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Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs) Submission Title: [An Evaluation of Indoor Ultra-Wideband Communication Channels] Date Submitted: [8 July, 2002 ] Source: [R. Jean-Marc Cramer] Company [TRW Space & Electronics] Company [] - PowerPoint PPT Presentation
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July 9, 2002
J.M. Cramer, TRW Space and Electronics
IEEE 802.15-SG3a-02/325
Submission
Project: IEEE P802.15 Working Group for Wireless Personal Area Networks Project: IEEE P802.15 Working Group for Wireless Personal Area Networks (WPANs)(WPANs)
Submission Title: [An Evaluation of Indoor Ultra-Wideband Communication Channels]Date Submitted: [8 July, 2002]Source: [R. Jean-Marc Cramer]Company [TRW Space & Electronics]Company []Address [One Space Park DriveMail Stop 02/2743Redondo Beach, CA 90278 ]Voice [310-812-9073], FAX: [] E-Mail:[[email protected]]Re: []Abstract: []Purpose: [UWB channel model presentation.]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.
July 9, 2002
J.M. Cramer, TRW Space and Electronics
IEEE 802.15-SG3a-02/325
Submission
An Evaluation of Indoor Ultra-Wideband Communication Channels
R. Jean-Marc Cramer
9 July, 2002
July 9, 2002
J.M. Cramer, TRW Space and Electronics
IEEE 802.15-SG3a-02/325
Submission
Overview
• Introduction and motivation– UWB propagation experiment
• UWB array signal processing– Application to measured data
• Channel models for UWB signal propagation• Conclusions
July 9, 2002
J.M. Cramer, TRW Space and Electronics
IEEE 802.15-SG3a-02/325
Submission
Introduction and Motivation• Accurate models of the propagation channel are
required for the design of UWB systems– UWB radio algorithm verification and design trades– Performance prediction
• Previous studies have reported characterizations of more narrowband channels– These studies may not adequately reflect the bandwidth-
dependent effects of the propagation of UWB signals.
• Propose channel models of the form:
where the pulse shape and amplitude are dependent on the particular multipath component
n n nn
r t a p t
July 9, 2002
J.M. Cramer, TRW Space and Electronics
IEEE 802.15-SG3a-02/325
Submission
UWB Propagation Experiment• Measurements made at 14 different locations in an office building• At each location data collected on a 7x7 array of sensors with 6”
spacing– Array located 1.65 meters above the floor and 1.05 meters below the ceiling
∙
4 4.5 5 5.5 6 6.5 7 7.5 8-6
-4
-2
0
2
4
Time (ns)
Sig
nal A
mpl
itud
e (V
olts
)
Pulse at 1m separation from the transmit antenna(Direct path pulse)
July 9, 2002
J.M. Cramer, TRW Space and Electronics
IEEE 802.15-SG3a-02/325
Submission
-0.15
-0.1
-0.05
0
0.05
0.1
0.15
15 20 25 30 35 40 45 50 55
Am
pli
tud
e
Time (nanoseconds)
-0.1
-0.05
0
0.05
0.1
15 20 25 30 35 40 45 50 55
Am
pli
tud
e
Time (nanoseconds)
-0.1
-0.05
0
0.05
0.1
15 20 25 30 35 40 45 50 55
Am
pli
tud
e
Time (nanoseconds)
(1,7)
(7,7)
6 in.
(1,1)
(7,1)
6 in.
Typical Received Signal Profiles
Measurement array
July 9, 2002
J.M. Cramer, TRW Space and Electronics
IEEE 802.15-SG3a-02/325
Submission
Sensor-CLEAN Algorithm• Processed the measured data with a variation of the
CLEAN algorithm• Delay-and-sum beamforming used as a first step
– Constructed beamformer response over of direction and time• Signal detection at peak in the response over time and angle
– Only assumption on the incident signal is that it exists in a short window of time at beamformer output• No canonical wave shape is assumed• Permits study of incident waveform shape and signal statistics
• Iteratively reduce sensor data based on detected signal locations (peaks in the beamformer output)– Generate updated beamformer output and repeat until residual
threshold is satisfied
• Refer to the algorithm used here as Sensor-CLEAN– Relaxation step conducted directly on the sensor data
July 9, 2002
J.M. Cramer, TRW Space and Electronics
IEEE 802.15-SG3a-02/325
Submission
UWB Channel Modeling
• UWB signal processing techniques applied to measured propagation data
• Resulting recovered UWB signal information used to study– Received waveform shapes– Path-loss models– Clustering models for indoor signal propagation– Spatio-temporal distributions of the received signal
energy– Ray tracing based on single bounce elliptical
models– UWB channel synthesis
July 9, 2002
J.M. Cramer, TRW Space and Electronics
IEEE 802.15-SG3a-02/325
Submission
Application of Algorithm to Measured Data• Recover measurement locations from time-of-arrival and
azimuth angle-of-arrival of first detected signal• Corresponding direct path length is 1 / 1 metersLOS d sd n n f c
Location dL OS (m.) AOA (o)P 5.47 49B 16.92 191F2 5.61 203H 10.20 149C 17.23 198F1 8.68 172L 7.04 136N 5.29 107A 16.13 184E 13.54 156M 13.07 255T 10.48 293U 10.57 41W 8.87 327
• X indicates recovered measurement locations• Squares are actual measurement locations
July 9, 2002
J.M. Cramer, TRW Space and Electronics
IEEE 802.15-SG3a-02/325
Submission
Recovered Signals at Location P• Plot shows recovered signal amplitude versus time and azimuth at P
– Dependence on elevation angle has been integrated out
• Existence of clusters of multipath signals is noted is the plots
LOS signal at 5.47m and 49o
July 9, 2002
J.M. Cramer, TRW Space and Electronics
IEEE 802.15-SG3a-02/325
Submission
Recovered Signals at Location H
LOS signal at 10.2m and 149o
July 9, 2002
J.M. Cramer, TRW Space and Electronics
IEEE 802.15-SG3a-02/325
Submission
Recovered Signals at Location M
LOS signal at 13.07m and 255o
July 9, 2002
J.M. Cramer, TRW Space and Electronics
IEEE 802.15-SG3a-02/325
Submission
Recovered LOS Waveforms
• Each plots displays two curves corresponding to the waveform recovered by processing algorithms using different time windows
– A larger window gives more complete picture of isolated signals– Smaller window is better for resolving dense multipath
• Compare to direct path waveform shown earlier
-3
-2
-1
0
1
2
3
4
0 0.5 1 1.5 2 2.5 3 3.5 4
Rec
over
ed s
igna
l am
plit
ude
(Vol
ts)
Time (ns)
dLOS = 5.47 mLocation P
-8
-6
-4
-2
0
2
4
6
8
0 0.5 1 1.5 2 2.5 3 3.5 4R
ecov
ered
Sig
nal A
mpl
itud
e (V
olts
)Time (ns)
dLOS = 5.61 mLocation F2
July 9, 2002
J.M. Cramer, TRW Space and Electronics
IEEE 802.15-SG3a-02/325
Submission
Clustering Models for UWB Propagation
• Previous models for indoor propagation reported the existence of clusters of multipath components
• This model is justified for the UWB channel by the apparent existence of clusters seen in the scatter plots– Further justified by use of a sliding window on the recovered
signal information over time and angle
• Assume channel impulse response is separable as a function of time and azimuth angle:
• Final cluster locations determined by manual inspection of the recovered signal locations over time and angle– 65 clusters identified at 14 different measurement locations
( , ) ( ) ( )h t h t h
July 9, 2002
J.M. Cramer, TRW Space and Electronics
IEEE 802.15-SG3a-02/325
Submission
Clustering Models for UWB Propagation
29328126925624423222020819518317115914613412211097.785.473.2
6148.836.624.412.2
0
Angle-of-Arrival (degrees)
Sliding window over the recovered signals at location M shows theexistence of clusters of multipath
July 9, 2002
J.M. Cramer, TRW Space and Electronics
IEEE 802.15-SG3a-02/325
Submission
Clustering Models for UWB Propagation• Model the received signal amplitude by a Rayleigh
distributed RV with MS value given by,
– is the average power in first arrival of first cluster– The variable Tl represents the arrival time of the lth cluster– The variable kl is the arrival time of the kth signal within the lth
cluster, relative to Tl
• The parameters and determine the inter-cluster (cluster) and intra-cluster (or ray) rates of decay– The exponent is generally determined by building
architecture– The exponent is determined by objects close to the receive
antenna
/ /2 2 0,0 l klTkl e e
2 0,0
July 9, 2002
J.M. Cramer, TRW Space and Electronics
IEEE 802.15-SG3a-02/325
Submission
Inter-Cluster Decay Rate
10-3
10-2
10-1
100
101
102
0 50 100 150 200
LS
= 30.4 ns
Nor
mal
ized
Rel
ativ
e E
nerg
y
Relative Delay (ns)
med
= 25.3 ns
mean
= 30.5 ns
July 9, 2002
J.M. Cramer, TRW Space and Electronics
IEEE 802.15-SG3a-02/325
Submission
Intra-Cluster Decay Rate
10-3
10-2
10-1
100
101
102
0 50 100 150 200 250 300
med
= 78.2 ns
mean
= 84.1 ns
Me
dian
gam
ma
- re
lativ
e
Relative Delay (ns)
Nor
mal
ized
Rel
ativ
e In
ter-
Clu
ster
Ene
rgy
LS = 97.8 ns
July 9, 2002
J.M. Cramer, TRW Space and Electronics
IEEE 802.15-SG3a-02/325
Submission
Energy Deviation from Mean
• Deviation from the mean is hypothesized to follow Rayleigh dist• This distribution represents best-fit to the recovered UWB signal
information when considering Rayleigh, lognormal, Nakagami-m and Rician distributions
Pro
babi
lity
Den
sity
Volts
0
0.2
0.4
0.6
0.8
1
1.2
1.4
0 0.5 1 1.5 2 2.50
0.01
0.02
0.03
0.04
0.05
0.06
0 0.5 1 1.5
Pro
babi
lity
Den
sity
Volts
2
222
, 0.46x
x
xf x e
July 9, 2002
J.M. Cramer, TRW Space and Electronics
IEEE 802.15-SG3a-02/325
Submission
Cluster Angle-of-Arrival
• Cluster angle-of-arrival is hypothesized to follow a uniform distribution
• Ray angle-of-arrival is hypothesized to follow a Laplacian distribution, according to
• Recovered ray or intra-cluster arrivals were tested against Gaussian and Laplacian hypothesis.– Best fit distribution and resulting standard deviation were
reported. – Laplacian with =38° is the best fit distribution.
2 /1
2p e
July 9, 2002
J.M. Cramer, TRW Space and Electronics
IEEE 802.15-SG3a-02/325
Submission
Cluster and Ray Angles-of-Arrival
-180 -135 -90 -45 0 45 90 135 1800
20
40
60
80
100
Cluster Angle-of-Arrival Relative to Reference Cluster
CD
F (
%)
0
0.005
0.01
0.015
0.02
-180 -135 -90 -45 0 45 90 135 180
p()
(Degrees)
=38
• Distribution of cluster angles is relatively uniform below 135o
• Additional measurement would probably provide clusters above 135o
July 9, 2002
J.M. Cramer, TRW Space and Electronics
IEEE 802.15-SG3a-02/325
Submission
Rate of Signal Arrivals
• Signal inter-arrival times are hypothesized to follow an exponential rate law according to,
where is the cluster arrival rate and is the ray arrival rate
• Following this model, best-fit distributions were determined for recovered UWB signal arrival times– Faster arrival rates were found than in previous reports
• Could be due at least in part to finer time resolution
1
1,
1
1,
|
|
l l
kl k l
T Tl l
kl k l
p T T e
p e
July 9, 2002
J.M. Cramer, TRW Space and Electronics
IEEE 802.15-SG3a-02/325
Submission
Ray Arrival Rates
10-4
10-3
10-2
10-1
100
0 10 20 30 40 50
1/ = 2.30 ns
1/ = 5.41 ns
1 -
CD
F
Delay (ns)
July 9, 2002
J.M. Cramer, TRW Space and Electronics
IEEE 802.15-SG3a-02/325
Submission
UWB Channel Parameter Summary
• Many potential reasons for differences in the values.– Finer time resolution of UWB signals.– Larger fractional bandwidth and better penetration
performance of UWB signals.– Differences in the building materials and/or architecture.– Differences in the orientation of the transmitter and the
receiver
• Bottom line: More UWB studies need to be made before concrete conclusions can be drawn
Parameter UWB Propagation Spencer et al. Spencer et al. Saleh-Valenzuela¡ 27.9 ns 33.6 ns 78.0 ns 60 ns° 84.1 ns 28.6 ns 82.2 ns 20 ns1=¤ 45.5 ns 16.8 ns 17.3 ns 300 ns1=̧ 2.3 ns 5.1 ns 6.6 ns 5 ns¾ 37o 25.5o 21.5o -
July 9, 2002
J.M. Cramer, TRW Space and Electronics
IEEE 802.15-SG3a-02/325
Submission
UWB Channel Synthesis• Synthesis of UWB channels permits accurate simulations of
UWB systems• Multipath arrivals for two UWB channels synthesized from the
clustering model parameters are shown below
0
50
100
150
200
250
300
3500 45 90 135 180 225 270 315 360
Tim
e-of
-Arr
ival
(ns
)
Angle-of-Arrival (Degrees)
0
100
200
300
400
5000 45 90 135 180 225 270 315 360
Tim
e-of
-Arr
ival
(ns
)
Angle-of-Arrival (Degrees)
July 9, 2002
J.M. Cramer, TRW Space and Electronics
IEEE 802.15-SG3a-02/325
Submission
Conclusions
• UWB signal processing techniques applied to data measured on an array of sensors
• Resulting received signal information used to develop models of the indoor UWB propagation channel– Comparisons drawn with more narrowband channel models
• UWB channel parameters derived from measurements taken in a single building with a single type of UWB pulse– Building architecture and the geometry of the experiment can impact
the received signal statistics– Statistics of other UWB waveforms may be different
• Main result may be development of techniques for analysis and processing of UWB signals– Techniques can be applied to other UWB waveforms