This document summarizes a study that characterized the multipath channel aboard an AnsaldoBreda ETR 212 train to evaluate wireless signal propagation. Measurements were taken using vector network analyzers along the train in the WiFi band. Key multipath channel parameters were extracted from the data including path loss, RMS delay spread, coherence bandwidth, and Rician K-factor. Analysis found the path loss exponent followed free space propagation. Delay spread and coherence bandwidth increased with distance and were more impacted by vertical polarization. The Rician K-factor showed less dependence on distance and polarization. Further measurement campaigns and modeling of the channel response were recommended.

1. Università degli Studi di Napoli Federico II
Master’s Degree in Electronics Engineering
Multipath channel characterization aboard
AnsaldoBreda ETR 212 Train
Supervisors
Prof. Nicola Pasquino
Ing. Attilio Marrese
Candidate
Giuseppe Papa
M61/27
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2. Multipath channel characterization aboard AnsaldoBreda ETR 212 Train
Multipath channel characterization aboard SFSM ETR 212
AnsaldoBreda – Firema (WiFi band)
• Objective: Evaluation of multipath channel influence on indoor signal
propagation aboard train
• Context: Wireless network planning
• Measurements: Channel impulse response capture through Vector
Network Analyzer
Data analysis and Multipath Channel parameters
• Data extrapolation from .dat and .csv files, impulse response function and
frequency response function evaluation through MATLAB code
• Multipath channel parameters evaluation: Path Loss, RMS Delay
Spread, Coherence Bandwidth, Rician K-Factor
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3. Multipath channel characterization aboard AnsaldoBreda ETR 212 Train
Multipath Channel
•
Multiple Paths
•
LOS Propagation (Line Of Sight)
•
NLOS Propagation (No Line of Sight)
Impulse response
•
Signal repetition
•
Random amplitude and phase
•
Impulse response dependence on time and
receiver position
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4. Multipath channel characterization aboard AnsaldoBreda ETR 212 Train
Relative Path Loss
PL is the reduction in power density (attenuation) of an electromagnetic wave as it
propagates through space, expressed in dB. Relative PL as a mean value is [1]:
RMS Delay Spread
Delay Spread is defined as the difference between the time of arrival of the earliest
significant multipath component (typically the LOS component) and the time of arrival
of the latest multipath component. In terms of root mean square:
[1] Rappaport, S. T., “Wireless communications – principles and practice”, Prentice-Hall, 2002
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5. Multipath channel characterization aboard AnsaldoBreda ETR 212 Train
Coherence Bandwidth
Coherence bandwidth is a statistical measurement representing the approximate
maximum frequency interval over which two frequencies of a signal are likely to
experience comparable or correlated amplitude fading. Heuristically [2]:
Rician K Factor
Rician K Factor is defined as the ratio between the power in the direct path and the
power in scattered paths [1]:
[1] Rappaport, S. T., “Wireless communications – principles and practice”, Prentice-Hall, 2002
[2] John G. Proakis, "Digital Communications", McGraw-Hill Book Co., New York, (1989)
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6. Multipath channel characterization aboard AnsaldoBreda ETR 212 Train
Measurement Setup
Train
Ansaldo Breda – Firema SFSM ETR 212
Tx Antenna
Schwarzbeck BBHA 9120D (Horn)
Rx Antenna
Electrometrics EM6865 (Biconical)
VNA #1
Agilent FieldFox N9918A
VNA #2
Rohde&Schwarz ZVL13
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7. Multipath channel characterization aboard AnsaldoBreda ETR 212 Train
Measurement Setup
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8. Multipath channel characterization aboard AnsaldoBreda ETR 212 Train
Tx Antenna
Rx Antenna
POL
VNA
Distance
Points
Fixed (0 m)
Mobile (1 m – 20 m)
VER
FieldFox
Variable (1 m – 20 m)
171/151
Mobile (0 m – 10 m)
Mobile (5 m – 15 m)
VER/HOR
ZVL13
Fixed(5 m)
89/85
Mobile (0 m – 10 m)
Mobile (10 m – 20 m)
VER/HOR
FieldFox
Fixed (10 m)
77/76
Mobile (0 m – 10 m)
Mobile (15 m – 25 m)
VER/HOR
ZVL13
Fixed (15 m)
82/75
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9. Multipath channel characterization aboard AnsaldoBreda ETR 212 Train
Path Loss Exponent
Mean
95%
Confidence
Interval
Path Loss
Exponent
Middle
DX Side
[1.61; 1.81]
[1.58; 1.88]
[1.59; 1.89]
1.72
1.77
Free
Space
Urban
Context
Buildings
(NLOS)
1.6 ~ 1.8
1.74
Buildings
(LOS)
2
2.7 ~ 3.5
4~6
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10. Multipath channel characterization aboard AnsaldoBreda ETR 212 Train
Experimental distribution – Rician K Factor
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11. Multipath channel characterization aboard AnsaldoBreda ETR 212 Train
Experimental distribution - RMS Delay Spread
As expected, CDF fit a Normal distribution [3]
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[3] P. A. Bello, “Characterization of randomly time-variant linear channels,” IEEE Trans. Commun. Syst., (1963)

12. Multipath channel characterization aboard AnsaldoBreda ETR 212 Train
Experimental distribution – Coherence Bandwidth B09
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13. Multipath channel characterization aboard AnsaldoBreda ETR 212 Train
Coherence Bandwidth VS RMS Delay Spread [4]
[4] Howard, S. and Pahlavan, K., "Autoregressive Modeling of Wide-Band Indoor Radio Propagation,“
IEEE Transactions on Communications, (1992)
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14. Multipath channel characterization aboard AnsaldoBreda ETR 212 Train
Delay Spread VS distance and polarization
• Delay increase as length increases
15 m
10 m
V
H
• Vertical
Polarization
is
more
affected
5m
0
1
2
3
4
5
6
7
8
τ [ns]
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15. Multipath channel characterization aboard AnsaldoBreda ETR 212 Train
Coherence Bandwidth
VS distance and polarization
• BC decrease as length increases
15 m
10 m
V
H
5m
0
5
10
15
20
• Vertical Polarization is less affected
25
BC[MHz]
Rician K Factor
VS distance and polarization
15 m
• Rician K Factor increase as length increases
10 m
V
H
5m
8.5
9
9.5
10
• Vertical Polarization is less affected
10.5
Rician K-Factor [dB]
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16. Multipath channel characterization aboard AnsaldoBreda ETR 212 Train
Conclusions
• Path Loss Exponent suggests a space free propagation law
• Delay Spread and Coherence Bandwidth behaviour depends on distance and
polarization
• Rician K Factor analisys shows a less strong dependence
Further developments
• Additional measurement campaigns (more points, alternative configurations)
• Mathematical model creation from IRF (parametric – non parametric)
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