REVIEW PAPER

Recent trends in Wireless Body Area Network (WBAN) researchand cognition based adaptive WBAN architecture for healthcare

Dheeraj Rathee & Savita Rangi & S. K. Chakarvarti &V. R. Singh

Received: 31 January 2014 /Accepted: 7 May 2014# IUPESM and Springer-Verlag Berlin Heidelberg 2014

Abstract In healthcare domain, Wireless Body AreaNetwork (WBAN) has transpired as a prominent technologywhich is capable of providing better methods of real timepatient health monitoring at hospitals, asylums and even attheir homes. In recent times, WBAN has gained great interestand proved one of the most explored technologies by healthcare facilities because of its vital role and wide range ofapplication in clinical sciences. WBAN involve communica-tion between very small sensor nodes with frequently chang-ing environment, hence lots of issues still need to be ad-dressed. Some of the major issues are Physical layer issues,interoperability &mobility issue, reliability, resource manage-ment, usability, Energy consumption and QoS issues. Thisresearch paper includes a comprehensive survey of recenttrends in WBAN research, provides prospective solutions tosome major issues using cognitive approach and a proposedconcept of Cognitive Radio basedWBAN architecture. Thus aconventional WBAN architecture can be improvised to anadaptive, more reliable and efficient WBAN system usingCognitive based approach.

Keywords Wireless Body Area Networks . CognitiveRadio . MAC layer . Healthcare . WBAN applications

1 Introduction

WBAN is a wireless networking technology, based on RadioFrequency (RF) that interconnects a number of small nodeswith sensor or actuator capabilities. These nodes operate inclose vicinity to, on or few cm inside a human body, to supportvarious medical area and non-medical area applications [1].WBAN technology is highly appreciated in the field of med-ical science and human healthcare [2–5]. Also significantcontribution is delivered in the field of Biomedical and otherscientific areas [6]. Moreover, its applications are widespreadin non-medical areas like consumer electronics and personalentertainment.

In late 1990s, researchers & academicians showed interestin cognitive radio (CR) technology. The general idea of CRwas given in 1999 byMitola [7]. Cognitive radio enhances thesoftware radio with radio-domain protocols, and extends theflexibility of user defined services using a radio knowledgebased programming language. Thus an ideal platform is pro-vided by Software radio for the practical realization of cogni-tive radio. Cognitive Radio (CR) is a platform for opportunisticand cooperative control to primary (licensed) section of theelectromagnetic spectrum by secondary (unlicensed) users.CRT includes sensing its electromagnetic operational environ-ment by sensors. CR enabled BANwill plan and take decisionson its outcomes considering system’s priorities, end goals andother constraints and further focus on improving the efficiencyof wireless resource usage. With these self-awareness andenvironment awareness capabilities the novel WBAN systemcan apply best strategies to meet its requirements.

Further details about CRT can be referred from [8–19].During the last 12 years, the technology grows at rapid speed.

D. Rathee (*) : S. Rangi : S. K. ChakarvartiDepartment of ECE, FET, Manav Rachna International University,Faridabad, Indiae-mail: dheeraj.fet@mriu.edu.in

S. Rangie-mail: savita.fet@mriu.edu.in

S. K. Chakarvartie-mail: skchakravarti.fet@mriu.edu.in

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

V. R. SinghPDM Educational Institutions, Bahadurgarh, India

Health Technol.DOI 10.1007/s12553-014-0083-x

The utility of CR has been recognised by ETSI and IEEE.IEEE is playing an important role in developing CR technol-ogy by forming IEEE standard 1900 with its workgroups 1–6[20].

2 Current trends in WBAN research

A lot of research work is undergoing on WBANs. The mainissues concentrated upon are scale of network, result accuracy,node density, power supply, mobility, data rate, energy con-sumption, QoS, and Real time communication. WBAN nodesuse miniaturized batteries due to their small size. Hence thenetwork must work and perform in a power efficient mannerso that the life duration of power sources can be maximized.Most of the work in this particular domain has been ondevelopment of better MAC protocols for energy efficientprocessing.

Presently, there are two different approaches of MACprotocol designing for sensor networks. First one isContention- based MAC protocol design. Example of thistype of MAC protocol is Carrier Sense Multiple Access –Collision Avoidance (CSMA/CA). This design has theirnodes priorities for channel access before transmitting data.The benefits of CSMA/CA based protocols include almost notime synchronization constraints, easy adaptability to networkvariations and scalability. The other approach is Schedule-based MAC protocol. Example of this type of protocol is aTDMA based, in which time slotted access to the channel isprovided. Hence different users get separate time slots for datatransmission. These slots can be of fixed or variable duration.Time Slot Controller (TSC) is used for providing time slots.The benefits of this approach are reduced idle listening,overheading and collision. TDMA based approach is highlyused in energy efficient MAC protocol [21].

According to [22], IEEE 802.15.4 is not capable of provid-ing energy efficient communication for WBAN applications.There are many loop holes that must be filled for their use inmedical area. Hence another improved standard, i.e. IEEE802.15 with task group 6 (BAN) has been formulated [23].The purpose of this standard is to provide new MAC andphysical layers for WBAN. The Physical layer (frequencybands) is categorized as Narrowband, Ultra Wide Band(UWB) and Human Body Communication (HBC). TheMAC layer includes following three modes [24]:

1. Beacon mode with a beacon period superframeboundaries

2. Non Beacon mode with superframe boundaries3. Non Beacon mode without superframe boundaries

In [24], it is also shown that the efficiency for CSMA\CAbased MAC layer can be improved by increasing payload size

and thereby bandwidth. Another work undertook the approachof Clear-Channel Assessment and Collision Avoidance(CCA\CA) with TDMA in generation of energy-efficientMAC layer [25].

Marinkovic et al. [26] presents a low duty cycle, TDMAbased energy efficient MAC protocol. The novel MAC pro-tocol includes collision free data transfer (TDMA) and energyefficiency because of sleep time application for sensors, with-out the need of channel listening. Hence, communication isdone for small overhead and minimum time spent on idlelistening. The protocol is implemented on analog device de-velopment platforms (ADF70XXMBZ2) with RFtransceivers.

A novel approach of heartbeat powered the MAC protocolis given by [27]. This protocol is TDMA based and used forbody sensor networks (BSNs). The work includes usage ofheart beat rhythm to perform time synchronization and henceprovides an energy-efficient MAC layer by avoiding powerconsumption associated with time synchronization beacontransmission.

Fang, et al. proposed a new MAC protocol, BODYMAC,for WBANs [28]. This protocol uses efficient and flexiblebandwidth allocation schemes and introduction of sleepmodes to reach the desired requirements of dynamic applica-tion in WBANs. The bandwidth allocation flexibility ofBodyMAC is improved by dynamic bandwidth allocationmechanism like burst bandwidth. Results showed that theaverage delay is decreased by almost 30 % and improvedbandwidth utilization efficiency was achieved. But the effectof deep channel fading and central packet introduction is notconsidered during the simulation process.

In [29], Timmons, et al. introduced another novel Macprotocol, MedMAC. The protocol features contention freeTDMA channel access scheme, a novel low-overheadTDMA synchronization mechanism, energy-efficient, and dy-namically adjusting time slots, optimal contention period anduse of sleep modes. Adaptive Guard Band Algorithm(AGBA) is used to maintain synchronization of devices dur-ing sleeping period, using beacons. The protocol is useful inonly low & medium data rate medical application of WBAN.

A cross-layer fuzzy-rule scheduling algorithm was intro-duced to replace conventional first-come-first-serve transmit-ting discipline for MAC layer processing by Otal et al. [30].Hence a new Distributed Queuing Body Area Network(DQBAN) MAC protocol was introduced to get high reliabil-ity and application based QoS requirements (reliability &message latency) for packet transmission. Energy consump-tion was reduced but not significantly.

Latre, et al. also proposed a cross-layer protocol, CICADA,for WBAN application [31]. CICIADA or CascadingInformation by Controlling Access with Distributed slotAssessment was based on tree structures. A control cycleand a data sub-cycle were used collectively to achieve low

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delays and better energy efficiency while preserving networkflexibility.

Al Ameen et al. [32] proposed a novel wake-up mechanismfor implanted devices to communicate inWireless BANs. Theproposed MAC protocol was energy-efficient and minimizestime delays, but functionality is restricted to implant devicesonly. In [33], Liu et al. introduced a novel dynamic model forsmall scale direct methanol fuel cells. In this fuel cells aredirectly coupled with PSO algorithm to increase the batterylife.

A hybrid approach to context –aware MAC protocol wasintroduced using TDMA-based and contention-based algo-rithms by Choi et al. [34]. Channel fading due to adaptivelymodified frame structure was also managed using a newcontrol mechanism while bursty, periodic and emergency datatraffic was controlled by polling-based and scheduled-basedtechniques. Simulation results were better than conventionalsystem but reliability and efficiency was quite low.

Huq et al. [35] proposed an energy efficient MAC layerprotocol for master node and attached nodes in WBAN sys-tem. Performance of the system was better with high numberof nodes as the size the conventional MAC superframe struc-ture was reduced by removing redundant periods. Thus theaverage power consumption per bits was drastically reducedbut reliability was still an issue. In [36], a highly reliableMedical emergency body (MEB) MAC protocol was pro-posed by dynamical insertion of listening windows in conten-tion free periods. The results showed better and reliable sys-tem but high power consumption and susceptibility to outerinterferences were still present.

In [37], increased sleep time and low duty cycle per beaconwas introduced in form of a statistical MAC layer protocol forheterogeneous traffic networks. The systemwas experimentedin HBC platform and resulted in an energy efficient andcompact protocol but the system reliability was low becauseof non-transmission of lost messages during inactive periods.A survey on various context-aware MAC layer and applica-tion layer protocols was given in [38]. It was concluded thatlimited solutions are available particularly in MAC layer areafor context-aware data transmission.

Most of the work that has been discussed above speaksabout providing novel energy-efficient MAC layer protocolsor better power supplying devices. Although none of themhave succeeded in making significant energy efficient systemswith better throughput.

3 Proposed architecture for adaptive WBAN using a CRT

The proposed architecture is to merge two most significanttechnologies of current time i.e. Conventional WBAN andCognitive Radio Technology (CRT), to get a highly efficientand reliable Wireless Body Area Network that revolutionizes

the future of WBAN. The novel cognitive approach basedwireless BAN, can lead to a considerable improvement inresource efficiency (spectrum management), networking effi-ciency and energy efficiency.

Research Design includes proposed architecture ofWBANwith Cognitive abilities. The architecture includes the follow-ing three levels of communication (Fig. 1).

3.1 Level 0

This level includes Intra-WBAN communication. This in-cludes the following components:

3.1.1 Core and actuator nodes (sensors/actuators)

A number of sensor nodes operating on the body, inside thebody or in close proximity (less than 2 cms) to collect data onphysical signals (bio-signals) from human body(detection\acquisition), process them (if necessary) accordingto requirements and finally transmit them to a centralized onbody network controller. It consists of a micro sized processorwith memory, a power unit & a transceiver.

Intelligent Core and access nodes (sensors/actuators) can bedesigned with the help of cognitive approach. Sensor nodes aredesigned using appropriate methods and ability to access selfand environment information. Thus intelligent nodes will per-form their operation in highly reliable and energy efficientmanner, using cognitive approach. The intelligent sensors arecapable of adjusting not only to communication limitations butalso to the information requirements. Cognitive features thatcan be incorporated in sensors are goal evaluation, real time andenergy efficient monitoring, intelligent processing and wirelesscognitive connectivity with Network Coordination Unit.

3.1.2 CRT based Network Coordination Unit (NCU)

This device is placed on body of a patient or the person underconsideration itself. The main purpose of NCU is to commu-nicate core and access nodes (sensors/actuators), process thecompiled data and transmit to Central Controlling Unit (CCU)at Level 1. CRT based NCU is capable of performing anumber of cognitive functions like to improve Data fusion,spectrum sensing (b/w nodes & NCU), configurable network-ing, node parameters (mobility, battery life, working, connec-tivity) sensing, energy efficient and reliable data routing andwireless cognitive connectivity with CCU. The basic compo-nents of CRT based NCU would be a small size processingunit, memory unit and a transceiver.

3.2 Level 1

This communication level consists of Inter-WBAN network-ing. Here a number of NCUs are connected wirelessly to a

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CRT enabled the Central Controlling Unit (CCU) and mainfunction of CCU is to communicate with a number of NCUswithin a particular area (hospital, building, asylum etc.) usingCRTapproach. This unit will be static and hence power supplyand connectivity issues are not so important, but the rest of theissues are quite vital. Cognitive functions that can be incorpo-rated in CRT enabled CCU are spectrum sensing (b/w NCUs& CCU), Energy efficient and highly reliable routing proto-cols, Efficient MAC protocol, NCU parameters (mobility &location, battery life, working, calibration and connectivity)maintenance, QoS awareness and end-to-end goal mainte-nance. The basic components of the CRT based CCU willbe a heavy processor, large memory unit and a transceiver.

3.3 Level 2

This communication level will be beyond WBAN network-ing. CRT based CCU will be connected wirelessly to any ofthe following:

& Doctor or Medical Attendant or Supporting staff

& Emergency Services e.g. ambulance or risk managementunit

& Hospital or Healthcare Unit

3.4 Cognitive functions incorporated

The cognitive functions that would be applied to differentnetworking layers in CRT enabled WBAN are as follows:

3.4.1 Spectrum sensing

The major cognitive approach to the WBAN is SpectrumSensing. WBAN can communicate through licensed bands(MICS, WMTS) or through the unlicensed band like ISM(2.4 GHz) band. Both communication systems require infor-mation about the primary users (licensed) and white spaces(empty spectrum holes) in the spectrum. It has been seen thatmuch of the licensed spectrum remains unused most of thetime and unlicensed band is overcrowded as most of themedical devices communicate in this band only. Thus efficient

Fig. 1 Basic architecture of CR enabled WBAN

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exploitation of the spectrum is quite vital. CR enabledWBANcan use cooperative or opportunistic spectrum sensing tech-niques for spectrum aware processing.

3.4.2 Resource allocation

Resource Allocation in CR enabled WBAN is very crucial asit controls the interference caused to other communicationsystems as well as to its own network. It includes Power andfrequency allocation schemes which can be done in propermanner to minimize the interaction of WBAN with othernetworks like Bluetooth, LANs etc. and to minimize interfer-ence between different BNUs (inter-WBAN). QoS and end-to-end goals consideration is also taken into account duringresource allocation in CR enabled WBAN. This function inthe CR - WBAN will be able to utilize dynamic spectrumresources efficiently to maximize network throughput perfor-mance. It will also ensure minimization of harmful interfer-ence from Secondary Users to Primary Users. Moreover, CRTis capable enough to convert the resource gains into perfor-mance gains efficiently.

3.4.3 CRT enabled MAC protocol

Energy efficiency is another important requirement in WBAN(as explained earlier) and an efficient MAC protocol is themost suitable level in the protocol stack to address the energyconsumption issue. CR enabled MAC protocol will use theinformation about spectrum, resource allocation and QoSissues to provide an optimum Spectrum access scheme. Thenovel MAC layer will support distinct applications and trans-mission of heterogeneous data with high level QoS. Thefundamental task of CR-enabled MAC protocol is to avoidcollisions and repeated data transmissions while maintainingmaximum throughput, communication reliability, minimumlatency and maximum energy efficiency. In CR enabledWBAN MAC layer is tightly coupled with high level layersand PHY layer.

3.4.4 Spectrum-aware routing protocol

Spectrum-aware routing protocol enhances the cognitive func-tions of link and network layers. This protocol became crucialwhen the physical layer nature is dynamical. In WBAN, highoverhead problem is quite natural hence intelligent routingprotocol is must. Spectrum awareness feature gives conven-tional routing protocol a fair idea about changing spectrumand hence CR enabled BAN will possess adaptable routingprotocol for better performance. CR-BAN transport protocolswill constitute efficient end-to-end layer applications.Spectrum sensed data can be implemented during protocolgeneration.

3.4.5 QoS awareness and end-to-end goal achievement

QoS and end-to-end goals are crucial parameters for anyEfficient & reliable system. QoS awareness is a CRT functionthat is very much related to multiple layers of the networkwhile end-to-end goals are directly related to the applicationlayer. Desired goals would be achieved by intelligent process-ing and smart communication of data within different layers ofnetwork while considering QoS awareness. Also reliability ofthe system would improve by constant monitoring of end-toend goals, comparing them with desired QoS parameters andreconfiguration of network.

Another view of CRT based WBAN architecture is shownbelow in Fig. 2 which includes layer wise WBAN workingusing cognitive approach.

4 Conclusion

This paper included current research trends in WBAN withdeep review of MAC layer research. We also proposed theconcept of CRT based Adaptive WBAN architecture for effi-cient and reliable results. CRT based functions for differentlayers of the network were also modelled and discussed indetail. Future work may involve practical testing of the pro-posed concept.

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

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