Transcript doc.: IEEE 802.15-04-0325-00-004a

July 12, 2004
doc.: IEEE 802.15-04-0325-00-004a
Project: IEEE 802.15 Study Group for Wireless Personal Area Networks (WPANs)
Submission Title: [An Ultra-Wideband Channel Model and Coverage for Farm/Open-Area Applications]
Date Submitted: [12 July, 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
July 12, 2004
doc.: IEEE 802.15-04-0325-00-004a
An Ultra-Wideband Channel Model
and Coverage for Farm/Open-Area
Applications
Shahriar Emami, Celestino A. Corral and Gregg Rasor
Freescale Semiconductor
Contribution
Slide 2
Shahriar Emami, Freescale Semiconductor
July 12, 2004
•
•
•
•
Preliminaries
- Prior Art
- Simulated Environment
- Approach
- Simulation Setup
Proposed Channel Models
- 2 Ray and 3 Ray Models
- Amplitude Statistics
- Model Parameters
- Ray Locations
Simulation Results
- Terrain Variations
- Ground Conditions
- Polarization Diversity
- Additional Scatterers
Summary and Conclusions
Contribution
doc.: IEEE 802.15-04-0325-00-004a
Outline
Slide 3
Shahriar Emami, Freescale Semiconductor
July 12, 2004
doc.: IEEE 802.15-04-0325-00-004a
Prior Art
• 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.
– Hybrid deterministic/statistical narrowband approach for roadways:
• A. Domazetovic, L.J. Greenstein, N.B. Mandayam, I. Seskar, “A new
modeling approach for wireless channels with predictable path
geometries,” VTC 2002-Fall Proceedings, Volume 1, pp. 24-28, Sept.
2002..
– 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
July 12, 2004
doc.: IEEE 802.15-04-0325-00-004a
Simulated Environment
• Farm areas feature isolated clusters of
scatterers
• Scatterers include wooden house, silo and
up to three tractors
• Ground is not flat
• Impact of dry/wet conditions
Contribution
Slide 5
Shahriar Emami, Freescale Semiconductor
July 12, 2004
doc.: IEEE 802.15-04-0325-00-004a
Approach
• Use narrowband deterministic 3-D ray tracing simulator
- Employs
– Geometric Optics (GO)
– 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
- FCC emissions mask scaled channel sounding (constrained channel
sounding)
Contribution
Slide 6
Shahriar Emami, Freescale Semiconductor
July 12, 2004
doc.: IEEE 802.15-04-0325-00-004a
Approach- Cnt’d
• Constrained Channel Sounding
Energy of band concentrated
in high band frequency
-12.8
-11.4
-11.2
-13.8
-14.8
3.10
Contribution
4.24
5.34
Slide 7
6.72
8.64
10.6
Shahriar Emami, Freescale Semiconductor
July 12, 2004
doc.: IEEE 802.15-04-0325-00-004a
Simulation Set-Up
3-D omni antenna
pattern used
Omni pattern
assumed at all
frequencies
omni antenna
above house
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 8
Shahriar Emami, Freescale Semiconductor
July 12, 2004
doc.: IEEE 802.15-04-0325-00-004a
Coverage Results
Wet soil
•
Contribution
Slide 9
Highest level -64.4 dBm
Shahriar Emami, Freescale Semiconductor
July 12, 2004
doc.: IEEE 802.15-04-0325-00-004a
Towards a Channel Model
• These are only a small number of rays in each CIR
• Majority of energy is contained in 2 or 3 rays
. 2 Ray Model
h(t )  a1 exp( j1 ) (t  t1 )  a2 exp( j 2 ) (t  t 2 )
. 3 Ray Model
h(t )  a exp( j ) (t  t )  a exp( j ) (t  t )  a exp( j ) (t  t )
1
1
1
2
2
2
3
3
3
Contribution
Slide 10
Shahriar Emami, Freescale Semiconductor
July 12, 2004
doc.: IEEE 802.15-04-0325-00-004a
Block Diagram Representation
• 2 Ray Model
t1
a1
t2
a2
t1
• 3 Ray Model
a1
t2
a2
t3
a3
Contribution
Slide 11
Shahriar Emami, Freescale Semiconductor
July 12, 2004
doc.: IEEE 802.15-04-0325-00-004a
Simulation Results—Ray Statistics
• Statistics of the two rays are found to be Rayleigh
distributed.
Histogram of the Largest Ray
150
100
50
0
0
1
2
3
4
5
6
7
8
-6
x 10
Histogram of the Second Largest Ray
200
150
100
50
0
0
0.5
1
1.5
2
2.5
3
3.5
4
4.5
5
-6
x 10
Contribution
Slide 12
Shahriar Emami, Freescale Semiconductor
July 12, 2004
doc.: IEEE 802.15-04-0325-00-004a
Comparison
• Figure of Merit: Percentage of
locations that a model captures
90% or more of their PDP
power.
• 2 ray model and 3 ray models
work well for about 76% and
91% of locations.
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
65
70
75
80
85
90
95
100
3 ray model is superior to
2 ray model.
Contribution
Slide 13
Shahriar Emami, Freescale Semiconductor
July 12, 2004
doc.: IEEE 802.15-04-0325-00-004a
Channel Model Parameters
CM1 (5 m)
•
•
•
CM2 (15 m)
CM3 (75 m)
Ray 1 (m, s)
(1.8e-5, 1.5e-10)
(8e-6, 1.36e-11)
(4.8e-6,1.49e-12)
Ray 2 (m, s)
(1.6e-6, 2.35e-14)
(2.2e-6, 1.3e-12)
(6.7e-7, 9.16e-15)
Ray 3 (m, s)
(3.2e-6, 1.32e-12)
(1.06e-6,1.82e-13)
(5.38e-7,2.68e-15)
MED (ns)
113.27
177.46
1257.6
RMS Delay (ns)
100.44
17.78
25.36
d (ns)
496
118
110
Phase angles have uniform distributions over [0 2p].
Amplitude statistics are provided in the table.
MED , RMS delay spread and channel length are used to compute the ray
locations.
Contribution
Slide 14
Shahriar Emami, Freescale Semiconductor
July 12, 2004
doc.: IEEE 802.15-04-0325-00-004a
Ray Locations (2 Ray Model)
•
Two ray model is
h(t )  a1 exp( j1 ) (t  t1 )  a2 exp( j 2 ) (t  t 2 )
•
Second moment of power delay profile can be computed using mean excess
delay and rms delay spread
2
2
2
   rms  ( )
•
Two Rayleigh random variables with mean and variance corresponding to
mean and variance of the two rays are generated.
•
Two uniformly distributed random phases over [0, 2p] are generated as well.
•
We have
Contribution
(a12t1  a22t 2 )

and
(a12  a22 )
Slide 15
(a12t12  a22t 22 )
 
(a12  a22 ) .
2
Shahriar Emami, Freescale Semiconductor
July 12, 2004
doc.: IEEE 802.15-04-0325-00-004a
Ray Locations (2 Ray Model) - Cont’d
•
Ray locations are found by solving the system of equation:
t1 
and
where
Contribution
a12 k1  a14 k12  (a12 a 22  a14 )( k12  a 22 k 2 )
a12 a 22  a14
k1  a12t1
t2 
a22
k1  (a12  a 22 ) and
k 2  (a12  a22 ). 2
Slide 16
Shahriar Emami, Freescale Semiconductor
t 3  t1  d
t 3  t1  d
July 12, 2004
doc.: IEEE 802.15-04-0325-00-004a
Ray Locations (3 Ray Model)
•
Three ray model is
h(t )  a exp( j ) (t  t )  a exp( j ) (t  t )  a exp( j ) (t  t )
1
1
1
2
2
2
3
3
3
•
Second moment of power delay profile can be computed using mean excess
delay and rms delay spread
2
 2   rms
 ( ) 2
•
and
t 3  t1  d.
Three Rayleigh random variables with mean and variance corresponding to
mean and variance of the two rays are generated.
•
Three uniformly distributed random phases over [0, 2p] are generated as well.
•
(a12 t1  a 22 t 2  a32 t 3 )
We have  
and
(a12  a 22  a32 )
Contribution
Slide 17
(a12 t12  a 22 t 22  a32 t 32 )
.
 
2
2
2
(a1  a 2  a3 )
2
Shahriar Emami, Freescale Semiconductor
July 12, 2004
doc.: IEEE 802.15-04-0325-00-004a
Ray Locations (3 Ray Model) - Cont’d
• The first ray locations are found by solving the following
equation:
A t12  B t1  C  0
where
a12  a32
A  (a  a )(1 
)
a 22
2
1
2
3
,
K  (  ( ) )(a
and
Second and third rays are given by
K1   (a12  a22  a32 )
•
2( K1  a32 d )( a12  a32 )
B  2a d 
a 22
2
3
2
2
rms
2
2
1
 a22  a32 )
,
( K1  a32 d ) 2
C  a d  K2 
a 22
2
3
2
.
( K1  a32 d  (a12  a32 )t1 )
t2 
a 22
and
Contribution
t 3  d  t1 .
Slide 18
Shahriar Emami, Freescale Semiconductor
July 12, 2004
doc.: IEEE 802.15-04-0325-00-004a
Terrain variations
•
High correlation
•
Low correlation
Contribution
Environment A
Height = 0.1 m & high correlation
Environment B
Height = 0.1 m & low correlation
Environment C
Height = 0.3 m & high correlation
Environment D
Height = 0.3 m & low correlation
Environment E
Height = 0.5 m & high correlation
Environment F
Height = 0.5 m & low correlation
Slide 19
Shahriar Emami, Freescale Semiconductor
July 12, 2004
doc.: IEEE 802.15-04-0325-00-004a
Terrain variations- Cont’d
Contribution
Environment
2 ray model
3 ray model
A
68.97
85.55
B
76.09
94.35
C
77.37
91.79
D
75.12
91.57
E
80.21
90.75
F
83.32
93.92
Slide 20
Shahriar Emami, Freescale Semiconductor
July 12, 2004
doc.: IEEE 802.15-04-0325-00-004a
Received Power, Mean Excess Delay
(MED) and RMS Delay Spread
• Estimated over a number of environments
A
B
C
D
E
F
Rx. Power (dBm)
-80.8
-80.8
-80.8
-81
-80
-80.6
MED (ns)
1980
1985
1990
2041
1997
1970
45
45
47
46
46
47.35
RMS Delay (ns)
Contribution
Slide 21
Shahriar Emami, Freescale Semiconductor
July 12, 2004
doc.: IEEE 802.15-04-0325-00-004a
Simulation Results—Ground Conditions
• Ground conditions (wet or dry) has very little
impact on received signal power or delay
spread.
Constrained Channel Sounding
1
0.9
Dry
Wet
0.8
Probability (X < Xo)
0.7
0.6
0.5
0.4
0.3
0.2
0.1
0
-180
Contribution
-160
-140
-120
Power (dBm)
Slide 22
-100
-80
-60
Shahriar Emami, Freescale Semiconductor
July 12, 2004
doc.: IEEE 802.15-04-0325-00-004a
Polarization Diversity
1
Probability (X < Xo)
0.8
0.6
0.4
0.2
0
-250
Vertically Polarized Transmit Antenna
Horizontally Polarized Transmit Antenna
-200
-150
-100
-50
Power (dBm)
• Polarization diversity is not beneficial.
Contribution
Slide 23
Shahriar Emami, Freescale Semiconductor
July 12, 2004
doc.: IEEE 802.15-04-0325-00-004a
Additional Scatterers
Typical simulation result for 1 tractor
Tractor
Contribution
Slide 24
Shahriar Emami, Freescale Semiconductor
July 12, 2004
doc.: IEEE 802.15-04-0325-00-004a
Additional Scatterers
• Consider a few scenarios where additional scatterers are tossed in the
farm environment
• Determine the figure of merit for each
2 ray mode
3 ray model
Scenario 1
70.79
91.94
Scenario 2
68.40
86.30
Scenario 3
64.82
85.56
• Considerable amount of scattering occurs in some regions in
Scenario 3. Even three ray model is insufficient.
Contribution
Slide 25
Shahriar Emami, Freescale Semiconductor
July 12, 2004
doc.: IEEE 802.15-04-0325-00-004a
Summary and Conclusions
UWB Ray Tracing:
• UWB channel sounding is accomplished with the aid of narrow band ray tracing.
• Ray tracer utilizes realistic antennas and appropriate material properties.
• CIR of UWB channel is found by superposition of CIR of individual narrow bands
responses.
Channel Modeling Results:
• Two ray and three ray channel models were proposed.
• Procedures for generating channel models were discussed.
• Percentage of locations capturing 90% of PDP energy was selected as the figure of
merit.
• Three ray channel model is superior to two ray model .
• Both models were found to be insensitive to terrain variations.
Simulation Results.
• RF parameters appear almost insensitive to ground conditions.
• Ground conditions (wet or dry) have little impact on coverage and delay spread.
• Transmit polarization diversity not helpful in farm environment.
Contribution
Slide 26
Shahriar Emami, Freescale Semiconductor
July 12, 2004
doc.: IEEE 802.15-04-0325-00-004a
Back-up Slides
Contribution
Slide 27
Shahriar Emami, Freescale Semiconductor
July 12, 2004
doc.: IEEE 802.15-04-0325-00-004a
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 28
Shahriar Emami, Freescale Semiconductor
July 12, 2004
doc.: IEEE 802.15-04-0325-00-004a
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 29
-160
-140
-120
Power (dBm)
-100
Shahriar Emami, Freescale Semiconductor
July 12, 2004
doc.: IEEE 802.15-04-0325-00-004a
Simulation Results—
“High-pass” or “Band-pass” Sounding
High-pass
Contribution
0.9
High Pass
Band Pass
0.8
0.7
Probability (X < Xo)
• “Band-pass”
sounding results in
+1 dB higher
received power
compared to “highpass” sounding.
HP and BP Constrained Channel Sounding
1
0.6
0.5
0.4
0.3
0.2
0.1
0
-160
-140
-120
-100
Power (dBm)
-80
-60
-40
Band-pass
Slide 30
Shahriar Emami, Freescale Semiconductor
July 12, 2004
doc.: IEEE 802.15-04-0325-00-004a
Simulation Results—
Channel Impulse Response
• CIR is similar to two-ray model.
-6
x 10
2
Amplitude
1.5
1
0.5
1.01
Contribution
1.02
1.03
time (s)
1.04
Slide 31
1.05
1.06
-6
x 10
Shahriar Emami, Freescale Semiconductor