Enhancing Vehicular Internet Connectivity using - PowerPoint Presentation

Slide1

Enhancing Vehicular Internet Connectivity using Whitespaces, Heterogeneity and A Scouting Radio

Tan Zhang★, Sayandeep Sen†, Suman Banerjee★★University of Wisconsin Madison, †IBM Research IndiaSlide2

Motivation

InfotainmentEntertainmentRoad Safety

Growing trend of vehicular Internet accessSlide3

Motivation300 million vehicles connected to Internet by 2020 [Cisco report]Slide4

MotivationPresent-day approaches

WiFi

Small (0.2km)

Cellular

Congested

Large (10km)Slide5

Motivation

New opportunity in TV whitespacesFCC released vacant TV channels for unlicensed useTV

(2km)

Whitespace

Large

Vacant

Long propagation range

“This new unlicensed spectrum will be

a powerful platform for innovation…”

- FCC Chairman

Up to 180MHz spectrumSlide6

GoalDesign robust communication protocols to use TV whitespaces for vehicular Internet accessSlide7

OutlineScout – TV whitespace network for vehiclesHeterogeneous architectureScouting radio based channel estimationScouting based communication stackImplementationEvaluationConclusionSlide8

OutlineScout – TV whitespace network for vehiclesHeterogeneous architectureScouting radio based channel estimationScouting based communication stackImplementationEvaluationConclusionSlide9

A Metro Hotspot

Super Slide10

Whitespaces Base Station

A Metro Hotspot

Whitespaces

Gateway

Super Slide11

Problem of Power Asymmetry

Primary

Incumbents

Whitespaces

B

ase

S

tation

Asymmetric

P

ower

L

imits (FCC 10-174)

2 km

0.5 km

Whitespaces

GatewaySlide12

A Simple Symmetric Network Solution

16x base stationsSlide13

Scout – A Heterogeneous Network

Cellular BS

Whitespaces BS

40 Kbps downlink TCP throughput

Additional advantages:

Offloading the majority of traffic

Zero

interference to primary incumbentsSlide14

Challenges in Heterogeneous NetworksCellular path has high latency

TechnologyOne-way Latency3G100 – 150ms4G

25 – 40msWhitespaces

< 5ms

Delayed

F

eedback

Poor Protocol

Decisions

Fast Changing Environment

Slide15

Problem of Delayed Feedback

ACK

Whitespaces BS

Cellular BS

6Mbps

6Mbps

6Mbps

Can the client foresee channel at a future location?Slide16

OutlineScout: TV whitespace network for vehiclesHeterogeneous architectureScouting radio based channel estimationScouting based communication stackImplementationEvaluationConclusionSlide17

Intuition behind Scouting Radio

Whitespaces BSCellular BS

Rear

Front

Scout

ReceiverSlide18

Whitespaces BS

Candidate Rates9Mbps6Mbps1MbpsScouting Based Rate Adaptation

NACK

Rear(receiving)

Cellular BS

Future

Reception

L

ocation

Front(

scouting

)

1Mbps

6Mbps

6Mbps

1Mbps

Front

6Mbps

Current

Reception

L

ocation

How does base station identify relevant feedback?Slide19

Calculate loss rates in a small window around aligned timeTime based Feedback Alignment

Time (s)Feedback1234

5

6

Base station stores scouted feedback according to its received time

Now

Delay for rear radio to reach front location:

Loss = 0.5Slide20

OutlineScout: TV whitespace network for vehiclesHeterogeneous architectureScouting radio based channel estimationScouting based communication stackImplementationEvaluation

ConclusionSlide21

Scouting based Communication Stack

Base Station

Packet Buffer

Client

Packet

Loss

Over the AirSlide22

Scouting based Communication Stack

Base Station

Packet Buffer

Client

Rate

Loss

Throughput

1Mbps

0.1

0.9Mbps

6Mbps

0.4

3.6Mbps

9Mbps

0.8

1.8Mbps

1

2

3

4

5

1

2

3

6

6

6

Assign PHY rate

6

6

Packet Batch

Over the Air

k redundant packets to

t

olerate

<= k

lost packetsSlide23

Scouting based Communication Stack

Base Station

Packet Buffer

Client

TV Whitespaces

Cellular

Rate

Loss

Throughput

1Mbps

0.1

0.9Mbps

6Mbps

0.4

3.6Mbps

9Mbps

0.8

1.8Mbps

1

2

3

4

5

6

6

6

6

6

Over the Air

If Loss >= 0.75Slide24

Successful Error Correction

Base Station

Packet Buffer

Client

TV Whitespaces

Cellular

1

2

3

4

5

Loss <= k Packets

1

3

1

2

3

1

2

3Slide25

Error Correction Failure

Base Station

Packet Buffer

Client

TV Whitespaces

Cellular

1

2

3

4

5

3

3

3

Link-layer Retransmission

Feedback

Missing Packets

Loss > k PacketsSlide26

System Implementation

Downlink: translate WiFi to TV whitespacesWide Band Digital Radio (WDR)Uplink: use a 3G linkRF chain 1

RF chain 2Slide27

OutlineScout: TV whitespace network for vehiclesHeterogeneous architectureScouting radio based channel estimationScouting based communication stackI

mplementationEvaluationConclusionSlide28

EvaluationExperiment setupMount a base station on top of a 8-floor buildingDrive about 500 miles along multiple routesSlide29

Advantage of Scouting RadioApproach: measure how accurate a previous observation to the current channel conditionMetric: packet loss ratesTraffic:

200 byte UDP packets at 12Mbps

29

Single

Static

Single

10mph and 25mph

Scout

25mphSlide30

Advantage of Scouting Radio

Low variation in static scenariosSingle has 27% - 34% estimation error

Typical 3G Delay

Scout

has

5x

lower estimation error

Single

has high variation under mobility

Lag (

ms

)Slide31

Overall Performance

SystemRate AdaptationDual-radioCombineA-1RRAANoA-2Minstrel

NoA-3RRAA

Yes

A-4

Minstrel

Yes

Approach:

measure downlink performance during 5 drives for each system

Metric:

TCP throughput averaged over 1 second bins

8

x

and

3x

gain over A-3 and A-4

2.5xSlide32

ConclusionExplored the opportunity in using TV whitespaces to provide vehicular network connectivity.Designed a heterogeneous network to extend network coverage under asymmetric power limits.Designed a scouting radio to improve channel estimation under feedback delay.

Designed a scouting based communication stack to enhance link robustness.Slide33

Thanks a lot! Contact: tzhang@cs.wisc.eduVideo demo: http://youtu.be

/_rnzH7owtBw