2005-01-1484

A Multi-hop Mobile Networking Test-bed for Telematics

Carnegie Mellon University: Rahul Mangharam (Speaker)

Jake Meyers, Raj Rajkumar, Dan Stancil{rahulm, jjmeyers, raj, stancil}@ece.cmu.edu

General Motors: Jay Parikh, Hariharan Krishnan, Chris Kellum{jayendra.s.parikh, hariharan.krishnan, christopher.kellum}@gm.com

April 2005

2005-01-1484

Network Protocol Design

Multi-hop Wireless Test-bed

Vehicular Networking Applications

What this talk is about

Wireless Channel & Protocol PerformanceBottom-UpApproach

Top-DownApproach

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O u t l i n e

1. The Need for Wireless Vehicular Networking

2. Unique Multi-hop Protocol Design Challenges

3. GrooveNet - Geographic Routing

4. Vehicular Networking Test-bed

5. On-road Communication Performance Analysis

6. Multi-hop Wireless Vehicular Applications

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Experimental Ad Hoc Test-bed

Mobile Node

Internet

V

Remote Monitoring of Experiment

1XRTT Cellular Data Network

GPS

Differential GPS reference station beacons

1. Vehicle-to-Vehicle Multi-hop

2. Vehicle-to-Mobile Gateway

3. Vehicle-to-Infrastructure

5.9 GHz DSRC Dedicated Short Range CommunicationsBetween vehicles

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Vehicular Networking Application Categories

1. Safety Alerts– Sudden Breaking– Airbag deployment– Skidding

2. Traffic Congestion Probing– Travel Time– Dynamic Route Planning– Road Condition Notification

3. Interactive Applications– Social Networking– Multimedia Content Exchange– Advertising

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Geographic Routing – Overview• Why Geographic Routing?

– Events are locally relevant– Path is more important than Destination

• Identity & Position Reference– Relevance: Messages for specific target vehicles– Direction: Messages for on-coming vehicles only – Zone-based: Map is overlaid with a grid and divided into zones– Navigation-based: Route along specific road segments

• Packet Exchanges– KISS: DATA and ACK only– No Handshaking Sequence– Accept / Reject / Forward based on message and state info– Restricted Flooding

• Triggers– EVENT SEND_MSG RECV ACK– RECV_MSG DECISION ? ACCEPT : FWD_MSG : DROP_MSG

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Broadcast Scenarios

Highway Driving City Driving Rural Driving

• Path with Intermediate points• Static Source Routing

• Radial Broadcast • Bounding Box• Controlled Flooding

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Routing Bounding Boxes

Rectangles

Cones

Circles

Requires a systematic study

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GrooveNet Protocol Details

• Network foundation - caters to each application category

• Packet Types and Exchange Sequences

• Addressing

• Packet Formats

• Route Search & Route Persistence Rules

• Route Table Representation

• State Information & Neighbor Interaction

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GrooveNet Network Architecture

• Fast Path – Critical Messages

• Control Path – Route Update & Filtering

PHY - Wireless Interface

MAC - Firmware

Linux - Device Driver

Linux – Networking Stack: RT & Filter

Linux – Networking Services

Linux – Application LayerDelay A

Delay B

Delay C

Delay D

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Packet Types & Exchange Sequences

• DATA Packet with MESSAGE field– Critical Alerts– Non-Critical Updates– Subscribed Services

• ACK Packet (Optional)

• No Route Request, No Route Reply, No Route!

• Broadcast, Multicast and Unicast: DROP Rules

• Parse Message & Maintain State Information

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GrooveNet Vehicle Addressing

• Message Type: Broadcast, Multicast, Unicast

• Filter Array:1. Logical: “I want to talk to Buick FJF2323”2. Geographic: “Message for Downtown Warren”3. Non-Geographic: “If you have this capability….”

i. Hop count: “Message for - All cars within 6 hops radius”ii. Navigation: “Message for - All cars headed for Exit 22”iii. Direction: “Message for - All neighbors driving east on I-90”iv. Speed: “Message for - All cars moving within +/- 8mph of my speed”v. Connectivity: “Message for ANY mobile gateway”

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Route Search and Route Persistence Rules• Scope: Region of Validity for each packet

• Path with intermediate hops (optional)

• Greedy Routing

• Message Lifetime

• Retransmission frequency and event

• Nodes moving in opposite direction Forward packets

• Periodic HELLO Messages for Neighbor identification

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GrooveNet – Scalability & Performance

• On Road Testing– Implement in Linux as a kernel module

• Congestion Analysis – Route Virtual Vehicles over Map with actual protocols– Test for (a) Safety Alerts and (b) Congestion Probes

• Basic Connectivity Analysis– Test-bed with straight road– Determine end-to-end throughput & delay– Given speed distribution, max num nodes, density distributions

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Simulation DemoAudio +Video

SendAlerts!

View Network at Runtime

Playbacklogs

GPS Info

NetworkConnectivity

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Simulation Demo

Over 1000 simultaneous vehicles simulated!

2005-01-1484

Experimental Ad Hoc Test-bed

Mobile Node

Internet

V

Remote Monitoring of Experiment

1XRTT Cellular Data Network

GPS

Differential GPS reference station beacons

1. Vehicle-to-Vehicle Multi-hop

2. Vehicle-to-Mobile Gateway

3. Vehicle-to-Infrastructure

5.9 GHz DSRC Dedicated Short Range CommunicationsBetween vehicles

2005-01-1484

GrooveNet Test Kit

5.8 GHz ANTENNAS

GPS ANTENNA

LAPTOP COMPUTER

w/ RADIO CARD

HEADPHONES W/ MICROPHONE

GPS RECEIVER

POWER CORD (12 DC)

WEB CAM

• Driven 5 vehicles over 400 miles – Urban, Rural and Highway• Over 625,000 link measurements

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Average Signal Attenuation vs. Distance

100

101

102

80

85

90

95

100

105

110

115

120

Distance [m]

Sig

nal A

tten

uati

on

[d

B]

Average Signal Attenuation

10log10(1/rn) Model

• Log-Distance Path Loss Model (PR(d) [dBm] = PR(do) – 10nlog10(d/do))

• Current data analysis suggests a path loss exponent of approximately 2

Residential (Suburban) Environments(Pittsburgh, PA)

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Packet Error Rate vs. Distance

Residential (Suburban) Environments(Pittsburgh, PA)

0 50 100 150

10-2

10-1

100

Distance [m]

Packet

Err

or

Rate

• Packet Error Rate generally less than 10% at distances approaching 100 m

• Large PER spike at ~ 10 m currently not understood

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Packet Error Rate vs. Absolute Speed

Residential (Suburban) Environments(Pittsburgh, PA)

0 5 10 15 20 25 300

0.1

0.2

0.3

0.4

0.5

Absolute Speed [MPH]

Packet

Err

or

Rate

TransmitterReceiver

• Packet Error Rate generally less than 10% at speeds up to 30 MPH

• No observed difference between effects of transmitter and receiver speed

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Packet Error Rate vs. Relative Speed

Residential (Suburban) Environments(Pittsburgh, PA)

-30 -20 -10 0 10 20 300

0.1

0.2

0.3

0.4

0.5

Relative Speed [miles/hour]

Packet

Err

or

Rate

• Packet Error Rate generally less than 10% at speeds up to +/- 30 MPH

• Relative speed does not appear to have a significant effect on PER values

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Summary and Conclusions

• The Time has come for Vehicular Networking– Several Killer Apps! – Safety, Congestion Probing, Collaborative Driving, Ads

• Robust Vehicular Networking Test-bed– Extensive on Road Testing with over 400 miles logged

• GrooveNet Software Simulator– Realistic & Scalable with both real and virtual vehicles

• Network & Wireless Channel Performance Analysis– Encouraging Results with DSRC equipment!

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BACKUP SLIDES

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