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
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 . In WBANs, sensors con-tinuously monitor humans 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) , 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 by highlighting the technological aspects of biomed-ical and scientific applications.
B. Malik (*)Mewar University, Chittorgarh, Rajasthan, Indiae-mail: firstname.lastname@example.org
V. R. SinghNational Physical Laboratory, New Delhi 110012, Indiae-mail: email@example.com
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 1960s 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 patients 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.
They have performed measurement campaigns and pathloss studies for wireless nodes on the body . Somehave also considered implanted devices, an area of WBANcalled Intra-body Communication . 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 .
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 Maxwells equations for each point of the body. In effectthis determines which propagation mechanism is takingplace, i.e. diffraction, reflection, transmission, surface waves. An elegant manner of doing this task is using thedyadic Greens function. Dyadic Greens functions havebeen used in Electromagnetic (EM) theory and have solu-tions for canonical problems, such as cylinders, multilayeredcylinders and spheres . 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
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  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, so25 m range is enough .
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 24networks 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 . 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, 2931].
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 .
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.
There are several advantages introduced by using wirelessWBANs which include:
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. 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 . As the first option, they may sendmeasured information continuously. This seems to bemore intuitive but it i...