The document discusses a study of wireless communications technologies for use in freight rail systems. It provides background on the need to upgrade aging voice and data networks for trains. It then summarizes initial research on the feasibility of WiFi networks for high-speed train communication. Testing of WiFi networks in a 3.5 mile rail corridor showed it can support mobility up to 70 mph but is limited to 1 mile communication distances. The document outlines future work to study the use of Mobile WiMAX technology which is designed to support longer communication distances of up to 30 miles needed for rail systems.

1. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
State of Wireless Communications in
North American Freight Railroads
Hamid Sharif
Computer and Electronics Engineering Department
Advanced Telecommunications Engineering Laboratory (TEL)
University of Nebraska – Lincoln
September 28, 2012
Advanced Telecommunications Engineering Laboratory (TEL)

2. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Wireless in Railroads
• The Five-Year US Federal Railroad Administration (FRA)
Strategic Plan for Railroad Research and Development
identifies mobile wireless communication as one of the
most critical areas to collect, process, and disseminate
information to improve the safety, security, and operational
effectiveness of railroads. *
* From: The vision for the future of intelligent railroad systems
Advanced Telecommunications Engineering Laboratory (TEL)

3. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
State of Wireless in Railroads
• Voice
– Portions of the voice wireless infrastructure are
more than 30+ years old.
• Data
– The Advanced Train Control System (ATCS) wireless
data networks (developed in 80s) are only
supporting at best 4800/9600 bps and not designed
to support today’s multimedia and Internet type
applications.
Advanced Telecommunications Engineering Laboratory (TEL)

4. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Project’s Objectives
• Study the suitable wireless technology for current
and future of mobile railroads to support:
– high-speed data network for moving trains
– real-time Internet accessibility for trains’
crews, passengers, and ground crews
– improving railroad operating safety and effective
operations
Advanced Telecommunications Engineering Laboratory (TEL)

5. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Industry Partners
• Federal Railroad Administration (FRA)
• American Association of Railroad (AAR)
• Freight Railroads of North America:
– Union Pacific Railroad
– BNSF Railway
– CSX Transportation
– Norfolk Southern Railway
– Canadian National Railway
– Canadian Pacific Railway
Advanced Telecommunications Engineering Laboratory (TEL)

6. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Research Methodology
• Build comprehensive simulation models to complement our
theoretical study for wireless standard protocols.
• Testbed experiments to study and evaluate the implementation of
these technologies for the railroad environments.
Advanced Telecommunications Engineering Laboratory (TEL)

7. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
PHASE 1 - WIFI
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8. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Overview of WiFi Project Phase
• Feasibility of WiFi in mobile railroad
environment
• Performance evaluations of WiFi throughput in
mobile railroad scenarios
• Study of handoff and Quality of Service (QoS) in
WiFi for mobile railroad applications
• Performance evaluations of multimedia
applications over WiFi in railroad environments
Advanced Telecommunications Engineering Laboratory (TEL)

9. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Theoretical Approach
• Investigation of the mobility impact on performance of
the 802.11x system with fading under different client
velocities
• Analysis of the impact of Doppler shift caused by the
velocity of transmitter and receiver
• The multipath interference due to reflections and
diffractions from terrain and objects in the radio
coverage area and other serious impairment factors
• Study of the bit error rate performances for various
velocities with different data rates
Advanced Telecommunications Engineering Laboratory (TEL)

10. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Simulation Models
• 802.11x features designed and implemented:
• PHY:
– Determines the impact of noise, fading and Doppler shift
– Calculates effects of shadowing, Rician and Rayleigh
fading
• MAC:
– Fragmentation and Defragmentation, Data
Retransmission
– Multirate support (fixed as well as rate adaptation)
– Multiple channels, Channel scanning
– Synchronization, Power management
– Authentication, Association, Re-Association, Handoff
Advanced Telecommunications Engineering Laboratory (TEL)

11. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
WiFi Test bed
• A 3.5 mile section of BNSF track at Crete Nebraska
was chosen for it’s close proximity to the UNL, low
traffic volumes, and challenging environment
(heavy foliage, curves, surrounding hills).
• Test bed utilizes the 802.11 technology to support
wireless connectivity between moving trains and
fixed Access Points.
• Involved with the design of Testbed were:
AAR, BNSF, UP, CSX and CN
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12. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Test Bed
BNSF Core Network
Router/Gateway Router/Gateway
BNSF WAN
VPN into
CC
BNSF WAN
Internet
Microwave Link
DSL Link Microwave Microwave
NC
NC CC NC CC NC CC NC CC NC CC NC CC NC CC
AP8 AP7 AP6 AP5 AP4 AP3 AP2 AP1
Crete Depot Berks East
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13. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Test Bed Area Map
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14. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Advanced Telecommunications Engineering Laboratory (TEL)

15. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Advanced Telecommunications Engineering Laboratory (TEL)

16. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Advanced Telecommunications Engineering Laboratory (TEL)

17. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Advanced Telecommunications Engineering Laboratory (TEL)

18. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Advanced Telecommunications Engineering Laboratory (TEL)

19. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Advanced Telecommunications Engineering Laboratory (TEL)

20. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Advanced Telecommunications Engineering Laboratory (TEL)

21. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Advanced Telecommunications Engineering Laboratory (TEL)

22. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
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23. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
WifiTools Features
• GPS with real-time mapping
– GPS integrated into user interface
– Retrieves current location in test bed from GPS device, displays location
of test client and all APs in test bed, calculates distances to all APs and
records all information
• WifiPoll with real-time plotting
– WifiPoll measures all Wifi adapter information, such as link speed and
status, signal strength, channel, current associated AP, throughput, etc.
– Real-time plotting of these results allows real-time evaluation of testing
progress
– Graphs include: Tput vs. Time, Tput vs. Distance, Tput histogram, RSSI
(signal strength) vs. Time, RSSI vs. Distance, RSSI histogram, AP
association vs. Time
Advanced Telecommunications Engineering Laboratory (TEL)

24. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Developed test tools (WifiViz)
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25. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Antenna Field Pattern
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26. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Comparison of Test Bed Results and Simulation
Comparison of Field Test Results and Simulation Results using
GPS Log Information
7000
6000
5000
Throughput (kbps)
4000
3000
2000
1000
0
12:21:01 12:23:54 12:26:47 12:29:40 12:32:33 12:35:25 12:38:18 12:41:11
Time
Field Test 04/27/2006 Simulation using GPSLog
Advanced Telecommunications Engineering Laboratory (TEL)

27. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Mobility test results
Throughput vs. Time
7
Throughput
6
Throughput (Mbps)
5
4
3
2
1
0
10:33:36 11:45:36 12:57:36 14:09:36 15:21:36
Time
Velocity vs Time
70
Velocity
60
50
Velocity (mph)
40
30
20
10
0
10:33:36 11:45:36 12:57:36 14:09:36 15:21:36
Time
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28. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Throughput vs. Distance Comparisons
Throughput vs Distance Comparison - 802.11b 1 Mbps
1000
900
800
700
Throughput (kbps)
600 NS-2
Qualnet
500
Theory
400 Field Cutoff
300
200
100
0
0 200 400 600 800 1000 1200 1400 1600 1800 2000
Distance (meters)
Advanced Telecommunications Engineering Laboratory (TEL)

29. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Summary of Findings
• Benefits of WiFi:
– Operates in unlicensed frequency band, easily accessible for railroads
– Good network throughput (about 6 Mbps in good channel)
– Supports mobility (tested up to 70 mph)
– Inexpensive and readily available equipment and setups
– Supports real time multimedia applications
• Drawbacks of WiFi:
– Communication Distance limited to only a mile (under excellent LOS
conditions only)
– Limited number of channels in unlicensed band creates competition
among all WiFi networks in an area
• Interference becomes a problem
– Contention-based multiuser access scheme creates problems for
coexistence
– No Quality-of-Service mechanism for multimedia applications
– No standardized approach for interconnecting WiFi access points
Advanced Telecommunications Engineering Laboratory (TEL)

30. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
PHASE 2 – MOBILE WIMAX
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31. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Mobile WiMAX - Overview
• Is designed to be a 4G network technology
– All-IP network infrastructure, based on IEEE 802.16e
• 802.16e/802.16-2007 is air interface only
• Mobile WiMAX defines end-to-end system
– Supports large communication distances
• Initial target distance for Mobile WiMAX was 30 miles
– Supports high throughput
• 20 MHz channel provides up to 70 Mbps throughput
– Supports mobility
• Mobile nodes are supported even at 120 mph
– Supports QoS and streaming applications
• Mobile WiMAX has robust QoS for video and voice applications over wireless
channels
Advanced Telecommunications Engineering Laboratory (TEL)

32. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Mobile WiMAX – RF Frequency Space
• UNL has 5 EBS licenses, centered around
Omaha, Lincoln, Kearney (35 miles radius), among
them:
WCG671 – around Lincoln WHR724 – around Omaha
Advanced Telecommunications Engineering Laboratory (TEL)

33. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Advanced Telecommunications Engineering Laboratory (TEL)

34. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Mobile WiMAX Simulation Model
Results from Lab Testing and Computer Simulations
Advanced Telecommunications Engineering Laboratory (TEL)

35. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
WiMAX Simulation Model Comparison
Features QualNet 4.0 OPNet NS-2 Models:
Taiwan Italy NIST TEL (our model)
Air Interface 802.16e 802.16e 802.16-2004 802.16d 802.16e 802.16-2009
Duplex TDD n/a TDD n/a TDD TDD
PHY Mode OFDMA OFDMA OFDMA n/a OFDM OFDM, OFDMA
ARQ, Hybrid-ARQ Y, N Y, N N, Y N, N N, N Y, Y
Multihop Backhaul n/a n/a N Y N Y
QoS Y Y Y N N I/P
Flow Scheduling Y Y Y N N Y
AMC Support n/a n/a N n/a N Y
Mode Pt-to-MPt n/a Pt-to-MPt Mesh Pt-to-MPt Pt-to-MPt
Realistic RF model n/a n/a N n/a N Y
Mobility Support Y Y N N Y Y
Handoff Schemes Y Y, limited n/a n/a Y Y
Multimedia Support n/a n/a N n/a N Y
Device Emulation n/a n/a N n/a N Y
ASN-GW Support N n/a N N N I/P
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36. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Mobile WiMAX Simulation Results
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37. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Comparison of Theory, Simulation, Tests
Total Throughput for Simulation, Lab-Test, and Theory
25000
20000
15000
Throughput (kbps)
10000
5000
0
qpsk-1/2 qpsk-3/4 16qam-1/2 16qam-3/4 64qam-2/3 64qam-3/4
Simu-wimax Test-pBst Theory
Advanced Telecommunications Engineering Laboratory (TEL)

38. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Predicted Distance for Test Equipment
Mobile WiMAX Throughput vs Distance
18000
16000
14000
12000
Throughput (kbps)
64QAM34 DL
10000
64QAM23 DL
8000 16QAM34 DL
16QAM12 DL
6000 QPSK34 DL
QPSK12 DL
4000
2000
0
0 2000 4000 6000 8000 10000 12000 14000
Distance (meters)
Advanced Telecommunications Engineering Laboratory (TEL)

39. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Sample Simulation Scenarios we are studying
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40. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Event Recorder Data Upload
Key Parameters:
• 70 mph train speed
• 5 km AP Spacing (~3.1 miles)
• Total length of 20 km
• Uses maximum data transfer rate
Event Recorder UL - Throughput Event Recorder UL – File Size
6000 4.5 140 4.5
4 120 4
5000
Data Throughput (kbps)
3.5 3.5
100
FileSize (Mbyte)
4000 3 3
2.5 80 2.5
AP ID
AP ID
3000
2 60 2
2000 1.5 1.5
40
1 1
1000 20
0.5 0.5
0 0 0 0
0 50 100 150 200 250 0 50 100 150 200 250
Time (s) Time (s)
TCP Throughput AP Association FTPFileSize AP Association
Advanced Telecommunications Engineering Laboratory (TEL)

41. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Video Streaming Fairness Comparison
Fairness Impact on Image Quality Fairness Impact on Throughput
Throughput Fairness vs. Total Station Number
1 1
0.95 0.95
0.9 0.9
Throughput Fairness Index
0.85 0.85
PSNR Fairness Index
0.8 0.8
0.75 0.75
0.7 0.7
0.65 0.65
0.6 0.6
0.55 802.16 0.55 802.16
802.11 802.11
0.5 0.5
0 2 4 6 8 10 12 14 16 0 2 4 6 8 10 12 14 16
Total Station Number Total Station Number
Advanced Telecommunications Engineering Laboratory (TEL)

42. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Mobile WiMAX Video: PKI Neighborhood
Drive around the new Aksarben Neighborhood: Distance to PKI is about 0.5 miles
Several signal obstructions from buildings in the area.
This is all done under the coverage of a SINGLE WiMAX Base Station!
Advanced Telecommunications Engineering Laboratory (TEL)

43. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Mobile WiMAX Video: Park
Drive around Elmwood Park: Distance to PKI is about 0.4 miles at farthest point
Extreme signal obstruction and scattering from trees in park!
WiFi would fail after the first few yards into the park area!
Advanced Telecommunications Engineering Laboratory (TEL)

44. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Mobile WiMAX Video: Speed and Distance
Drive on West Center road: Distance to PKI is between 0.6 miles and 1.0 miles at end!
Signal obstructions from buildings between road and PKI, Doppler shift from 60 mph!
Under the coverage of a SINGLE WiMAX Base Station, with LOS RSSI=-66dBm at 1 mile!
Advanced Telecommunications Engineering Laboratory (TEL)

45. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Multiuser Comparison – WiFi and WiMAX
• WiMAX exhibits more
efficiency (less overhead) Total Throughput vs. No. of Subscribers
Uplink Performance under N STAs
13
– WiFi degrades with increased 12
no. of subscribers
11
– Outcome of contention-based 10
operation in WiFi
Throughput(Mbps)
9
– Central resource 802.11
802.16
8
management eliminates
these issues for 7
downlink, drastically reduces 6
its impact for uplink 5
• WiMAX also demonstrates 4
0 2 4 6 8
Station Number
10 12 14 16
better fairness among
multiple subscribers
Advanced Telecommunications Engineering Laboratory (TEL)

46. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Mobile WiMAX Field Tests
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47. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Field Tests - Overview
• Field tests designed to provide real-world
performance data
– Maximum communication distance
– Maximum throughput at different velocities
– Handover performance with and w/o ASN-GW
– Latency, Packet Loss, Quality-of-Service, etc.
• We are utilizing microwave tower sites made
available to us by Union Pacific and BNSF
• Preliminary Field Tests have been performed
around our campus
Advanced Telecommunications Engineering Laboratory (TEL)

48. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Test Site 1 – UP: Logan, IA
Road for WiMAX Tests
120degree coverage area
of antenna (shaded area)
Main Antenna Direction
Indicator
Logan, IA - Tower
3 miles (approx.)
Advanced Telecommunications Engineering Laboratory (TEL)

49. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Test Site 2 – BNSF: Ashland, NE
Road for WiMAX Tests
Ashland, NE - Tower
Main Antenna Direction
Indicator
120degree coverage area of
antenna (shaded area)
3 miles (approx.)
Advanced Telecommunications Engineering Laboratory (TEL)

50. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Summary
• High-speed data networks is critical for effective
railroad operations in mobile environments.
• One technology may not be the solution for all
railroad needs.
• Combination of WiFi and WiMAX is a promising
solution.
• An integrated solution is needed to support
audio and video (multimedia type) applications.
Advanced Telecommunications Engineering Laboratory (TEL)

51. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Advanced Telecommunications Engineering Laboratory (TEL)

52. UNIVERSITY OF NEBRASKA – LINCOLN COLLEGE OF ENGINEERING
Contact Information
• Hamid Sharif
• Email: hsharif@unl.edu
• Phone: (402) 554-3628
• Web: www.tel.unl.edu
• Thank you!
Advanced Telecommunications Engineering Laboratory (TEL)