May 7, 2004
doc.: IEEE 802.15-04-0215-00-004a
Project: IEEE 802.15 Study Group for Wireless Personal Area Networks (WPANs)
Submission Title: [Ultra-Wideband Channel Model for Farm/Open-Area Applications]
Date Submitted: [11 May, 2004]
Source: [Shahriar Emami, Celestino A. Corral, Gregg Rasor]: Company1 [Freescale Semiconductor],
Address [8000 W. Sunrise Blvd., Plantation, FL 33322], Voice:[(954) 723-3854], FAX: [(954) 723-3883]
Re: [Channel Model Submission]
Abstract: [An ultra-wideband channel model for open area/farm applications is submitted. The channel
model is based on ray tracing that captures signal descriptors including frequencies. The rationale behind
the channel model is developed and presented in support of the presentation.]
Purpose: [An understanding of the open area outdoor environment for ultra-wideband (UWB) signal
coverage is needed for 802.15 TG4a. This channel model should assist in predicting UWB range and
proper signal design for open area applications.]
Notice: This document has been prepared to assist the IEEE P802.15. 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 P802.15.
Contribution
Slide 1
Shahriar Emami, Freescale Semiconductor
May 7, 2004
doc.: IEEE 802.15-04-0215-00-004a
Ultra-Wideband Channel Model
for Farm/Open-Area Applications
Understanding UWB Propagation
in Open Areas Subject to
Selected Environmental Factors
Shahriar Emami, Celestino A. Corral, Gregg Rasor
Freescale Semiconductor
The presenters wish to acknowledge the support and
contributions of:
• Glafkos Stratis/Motorola
• Salvador Sibecas/Motorola
Contribution
Slide 2
Shahriar Emami, Freescale Semiconductor
May 7, 2004
doc.: IEEE 802.15-04-0215-00-004a
Outline
• Ultra-wideband Outdoor Channel Model Status
• Special Considerations
– Approach
– Frequency Selection
– Simulation Setup
• Simulation Results
– Ground conditions
– Channel Impulse Response and Ray Statistics
– Coverage
• Summary and Conclusions
• Proposed Continuing Investigations
Contribution
Slide 3
Shahriar Emami, Freescale Semiconductor
May 7, 2004
doc.: IEEE 802.15-04-0215-00-004a
Channel Model Status
We shall show this
in simulation
• Prior Efforts:
– Two-ray UWB path loss model:
• S. Sato and T. Kobayashi, “Path-loss exponents of ultra
wideband signals in line-of-sight environments,”
IEEE802.15-04-0111-00-004a, March 2004.
– Deterministic UWB channel model based on ray
tracing approach:
• B. Uguen, E. Plouhinec, Y. Lostanlen, and G. Chassay, “A
deterministic ultra wideband channel modeling,” 2002
IEEE Conf. Ultra Wideband Syst. Tech.
We use approach
considered here
Contribution
Slide 4
Shahriar Emami, Freescale Semiconductor
May 7, 2004
doc.: IEEE 802.15-04-0215-00-004a
Special Considerations
• Farm areas feature isolated clusters of
scatterers
• Material properties may change with
frequency. (For our simulations, we assume
material properties constant over frequency.)
In addition, the outdoor channel is subject to
environmental changes
– Seasonal changes (snow, ice, etc. in some
regions)
– Rain/wet conditions
Contribution
Slide 5
Shahriar Emami, Freescale Semiconductor
May 7, 2004
doc.: IEEE 802.15-04-0215-00-004a
Different Absorption Regions
Frequency Range
Of Interest
Conduction
Dipole and
We assume no
dielectric changes
over frequency
Ionic
Relaxation
Space
Charge
Polarization
-6
-4
Log frequency (Hz)
-2
0
Atomic
Electronic
Absorption
2
4
6
8
10
60Hz
R. C. Dorf (Ed.), The Electrical Engineering Handbook, 2nd Ed., Boca Raton,
Florida: CRC Press, 1997.
Contribution
Slide 6
12
14
16
18
Dielectric practically
constant over frequency
range of interest.
Shahriar Emami, Freescale Semiconductor
May 7, 2004
doc.: IEEE 802.15-04-0215-00-004a
Approach
• Use deterministic 3-D ray tracing simulator
- Employs
– geometric optics
– uniform theory of diffraction (UTD)
– Generates
• Received signal strength
• Ray statistics (path length/delay)
• Signal descriptors include frequency, polarization, etc.
• UWB channel sounding is achieved by superposition
of NB channel sounding
- Conventional channel sounding
- FCC emissions mask scaled channel sounding
M. F. Iskander and Z. Yun, “Propagation prediction models for wireless communication systems,” IEEE Trans.
Microwave Theory Tech., vol. 50, pp. 662—673, March 2002.
Contribution
Slide 7
Shahriar Emami, Freescale Semiconductor
May 7, 2004
doc.: IEEE 802.15-04-0215-00-004a
Frequency Selection
Energy of band
concentrated in high
band frequency
0 dBm
-11.2
-11.4
-12.8
-13.8
-14.8
3.10
4.24
5.34
6.72
8.64
10.6
3.10
4.24
6.72
8.64
10.6
“High-Pass” Sounding
Channel Sounding
Energy of band
concentrated in
geometric center
frequency
-13.8
-14.8
3.62
Contribution
5.34
Slide 8
-12.8
-11.4
-11.2
4.76
5.99
7.62
9.57
“Band-Pass” Sounding
Shahriar Emami, Freescale Semiconductor
May 7, 2004
doc.: IEEE 802.15-04-0215-00-004a
Simulation Set-Up
3-D omni antenna
pattern used
Omni pattern
assumed at all
frequencies
omni antenna
above house
Provides worst-case
delay modeling
omni antenna
near ground
Farm area consists of two-story
wood home and metal grain
silo. Ground is not flat; has
slight variations in height.
Contribution
•
Receiver grid placed around home, 200m
X 200m
•
Receiver spacing was 4m X 4m
•
Receiver height was at 1.3m
•
For omni antenna above house, antenna
was at 12.5m height
•
For omni antenna near ground, antenna
was at 1.5m height.
Slide 9
Shahriar Emami, Freescale Semiconductor
May 7, 2004
doc.: IEEE 802.15-04-0215-00-004a
Coverage Results
Lowest Frequency – 4.24 GHz
Dry soil
Wet soil and
wet roof
200 m
200 m
Contribution
TX power = 0 dBm
TX power = 0 dBm
•
Highest level -64.4 dBm
•
Highest level -66.5 dBm
•
Shadowing due to metal
silo evident
•
Smoother ripple closer
to antenna
•
Ripple due to two-ray
phenomenon evident
•
Impact of roof more
significant
Slide 10
Shahriar Emami, Freescale Semiconductor
May 7, 2004
doc.: IEEE 802.15-04-0215-00-004a
Coverage Results
Full Frequencies -- Channel Sounding
Dry soil
Wet soil
TX power = 0 dBm
Contribution
TX power = 0 dBm
•
Highest level -64.4 dBm
•
Highest level -66.5 dBm
•
Some deep fades are
eliminated, others
softened
•
Higher signals closer to
antenna
•
•
Ripple due to two-ray
phenomenon still
evident, although
smooth ripple closer
Shadowing due to silo
and roof still significant
Dry/wet conditions
are fairly similar
Slide 11
Shahriar Emami, Freescale Semiconductor
May 7, 2004
doc.: IEEE 802.15-04-0215-00-004a
Coverage
“High-pass” and “Band-pass” Sounding
Dry soil
Dry soil
TX antenna placed at 1.5m
height and at the side of
the house
•
High-pass sounding
•
Band-pass sounding
•
Highest level -61.8 dBm
•
Highest level -60.2 dBm
•
Significant shading by
house as well as silo
•
Range for -75 dBm
sensitivity is quite low,
on the order of 15 m.
High-pass and bandpass sounding are
similar
Contribution
Slide 12
Shahriar Emami, Freescale Semiconductor
May 7, 2004
doc.: IEEE 802.15-04-0215-00-004a
Simulation--Validation
UWB Path Loss
-50
-60
• Powers in the
different frequency
bands are summed
together
• Received power
profile in agreement
with the work of
Sato and Kobayashi
Power (dBm)
-70
-80
-90
-100
-110
-120
0
10
1
2
10
10
Transmitter-Receiver Separation (m)
3
10
40
P a th lo ss [dB ]
60
80
100
120
140
160
10
100
1000
D is tan ce m
[ ]
TX antenna placed at 1.5m
height and at the side of
the house
Contribution
Slide 13
Shahriar Emami, Freescale Semiconductor
May 7, 2004
doc.: IEEE 802.15-04-0215-00-004a
Simulation Results—Ground Conditions
Contribution
Constrained Channel Sounding
1
0.9
Dry
Wet
0.8
0.7
Probability (X < Xo)
• Ground conditions
(wet or dry) has
almost no impact on
received signal
power or delay
spread.
• Subsequent
simulations were
assuming dry
conditions
0.6
0.5
0.4
0.3
0.2
0.1
0
-180
Slide 14
-160
-140
-120
Power (dBm)
-100
-80
-60
Shahriar Emami, Freescale Semiconductor
May 7, 2004
doc.: IEEE 802.15-04-0215-00-004a
Simulation Results—
Channel Impulse Response
• CIR is similar to two-ray model.
-7
5
CIR of Real Part of the received signal
x 10
-8
6
4
4
3
Received Amplitude (V)
Received Amplitude (V)
CIR of Imaginary Part of the received signal
x 10
2
1
2
0
-2
-4
0
-6
-1
0
20
Contribution
40
60
80
100
t (ns)
120
140
160
-8
180
Slide 15
0
20
40
60
80
100
t (ns)
120
140
160
180
Shahriar Emami, Freescale Semiconductor
May 7, 2004
doc.: IEEE 802.15-04-0215-00-004a
Simulation Results—
Channel RF Parameters
Table I. 90 percentile received power
Scenario
Received
Power
(dBm)
Table II. 90 percentile delay spread
Scenario
Scenario
A
B
Scenario
A
B
-83
-74
Mean
Excess
Delay
(ns)
RMS Delay
(ns)
380
365
19
26
- Scenario A: transmit antenna is placed on the top of farm house
- Scenario B: transmit antenna is placed along the side of the house
Contribution
Slide 16
Shahriar Emami, Freescale Semiconductor
May 7, 2004
doc.: IEEE 802.15-04-0215-00-004a
Simulation Results—Ray Statistics
• Statistics of the two rays are found to be
Rayleigh distributed.
Histogram of I of the Largest Component
Histogram of I of the Second Largest Component
400
400
300
300
200
200
100
100
0
0
0.5
1
1.5
0
0
0.5
1
1.5
2
2.5
3
3.5
4
-6
Histogram of Q of the Largest Component
-7
x 10
400
300
300
200
200
100
100
0
0.5
1
1.5
-6
0
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
-7
x 10
Contribution
x 10
Histogram of Q of the Second Largest Component
400
0
4.5
x 10
Slide 17
Shahriar Emami, Freescale Semiconductor
May 7, 2004
doc.: IEEE 802.15-04-0215-00-004a
Simulation Results—Channel Sounding
Constrained Channel Sounding
1
Dry
Wet
0.9
• Channel (uniform)
sounding leads to
larger received
power as compared
to constrained
channel (FCC-mask
compliant)
sounding.
0.8
FCC-mask complaint
Probability (X < Xo)
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
-180
-160
-140
-120
Power (dBm)
-100
-80
-60
-80
-60
Channel Sounding
1
0.9
Dry
Wet
0.8
Probability (X < Xo)
0.7
Uniform sounding
0.6
0.5
0.4
Over 10dB difference
0.3
0.2
0.1
0
-180
Contribution
Slide 18
-160
-140
-120
Power (dBm)
-100
Shahriar Emami, Freescale Semiconductor
May 7, 2004
doc.: IEEE 802.15-04-0215-00-004a
Simulation Results—
“High-pass” or “Band-pass” Sounding
1
0.9
High Pass Channel Sounding
Band Pass Channel Sounding
0.8
0.7
Probability (X < Xo)
• “Band-pass”
sounding results in
+1 dB higher
received power
compared to “highpass” sounding.
0.6
0.5
0.4
0.3
0.2
0.1
0
-160
High-pass
Contribution
-140
-120
-100
Power (dBm)
-80
-60
-40
High-pass and bandpass sounding are
similar
Band-pass
Slide 19
Shahriar Emami, Freescale Semiconductor
May 7, 2004
doc.: IEEE 802.15-04-0215-00-004a
Simulation Results—Coverage
Table III. % grid Coverage, if the receiver sensitivity is -90 dBm.
100x100
Coverage
(%)
85
85
Constrained Channel Sounding (30mx30m)
1
0.9
0.9
0.8
0.8
0.7
0.7
Contribution
Probability (X < Xo)
Probability (X < Xo)
Constrained Channel Sounding
1
0.6
0.5
0.4
0.6
0.5
0.4
0.3
0.3
0.2
0.2
0.1
0.1
0
-120
-110
-100
-90
-80
Power (dBm)
30x30
-70
-60
0
-120
-50
Slide 20
-110
-100
-90
-80
Power (dBm)
-70
-60
-50
Shahriar Emami, Freescale Semiconductor
May 7, 2004
doc.: IEEE 802.15-04-0215-00-004a
Simulation Results—Channel Model
CM1*
CM2*
CM3*
I mean
1.4092e-007
3.1052e-008
-5.8368e-009
Q mean
-1.8287e-008
5.9910e-009
-4.2345e-009
MED (ns)
RMS Delay
(ns)
22.654
20
35.491
251.53
3.5565
5.0733
* The transmitter receiver separation distances are 5, 15 and 75 meters in
CM1, CM2 and CM3, respectively.
Contribution
Slide 21
Shahriar Emami, Freescale Semiconductor
May 7, 2004
doc.: IEEE 802.15-04-0215-00-004a
Summary and Conclusions
UWB Ray Tracing:
• Ray tracing with realistic antennas and appropriate material properties
was implemented.
• Analyses included all ray statistics/parameters (ray physics).
• CIR of UWB channel is found by superposition of CIR of individual bands
with appropriate power weighting.
Channel Modeling Results:
• 5-band approach is adequate for predicting outdoor coverage in farm
scenario as verified by prior two-ray modeling.
• “High-pass” sounding yields most conservative results.
• RF parameters appear almost insensitive to ground material/conditions.
• 100m range achievable with -90dBm RX sensitivity.
• CIR is similar to that of two-ray model. RMS delay depends on location of
antenna and statistics of the rays.
• Two-ray statistics are verified to have Rayleigh distribution.
Contribution
Slide 22
Shahriar Emami, Freescale Semiconductor
May 7, 2004
doc.: IEEE 802.15-04-0215-00-004a
Ongoing Investigations
• Incorporate uplink simulations.
• Alternative frequency domain based
approach.
• Measurement and verification.
Contribution
Slide 23
Shahriar Emami, Freescale Semiconductor
May 7, 2004
doc.: IEEE 802.15-04-0215-00-004a
Back-up Slides
Contribution
Slide 24
Shahriar Emami, Freescale Semiconductor
May 7, 2004
doc.: IEEE 802.15-04-0215-00-004a
Material Properties
Pellat-Debye Equations for loss at
single relaxation time.
Real permittivity exhibits lowpass frequency response.
Imaginary part exhibits bandpass response. Regions can be
separated for different relaxation
times.
Temperature effects are not
modeled, but only affected by
change in density of dielectric
material.
Reference Data for Engineers: Radio, Electronics, Computer & Communications, 8th Ed., Carmel, Indiana:
SAMS, Prentice-Hall Computer Pub., 1993.
Contribution
Slide 25
Shahriar Emami, Freescale Semiconductor