation.
5) Artificial Retina: Retina prosthesis chips can be
implanted in the human eye that assists patient with lim-
ited or no vision to see at an adequate level.
6) Battlefield: WBANs can be used to connect sol-
diers in a battlefield and report their activities to the
commander, i.e., running, firing, and digging. The sol-
diers should have a secure communication channel in
order to prevent ambushes.
6. Conclusions
In this paper, we proposed a WBAN infrastructure that
supports on-demand, emergency, and normal traffic us-
ing wakeup and main radios. This infrastructure proves
to be adequate for unobtrusive health monitoring. We
further provided a technical discussion on the in–body
antenna design and supported patch antenna for in-body
communication. We also discussed low-power MAC
protocol for a WBAN. Existing low-power MAC proto-
cols have several limitations to accommodate the het-
erogeneous traffic in a reliable manner and hence require
new power-efficient solutions. We finally outlined the
potential of a WBAN for ubiquitous healthcare, enter-
tainment, and military applications.
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