ORIGINAL PAPER

A survey of research in WBAN for biomedicaland scientific applications

Bhavneesh Malik & V. R. Singh

Received: 17 January 2013 /Accepted: 27 March 2013# IUPESM and Springer-Verlag Berlin Heidelberg 2013

Abstract A review of earlier work on Wireless Body AreaNetworks (WBANs) is given here as these networks havegained a lot of research attention in recent years since theyoffer tremendous benefits for remote health monitoring andcontinuous, real-time patient care. However, as with anywireless communication, data security in WBANs is a chal-lenging design issue. Since such networks consist of smallsensors placed on the human body, they impose resourceand computational restrictions, thereby making the use ofsophisticated and advanced encryption algorithms infeasi-ble. This calls for the design of algorithms with a robust keygeneration management scheme, which are reasonably re-source optimal. The main purpose of the WBAN is to makeit possible for patients who need permanent monitoring tobe fully mobile. The WBAN is worn by a patient andbasically consists of a set of lightweight devices that mon-itor and wirelessly transmit certain bio signals (vital signs)to a Backend System at a Healthcare center. A monitoringhealthcare specialist retrieves the patient data over a reliablewired connection. The focus is on the wireless technologiesBluetooth and Packet Radio Switching (GPRS), because oftheir important role of communication. This paper discussesseveral uses of the WBANs technology, the most obviousapplication of a WBAN is being in the medical sector.However, there are also more recreational uses to WBANswhich are mentioned here. This paper discusses the technol-ogies about WBANs, as well as different applications forWBANs. A survey of the state of the art in Wireless Body

Area Networks is given to provide a better understanding ofthe current research issues in this emerging field.

Keywords Wireless Body Area Networks . WBANapplications . Healthcare . Physiological signal device .

Sensor networks . Personal area networks . Healthcareapplications . Low powerMAC . Implant communication

1 Introduction

Recently, there has been increasing interest from re-searchers, system designers, and application developers ona new type of network architecture generally known asBody Sensor Networks (BSNs) or Wireless Body AreaNetworks (WBANs), made feasible by novel advances onlightweight, small-size, ultra-low-power, and intelligentmonitoring wearable sensors [1]. In WBANs, sensors con-tinuously monitor human’s physiological activities and ac-tions, such as health status and motion pattern.

Modern health care related technologies and many otherfield key technologies rely on it as WBANs have manyapplications. One of them is medical monitoring which havethe specific hardware and network requirements to insuretheir functions and to solve encountered problems. Sensor,battery, and processor have built up WBAN. The security ofWBAN is also another very critical issue. Although manyprotocols and algorithms have been proposed for traditionalWireless Sensor Networks (WSNs) [2], they are not wellsuited to the unique features and application requirements ofWBANs.

WBANs describe the networks and applications com-posed and supported by sensors which are safe and portablethat able to communicate over wireless environment. It is atechnology for communications in, on and around the hu-man body. A critical survey of current WBANs is given here[1–40] by highlighting the technological aspects of biomed-ical and scientific applications.

B. Malik (*)Mewar University, Chittorgarh, Rajasthan, Indiae-mail: b.malik7@gmail.com

V. R. SinghNational Physical Laboratory, New Delhi 110012, Indiae-mail: vrsingh@ieee.org

V. R. SinghPDM Educational Institutions, Bhadurgarh, Haryana, India

Health Technol.DOI 10.1007/s12553-013-0056-5

2 Body Area Network

AWBAN consists of a collection of small sensor nodes thatare placed around the body. These may be attached directlyto the skin or as part of special clothing. Each node haseither a small power source or takes power from the body.The nodes can collectively communicate with a central node(like a PDA) which can in turn connect to the internet and indoing so can relay the data from the sensors to a particularapplication or person.

WBAN can be used not only on remote patients but alsoenables to make patients wireless within the hospital, espe-cially, in intensive care units and operating theatres. Notonly this would enhance patient comfort but also it wouldmake the work of doctors and nurses a lot more efficient andeasy. On accident site communication is performed viaWBAN, wherein a paramedic strap on the WBAN sensorsstart providing vital information to the hospital directly, toincrease efficiency, reduced reaction time, and saving ofcrucial life.

Body Area Networks take advantage of the low powerradio frequencies (RF) and enable the Body Area Networkto supply the patients’ data in real time. There is a frequencyrange dedicated to Body Area Networks, known as MICS(Medical Implantable Communication Service) band, itoperates between 402 and 405 MHz and is specifically forimplanted devices to communicate with other external de-vices reaches the doctor in real-time. If at any stage in life apatient encounters problems with their current pacemakerthen it is quite possible that they will have to endure moresurgery simply to alter the settings on the pacemaker. There-fore the added benefit of the ‘Healthy Aims’ project is thefact that the patient will only ever need to have surgeryperformed once and this is only to have the device fitted.

Not only will doctors be able to monitor patients’ generalhealth but they will also have the ability to change thesettings for specific implanted devices so that they performmuch better, thus improving the patients health. Currentlyindividuals requiring pacemakers have to endure the painand stress of surgery in order to have their pacemaker devicefitted. The very first implantable pacemaker invented wasproduced in the 1960’s and has evolved tremendously since.The pacemakers set up as part of a Body Area Networkwirelessly send the patients’ health status to a near-by RFtransceiver. From this RF transceiver the data is transmittedto a doctor. The fact that the patient’s health status is regu-larly being forwarded to the doctor means that their healthrecord is always up-to-date and the information is reconciledand updated.

As WBAN deals with connecting the body to wire-less devices, it has applications in numerous other areasas well, such as sports, entertainment, and defenseforces. To build any wireless device, the first essential

step is to study the transmission channel and model itaccurately. In this attempt, a few research groupsthroughout the world have initiated channel modeling[3].

They have performed measurement campaigns and pathloss studies for wireless nodes on the body [4–10]. Somehave also considered implanted devices, an area of WBANcalled Intra-body Communication [11]. Due to the short-range low data-rate communication in WBAN scenarios,measurement groups have considered UWB as the appro-priate air-interface.

Although there are quite a few measurement campaigns,each model developed by them is only a path loss model anddoes not provide any detail description of the propagationchannel.

In order to develop a general and accurate WBAN chan-nel model, it is important to study the propagation mecha-nism of wireless radio waves on and inside the body. Such astudy will reveal the underlying propagation characteristics.This will assist in the development of enhanced WBANtransceivers, which are more suited to the body environ-ment. The human body is a very complex environment andhas not been studied explicitly for wireless communication.Although, a while ago the human body was under focus forthe measurement of electromagnetic absorption studies,such as specific absorption rate and dosimeter [12–15].

For a WBAN channel model, it is required to determinethe electromagnetic field at each point on inside the body fora given position of the transmitter on inside the body. This isa huge problem numerically, which requires enormousamounts of computational power. Therefore, it is desirableto derive an analytical expression which performs this ob-jective. Analytically resolving this problem means solvingthe Maxwell’s equations for each point of the body. In effectthis determines which propagation mechanism is takingplace, i.e. diffraction, reflection, transmission, surface waves[16]. An elegant manner of doing this task is using thedyadic Green’s function. Dyadic Green’s functions havebeen used in Electromagnetic (EM) theory and have solu-tions for canonical problems, such as cylinders, multilayeredcylinders and spheres [17–19]. Wireless Body Area Net-works (WBANs) are composed of wireless nodes, rangingfrom hand-held devices such as mobile-phones, over smartobjects in the environment to miniaturized sensor nodesinteracted into garments. These devices provide a heteroge-neous collection with varying capabilities in terms of sen-sors, actuators, processing power, memory, and availableenergy. The number and type of devices forming a WBANschange over time, as a result of the interaction with otherWBANs, e.g. people exchanging objects, or between theWBANs and the environment, e.g. clothes or objects takenfrom chairs. Wireless Body Area Networks are formeddynamically because the connectivity between nodes

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depends on their position and their position variation overthe time. A sensor node is composed by a transmitter, areceiver, and it offers services of routing between nodeswithout direct vision, as well as records data from othersensors.

3 Design aspects of WBANs

Medical monitoring applications have specific hardware andnetwork requirements [20] to insure their functions and tosolve encountered problems.

1. Network requirements can be listed as follows:

1. Range: WBAN allow the sensors in on or aroundthe same body to communicate with each other, so2–5 m range is enough [29].

2. Interference: Between the transmissions of dif-ferent sensors from the same application andalso from the different applications (because itwould be possible to have a lot of sensors onthe same body) and with other sources (peopleclose to each other can also have their ownWBAN), interference should be suppressed asmuch as possible to satisfy reliable wirelesscommunication.

3. Network density: With the diversification ofWBAN applications, people should be able tohave sensors for different applications and differ-ent body area networks on them. WBAN standardallows 2–4networks per m2.

4. Sensors number per network: Monitoring appli-cations need a lot of sensors or actuators on thesame body area network. WBAN standardizationgroup expects a maximum of 256 devices pernetwork.

5. Quick time of transmission: The goal of moni-toring applications is a collection of information inthe real time, so rapid transmission is necessary.

6. In-body environment: Wireless network technol-ogies have always been confronted to the problemof obstacle between transmitter and receiver andthe path loss in the propagation medium [32]. Theproblem here is more important because most ofthe time, signal must propagate through humantissue.

7. Security/encryption: The transmitted data needsto be protected and integrity of received informa-tion should be provided.

8. Quality of Services (QoS) and reliability: Theyare crucial for the real time vital informationand the alarm message transmission. WBANstandard has to provide error detection and

methods of correction. The QoS needs to mea-sure delay and delay variation, it must be flex-ible because each application has specificrequirements, and must support real time trans-mission. Latency (time delay) must be inferiorto 125 ms for the medical applications and to250 ms for the non-medical applications. Jitter(variation of latency) also must be controlled[27, 29–31].

9. Enabling priority: WBAN has to support differ-ent type of traffics: periodical and burst traffic.Emergency traffic (alert in the case of heart attackor other serious problems) must have the priorityon other messages on the network.

10. Support for different data rates: Applicationshave very different requirements of the data rate(from 10 kb/s to 10 Mb/s). Most of the time,medical applications need lower data rate whereasnon-medical applications (particularly multimediaapplications) need the most important data rate.

11. Compatibility with other PANs: WBAN shouldbe able to communicate with devices using otherPAN, such as Bluetooth.

2. In addition, there are some hardware requirementsgiven as:

1. Ultra low power consumption: This depends onapplications and on the nature of the sensors (in oron body). This constraint exists to allow sensors tohave the smallest batteries and to avoid people whohave to always change their batteries. An effectivesaving mode should be desirable [28].

2. Parallel solutions can be mentioned: some sensorswith very low power consumption can harvest thebody power: temperature, vibration instead of bat-teries. Another one could be to charge batteries byinduction.

3. Suitable sensors: Sensors should be small; theymust not hinder mobility and users’ life. Monitoringshould be as transparent as much as possible forthem.

4. Lifetime: Sensors must have a long lifetime, partic-ularly in-body sensors.

5. Low complexity: They are associated with the lowcost which need to be easily produced to have a lowcomplexity. An easy way to implement the systemis mass adoption of the system by everyone.

4 Features

There are several advantages introduced by using wirelessWBANs which include:

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1. Flexibility:Non-invasive sensors can be used to automatically

monitor physiological readings, which can be forwardedto nearby devices, such as a cell phone, a wrist watch, aheadset, a PDA, a laptop, or a robot, based on theapplication needs.

2. Effectiveness and efficiency:The signals that body sensors provide can be effec-

tively processed to obtain reliable and accurate physio-logical estimations. In addition, their ultra-low powerconsumption makes their batteries long-lasting due totheir ultra-low power consumption.

3. Cost-effective:With the increasing demand of body sensors in the

consumer electronics market, more sensors will bemass-produced at relatively low cost, especially in gam-ing and medical environments.

4. Architecture of a Wireless Body Area Networks:Awireless body area network is composed by one or

more Body Sensor Units (BSU), one Body Central Unit(BCU) and eventually a link with long range network[21]. Different BSUs collect information about respira-tion rate, pulse, glucose rate, ECG, and other physio-logical signs. Each BSU transmits its data to the BCU.Sensors can have different behaviors to communicatewith BCU [20]. As the first option, they may sendmeasured information continuously. This seems to bemore intuitive but it is a power consuming methodbecause transmitting signals using wireless communica-tion results with high power consumption. Thereforemost of the time, this solution is not acceptable. Sec-ondly, they send measured data periodically. This oneallows real time monitoring which reduce power con-sumption for sensors. As another option, they can trans-mit a log file once a day. Physiological signs aremeasured periodically and values are recorded on a filethat sent by sensors, for example, once a day. It allowsmonitoring while minimizing the number of sent

messages and so energy consumed. Finally, they maysend an alert message when measured physiologicalsignal gets an abnormal value. The previous behaviorsare for the normal cases, while this one is for emergen-cies. We do not want this message interferes with otherones so it needs more energy. The MAC layer also hasto support priority message because of the time is pre-cious in emergencies. The BCU analyzes all collectedinformation, and acts in serious cases.

5 Infrastructure

There are three different infrastructures for body sensornetworks [22]:

1. Managed Body Sensor Networks (MBSNs): If a problemhas been detected, BCU sends an alert message to theclosest hospital or the user’s doctor. The third person makesa decision and sends it back to the BCU which executes itby actuators. To do that, the network needs to be linkedwitha long range connection such as GSM,Wi-Fi to the internet,or another “extra-WBAN communication” (EBAN).EBANs are the networks which are not belong to WBAN.A system overview of MBSNs is given in Fig. 1.

Sometimes, the BCU also can send report or realtime information to a third person to allow thepatient monitoring. In this mode, the BCU is justa bridge between WBAN and EBAN. However, itcannot take a decision by itself. It just acts according tothe third person’s order. The advantages of this solutionare that doctors can follow vital signs of their patients atthe same time and can be alerted if one of them has got aproblem. Additionally, the system can act on the patient’sbody but only under doctor’s supervision. On the con-trary, the disadvantages are that it is going to be a reallybad situation when the patients have got a problem but thedoctors are too busy, or if there is no long range network.

Fig. 1 Different networks usedby the MBSNs

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2. Autonomous Body Sensor Networks (ABSNs): In thismode, The BCU has no connection with long rangenetwork. The BCU is a more intelligent device thathas been programmed to take the decision by itself.Therefore, if a problem is detected, the BCU is able toanalyze the different inputs, make a diagnosis and givesorders to the actuators which act on patient’s body tosolve it. For example, a BSU can measure the glucoselevel of the user. When it becomes high, a body actuatorcan inject one dose of insulin. For simple tasks likeinsulin injection where actions depend only on one rate,we can imagine more intelligent body sensors and actu-ator units which could measure, interpret and act at thesame time. The goal is to use more and more autono-mous body sensor network to allow the patients to bemore and more independent. One of the advantages ofthis solution is that the system is autonomous, and itdoes not need doctor intervention. Moreover, BCU doesnot have to send the message using long range networkand the system power consumption is lower. However, aprognosis from a computer may not be as good as adoctor. Furthermore, if the computer has not beenprogrammed for a specific disease, it will not act at all.

3. Intelligent Body Sensor Networks (IBSNs): This is aproposal for a new type of body sensor networks. Thebest solution is the combination of both managed andautonomous systems. For simple case, the Body areanetwork can act by itself (ABSN) but when it facesmore difficult situations which require proper humanskills, it sends alerts to the doctors who will decide whatis the best for the patients. Moreover, for a sophisticatedsituation, the combination of both is also the best. Theinformation is sent to the doctor and if the doctor doesnot give any decisions because he/she is busy or he/shedoes not receive the alert, the system acts alone after thetimeout occurs. Here, sophisticated stands for a situationin which a doctor’s diagnosis would be appreciated, or,in some cases is made mandatory. If the values collectedfrom sensors lead BCU to several different diagnoses,doctor diagnosis is appreciated. In those situations, bydefault diagnoses could be programmed into BCU.BCU can select the most probable solution. At the sametime it increases the level of risk to control if its decisionmakes the situation worse. BCU should be prohibited togo further than some threshold risk level to avoid anirreversible process.

Sometimes, doctor’s diagnosis is mandatory becausethis situation is not yet programmed on the BCU. There-fore, the system cannot solve it with actuators. More-over, risk level can increase by the treatment that BCUsuggests. In these situations, the system does not sug-gest any solution, and transmits the alert message withincreased risk level again. The alerts with increasing

risk levels can be broadcasted to increasing number ofnetworks such as the cellular network over which doc-tor’s mobile phone works. In conclusion, monitoringbecomes cheaper and more autonomous for easy cases,and people still have doctor’s prognosis for more com-plicated cases. The only problem is when there is aserious problem, no long range network, and when theBCU is not able to make a diagnosis. Security is one ofthe most important goals of WBAN for monitoringapplications. Security on body area networks is provid-ed in three steps. First, in physiological monitoring,there is a lot of information about people’s health transitin the network. People do not want this kind of data tobe readable by everybody. So the system has to encryptprivate information to avoid that. Then, Body SensorNetwork can measure physiological signs. Note that theactuators can also act in human body. Access of anyonewho could act on people’s health without authenticationcould be very dangerous. Therefore, authenticationshould be done. In the final step, protection againsttransmission errors is fulfilled. Doctors can send anorder to BCU which will be executed through actuators.But if there is a transmission error, it would be differentbetween the wanted action and the effective action. Soerror detection and correction methods are prominentfor this kind of applications.

6 Applications of WBANs

WBAN promises innovative solutions in various kinds ofapplications, like intelligent personalization, gaming, enter-tainment, lifestyle, medical, health and fitness. Below Fig. 2lists most of the applications whereWBAN can be useful [23].

Wireless Body Area Networks (WBANs) Technologyhas a lot of applications. Among the many possible appli-cations that have been thought up for WBANs are commu-nication in hospitals, communication on aeroplanes orspaceships, monitoring of patients at home (post operativecare), modern Warfare, monitoring of babies, interlinking ofcomponents in home entertainment products and athletemonitoring and sports analysis.

6.1 Medical applications

The main applications are used in the medical domain (Fig. 3)but this technology will not be restricted only to the medicalapplications, non-medical applications are also predicted.WBANs can provide interfaces for diagnostics, for remotemonitoring of human physiological data, for administrationof drugs in hospitals and as an aid to rehabilitation. In thefuture, it will be possible to monitor patients continuously andgive the necessary medication whether they are at home, in a

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hospital or elsewhere. Patients will no longer need to beconnected to large machines in order to be monitored.

1. Healthcare sensor networks applications:WBAN have been widely used at the medical

healthcare field. It makes physiological monitoring ofpatient much easier, cheaper and less binding for thepatients. Example of applications: Glucose sensor, pace-maker, endoscope capsule, diabetes (inject insulin)

On-body sensor networks applications On-bodymedical applications: Heart rate, blood pressure, tem-perature, respiration On-body non-medical applications:Forgotten things, establishing a social network,assessing soldier fatigue, battle readiness.

2. Vital Signs Monitoring:Monitor vital signs with a smart band-aid, allowing

increased mobility and comfort while delivering essen-tial real-time information. This could range from mon-itoring someone who is critically ill, to an iphone appthat collects detailed data from athletes in training.

3. Organ Implantation Monitoring:Monitor organ transplant recipients after discharge

for signs of transplant rejection using implanted sensors.4. Dosage Control:

Automatically control the dosage and release ofmedication within the body using a WBAN in con-junction with an outside device (which has processingpower) that determines when medication is needed. In-sulin delivery is one notable notification for this usecase, though numerous others are being explored, aswell. By improving Compliance, this can improve med-ical outcomes, and also ensure that drugs are being used(and thus revenue are flowing to pharmaceuticalcompanies).

6.2 Sports applications

In the sporting area (Fig. 4) it will be possible to take manydifferent readings from an athlete without having them on a

Fig. 2 Applications of WBAN[23]

Fig. 3 Medical applications ofWBAN [24]

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treadmill in a laboratory. The ability to measure variouslevels during real life competition, a race for example,would give coaches a more accurate picture of their athlete’sstrengths and weaknesses. Another application of usingWBANs is in sports to monitor athletes closely.

6.3 Military applications

The opportunities for using WBANs in the military arenumerous. Some of the military applications for WBANsinclude monitoring health, location, temperature and hydra-tion levels. These readings can then be used to administerCasualty care (e.g.: morphine), knowledge of when to en-hance strength, concentration, accuracy (e.g.: drugs) andpossibly to reduce friendly fire incidents (tell them whoeach other is and where).

6.4 Interactive gaming

Body sensors enable game players to perform actual bodymovements, such as boxing and shooting, that can be feed-back to the corresponding gaming console, thereby enhancingtheir entertainment experiences. Typically gaming sensorsconnect a gaming console where the data is collected forinteractive gaming and entertainment systems connect to adevice which provides data.

6.5 Secure authentication

This application involves resorting to both physiologicaland behavioral biometrics schemes (Fig. 5), such as facialpatterns, finger prints and iris recognition. The potentialproblems, e.g., proneness to forgery and duplicability,

Fig. 4 AWBAN on an athlete(Latré, 2005) [25]

Fig. 5 Secure authenticationusing WBAN [26]

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however, have motivated the investigations into newphysical/behavioral characteristics of the human body, e.g.,Electroencephalography (EEG) and gait, and multimodalbiometric systems.

6.6 Lifestyle

In these applications environment and devices around theuser are sensitive to the users, their mood and their activi-ties. Using WBANs, which can provide facilities to unique-ly identify each user, recognize user mood and monitoractivity, one can achieve the goals of these applications.The WBAN connects to access points which activate per-sonalization and identification of users with digital signa-tures. By periodically transmitting sensor data, the systemcan recognize the mood and activity of the user.

7 Comparative analysis

Applications Technology

Medical In Medical field, WBANs can provideinterfaces for diagnostics, for remotemonitoring of human physiological data,for administration of drugs in hospitals andas an aid to rehabilitation.

Sports WBAN’s main ability to measure variouslevels during real life competition, a race isexample of it.

Military The military applications for WBANsinclude monitoring health, location,temperature and hydration levels.

Interactive gaming The gaming sensors connect a gamingconsole where the data is collected forinteractive gaming and entertainmentsystems connect to a device whichprovides data. The gaming applicationswould need wireless devices which cansense different body postures and provideinput to them.

Personalinformationsharing

There are many applications such asshopping in which data can storeinformation using WBAN sensors.

Secureauthentication

This application involves resorting to bothphysiological and behavioral biometricsschemes, such as facial patterns, fingerprints and iris recognition.

Life Style WBAN, which can provide facilities touniquely identify each user, recognize usermood and monitor activity

All these applications have different requirements interms of communication bandwidth, type of payload, qualityof service, reliability, power consummation, communicationframework, security and privacy. These different require-ments may demand different communication architectureand pose different security threats.

8 Conclusion

In this paper, we have presented technology and appli-cations of WBANs. The WBANs provide patients withincreased confidence and a better quality of life, andpromote healthy behavior and health awareness. AWBAN intended for medical applications is seen as awireless sensor network since most medical applicationswould rely on sensors to collect data about, e.g., theheart and the brain. As such the sensor nodes are keptsimple in order to fulfill requirements on energy-efficiency and long battery life time. Parameters thatinfluence the battery life time is the duty cycle of thesensing node, i.e., the active time period of the sensornode. In order to conserve energy, the sensor nodeshould be kept as long as possible in power-down orsleep mode. A drawback with long sleep periods is theclock drift implying that a node must also be awakelonger once it wakes up due to clock drifting apart fromother sensor nodes in the network making a rendezvousin time more complicated. The communication protocolswithin the node are kept simple which do not require alot of computation and to avoid more advanceddata/signal processing in the sensor node. Earlier re-search has been reviewed for possible applications indifferent fields. A comparative analysis of design as-pects of WBANs is given with main emphasis of bio-medical and scientific applications.

Conflict of interest The authors declare that they have no conflict ofinterest.

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