School of Electronic Engineering and Computer Science
The Future of Body-Centric Communications:
Antennas, Propagation and Cognition
Wireless Conference 2009
@ University of Engineering and Technology, Pakistan
Dr Akram Alomainy
Antennas & Electromagnetics Research Group
Contributors …

Queen Mary University of London
–
–
–
–
–

Yang Hao
Clive G. Parini
Yan Zhao
Andrea Sani
Qammer H. Abbasi
University of Birmingham
– Peter S. Hall
– Yuri Nechayev
– Costas Constantinou

Others
–
–
–
–
–
Frank Pasveer, Philips Research
Gary Pettitt, DSTL
David Davenport, GE Healthcare
EPSRC, UK
Toumaz Technologies, UK
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Talk Outline

Introduction
– Why Body-Centric Communications?
– Applications
– Challenges

Domains of Body-Centric Communications
– In-Body
– On-Body
– Off-Body

The Future
– From Recognition to Cognition!
Wireless Conference 2009 @ UET
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In theory, there is no
difference between
theory and practice.
But, in practice, there is.
Jan L. A. van de Snepscheut,
Computer Scientist
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Why Body-Centric Wireless Comms?



Replaces cables and
provide flexibility to
today’s demanding users
Natural progression of
Wireless PAN
Should provide constant
availability, reconfigurability,
unobtrusiveness and true
extension of a human’s
mind
© Reima Smart Clothing, Finland
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Why Body-Centric Wireless Comms?

Wearable computers used
in various applications such
as:
–
–
–
–
–
–
–
Military
Healthcare
Sport
Education
Industrial control
Research
Fashion
Wearable computers courtesy of Xybernaut, Germany
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Alternative Solution – Human Transmission
Auto Lock Door
Auto Login
Electric Money
Amusement
Data
Charge
ID code
ID
Applications
Security
Electric Money
Amusement
etc.
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Alternative Solution – Near Field Communications




Short range communication
(around 10 cm) uses readers
and smartcards.
Mobile companies keen on
NFC for sales and marketing.
Frequency similar to low
RFID 13.56 MHz.
Limited data rate and restrict
freedom of user’s data
communication
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Body-Centric Wireless Comms (BCWC)



Human-self and human-to-human networking with
the use of wearable and implantable wireless
sensors.
It combines wireless body-area networks (WBANs),
Wireless Sensor Networks (WSNs) and Wireless
Personal Area Networks (WPANs).
IEEE 802.15 WPANTM Task Group 6 Body Area
Networks (BAN)
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IEEE 802.15 Task Group 6 - BAN


formed in November 2007
is developing a communication standard optimized for low power
devices and operation on, in or around the human body (but not
limited to humans) to serve a variety of applications including
medical, consumer electronics, personal entertainment and other.
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Wide Range of Applications
In-body
On-body
Sport Performance
Monitoring
Off/on-body
Healthcare &
Medical Applications
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Revolutionary Concepts
Nike + iPod
Wireless sensor measures
forces on human knee
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Challenges

Technology
–
–
–
–

Antennas
Wave propagation
Radio transceivers
Power consumption
Architecture
– Context-awareness
– application-specific
– user friendly

Software Systems
– Recognition of gestures and commands
– Communication adjustment
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Antennas and Propagation Issues




The human body is an uninviting and often hostile
environment for a wireless signal.
Compact yet efficient antennas need to be fully
characterized and integrated with the RF transceiver.
Some of these are conformability and immunity to
frequency and polarization detuning.
It is important to understand material properties of
fabrics and potential use of microwave metamaterials to
minimize the specific absorption rate (SAR).
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One Size to Fit All?!
Standard
Frequencies
(MHz)
Data Rate
Max. Power
Medical implant
(licensed)
402-405
low
low
BodyLAN
900
32 kb/s
0 dBm
2-10
Bluetooth
2400-2480
1 Mb/s
0 dBm
0.1-10
ZigBee
2400
915
868
250 kb/s
40 kb/s
20 kb/s
Low
1-100
UWB
3100-10,600
1 Gb/s
-41 dBm/MHz
10
Wireless Conference 2009 @ UET
Range (m)
15
Research Activities for Body-Centric Wireless
Chamber (Rx1-Rx6)
LogNorm PDF-Chamber
Lab (Rx1-Rx6)
LogNorm PDF-Lab
0.05
0.045
Rx4
Rx3
Data
Collection
VNA
Rx1 Rx2
Rx6
Tx
Statistical
Analysis
Rx5
0.04
Analysis
Software
IDFT
0.035
Radio channel
characterisation and
modelling
PDF
170 cm
0.03
0.025
0.02
0.015
0.01
0.005
0
Initial
Model
Channel
Characterisation
PostProcessing
30
40
50
60
Path Loss (dB)
70
80
90
In-house conformal FDTD
VCO
Data In
GFSK
Modulator
OSC
Measured onbody channel
results
Recovered
Data
GFSK
Demod.
IF
Radio Channel
System-level modelling
PA
LNA
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Talk Outline

Introduction
– Why Body-Centric Communications?
– Applications
– Challenges

Domains of Body-Centric Communications
– In-Body
– On-Body
– Off-Body

The Future
– From Recognition to Cognition!
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Domains of Body-Centric Communications

Off-body
– Human-to-Human or
Human-to-Base Units

On-body
– Within on-body
networks and wearable
systems

In-body
– With medical implants
and sensors using
hierarchal or direct links
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Antennas and Propagation for Wireless Implants



Flexibility to the patience and the surgeon in terms of replacement and
long life time.
Constant availability and ease of operation is required for future patient
monitoring and diagnosis systems.
Applications include but not limited to:
–
–
–
–
–
Accurate drug delivery.
Non-Invasive Endoscopy.
Patient diagnosis and locator.
Muscle stimulator.
Brain signals analysis and control.
Kenneth R. Foster and Jan
Jaeger, “RFID Inside”, IEEE
Spectrum, March 2007, INT
Source: http://www.givenimaging.com/
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Digital Human Phantom for Wireless Implants
Implanted sources for imaging and
data gathering
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Electric Field Attenuation

Radio Propagation from Implants
Air
Human Body
Air
0
402 MHz
868 MHz
2.4 GHz
-20
402 MHz
-40
Normalised E (dB)
-60
Empty
Stomach
-80
-100
-120
-140
-160
-180
-200
Stomach
0
10
20
30
40
50
Air
60 70 80 90 100 110 120 130 140 150
Cells in X-axis
Human Body
Air
0
402 MHz
868 MHz
2.4 GHz
-20
-40
Physical Phantom
Wave propagation from implants at 402,
868 and 2400 MHz
Normalised E (dB)
-60
Solid
Stomach
-80
-100
-120
-140
-160
Queen Mary, University of London and Philips Research East Asia,
Shanghai, China
-180
-200
Stomach
0
10
20
30
40
50
60 70 80 90 100 110 120 130 140 150
Cells in x-direction
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Source Tracking Possibility


Locate the wireless
implants with a couple
of scans
Needs accurate probes
and fast sweep systems
0.12
402 MHz
LogNorm,  =3.3 and  =0.17
868 MHz
0.1
LogNorm,  =3.5 and  =0.17
2.4 GHz
PDF
0.08
LogNorm,  =3.9 and  =0.16
0.06
0.04
0.02
0
20
30
40
50
Path Loss (dB)
60
70
80
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Radiation from a stomach implanted device

188
cm
173
cm
Hugo American
model

Japanese male
model
161
cm
Using different digital
phantom to highlight
subject-specific
propagation characteristics
Japanese female
model
Radiation performance is
different due to varying
distribution oh lossy
human tissues
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On-Body Communication Channels


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
Measurement of radio propagation channels when both
transmitter and receiver placed on the body.
Investigating different on-body links for different body
movements and postures.
Applying both narrowband signals (2.45 GHz) and UWB
measurement.
Various antenna types to highlight their effects on the
radio link
Statistical channel models for path loss and time delay
profiles
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Narrowband On-Body




Transmitted power measurement
every 1 sec at 2.4 GHz with power
set at 0 dBm
In the laboratory (Typical
multipath and interference
environment) and in the anechoic
chamber
Changes in body positions and
postures every 20 seconds
Considering different antenna
positions for various possibilities
of worn units placement on body
Rx3
Rx4
Rx1 Rx2
Tx
Rx6
Wireless Conference 2009 @ UET
Rx5
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On-Body Antennas


For on-body communication antennas need to be insensitive to
body proximity and have radiation pattern that minimises link
loss.
On-body communication channels depend on antenna type and
link geometry which is determined by antennas positions that
also influence propagation mode.
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Antennas and Path Loss


Different antenna types applied in the measurement with Tx
antenna kept as monopole.
As expected, monopole-monopole link provided the lowest link
loss for all on-body channel cases.
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Sensor Transceiver Module
Top Layer - Transceiver
Bottom Layer - Transceiver
Antenna printed around
the circumference of
the sensor transceiver
board
Sensor Prototype
Akram Alomainy, Yang Hao and Frank Pasveer,
Chapter 6: Antennas for Wearable Devices, in
“Antennas for Portable Devices”, Wiley & Sons, Inc.,
2007
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Applied Sensor Models

The performance of the sensor antenna is investigated using full
wave EM numerical modelling techniques.
Illustration of
production sensor
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Improved Antenna Performance
-50
Transceiver
module
monopole antenna.
with
external
Transceiver module with modified QMUL
antenna.
Initial quarter-wavelength printed strip
antenna.
External Monopole Antenna
QMUL Antenna
Initial Printed Strip Antenna
-55
-60
Received Power (dBm)
Measurement performed with Microstrip
Patch at 2.4 GHz working as the receiver.
Output power of 0dBm. Three cases are
applied for transmitter:
-65
-70
-75
-80
-85
-90
2.375
2.38
2.385
2.39
2.395 2.4 2.405
Frequency (GHz)
Wireless Conference 2009 @ UET
2.41
2.415
2.42
2.425
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Wave Propagation around the Body
Top view
Illustration of electric field distribution at 2.4 GHz when the sensor is placed
on the centre of the chest.
Existence of creeping waves caused by diffraction from body curvature.
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System-Level Modelling of BCWC
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Why UWB for Body-Centric Communications?
Ultra High
Bandwidth
Per User
ChannelizationHighly
Efficient Use
Of Spectrum
Low Cost
& Interoperability
“Fused” Capability
Inherent Radar
& Tracking
Ultra Low Power
Robust
Indoor
Performance
Private –
Inherently
Encrypted
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UWB Antenna Parameters

Conventional antenna performance measures
– Impedance matching
– Radiation patterns
– Gain, directivity, radiation efficiency and half power beam
width

In addition other parameters related to spatial and
transient characteristics of the antenna need to be
considered:
– Group delay  Derivative of the unwrapped phase
– Constant performance across a wideband
– Spatial performance with respect to pulse shape
preserving factors (Fidelity)
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Compact Body-Worn UWB Antennas
Planar Inverted Cone Antenna
(PICA)
Tapered Slot Antenna (TSA)
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Transient Characteristics in Free Space.


Performance of the antennas as a spatial filter.
The two antennas facing each other is the best case and it is
used as a reference for the fidelity calculation.
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Transient Characteristics in Free Space.
Mean value of pulse fidelity
considering different antenna
orientations:
PICA: 89.5%
TSA: 85.1%
For the miniaturized TSA antenna results demonstrate slightly higher distortion,
however the pulse fidelity values are acceptable for short distance
communications.
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UWB for Off-Body Communications
Measurements were performed in the anechoic chamber and in indoor
environment in the range 3-10 GHz, with intervals of 4.375 MHz, and sweep
rate of 800 ms
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Experimental Investigations


Statistical and
deterministic modelling
of radio channels in
various environments.
Both narrowband and
ultra wideband
technologies are
explored extensively for
body-centric networks.
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Path loss Analysis
PL[dB]  10  log (d / d 0 )  P0 [dB]  X 
PICA:
TSA:
6.8 in the anechoic chamber
8.2 in the anechoic chamber
8.0 in indoor environment
6.7 in indoor environment
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Transient Radio Analysis
Identifying multipath components and possibly analysing user’s
behaviour and habits within a healthcare settings.
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Effect of the body movements
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Talk Outline

Introduction
– Why Body-Centric Communications?
– Applications
– Challenges

Domains of Body-Centric Communications
– In-Body
– On-Body
– Off-Body

The Future
– From Recognition to Cognition!
Wireless Conference 2009 @ UET
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Multidisciplinary Topic
Metamaterials
Novel Antennas
Body-Centric
Networks
Bio-Engineering
Intelligent
Networking
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Low-Power Efficient Sensor Networks




The move is towards cooperative network with nodes assisting
each other in delivering data in the most efficient way.
Reducing power requirements on each node.
Adapting to available network requirements.
Antennas need to be multi resonant and multi-mode operations
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How about Cognitive Radio for BCWC?




The first step is cooperative networks!
Recognising available less congested bands and
communicating through advanced antenna systems.
Advanced post processing algorithms using
environmental parameters and system requirements.
Enabling reliable and always-on communication for
body-centric wireless networks.
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Summary





Comprehensive antenna and radio channel parameters and
models for body-centric wireless networks are essential for future
progress.
Guidelines for radio system designers to be applied in upcoming
Medical Body Area Networks.
Increasing interests in user-centric approaches to wireless
personal communications is the main drive for continuous and
active research in body-centric networks.
In addition to academic interests, industrial applications and
potential commercialisation will always provide the platform for
further funding and collaborations.
As long as wireless communication evolves, convenient, easily
accessible and efficient means of utilising the available resources
will always be in demand.
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Thank you
Akram Alomainy
School of Electronic Engineering and Computer Science
Queen Mary University of London
Mile End Road
London E1 4NS, UK
Tel: +44 (0) 20 7882 3324
E-mail: akram.alomainy@elec.qmul.ac.uk
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