Medical Body Area Network, Architectural Design and Challenges: A Survey

Abstract

Medical body area network is a human-centric application of wireless sensor network which has recently gained much significance. The application includes both wearable and implantable sensors for continuous monitoring of patients in hospitals, old houses or at any remote location. These sensor nodes in medical body area network possess all the characteristics of nodes in wireless sensor network. In this paper a survey of medical wireless body area network, its architectural design issues and challenges have been discussed.

Full text

Medical Body Area Network, Architectural Design and Challenges: A survey
Madiha Fatima, Adnan K. Kiani , Adeel Baig
School of Electrical Engineering and Computer Science (SEECS)
National University of Science and Technology (NUST), Islamabad, Pakistan
{11msitmfatima, adnan.khalid, adeel.baig}@seecs.edu.pk
Abstract. Medical body area network is a human-centric application of wireless sensor network which has re-
cently gained much significance. The application includes both wearable and implantable sensors for continuous
monitoring of patients in hospitals, old houses or at any remote location. These sensor nodes in medical body area
network possess all the characteristics of nodes in wireless sensor network. In this paper a survey of medical
wireless body area network, its architectural design issues and challenges have been discussed.
Keywords: Wireless sensor network, medical body area network: architectural design, reliability, energy effi-
ciency and routing
1 INTRODUCTION
Wireless sensor network is composed of thickly inhabited low-cost and low-power tiny sensor devices which inte-
ract with the environment by sensing or monitoring the physical or environmental variables e.g. temperature and
cooperatively pass their data to base station for further processing and controlling actions. WSNs have a wide varie-
ty of applications[1] including but not limited to industrial, agriculture, habitat, forest and environmental monitor-
ing, home and office automation, healthcare and medicine, urban sensor network and energy management. WSNs
can also be used in the application areas of security, defense, military and disaster monitoring. Using wireless sensor
networks in battle field surveillance is one of the most important and mature applications of wireless sensor net-
work. Urban sensor networks are placed throughout the city to manage the city i.e. traffic signals, street lights and
other energy management projects. WSNs can be used in irrigation as well. These sensor networks can also be used
to detect the chemical or biological reactions. Monitoring a nuclear plant is another very important application of
wireless sensor network. Human-centric applications of wireless sensor network include health science and the
healthcare systems. WSNs keep track of patients’ vital signs in hospitals, in homes and even when patients are mo-
bile through continuous real-time monitoring. Healthcare applications [2] include home-based care, hospital or clini-
cal monitoring, management of disaster relief and medical facility, sports health and last but not least medical body
area network. Home-based care provides complete health services at home. This is very helpful application especial-
ly for old people who cannot frequently visit the doctor or hospital. Many types of sensor nodes are available for
monitoring different physical and biological parameters i.e. blood pressure, sugar level, and heartbeat and cholester-
ol level. Attachment of multiple sensors to human body for the purpose of continuous and real-time monitoring de-
fines medical body area network application of wireless sensor network.
Wireless sensor network have to monitor a specific region or application. Sensor nodes in the wireless sensor net-
work have local scope. These nodes monitor the application and send their data to base station. Due to local scope
these nodes require less functionality. Sensor nodes are small in size and memory, low cost, low power, and
equipped with low processing and computational power. These sensor nodes are of two types i.e. source and sink.
Source nodes monitor the environment, collect information and send it to the sink node. Sink node is a sensor node
which collects the information and sends it to base station. These nodes in wireless sensor network can be mobile
depending on the nature of application. In weather and temperature monitoring applications the sensor nodes are
usually static. Some applications such as flood forecasting, transportation etc contain mobile nodes. Mobility in
WSNs can be categorized as sensor mobility, sink mobility and event mobility. Sensor nodes can be mobile to moni-
tor a region or sense a phenomenon. For sink mobility it might be possible that a sink node is not a part of WSN e.g.
PDA or laptop which remain mobile. Event can also be mobile. E.g. water in a river, an application for forecasting

floods or patient that are moving in a healthcare application, are examples of mobile events. Sensor nodes in the
network can communicate with each other either in single hop or multi-hop fashion [3]. Single hop communication
is hierarchical communication which uses the star like topology. On the other hand relay nodes are involved in mul-
ti-hop communication and cooperatively pass on data to sink node. Single hop communication is supported in Blu-
etooth based wireless sensor network while multi-hop communication is supported in ZigBee based wireless sensor
network. Communication in the wireless sensor network is data centric and depending on the applications. Three
types of communication paradigms can be used in wireless sensor networks. These communication models are peri-
odic, event driven and query driven data reporting models. In periodic (continuous) data communication, the sensor
node senses the environment, processes data and periodically sends it to the sink node e.g. monitoring weather con-
ditions, temperature etc. In a query based communication (on-demand communication) sensor nodes sense the envi-
ronment and instead of forwarding this information, they store it in a local memory. They only send it when they
receive any query or request for information from the sink node. In an event driven communication, sensor nodes
remain in an inactive state. When an event occurs (rise in temperature to threshold level or rise of water level in
river or pressure in air etc.) they become active. They sense the event and send information to the sink node. Medi-
cal body area network can perform high level tasks from sensing to transmitting medical signals to high level
processing.
In a body area network, sensors usually sense and collect information and send it to base station from where doc-
tors/caretakers can access the patient’s information for taking necessary actions. Sensor devices used in medical
body area network are of two types i.e. internal and external sensor devices. Internal sensor devices are ingestible
capsules or implanted sensors. One example of this type of sensor is core temperature sensor. An implanted chip is
used to measure other medical conditions of body such as diagnosing paralysis and Parkinson's disease etc. Another
sensor is named as Endo-scope sensor. External sensors are actually electrical signaling devices which are wearable
and detachable. Examples of such devices are Pulse OXIMETER sensor, Electro-cardiograph and body temperature
sensor etc. Figure.1 represents a typical medical body area network including both wearable and implantable sensor
nodes.
Medical body area network is a healthcare application of wireless sensor network which slightly differs from other
applications of wireless sensor network. For example topology in medical body area network is usually known. Re-
placement of batteries of sensor nodes in body area network is difficult but it is not impossible. There is hybrid
communication in medical body area network. Some patients in medical body area network need continuous moni-
toring and some non critical patients need only periodic or query based reporting. Some patients require continuous
monitoring of their vital signs and if the vital signs exceed the threshold value, they instantly report the event to base
station and also generate emergency alarms. In body area network the information is both data and identity centric
because in these networks different patients are being monitored. Body area network performs in a way that data
comes from different sensors which belongs to different patients. In a medical body area network implantable and
wearable sensors are used for monitoring of patients in hospitals, old houses or in any remote locations while they
are moving. These sensors are attached to human body to collect and transmit the patient’s data to base stations.
Sensor nodes in body area network are small in size and memory space with low cost, low computational and
processing power. These sensor nodes have small transmission range and have low data rates. As in typical wireless
sensor network, there are two types of nodes in medical body area network i.e. source and sink. These nodes can be
static or mobile depending on the implementation of the network. For example body area network is implemented in
ICU rooms of hospitals where patients are static or in emergency rooms where patients are waiting for checkup and
they can be mobile. Communication model used in medical body area network mainly depends on patient’s condi-
tion. Similarly sensor nodes in the network can communicate with each other through single hop communication or
multi-hop communication. Single hop communication works in star like topology where all the nodes in the network
report to cluster heads in the network. In multi hop communication sensor nodes in medical body area network coo-
peratively pass on the data of other nodes along with their own data. This multi-hop communication can be done by
using relay nodes in the network. These relay nodes are sensor nodes in the network and act as router as well by
cooperatively passing on the data of other nodes to the sink or base station. Sensor nodes in medical body area have
limited energy resource and data

communication is most energy consuming process in the wireless sensor and medical body area network.
cult to change or rec
harge the batteries of nodes. Hence,
order to increase the network lifetime.
medical body area network as
health related data is
can lead the doctor or care
taker to take wrong decisions.
physical conditions of a patient. Energy efficiency and reliability are controversial issues in wireless sensor and
medical body area network. There
is need to draw a balanced line between the energy efficiency and reliability.
In this paper we present a
comprehensive survey
as follows: Section 2 presents
related work
Section 3 presents the functional
architecture
network which includes the r
eliabili
ensuring reliability and energy efficiency
followed by reference listing.
2 Related Work
Healthcare is an important
application of wireless sensor network.
monitoring
there is shortage of medical and nursing staff
s
ome patients need continuous or frequent monitoring of vital signs and it is difficult for nursing staff to take
quent readings
of vital signs of patients
done using sensor nodes on
patient’s body. In this section we present some implementations of medical body area
network.
Fig. 1. Typical medical body area network [15]
communication is most energy consuming process in the wireless sensor and medical body area network.
harge the batteries of nodes. Hence,
there is a
need to use the battery power of n
order to increase the network lifetime.
Besides energy efficiency
, reliability is another important requirement of
health related data is
quite sensitive.
Even a small amount of malicious or
taker to take wrong decisions.
Reliability should be ensured in measuring and reporting of
physical conditions of a patient. Energy efficiency and reliability are controversial issues in wireless sensor and
is need to draw a balanced line between the energy efficiency and reliability.
comprehensive survey
of medical body area network. We have
related work
which covers some examples of usage
of medical body area n
architecture
of M-BAN. Section 4
presents the challenges in
eliabili
ty, energy efficiency and routing. Section 5
includes the re
ensuring reliability and energy efficiency
in medical body area network.
We present the conclusions in Sec
application of wireless sensor network.
Due to increase in population,
there is shortage of medical and nursing staff
to attend a large number of
patients
ome patients need continuous or frequent monitoring of vital signs and it is difficult for nursing staff to take
of vital signs of patients
. In medical body area network continuous monitoring of pa
patient’s body. In this section we present some implementations of medical body area
communication is most energy consuming process in the wireless sensor and medical body area network.
It is diffi-
need to use the battery power of n
odes wisely in
, reliability is another important requirement of
Even a small amount of malicious or
wrong data
Reliability should be ensured in measuring and reporting of
physical conditions of a patient. Energy efficiency and reliability are controversial issues in wireless sensor and
is need to draw a balanced line between the energy efficiency and reliability.
organized rest of our paper
of medical body area n
etwork.
presents the challenges in
medical body area
includes the re
commendations for
We present the conclusions in Sec
tion 6
Due to increase in population,
during disaster
patients
at a time. Similarly
ome patients need continuous or frequent monitoring of vital signs and it is difficult for nursing staff to take
fre-
. In medical body area network continuous monitoring of pa
tients can be
patient’s body. In this section we present some implementations of medical body area

2.1 Medical Wireless Body Area Network
In the previous section, we briefly discussed the healthcare applications of wireless sensor networks and medical
body area network. Wireless sensor networks can be used in hospital or remote clinical monitoring of patients. In
this section we present state of the art work in the field of medical body area network.
Dorothy et al.[6] proposed a hospital monitoring system called SMART (Scalable Medical Alert Response Technol-
ogy).The system integrates wireless patient monitoring, geographical-positioning, signal processing, targeted alert-
ing, and also wireless interfaces for doctors/caretakers. SMART is implemented in waiting or emergency rooms of
hospital for monitoring of the patients who are sitting there and waiting for checkup and medical aid. SMART hos-
pital monitoring system is very useful in overcrowded emergency departments and also during disasters. SMART
protocol addresses the challenges such as selection of vital signs, location of sensors and light weight platform for
communication. An ultra sound based indoor positioning system is deployed for geo positioning. For wireless com-
munication Wi-Fi technology (802.11b) is used. Similarly Jeonggil et al. [7] presented a network model MEDiSN
for emergency detection using wireless sensor network. MEDiSN is developed for hospital and disaster monitoring.
MEDiSN is composed of physiological monitors, relay points and back end servers. Physiological monitors have the
ability to monitor, store and transmit encrypted vital signs. Relay points carry and pass on the data in multi-hop fa-
shion. The back end server can store this data and present a user friendly graphical interface to authenticate users. In
the paper authors have discussed the basic requirement for network such as scalability, geographic reach, and traffic
detection, its QoS and support for mobility and presentation of data. Octav et al. [8] discuss the shortcomings of
MEDiSN and conclude that the sensing reliability of body area network has been ignored in MEDiSN. They pre-
sented an analysis of system reliability of body area network and came to the point that sensing reliability is more
critical as compared to network reliability in body area network. This paper represents the deployment of wireless
clinical monitoring system for monitoring of pulse rate and oxygen saturation rate of patients. Figure.2 gives the
basic architecture of MEDiSN which shows the communication among the nodes and with other components of the
network.
Sharma et al. [9] presented a prototype for remote monitoring of vital signs of a patient i.e. ECG, breathing rate and
body temperature. Body area network can monitor and send the vital signs of patient to base station at hospital or
any remote location for consulting doctor or caregiver. Network coordinator controls the transmission of vital signs
to bases station. This paper presented the implementation of body area network in beacon mode in which network
coordinator wakes up the sensor nodes to sense and transmit the data to base station.
Medical body area network is used to monitor patients at homes, hospitals, in old houses or at any remote location.
Data accuracy and in time data delivery are important requirements of healthcare applications. There is a need to
select appropriate network architecture to fulfill all the requirements of healthcare applications of wireless sensor
networks. Designers of medical body area network are facing many research challenges for the architecture design.
In following section we will discuss some proposed architecture designs for medical body area network.
Fig. 2. MEDiSN a hospital and disaster monitoring system[5]

Fig. 3. Basic functional architecture of medical body area network
3 Functional Architecture
Architecture of medical body area network depends on distinct factors which make it unique compared to general
wireless sensor network applications. Many sensor nodes are attached to the human body which sense different
types of data. These nodes are of limited number and are strategically located on human body. In Figure.3 we
represent the basic functional architecture of body area network.
Yuan-Jen et al. [10] proposed a data driven architecture which connects sensor network to the internet. The architec-
ture has two parts connected with each other through databases server. In the first part there is communication be-
tween the sensor nodes and database and in second part a communication is between the database and user interface.
There is asynchronous interoperation between both parts of architecture. Users have no direct control over sensor
nodes. They update or acquire information from the sensor nodes via web applications. The sensor node senses data
in periodic or event driven environment but transmission will be demand based. In paper [11] authors presented the
comparison between 1-hop star architecture and the 2-hop extended star architecture on the basis of some investiga-
tions. They concluded that not any architecture fits the environment so they gave some guidelines to effectively
design the wireless body area network. Similarly Yu Ge et al. [12] investigated the impact of single hop star and
multi-hop architecture designs on body area network. Authors concluded that for reliable transmission of data multi-
hop network architecture is efficient as compared to star architecture. They used CTP protocol for making data col-
lection tree. They also suggested the optimal power of transmission signal by inspecting average number of packet
transmissions, energy consumption of network and average cost per hop.
Some patients need continuous monitoring in care rooms or in old houses. Maha et al. [13] proposed a service
oriented design for middle ware in body area network for this purpose. In proposed architecture sensor nodes are
capable of sensing and transmitting bio-signals to gateway. The gateway further transmits theses vital signs to a
remote central unit. The gateway can also receive the queries and control information from the central unit. Wireless
sensor nodes allow a patient to move in the care unit. The proposed architecture is composed of three components
(1) medical sensors network, (2) a coordinator node acting as a gateway and (3) a central node acting as a sink node.
Different types of sensor devices are used to monitor different variables of a patient in medical body area network.
Pulse rate and oxygen saturation in blood are two important factors to sense the respiratory and circulatory system of
human being. Sun et al. [14] presented architecture for M-BAN where different types of data are collected from
patients such as ECG, heart/pulse rate, EEG, body temperature, sugar or oxygen level in blood etc. Sensor nodes
send their data to network coordinator. Network coordinator merges the data and sends it to the data center or moni-
toring system. The authors also describe the hardware design and architecture of network and its software design.

Fig. 4. Location of sensor and sink nodes in medical body area network [10]
Sensor nodes in medical body area network have same characteristics as in traditional WSNs. There is a need to
wisely implement body area networks in both aspects i.e. hardware and software so that we can minimize the was-
tage of nodes’ battery power. Possible placement of sensor nodes on human body is represented in figure.4. Net-
work’s life time mainly depends on the battery power of nodes. Patient’s data in body area network is very crucial
and requires high reliability. There should be minimum packet drop rate and less delay in the network. Usually in-
formation in medical body area network is event driven. So the event reliability is most important as compared to
packet reliability. An intensive research has been taken on routing protocols in body area network which provide
reliability and energy efficiency. Following section comprises the state of the art work on energy efficiency, reliabil-
ity and routing in medical body area network.
4 Challenges
In this section we present challenges in medical body area network. Due to limited power supply of nodes and criti-
cal nature of patient’s data both energy efficiency and reliability have become very crucial issues in body area net-
work. These issues need to be addressed very wisely because there is inevitable tradeoff between energy efficiency
and reliability. Routing is important in a way that there is need of a routing protocol which should be efficient
enough that it consumes less energy of nodes in building and maintenance of routes and provides reliable data trans-
fer. We have to save energy in routing process so that we can efficiently perform sensing and transmission in net-
work. Following subsections present some related work of energy efficiency, reliability and routing in medical body
area.
4.1 Energy efficiency
Due to limited power resources of wireless sensor nodes, efficient power consumption is a big challenge in WSNs.
Reason for sensor nodes being limited in power resources are their inexpensive nature, limited size and weight.
Network lifetime directly depends on the battery life of sensor nodes. It might be possible but hard to replace or
recharge batteries of sensor nodes. Sensing of an event, transmitting or receiving data, processing or forwarding
queries are all power consuming activities. Some activities of nodes are taken as energy wasting activities such as
collision, idle listening, overhearing, over emitting, retransmitting etc. A sensor node can be in four states i.e. trans-
mitting, receiving, idle or sensing the channel. Transmitting or receiving data are most energy consuming states of a

sensor node. Idle listening and overhearing are energy wasting activities of sensor nodes. Many energy efficient
protocols and sleep and wake up mechanisms are introduced for power saving in wireless sensor networks.
Omeni et al. [15] proposed an energy-efficient MAC protocol for medical body area network for periodic data
transmission. The proposed MAC protocol achieves energy efficiency simply by avoiding collisions in the network.
Master-slaves architecture is followed in the network with single hop communication. The entire network is central-
ly managed. Joining of network and allocation of time slots to the nodes is centrally controlled in order to reduce
collisions within the cluster in network. Collisions of packets with the transmissions of neighboring cluster is
avoided by using an algorithm called clear channel assessment which is based on a “listen-before-transmit”. In order
to overcome the problem of overlapping of time slots a new concept of wakeup fallback time is used. Significant
energy efficiency is achieved in the network because of single-hop communication and centralized allocation of
sleep and wake up scheduling to nodes. HyungTae et al. [16] proposed an energy efficient MAC scheme in which a
coordinator node controls the medium access of the sensor nodes. This coordinator already knows the distance and
residual energy of the nodes. Coordinator node uses minimum spanning tree for routing in the medical body area
network and it allocates the time slots to nodes for medium access. The coordinator node periodically sends beacon
packets in order to synchronize the time slots among sensor nodes in body area network. Only during the assigned
time slots nodes can transmit their data by turning on their radio. Using MAC protocol along with a mechanism of
wake up radio proposed by Moshaddique et al. [17] improved the energy efficiency and delay in the medical body
area network. A wake up radio scheme is implemented in protocol by adding an additional radio circuit. Nodes
communicate in a star topology. This additional radio circuit uses radio signals which are out-of-band in network.
This extra radio circuit will be used to wake up a node to start its transmission. This wake radio signal has two chan-
nels; one for carrying data and control packet and other for waking up a node. Implementing this radio signal in
MAC protocol improves energy efficiency. Using TDMA with wake up signal reduces the chance of collision and
also increases the sleep time of nodes with acceptable packet delay in medical body area network.
Many types of sensor devices are used in medical body area network. They can be broadly classified as wearable
and implantable devices. To accommodate all these types of devices in a single network is also a big challenge. In
this context Timmons and Scanlon presented a medical MAC protocol named MedMAC [18] for energy efficiency
and adaptability of channel access in medical body area. The MedMAC protocol uses TDMA for periodic data and
also contains support for emergency data. Waking up nodes for transmission is also a cause of energy wastage.
Adaptive Guard Band Algorithm is used to maintain the synchronization between nodes during their sleep. Hence
nodes can sleep through many beacon periods without compromising on synchronization.
Reliability and energy efficiency are very important requirements of wireless sensor networks and medical body
area network. There is a tradeoff between reliability and energy efficiency depending on the application type. Litera-
ture review and research challenges for reliability in medical body area network are discussed in the coming subsec-
tion.
4.2 Reliability
Reliability is the most focused issue in the field of wireless sensor network. Reliability in detection and reporting of
event is necessary in medical body area network. Many approaches have been presented to ensure reliability e.g.
automatic repeat request, multipath routing and forward error correction coding etc. However, these approaches are
not suitable for wireless sensor networks due to sensor nodes’ limitation, poor link quality in wireless network, li-
mited power of nodes etc. These approaches also result into routing and data overhead. Reliability requirement be-
comes more critical in healthcare applications of wireless sensor network. Patient’s data is very sensitive in body
area network. In medical body area network event reliability is more important as compared to packet reliability.
There is tradeoff between the reliability and energy efficiency in body area network. Many mechanisms such as
sleep scheduling for energy efficiency have reliability constraint and similarly there are many approaches to ensure
reliability like multipath routing, using Acknowledgments, retransmission etc has energy efficiency constraint.
Octav et al. [19] proposed a mechanism named DRAP to cope with the patient’s mobility in the clinical monitoring
using wireless sensor network for achieving reliability on the cost of energy efficiency. Three types of nodes which
are involved in clinical monitoring system are (1) base station node, (2) relay nodes, and (3) the patient nodes. Two
metrics of reliability defined by the authors are (1) end to end reliability and (2) first-hop reliability. End to end re-

liability is for successful transmission of packet at base station node. The reliability between the sensor node and
first relay node is termed as first hop reliability. Mostly packet loss occurs between the patient node and relay node.
DRAP protocol helps in selecting best relay nodes and also adopts the mobility in the network. DRAP protocol helps
in collecting the patients’ data at relay node in order to send to base station. DRAP can easily integrate with CTP
which is a data collection protocol in wireless sensor and body area network. Patient’s mobility can cause the packet
loss in the body area network. Reliable communication is necessary for real time monitoring of patient in hospitals.
To overcome the packet loss we cannot increase the transmission power because high power has health related
harmful effects. A cooperative network coding based wireless body area network is proposed in [20] in which net-
work coding and cooperative communication schemes are combined for many to many network configurations.
Multi input multi output concept is used at relay nodes and receiver nodes which reduces the probability of packet
loss and increases the throughput of network. Multiple sensor nodes send their packets to multiple relay nodes.
These relay nodes combine all the packets and send to multiple sink nodes. There are rare chances of failure of all
the relay nodes or packet loss at all the nodes at the same time. The reason for preference of MIMO cooperation
presented among the source and relay nodes is the small size of nodes in the body area network. Due to their small
size it is practically not possible to attach more than one antenna in the nodes. This scheme also avoids the single
point of failure.
Increasing number of nodes in body area network decreases the performance of network because of single transceiv-
er devices using single channel for transmission. These single channel devices cannot handle the increasing number
of nodes in the network. Ivanov et al. [21] proposed an approach to solve this problem by introducing multiple
channels at MAC layer along with multi-hop cooperative communication between body area network and environ-
mental sensor nodes. The authors proposed a CAM-MAC-ARCB based cooperative technique which solves the
exposed node problem of CAM-MAC. Sampangi et al. [22] proposed a scheme to reduce the network delay and
packet loss for in time data transmission. The proposed scheme uses multiple intermediate sinks to lessen the burden
on single sink node. This scheme also reduced the contention between the sensor nodes when they were transmitting
to single sink node. In this way the packet loss probability can be reduced so the delay in the network can reduce and
fresh data can be achieved at base station.
Wireless sensors networks require higher event reliability as compared to packet reliability. Need of reliable data
transfer become inevitable in healthcare applications of medical body area network. Patient’s data is very sensitive.
It should be accurate, complete and in time data delivery is required. Similarly energy efficiency is also an important
factor in the wireless sensor network because of limited power of sensor nodes. Many MAC and data aggregation
protocols and sleep scheduling mechanism are introduced for energy efficiency in body area network. Both reliabili-
ty and energy efficiency are most important factors in medical body area network but there is tradeoff between them.
Medical body area network requires a routing protocol which provides reliable and energy efficient end to end data
delivery.
4.3 Routing
Two types of routing protocols used in medical body area network are cluster based routing protocol and flat routing
protocol. Cluster based routing protocols arrange the nodes in form of groups and use sleep mechanisms to save
energy. Flat routing protocols attain energy efficiency by reducing the routing overhead. In flat routing mechanisms
of flooding, forwarding or data-centric based routing is implemented. Flooding has low cost for topology mainten-
ance but it has some drawbacks such as implosion, overlap and resource blindness. Forwarding with local informa-
tion is used to overcome the problems of flooding. Topology in wireless sensor network is usually not predeter-
mined but in case of health care applications of WSNs topology is not much random. In healthcare wireless sensor
networks there should also be support for mobility because the network might be combination of both mobile and
stationary nodes. Nodes in the same observation area have related data so health care WSN should have the ability
to aggregate data of different node and discard the redundant packets. The routing protocol for healthcare applica-
tion of wireless sensor network must have the support for both periodic and event driven data. Support for periodic
data is necessary to continuously monitor the data and for reporting the vital signs of patient to doctor is necessary
for in time treatment of patient. Real time transmission of data is very important in medical body area network be-
cause of its critical nature.

Routing protocols in healthcare monitoring can be categorized [23] as (i) periodic sampling, (ii) event-driven moni-
toring and (iii) hybrid monitoring. In periodic sampling the patients are monitored continuously and the patient’s
data is periodically reported to monitoring system. For continuous monitoring cluster based algorithm LEACH can
be used. LEACH is a proactive routing protocol in which nodes periodically send their data to base station. TEEN is
another cluster based algorithm which is reactive protocol. It senses the network all the time but sends data only
when threshold level exceeds. APTEEN which is a hybrid protocol is developed to merge the properties of both
LEACH and TEEN protocols. Many sensors in the body area network are within same observation region and have
same type of information. Transmission of data at all nodes is not an efficient approach. A routing scheme has been
proposed [24] which selectively collects information from the nodes to reduce burden on sink node by reducing the
number of transmissions in the network. The information collected is on the basis of relationship between data. For
example to measure blood pressure of patient two types of information is needed i.e. ECG and PPG. In the Proposed
routing scheme PPG node will send its data to ECG node. ECG node will process and merge the data and send this
converted data to base station.
Ababneh et al. [25] proposed energy-balanced rate allocation and routing protocol in medical body area network for
load balancing and efficient rate allocation to nodes. EBRAR protocol builds routing path on the basis of residual
energy of nodes. Energy-balanced rate allocation and routing protocol force the packet to route through a path with
nodes of higher energy towards the sink node. In this way it protects the nodes having lower residual energy.
EBRAR works in two phases. First phase is tree construction and second phase is rate allocation. In the first phase
EBRAR protocol uses energy (residual energy of node), degree (number of neighboring nodes) and hop-count as
metrics in order to construct the routing tree to increase the lifetime of network and to increase its throughput ca-
pacity. They also calculated the utility function of nodes and turned off the nodes with low priority streams in order
to save the bandwidth of the network and also to improve the utility of monitoring system. The proposed algorithm
not only conserves the bandwidth of the system but also allows the nodes to transmit the data more intelligently and
equally divides the burden of data transmission. C-AODV [26] is a routing algorithm for monitoring system which
is based on cooperative communication among the nodes to obtain good performance tradeoff between the energy
efficiency and reliability in the network. The authors proposed some modifications in existing AODV protocol. The
modified AODV protocol divides and distributes the traffic load among the nodes in the network. In the routs dis-
covery phase of AODV the nodes store the information of current path and the alternative path as well. Hello mes-
sage is sent to neighboring nodes for the purpose of acquiring informing about the node’s queue length. On the basis
of congestion in queue length the nodes take decision of selecting next hop for required destination. Author com-
pared the proposed routing algorithm with existing protocols i.e. AODV, CASNCP and MPCR and showed that for
healthcare monitoring the cooperative communication based routing is most suitable.
Quwaider et al. [27] proposed routing algorithm for location based store-and-forwarding of packet with frequent
postural partitioning. Short range of radio links leads to disconnections of on-body topology. Other reasons are un-
predictable attenuation of RF and patients movements. To solve all these mentioned problems this location based
protocol has been developed. Main advantage of using information of node’s location provides the better routing
delay performance. The protocol forwards the packet on the basis of relative distance of nodes. Electromagnetic
interference has also critical effects on the operations of sensitive medical devices. These effects have safety related
issues in healthcare units and in hospitals. In order to reduce the electromagnetic interference from WSN is health-
care applications Quang et al. [28] proposed an adaptive and distributed routing protocol called EMI-aware routing
protocol (EMIR). The algorithm assigns a positional value to each node. This value is collected dynamically. On the
basis of this calculated value the traffic is diverted from the nodes with high electromagnetic interference. The traf-
fic is also diverted from the nodes located far away from the gateway node. EMIR is easy to implement because it
requires only one hop information and it performs better as compared to shortest past routing algorithms because it
reduce the electromagnetic interference effect significantly.
Security is also an important feature in the medical body area network. Security concerns and threats can cause pa-
tients to suffer dangerous conditions or even death. To improve reliability and security of network in healthcare
applications a routing protocol is proposed by Xiaohui et al. [29].The proposed protocol is named “distributed pre-
diction based secure and reliable routing framework” which can be easily integrated with the existing routing proto-
cols. The protocol provides reliability and prevention against the data injection attacks e.g. denial-of-service attack
etc. In this protocol each node estimates the quality of current link by calculating its past link quality. Protocol se-
lects the path with high link quality out of multiple paths. For the purpose of security, data authentication methods

are implemented. The node is capable of enabling or disabling the source authentication on the basis of predicted
neighbor set change and accuracy of prediction. By doing this node can filter the false requests of source authentica-
tion very quickly.
5 Recommendations
We can conclude that the main challenges in medical body area networks implementation are energy efficiency and
reliability. Routing vital signs of patients in medical body area network is an energy consuming process.
Reliability is most important requirement and critical issue in medical body area network. Both sensing and commu-
nication reliabilities are issues of concerned in medical body area network. There is a need of reliable sensing and
transmission of vital signs of patients to sink node or base station. In star topology there is single point of failure and
it can cover a small area. There is only communication between the sensor nodes and head nodes so for the nodes
which are located at long distance from the cluster head require large transmission range. In the long distance there
are more chances of packet drop in the network. Multi hop communication using relay node is good option for en-
suring reliability. For energy efficiency we can introduce some sleep scheduling mechanisms. But we will have to
draw a balance line of tradeoff between reliability and energy efficiency.
In the body area network energy efficiency and reliability are especially critical at first hop communication. In the
first hop there is communication between sensor and relay nodes. Sensor nodes have limited power supply and can
also be mobile. We can divide the network into two parts. In first part communication is between the sensor nodes
and relay nodes. The relay nodes are intelligent devices and are rich in resources i.e. power supply, processing and
computational power etc. In the second part there will be communication between relay nodes and gateway to send
the data to base station over wired or wireless channel. At first hop communication there is need of high reliability
and energy efficiency and we can focus on this part. In second part energy efficiency is not a big problem because
the devices are having rich resources. Here we can focus on reliable data transmission and solving interference prob-
lem.
The medical monitoring application involves transmission of vital signs of patients to the central base station. Main
requirement in medical body area network is transmission of data so routing in the network should not be resource
and bandwidth hungry. Building and maintenance of reliable routes should be efficient enough so that we can save
energy in the routing and use it in communication of vital signs. At some points in the network we need proactive
routing schemes and sometime we need reactive routing. Proactive routing scheme is more energy consuming and
have larger overhead. We have to efficiently select the routing scheme in order to achieve energy efficiency but not
on the cost of reliability in the network.
6 Conclusion
In this paper we have discussed the common properties of wireless sensor network and presented a survey of its
health related applications. We have surveyed of medical body area network and discussed its implementation in
hospital for clinical monitoring and disaster relief. We also discussed architecture design and challenges of body
area network. While discussing the challenges in body area networks applications in healthcare we have touched
upon reliability, energy efficiency and routing as these are the issues of great interest. There is a tradeoff between
reliability and energy efficiency. There is a need to develop an efficient communication protocol which achieves
both reliability and energy efficiency at acceptable tradeoff level.
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