Project: IEEE 802.15 Working Group for Wireless Personal Area Networks (WPANs)
March 2004
doc.: IEEE 802.15-04/120r0
Submission Title: [Body area channel modeling for IEEE 802.15.4a]
Date Submitted: [11Mar2004]
Source: [Andrew Fort, Julien Ryckaert, Bert Gyselinckx] Company [IMEC]
Address [Kapeldreef 75, Leuven, Belgium 3001]
Voice:[+32(0)16 28 12 11], FAX: [+32(0)16 22 94 00], E-Mail:[andrew.fort@imec.be]
Re: [Channel model for communication around the body]
Abstract: [Channel model for communication around the body]
Purpose: [Contribute to channel modeling for body area applications]
Notice: This document has been prepared to assist the IEEE 802.15. It is offered as a basis for
discussion and is not binding on the contributing individual(s) or organization(s). The material in this
document is subject to change in form and content after further study. The contributor(s) reserve(s) the right
to add, amend or withdraw material contained herein.
Release: The contributor acknowledges and accepts that this contribution becomes the property of IEEE
and may be made publicly available by 802.15.
Submission
Slide 1
Bert Gyselinckx, IMEC
March 2004
doc.: IEEE 802.15-04/120r0
Outline
•
•
•
•
Goal of our channel model
Simulation results
Proposed channel model
Link Budget
Submission
Slide 2
Bert Gyselinckx, IMEC
March 2004
doc.: IEEE 802.15-04/120r0
Goal Channel model
• Determine required transmit power for a
target BER as a function of the antenna
position on the body, and the distance to
walls or obstacles.
Submission
Slide 3
Bert Gyselinckx, IMEC
March 2004
doc.: IEEE 802.15-04/120r0
Propagation around the body through
creeping wave
EM waves propagate around the body via two paths:
– Penetration (dielectric losses, tissues interfaces losses)
– Creeping waves (diffraction mechanism)
Time
step
181
REMCOM XFDTD software
together with a complete
body model:
1 time step = 10ps
Submission
Slide 4
Bert Gyselinckx, IMEC
March 2004
doc.: IEEE 802.15-04/120r0
We determined the path loss near the
human body by simulation.
•
•
•
•
Submission
Exponential decay with angle difference
Height difference less important
Path loss is higher for higher frequencies
Variance is larger in the interference region
Slide 5
Bert Gyselinckx, IMEC
March 2004
doc.: IEEE 802.15-04/120r0
Model with exponentially decaying loss
Breakpoint angle:
Interferences between the
clockwise wave, the
counterclockwise wave
and the penetrating wave
 Lower decay factor
but larger variations
Creeping wave
propagation at
900MHz
Lcw
Submission
 P0   1(   0 )

Pb   2 (   b )
0    b
b    
Slide 6
Bert Gyselinckx, IMEC
March 2004
doc.: IEEE 802.15-04/120r0
We propose a Rician Model to simulate
nearby walls and obstacles
Specular
Component
Scattered
Components
•
Based on Rician “line of sight” channel model.
•
The variance and attenuation of creeping wave << reflected paths.
•
Ratio of Specular (Line of sight) power and Scattered (reflected power) must be estimated.
Submission
Slide 7
Bert Gyselinckx, IMEC
March 2004
doc.: IEEE 802.15-04/120r0
The specular and scattered component
powers can be estimated
•
Specular component power can be estimated based on our
simulated results.
• Scattered component power can be estimated based on the
classical exponential path loss model:
 d
Ls  P0 
 d0
Path loss
Path loss at
reference
distance (do)



n
d  d0
Path loss exponent
2
Distance traveled by
scattered components
Reference
distance
(1 meter)
Parameters to be confirmed with simulations
Submission
Slide 8
Bert Gyselinckx, IMEC
March 2004
doc.: IEEE 802.15-04/120r0
Rician Factor can now be estimated as a
function of distance to obstacles
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•
•
Rician factor increases as we move further from obstacles
Rician factor decreases with increasing carrier frequency
Rician factor decreases with increasing angle separation
Submission
Slide 9
Bert Gyselinckx, IMEC
March 2004
doc.: IEEE 802.15-04/120r0
Required Transmit Power (dBm)
Link Budget : Best case occurs either
very far or very close to obstacles.
Scattered components
dominates K << 0 dB
Submission
Target BER = 10-5
BPSK
900 MHz
Scattered components
begin to interfere with
creeping wave.
Slide 10
Creeping wave
dominates K >> 0 dB
Bert Gyselinckx, IMEC
March 2004
doc.: IEEE 802.15-04/120r0
Conclusions
• Creeping waves are a significant propagation
mechanism affecting communication around the
body.
• Reflected signal component from walls and
obstacles in an indoor environment influence the
required transmit power.
• We propose using a Rician model to perform a
link budget as a function of antenna separation on
the body and distance from obstacles.
Submission
Slide 11
Bert Gyselinckx, IMEC
March 2004
doc.: IEEE 802.15-04/120r0
Future Work
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Improve estimates of P0 and P0 for different antennas.
• Estimation of path loss exponent for different room
geometries.
•
Simulations to justify the Rician channel model and to
compare with other distributions.
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UWB channel modeling.
Submission
Slide 12
Bert Gyselinckx, IMEC