An Overview of

Body Area Networks

Submitted to : Engr Aqeel ur Rehman

For Subject : Wireless Networks

Semester : Spring 2012

Submitted By : Ali Yousuf Khan

: Iqbal Uddin Khan

An Over View of Body Area Network ( BAN ).

Introduction

As technology advances, the fables and fantasies of yesterday starts becoming reality. The advancement

is not specific for one or few areas, the advancement in todays world has a great impact, if one thing

increases it can effect may thing belongs it either directly or indirectly.

The same case is with the wireless technologies, they have emerged not only in wide ares transmission

but also in small area, becomes digitalized, multiple data rates and standards are emerged with respect

of time, required field and region. So as multiple wireless standards emerged there deployment areas

also emerged, as we talk about short ranged wireless network, multiple standards and their application

came in our minds. For example Wi-Fi comes with computer and Blue-tooth comes with data sharing

among cellphones.

As mentioned earlier, the advancement of wireless technology, had made new applications possible.

The remote health monitoring become area of interest for various researchers and as part of this project

the Body Area Network (BAN) has been developed. The main purpose of the BAN is to make it

possible for patients who need continuously monitoring.

In the light of discussion above a Body Area Network can be defined as”A communications technology

that is optimized for low power consumption and operates in, on or around the human body to enable a

variety of applications including medical, consumer electronics and personal entertainment”[1].

To achieve the goal a personal lightweight monitor system is created which is completely customized

according to the patients' needs. The BAN associated sensors are worn by a patient which are basically

lightweight devices that monitor and transmit certain signals via wireless medium to a Back-end

System. The remote monitoring Health care centers/ servers can then retrieve this data over any

connection, medium or PC[2].

Concept's illustration, using BAN in Medical applications.

Emergence of WBAN from BAN

The Body Area Network has defined it self to be well managed and efficient in wireless medium

rather than wired. Blow are the few points to elaborate that why Wireless Body Area Networks are

more focused for research and deployment and why do we not hear of wired connection among

deployed nodes.

Ultra Wide Band ( UWD ) has been studied as an approach for communication within the BAN. As it

can provide higher data rates at short distances, it is seen as a good candidate for these environments.

The IEEE 802.15.6 group uses UWB in one of the MAC/PHY options that they are defining for BAN

communication. There are several studies on the use of UWB in BANs measure the channel parameters

from 3 to 6 GHz UWB waves. The authors reached the conclusion that it is possible to use UWB for

small distances (15 cm), despite the strong variability in reception quality due to the human body. They

also suggest the use of multi-hop communications for front to back communication [3].

Currently the most frequent option in commercial products and research prototypes is to use wireless

communication between nodes. Blue-tooth and IEEE 802.15.4 are the most prominent approaches.

ZigBee is a network layer that stands over 802.15.4. ZigBee is a consortium based standard that, on top

of 802.15.4, defines application profiles and a network layer module. IEEE 802.11 is not considered as

an option, mostly due to its high energy consumption. If used, it is mainly for connecting the BS to the

rest of the infrastructure. The same applies for cellular technologies [3].

How ever there are some drawbacks in wireless communication:

• Energy consumption: There are great efforts have been made to reduce the energy necessities

in wireless communication but still it is the most power consuming component in any node.

Greater capacity currently implies bigger sized batteries and size in BANs is an extremely

critical.

• Data Rates: Blue-tooth in its last version 4.0 supports link rates of 1 to 3 Mbps. The low

power version has link rate of 1 Mbps. These are the over-the-air rates, while for the

application layer it amounts to “721.2 kbps for Basic Rate 2.1 Mbps for Enhanced Data Rate” .

802.15.4 is capable of throughputs of 250 kbps over the air. As the 802.15.6 draft defines 10

Mbps using UWB.

• Propagation: Signal barriers, multi-path effects and the presence of dielectrics can affect the

quality of the signal received. In BANs the link path is short, however the human body can

shadow the signal , water (50% to 65% of the human body) absorbs 2.4 GHz waves, which is

802.15.4 and Blue-tooth’s working frequency and reflections in the working environment are

also present.

• Interference: Most of these standards work within the 2.4 GHz frequency, have to face the

problems of coexistence. For example , Blue-tooth, is able to cope with 802.11 by hopping to

different channels, but there is a limit to this capability.

• Security: Wireless is a shared medium . As such, it is easier to eavesdrop on wireless

communications.

• Health Issues: International organizations provide guidelines for safe usage of devices that use

radio frequencies, where the World Health Organization's (WHO) International Commission on

Non-Ionizing Radiation Protection (ICNIRP) is a reference. This leads us to believe that current

radio frequency equipment is working within safe limits, however there are still studies and

concerns about the usage of wireless devices near the human body, where the recent report from

International Agency for Research on Cancer (IARC) is one .

The advantages of wireless are many and easily noted, one of all is that easily replaceable, as it ill be

difficult in wired connection. When talking about wearable or out side body sensors, there is a

possibility of having a wired connection or a network of sensors connected with wires, but there are

three main disadvantages which are mentioned on next page.

• Node Placement: Wired nodes are placed where it is already been noted, so in that cases

placement of nodes in future should be very care full and not easy to change the location.

• Full Mesh: To provide fully connected node network in wired connection is not possible as

number of nodes increases, or once deployed it will be not easy to add new nodes.

• Lack of Standards: As there in no specific standard available for wired connectivity in such

scenarios, although some wired connection's standards are available but not yet deployed on

BAN.

Some researchers are also working on a Smart wearable fabric, to reduce mechanics of wired or

wireless nodes' replacements and addition can be seen at Sensing Fabrics for Monitoring Physiological

and Bio-mechanical Variables: E-textile solutions” [4].

The 802.15.6

It is the standard for short range wireless communication, specially with in or around human body. It

uses ISM bands and to support QoS, it is extremely low powered and has data rates up to 10 Mbps. The

purpose of this standard is to provide standard to a very low power, short ranged and within or around

human body communication. As the current Personal Area network - 802.15, dose not meet the

requirement or standard of medical regulations.

The application targeted in WBAN 802.15.6 are than divided in to two main categories, one is Medical

an second one is Non Medical. This division can be seen in figure below.

Network Topology

All nodes and Hubs are organized in the same manner as illustrated in figure below, all nodes in one

star should only communicate to is hub H1 or H2, if any further communication required among

multiple stars a relay capable node is required [5].

Description of 802.15.6

First we discuss Physical Specifications. It consists of reference model described in IEEE 802.15.6.

All nodes and hubs are divided into to a PHY (Physical) Layer and MAC ( Media Accesses Control ),

the PHY layer and MAC layer of a node or a hub only uses one operating channel at a time. Message

security and encryption are done at the MAC layer, and key generation take place outside the MAC

layer at management entity part. Reference model is shown in figure below.

PHY layer Description

As described in IEEE's 802.15.6 standard, PHY supports three variants a) Narrow band (NB), Ultra

wide Band (UWB) and Human body Communication (HBC).

• Narrow Band : It is responsible for activation and deactivation of radio system clear channel

assessment of current channel and data transmission and receiving. The description of NB frame is on

next page.

The frame is known as Physical Protocol Data Unit (PPDU). It consists of Physical Layer Convergence

Procedure (PLCP) preamble used for synchronization, PLCP header used for necessary information

carrying for decoding and last is PHY Data Service UNIT (PDSU) containing MAC header, MAC

frame body and Frame Check Sequence (FCS). Differential Binary Phase-shift Keying (DBPSK),

Differential Quadrature Phase-shift Keying (DQPSK), and Differential 8-Phase-shift Keying (D8PSK)

modulation techniques are used in PHY NB.

• Ultra Wide Band: It operates in two bands one is Low band other is High band. Each of these

bands are divided into channels. Low band is consists of three channels ( 1 – 3 ), where channel 2 is

mandatory with the center frequency of 3993.6 MHz. In high band there are eight channels ( 4 – 11 ),

where channel 7 is considered as a mandatory channel with center frequency of 7987.2 MHz. Each

channel have bandwidth of 499.2 MHz. Typically UWB device must have at least support of one

mandatory channel. Below is the frame of UWB.

A UWB PPDU consists of a Synchronization Header (SHR), PHY Header (PHR) and Physical Service

Data Unit (PSDU). The SHR is consists of a preamble and a Start Frame Delimiter (SFD). The PHR

delivers information about the data rate of the PSDU, the data rates for UWB ranges from 0.5 Mbps up

to 10 Mbps with 0.4882 Mbps.

• Human Body Communication: It also operates in two bands, one centered at 16 MHz and

other Centered at 27 MHz with the bandwidth of 4 MHz. Only Europe uses 27 MHz stander while both

of are used in all other regions. The PPDU of HBC consists of a preamble, SFD, PHY header and

PSDU. The preamble and SFD are fixed data patterns. They are per-generated and sent ahead of the

packet header. The preamble sequence is transmitted four times in order to ensure synchronization

while the SFD is transmitted only once. per frame. Below is the frame of HBC

MAC layer description

MAC is divided into super frame structure, which are transmitted in three modes, a) Beacon mode with

super frame boundaries, b) Non beacon mode with super frame boundaries and c) Non beacon mode

with out super frame boundaries. Below is a super frame structure.

He super frame is further divided into Exclusive Access Phase 1 (EAP1), Random Access Phase 1

(RAP1),Type I/II phase, Exclusive Access Phase 2 (EAP 2), Random Access Phase 2 (RAP 2), Type I/II

phase, and a Contention Access Phase (CAP). EAP, RAP and CAP periods used for the resource

allocation in CSMA/CA or slotted Aloha. The EAP1 and EAP2 are used by emergency traffic. The

Type I/II phases are used for up link, Down link, Bi link and delay bi link allocation intervals [6].

Security Paradigm

The 802.15.6 define three levels of security, each has different parameters described below.

• Level 0: In this level there is no security measures are available for authentication and data

integrity. In other words communication in level zero is un-secured.

• Level 1: This is the medium level, where data is transmitted in secured authentication but

confidentiality and privacy is not available as data is not encrypted.

• Level 2: It is most secured as compared to above ones, it provides but authentication and

encryption. The security level is selected during the association, For uni-cast communication, a

pre-shared Master Key is used to establish a Pair wise Temporal (PTK) key for a session. For

multi-cast communication, a Group Temporal Key (GTK) is shared with the corresponding

group.

BAN Communication Architecture

To understand the communication architecture it can be divided into three tiers. As shown below.

A) Intra BAN communication, B) Inter BAN communication and C) Beyond BAN communication.

• Intra BAN: The term Intra – BAN communication, is about 2 meters around human body, in

reference to radio frequency. It is further divided in two: a) Communication among body

sensors, b) Communication among Body sensors and personal server. Intra BAN

Communication Could be Wired, Wireless, Hybrid, Direct connected to Access Point and

Clustered. Figure on Next page shows the possibility of Intra BAN communication [7].

• Inter BAN: It means communication between Personal servers and Access point, sometimes

between Access points and sensors. The communication can be a) Infrastructure based or b) Ad-

hoc based.

• Beyond BAN: It is intended for use in metropolitan areas. In order to bridge the two networks

for inter-BAN and beyond-BAN communications. A gateway device, such as a PDA can be

employed to create a wireless link between these two networks.

Hardware Devices in BAN

A body sensor node mainly consists of two parts:

• The physiological signal sensor(s) and the radio platform, to which multiple body sensors can

be connected.

• The general functionality of body sensors is to collect analog signals that correspond to

humans' physiological activities or body actions.

Sensors

• Sensors and actuators are the key components of BAN.

• They bridge the physical world and electronic systems.

• Because these sensors/actuators are in direct contact with persons or even implanted, their size

and physical compatibility to human tissues are crucial.

On the next page are two illustration of modules and core of BAN.

Below is the typical modules on a sensor node [7].

Below is the Core functional components for body sensor system design [7].

References

1. A.Bhatra, A.Xfaha, An Over view of IEEE 802.15.6, Texas Instrument, BWRC Wireless Sensor

Workshop 2011.

2. H.Schaap, Position of Body Area Network, University of Twente, January 2005.

3. P.Brando, Abstracting Information on Body Area Network, University of Cambridge, 2012.

4. M.Pacelli, G.Loriga., N.Taccini, R.Paradiso, Sensing Fabrics for Monitoring Physiological and

BiomechanicalVariables: E-textile solutions, Proceedings of the 3rd IEEE-EMBS,MIT, Boston,

USA, Sept.4-6, 2006

5. IEEE Standard for Local and metropolitan area networks Part 15.6: Wireless Body Area

Networks

6. K.S.Kwak, S. Ullah, N.Ullah, An Overview of IEEE 802.15.6 Standard,20 Feb 2011.

7. Body Area Networks- A Survey, Mobile Networks and Applications, Vol 16 # 2 ,2010.