Hi hHigh SdSpeed DtD ata Nt kN etworks in MbilM obile ...SiStrategic Plan for Ril dRailroad RRhesearch and DlDevelopment ... – Graphs include: Tput vs. Time, Tput vs. Distance, Tput

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UNIVERSITY OF NEBRASKA UNIVERSITY OF NEBRASKA –– LINCOLN LINCOLN COLLEGE OF ENGINEERINGCOLLEGE OF ENGINEERING

Hi hHi h S d D t N t k i M bilS d D t N t k i M bilHighHigh‐‐Speed Data Networks in Mobile Speed Data Networks in Mobile Railroad EnvironmentsRailroad Environments

Hamid SharifComputer and Electronics Engineering Department

Advanced Telecommunications Engineering Laboratory (TEL)University of Nebraska – Lincoln

March 12, 2010

Advanced Telecommunications Engineering Laboratory (TEL)Advanced Telecommunications Engineering Laboratory (TEL)

March 12, 2010

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OutlineOutlineOutlineOutline

• Background and introductionBackground and introduction

• High‐speed wireless communications in mobile g p

railroad environments

• Investigation of different wireless technologies

• Findings and results

SAdvanced Telecommunications Engineering Laboratory (TEL)Advanced Telecommunications Engineering Laboratory (TEL)

• Summary

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State of mobile wireless in railroadsState of mobile wireless in railroads

• Voice

State of mobile wireless in railroadsState of mobile wireless in railroads

– Portions of the voice wireless infrastructure are more than 30+ years old.

• Data – The Advanced Train Control System (ATCS) wirelessThe 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.


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MotivationMotivationMotivationMotivation

• The Five‐Year US Federal Railroad Administration (FRA) S i Pl f R il d R h d D lStrategic 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 operationalinformation to improve the safety, security, and operational effectiveness of railroads. *

* From: The vision for the future of intelligent railroad systems


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GoalGoalGoalGoal

• Feasibility and performance study of existing and future wireless standard technologies for mobile railroad environment to support:

– high‐speed data network for trains

– real‐time Internet accessibility for trains’ crews, passengers, and ground crews

i i il d i f d ff i– improving railroad operating safety and effective operations


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Research MethodologyResearch MethodologyResearch MethodologyResearch Methodology

• Build comprehensive simulation models to complement our theoretical study for wireless standard protocols including 802 11a/b/gtheoretical study for wireless standard protocols including 802.11a/b/g and 802.16/802.16e for mobiles in the railroad environments.

• Testbed experiments to study and evaluate the implementation of


Testbed experiments to study and evaluate the implementation of these technologies for the railroad environments.

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PHASE 1PHASE 1 ‐‐WIFIWIFIPHASE 1 PHASE 1 WIFIWIFI


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Overview of WiFi Project PhaseOverview of WiFi Project PhaseOverview of WiFi Project PhaseOverview of WiFi Project Phase

• Feasibility of WiFi in mobile railroad environment

• Performance evaluations of WiFi throughput in• 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


applications over WiFi in railroad environments

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Theoretical ApproachTheoretical Approach

• Investigation of the mobility impact on performance of h 802 11b i h f di d diff li

Theoretical ApproachTheoretical Approach

the 802.11b system with fading under different client velocities

A l i f h i f l hif d b h• Analysis of the impact of Doppler shift caused by the velocity of transmitter and receiver

f f• The multipath interference due to reflections and diffractions from terrain and objects in the radio coverage area and other serious impairment factorscoverage area and other serious impairment factors

• Study of the bit error rate performances for various velocities with different data rates


velocities with different data rates

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Simulation ModelsSimulation ModelsSimulation ModelsSimulation Models

• Simulator is enhanced version of NS‐2• 802.11a/b/g features designed and implemented:• PHY:

D t i th i t f i f di d D l hift– Determines the impact of noise, fading and Doppler shift– Calculates effects of shadowing, Rician and Rayleigh fading

• MAC: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


– Authentication, Association, Re‐Association, Handoff

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WiFiWiFi Test bedTest bedWiFiWiFi Test bedTest 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 andfor 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

• Designed to support equipment from different vendors as well as upgrading for the upcoming technologies such as the


pg g p g g802.16e (WiMax) and 802.20.

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Test BedTest BedBNSF Core Network

Test BedTest Bed

BNSF WAN

VPN into

Router/Gateway Router/Gateway

Microwave Link

VPN into BNSF WAN CC

Internet

DSL Link

NC

Microwave Microwave

AP7 AP6 AP5 AP4 AP3 AP2

NCNCNC CCCCCCCCNCNCNCNC CCCCCC

AP8 AP1


Crete Depot Berks East

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Test Bed Area MapTest Bed Area MapTest Bed Area MapTest Bed Area Map


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WifiTools FeaturesWifiTools Features

• GPS with real‐time mappingGPS i t t d i t i t f

WifiTools FeaturesWifiTools Features

– 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 informationrecords all information

• WifiPoll with real‐time plottingWifiP ll ll Wifi d t i f ti h li k d d– 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 progressprogress

– Graphs include: Tput vs. Time, Tput vs. Distance, Tput histogram, RSSI (signal strength) vs. Time, RSSI vs. Distance, RSSI histogram, AP association vs. Time


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Developed test tools (Developed test tools (WifiVizWifiViz))Developed test tools (Developed test tools (WifiVizWifiViz))


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Test Bed Performance DataTest Bed Performance DataTest Bed Performance DataTest Bed Performance Data

• Maximum Distances:– 1 Mbps channel mode: around 1600m, 1 mile

– 11 Mbps channel mode: around 1350m, 0.85 milesp ,

• Maximum Throughput:– 1 Mbps channel mode: 0 8 Mbps data– 1 Mbps channel mode: 0.8 Mbps data

– 2 Mbps channel mode: 1.6 Mbps data

5 5 Mbps channel mode: 3 8 Mbps data– 5.5 Mbps channel mode: 3.8 Mbps data

– 11 Mbps channel mode: 5.8 Mbps data


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Comparison of Test Bed Results and SimulationComparison of Test Bed Results and SimulationComparison of Test Bed Results and SimulationComparison of Test Bed Results and Simulation

Comparison of Field Test Results obtained 04/27/2006 and Si l ti R lt i GPS L I f ti

6000

7000Simulation Results using GPS Log Information

4000

5000

kbps)

2000

3000

Throughp

ut (

0

1000

12:21:01 12:23:54 12:26:47 12:29:40 12:32:33 12:35:25 12:38:18 12:41:11


TimeField Test 04/27/2006 Simulation using GPSLog

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Mobility test resultsMobility test resultsThroughput vs. Time

6

7

Throughput

Mobility test resultsMobility test results

2

3

4

5

6

hrou

ghpu

t (M

bps)

0

1

2

10:33:36 11:45:36 12:57:36 14:09:36 15:21:36

Time

T

Velocity vs Time

50

60

70

h)

Velocity

10

20

30

40

Vel

ocity

(mp


010:33:36 11:45:36 12:57:36 14:09:36 15:21:36

Time

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Throughput vs. Distance ComparisonsThroughput vs. Distance Comparisons

Throughput vs Distance Comparison - 802 11b 1 Mbps

Throughput vs. Distance ComparisonsThroughput vs. Distance Comparisons

Throughput vs Distance Comparison 802.11b 1 Mbps

800

900

1000

500

600

700

800

ghpu

t (kb

ps)

NS-2QualnetTheory

100

200

300

400

Thro

ug

TheoryField Cutoff

0

100

0 200 400 600 800 1000 1200 1400 1600 1800 2000

Distance (meters)


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Summary of FindingsSummary of FindingsSummary of FindingsSummary of Findings• Benefits of WiFi:

– Operates in unlicensed frequency band, easily accessible for railroadsp q y , y– 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– 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 Quality‐of‐Service mechanism for multimedia applications– No standardized approach for interconnecting WiFi access points

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PHASE 2PHASE 2 –– MOBILE WIMAXMOBILE WIMAXPHASE 2 PHASE 2 MOBILE WIMAXMOBILE WIMAX


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Mobile WiMAXMobile WiMAX ‐‐ OverviewOverviewMobile WiMAX Mobile WiMAX OverviewOverview

• 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 throughputpp g g p• 20 MHz channel provides up to 70 Mbps throughput

– Supports mobility• Mobile nodes are supported even at 120 mph• 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


channels

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Mobile WiMAXMobile WiMAX –– RF Frequency SpaceRF Frequency Space

• UNL has 5 EBS licenses, centered around Omaha, Li l K (35 il di ) h

Mobile WiMAX Mobile WiMAX RF Frequency SpaceRF Frequency Space

Lincoln, Kearney (35 miles radius), among them:WCG671 – around Lincoln WHR724 – around Omaha


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Mobile WiMAX Simulation ModelMobile WiMAX Simulation ModelMobile WiMAX Simulation ModelMobile WiMAX Simulation Model

Results from Lab Testing and Computer Simulations


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Simulation ModelSimulation Model –– Current StatusCurrent StatusSimulation Model Simulation Model Current StatusCurrent Status

• IEEE 802.16e Protocol implementation completed

• Highly accurate RF simulation component• Highly accurate RF simulation component, provides support for location‐based multipath simulation Rician fading channels shadowingsimulation, Rician fading channels, shadowing, Doppler impact simulation, etc.

• Comprehensive MAC layer protocol implementation, supports all mandatory


features of IEEE 802.16e‐2005 MAC

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WiMAX Simulation Model ComparisonWiMAX Simulation Model ComparisonWiMAX Simulation Model ComparisonWiMAX Simulation Model ComparisonFeatures 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 YFlow 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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Simulation ModelSimulation Model –– Current FocusCurrent FocusSimulation Model Simulation Model Current FocusCurrent Focus

• ASN Gateway simulation support currently in developmentHandover management Data aggregation– Handover management, Data aggregation

• QoS simulation framework– Multiple resource scheduling algorithms

• How each node and connection is allocated bandwidth resources– QoS management algorithms

• Controls the scheduling algorithms and assigns constraints– Latency requirements (end‐to‐end delay for data transmissions)– Bandwidth requirements– Etc.

• Implementation Design for MIMO RF simulation– Current simulations use SISO mode

I O hi ddi i l i i


– MIMO achieves additional processing gain

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Mobile WiMAX Simulation ResultsMobile WiMAX Simulation ResultsMobile WiMAX Simulation ResultsMobile WiMAX Simulation Results


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Comparison of Theory, Simulation, TestsComparison of Theory, Simulation, TestsComparison of Theory, Simulation, TestsComparison of Theory, Simulation, Tests

25000

Total Throughput for Simulation, Lab‐Test, and Theory

20000

25000

15000

(kbp

s)

5000

10000

Throughp

ut

0

qpsk‐1/2 qpsk‐3/4 16qam‐1/2 16qam‐3/4 64qam‐2/3 64qam‐3/4


Simu‐wimax Test‐pBst Theory

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Predicted Distance for Test EquipmentPredicted Distance for Test EquipmentPredicted Distance for Test EquipmentPredicted Distance for Test Equipment

18000

Mobile WiMAX Throughput vs Distance

14000

16000

18000

10000

12000

hput (kbp

s)

64QAM34 DL

64QAM23 DL

4000

6000

8000

Throug

h

16QAM34 DL

16QAM12 DL

QPSK34 DL

QPSK12 DL

0

2000

4000

0 2000 4000 6000 8000 10000 12000 14000


0 2000 4000 6000 8000 10000 12000 14000

Distance (meters)

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Sample Simulation Scenarios we are studyingSample Simulation Scenarios we are studyingSample Simulation Scenarios we are studyingSample Simulation Scenarios we are studying


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Event Recorder Data UploadEvent Recorder Data UploadEvent Recorder Data UploadEvent Recorder Data UploadKey Parameters:• 70 mph train speed• 5 km AP Spacing (~3.1 miles)• Total length of 20 km• Uses maximum data transfer rate

4.56000

Event Recorder UL ‐ Throughput4.5140

Event Recorder UL – File Size

2

2.5

3

3.5

4

3000

4000

5000

AP ID

oughpu

t (kb

ps)

2

2.5

3

3.5

4

60

80

100

120

AP ID

ize (M

byte)

0

0.5

1

1.5

0

1000

2000

0 50 100 150 200 250

Data Th

r

0

0.5

1

1.5

0

20

40

0 50 100 150 200 250

FileSi


0 50 100 150 200 250

Time (s)

TCP Throughput AP Association

0 50 100 150 200 250

Time (s)

FTPFileSize AP Association

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Video Streaming Fairness ComparisonVideo Streaming Fairness ComparisonVideo Streaming Fairness ComparisonVideo Streaming Fairness Comparison

Fairness Impact on Image Quality Fairness Impact on ThroughputFairness Impact on Image Quality

1

Fairness Impact on Throughput

1

0.8

0.85

0.9

0.95

Inde

x

0.8

0.85

0.9

0.95

ess

Inde

x0.6

0.65

0.7

0.75

PS

NR

Fai

rnes

s

0.6

0.65

0.7

0.75

Thro

ughp

ut F

airn

e

0 2 4 6 8 10 12 14 160.5

0.55

Total Station Number

802.16802.11

0 2 4 6 8 10 12 14 160.5

0.55

Total Station Number

802.16802.11


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Mobile WiMAX Video: PKI NeighborhoodMobile WiMAX Video: PKI NeighborhoodMobile WiMAX Video: PKI NeighborhoodMobile WiMAX Video: PKI Neighborhood

Drive around the new Aksarben Neighborhood: Distance to PKI is about 0.5 miles


gSeveral signal obstructions from buildings in the area.

This is all done under the coverage of a SINGLE WiMAX Base Station!

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Mobile WiMAX Video: ParkMobile WiMAX Video: ParkMobile WiMAX Video: ParkMobile WiMAX Video: Park

Drive around Elmwood Park: Distance to PKI is about 0.4 miles at farthest point


pExtreme signal obstruction and scattering from trees in park! WiFi would fail after the first few yards into the park area!

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Mobile WiMAX Video: Speed and DistanceMobile WiMAX Video: Speed and DistanceMobile WiMAX Video: Speed and DistanceMobile 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!

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Multiuser ComparisonMultiuser Comparison –– WiFi and WiMAXWiFi and WiMAXMultiuser Comparison Multiuser Comparison WiFi and WiMAXWiFi and WiMAX

• WiMAX exhibits more efficiency (less overhead)– WiFi degrades with increased

no. of subscribers11

12

13

Total Throughput vs. No. of Subscribers

– Outcome of contention‐based operation in WiFi

– Central resource t li i t

8

9

10

11

ughp

ut(M

bps)

802.11802.16

management eliminates these issues for downlink, drastically reduces its impact for uplink 5

6

7Thro

up

• WiMAX also demonstrates better fairness among multiple subscribers

0 2 4 6 8 10 12 14 164

Station Number


multiple subscribers

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Mobile WiMAX Field TestsMobile WiMAX Field TestsMobile WiMAX Field TestsMobile WiMAX Field Tests


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Field TestsField Tests ‐‐ OverviewOverviewField Tests Field Tests OverviewOverview

• Field tests designed to provide real‐world performance data– Maximum communication distance

– Maximum throughput at different velocities

– Handover performance with and w/o ASN‐GWHandover 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 campuscampus

• First Full‐Scale Field Tests are planned for October timeframe– Both railroads are currently installing our test equipment


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Test Site 1Test Site 1 –– UP: Logan, IAUP: Logan, IATest Site 1 Test Site 1 UP: Logan, IAUP: Logan, IA

Road for WiMAX TestsRoad for WiMAX Tests

120degree coverage area of antenna (shaded area)

Main Antenna Direction Indicator

Logan, IA - Tower


3 miles (approx.)

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Test Site 2Test Site 2 –– BNSF: Ashland, NEBNSF: Ashland, NETest Site 2 Test Site 2 BNSF: Ashland, NEBNSF: Ashland, NE

Ashland, NE - TowerRoad for WiMAX Tests

M i A t Di tiMain Antenna Direction Indicator

120degree coverage area of antenna (shaded area)


3 miles (approx.)

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SummarySummarySummarySummary

• High‐speed data networks is critical for effective railroad operations in mobile environments.

• One technology may not be the solution for allOne technology may not be the solution for all railroad needs.

• Combination of WiFi and WiMAX is a promising• Combination of WiFi and WiMAX is a promising solution.

A i t t d l ti i d d t t• An integrated solution is needed to support audio and video (multimedia type) applications.


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Contact InformationContact InformationContact InformationContact Information

• Hamid Sharif• Email: [email protected]• Phone: (402) 554‐3628• Web: www.tel.unl.edu

• Thank you!


Documents

Hi hHigh SdSpeed DtD ata Nt kN etworks in MbilM obile ...SiStrategic Plan for Ril dRailroad RRhesearch and DlDevelopment ... – Graphs include: Tput vs. Time, Tput vs. Distance, Tput