Wireless Vehicular Communications Challenges and Impact on 4G Research

Crossnet workshop, February 2008, IT Lisboa

Wireless Vehicular Communications: Challenges and Impact on 4G Research

Javier Gozálvez

Uwicore laboratory, University Miguel Hernandez

[email protected]

Uwicore, Ubiquitous Wireless Communications Research Laboratory

University Miguel Hernández, www.uwicore.umh.es

2Contents

• Introduction

• Opportunistic Transmission Schemes

• Contextual Communication Mechanisms

• Robust and Efficient Networking Protocols

• Research ‘Testbed’ towards 4G Systems

• Conclusions

Crossnet 2008



• Uwicore: Ubiquituous Wireless Communications Research laboratory

– Signal Theory and Communications Division at the University Miguel Hernandez (Elche, Spain)

– 5 full time researchers

– Active cooperation: eSafety, eMOV, CIO, Innovalia and UPV

• Research: resource management, system dimensioning & optimization

– Wireless Vehicular Communications: eTRANSIT

� Heterogeneous wireless ad-hoc communications platform for the management and optimization of road traffic

– Beyond 3G systems: Decision policies for the common radio resource management of heterogeneous wireless networks

– Wimax systems: RURAL-TUR

� Wireless Platform for the Deployment of Multimedia Services and Content in the Rural Tourism Sector

3Introduction

Crossnet 2008



4

• Wireless vehicular communication systems– Traffic safety, efficiency and infotainment

• V2V and V2I communications complemented with wireless sensor networking capabilities– Ubiquitous and ad-hoc connectivity– Real-time continuous monitoring

• Research activities already started and ‘mature’– Standardisation 802.11p, IEEE 1609.3 & 4– Frequency assignment US, Japan and Europe (5.8-5.9GHz)

Introduction

Crossnet 2008



• European ICT in vehicles research start around 2000– Mainly German participation

• Current European initiatives– eSafety forum– Framework research programs

• eSafety forum– Support entity for implementation of ICT technologies in vehicles

� Mainly traffic safety

– Working groups: discussion and analysys of European situation� Avoid defragementation

– Englobes all stakeholders– Important dissemination activities: eCall

5Introduction

Crossnet 2008



• Framework research programs– First ‘eSafety’ projects at the end of FP6: CVIS, Coopers, Safespot,

etc– Transport call beginning 2007 and ICT for Cooperative Systems end

2007

• CVIS (Cooperative Vehicle-Infrastructure Systems)– http://www.cvisproject.org– Develop and test new technologies to allow V2V and V2I– Focus on architecture and applications, multi-channel terminal,

enhance vehicle positioning

• SEVECOM (Secure Vehicular Communication)– http://www.sevecom.org/– Security and privacy

6Introduction

Crossnet 2008



• SAFESPOT (Cooperative vehicles and road infrastructure for road safety)– http://www.safespot-eu.org– Prevent road accidents developing a Safety Margin Assistant

� Detects in advance potentially dangerous situations and extends in space and time drivers´ awareness of the surrounding environment

� SMA: Intelligent Cooperative System based on V2V and V2I

• COOPERS (CO-OPerative SystEms for Intelligent Road Safety)– http://www.coopers-ip.eu– Road safety through V2I only: build upon existing infrastructure and

equipment� DAB, GSM/UMTS, etc

– Road sensor infrastructure and traffic control applications

7Introduction

Crossnet 2008



• MORYNE (Enhancement of public transport efficiency through the use of mobile sensor networks)– http://www.fp6-moryne.org/– Uses public transport vehicles (e.g. buses) as elements of a network

of mobile sensors, communicating with the infrastructure– Setts up co-operation between public traffic management and city

traffic management

• INTRO (Intelligent roads)– http://intro.fehrl.org/– Combines sensing technologies and local databases with real-time

networking technologies� Fusion of different sensor types data (infrastructure or car based):

possibility to predict

8Introduction

Crossnet 2008



• V2V and V2I have great potential but also important requirements and limitations

– Strict traffic safety QoS requirements– Decentralized communications management– High node’s mobility– Channel conditions

• Wireless vehicular communication research challenges

– Communications protocol reliability– Contextual communications– Reduce interference and channel congestion: system’s scalability– Robust and delay tolerant networking protocols– HMI, antennas, positioning, secutiry, etc

9Introduction

Crossnet 2008



• Uwicore wireless vehicular communications research

– Adaptive and opportunistic communication protocols� Satisfy application QoS requirements while efficiently using the radio

resources

– Contextual communications dimensioning

– Channel modelling effect on communications research

– Robust wireless vehicular routing and data dissemination policies

– Integrated traffic and wireless emulation platform

10Introduction

Crossnet 2008



11

5.9

00

5.8

90

5.8

80

5.8

70

5.9

10

5.9

20

5.8

60

(5M

Hz

-re

se

rve

d)US

A

Ro

ad

sa

fety

an

d

tra

ffic

eff

icie

nc

y

Ro

ad

sa

fety

an

d

tra

ffic

eff

icie

nc

y

Co

ntr

ol

ch

an

ne

l

Ro

ad

sa

fety

an

d

tra

ffic

eff

icie

nc

y

No

n-s

afe

tyre

late

d

5.9

00

5.8

90

5.8

80

5.8

70

5.9

10

5.9

20

5.8

60

No

n-s

afe

tyre

late

d

(5M

Hz

-re

se

rve

d)

Cri

tic

al

roa

d s

afe

ty

EU

RO

PE

WAVE (Wireless Access in Vehicular Environments)

• WAVE or IEEE 802.11p: evolution of IEEE 802.11a– MAC: basic CSMA/CA access method

– PHY: OFDM and 10MHz channel bandwidth

• USA and Europe: 7 channels in the 5.9GHz band– One Control Channel :reference channel to establish communication

links (ad hoc broadcast tx mode)

– Six Service Channels: public safety and private services

Crossnet 2008



• IEEE 1609 family of standards– PHY and MAC– IEEE 1609.1

� Services and interfaces for WAVE applications

– IEEE 1609.2� Security and privacy

– IEEE 1609.3� Transport and network functionality

– IEEE 1609.4� Multi-channel operation

– IEEE 802.11e� QoS provision and priorisation policies at the MAC level

12WAVE (Wireless Access in Vehicular Environments)

Crossnet 2008



• Communication policies require previous system dimensioning

• Urban intersection traffic safety scenario

– Distance from the crashing point at which vehicles receive the first message from the potentially colliding vehicle (D)

• Assumptions when first message received

1. The driver takes a period of time to react, RT. Between 1.5s and 3.5s

2. Then the driver push the brake pedal to try to avoid the collision. Emergency brake deceleration, 8 m/s2 Position of A

Reaction time (RT)

Emergency brake

Car Stopped

First message received

Opportunistic Transmission Schemes

Crossnet 2008



• Important impact of transmission power and channel congestion– Supported speeds decreased around 11% due to packet collisions

40 50 60 70 80 90 100-100

-80

-60

-40

-20

0

20

40

60

80

100

Pos

itio

n

Speed [km/h]

TxPower=0.25W, no surrounding vehicles

ReceptionReaction RT1.5Car Stopped RT1.5Reaction RT3.5Car Stopped RT3.5

RT 1.5

RT 3.5

40 50 60 70 80 90 100-100

-80

-60

-40

-20

0

20

40

60

80

100TxPower=0.75W, no surrounding vehicles

Po

sitio

n

Speed [km/h]

ReceptionReaction RT1.5Car Stopped RT1.5Reaction RT3.5Car Stopped RT3.5

RT 1.5

RT 3.5


40 50 60 70 80 90 100-100

-80

-60

-40

-20

0

20

40

60

80

100

Po

sitio

n

Speed [km/h]

TxPower=0.75W, IVS=40m

ReceptionReaction RT1.5Car stopped RT1.5Reaction RT3.5Car stopped RT3.5

RT 3.5

RT 1.5

Crossnet 2008



• Timing of packet’s reception

• Adaptive and opportunistic transmission schemes

-5 0 5 10 15 20 25 30 35 40 450

10

20

30

40

50

60

70

80

90

Number of messages before the Critical Time

Pe

rcen

tage

of v

eh

icle

s

TxPower=0.75W, IVS=40m, RT=1.5s

40km/h

70km/h

100km/h


0 1 2 3 40

0.2

0.4

0.6

0.8

1

1.2

1.4

1.6

1.8

2

Time to the intersection - TI [sec]

Num

ber o

f rec

eive

d pa

cket

s

TxPower=0.75W, speed=70km/h, IVS=20m, RT=1.5s

One sample

Mean valueCritical Time

Crossnet 2008



16

• Impact of channel modelling on wireless vehicular communications– Channel ‘sensitive’ communications at 5.9GHz– V2V communications represent: same tx and rx antenna height


0 20 40 60 80 100 1200

0.2

0.4

0.6

0.8

1

CD

F

Distance to the intersection [m]

Model 1Model 2Model 3Model 4

CD(RT0.75) CD(RT1.5)

0 2 4 6 80

20

40

60

80

100

Pe

rce

nta

ge

of v

eh

icle

s

Number of packets received before CD

Model 1Model 2Model 3Model 4

1 2 3 40

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

Model

Pro

bab

ility

of n

ot re

cept

ion

bef

ore

CD

No loadHigh channel load

19.3%

1.5%

4.2%

12.5%

Crossnet 2008



17

• OPRAM: OPportunistic-driven adaptive RAdio resource Management– Adapts tx parameters

� Guarantee the traffic safety application requirements: correct reception of at least one packet before CD

– Efficiently uses the tx resources and the radio channel� Minimise tx power

Po

sitio

n o

f A


Crossnet 2008



18

0 50 100 150 2000

0.5

1

1.5

2

2.5


Tra

nsm

issi

on

pow

er [

W]

NT=10packets

NT=20packets

NT=40packets

CD

AR

0 50 100 150 2000

1

2

3

4

5

6

Tra

nsm

issi

on

pow

er [W

]


NT=10packets

NT=20packets

NT=40packets

CD

AR

Fixed transmission power

RT=0.75s RT=1.5s

• OPRAM operation

– Final transmission power levels


Crossnet 2008



19

• System performance using fixed tx powers

– High tx powers needed to avoid a collision – Probability of reception rapidly decreases with the distance

– High inefficient use of the WAVE control channel

0 50 100 150 2000

0.2

0.4

0.6

0.8

1

CD

F


Pt=0.25WPt=0.5WPt=1.25WPt=2.5WPt=4W

CD(RT1.5)

CD(RT0.75)


Crossnet 2008



20

• OPRAM performance

– Same traffic safety performance than a constant high tx power

– Reduces the global transmitting power levels� Specially for high NT values

– OPRAM results in a more efficient use of the channel resources

0 2 4 6 8 10 120

5

10

15

20

25

Pe

rce

nta

ge

of v

eh

icle

s


NT=10packets

NT=20packets

NT=40packets

Pt=2.5W (constant)

Probability of not reception


Crossnet 2008



21

0 2 4 6 8 10 120

5

10

15

20

25

30

Pe

rce

nta

ge

of v

ehi

cle

s


W ithout congestionW ith congestion


NT=10packets

• Potential to overcome negative congestion or channel correlationeffects: Increase nb of tx packets in AR or their tx power

Co

nfig

ura

tion

Co

nfi

gu

rati

on

ppNP TNeR =−== )1()0(

0 2 4 6 8 10 120

5

10

15

20

25

30

Per

cent

age

of v

ehic

les


NT=10

Compensated: increase NT



Crossnet 2008



22

• OPRAM system level channel efficiency

RCV ERR COL ECO TRX0

2000

4000

6000

8000

10000

Type of packet

Pac

kets

/s/k

m

Fixed power, Pt=2WFixed power, Pt=0.25WOPRAM, N

t=10

RCV ERR COL ECO TRX0

10

20

30

40

50

60

70

Type of packet

Per

cent

age

Fixed power, Pt=2WFixed power, Pt=0.25WOPRAM, N

t=10


Crossnet 2008


University Miguel Hernández, www.uwicore.umh.esCrossnet 2008

23

6350

6575

6800

7025

7250

6350

6575

6800

7025

7250

0

10

20

Position X [m]

Position Y [m]

Per

cent

age

of c

ollis

ions

6350

6575

6800

7025

7250

6350

6575

6800

7025

7250

0

10

20

Position X [m]

Position Y [m]

Per

cent

age

of c

ollis

ions

6350

6575

6800

7025

7250

6350

6575

6800

7025

7250

0

10

20

Position X [m]

Position Y [m]

Per

cent

age

of c

ollis

ions




24

• Can we dimension communication protocols just on a user or system based?

• Need to consider effects derived from information exchange using wireless vehicular communication technologies– Rear-end collisions

– Contextual communications dimensioning: extend CD to CD+ED

Contextual Communication Mechanisms

Crossnet 2008



25

• Case PT=RT

– CD independent of IVS

– ED non-linearly depends on IVS

– High values of ED in dense traffic

– Null values of ED in smooth traffic

– Strong dependence of ED with speed(specially for low values of IVS)

Case: v=70km/h, N=2 vehicles and RT=1.5s

Case: N=2 vehicles and RT=1.5s

5060

7080

90 1020

3040

0

20

40

60

80

IVS [m]v [km/h]

ED

[m]

5 10 15 20 25 30 35 400

20

40

60

80

100

IVS [m]

Dis

tanc

es [m

]

TR=1.5s - TP=1.5s - v=70km/h

CDEDCD + ED


Crossnet 2008



26

• Dependence of ED with the number of vehicles

– Cumulative effect of the propagation time of the alert

– Dependence increases with PT

� High difference between visual propagation and routing

� ED could be avoided with efficient alert routing

� Routing also reduces the dependence of ED with RT

RT=0.75s RT=1.5s

PT (s) N=2 N=5 N=2 N=5

0.1 0.0 0.0 0.0 0.0

0.4 2.8 11.1 2.8 11.1

(=RT) 10.6 42.5 42.5 170.1

Case: v=70km/h, IVS=5m.


Crossnet 2008



27

• Communication protocols: influence of speed and context in communications dimensioning

– Increment of CD and ED with speed requires high tx power

– Power limitations reached in some cases

� Potential alternative solution: V2I

Case: RT=PT=0.75s, IVS=10m and p=0.99

0

5

10

15

20

25

30T

ran

smis

sio

n p

ow

er

[W]

Power for CD

Power for CD+ED

N=2 N=5

50km/h 50km/h70km/h

90km/h

70km/h

90km/h


Crossnet 2008



28

• Need to define adequate routing and broadcasting policies for relaying vehicular communications– Position based routing protocols: scalability and robustness against

topological changes– Selects next forwarding node based on positioning information to forward the

packet in the geographic direction of the destination

• Potential wireless vehicular routing protocols– Unicast protocols: based on beacons and list of neighbours

� GSPR: uses greedy forwarding to forward packets to nodes that are always progressively closer to the destination

� SAR: shortest path definition, graph model created, and routes over nodes in the graph closer to the destination

– Broadcast protocols: does not use beacons

� Contention Based Forwarding (CBF): sender broadcasts the message to all its neighbors and neighbors autonomously decide the one that will forward the packet

Robust and Efficient Networking Protocols

Crossnet 2008



• Do not underestimate radio channel effect on networking protocols!

Crossnet 2008

29Robust and Efficient Networking Protocols



• Broadcast policies outperform unicast schemes

– But overload the channel….

Crossnet 2008


Very low Low Medium High Very high0

10

20

30

40

50

60

70

80

90

100

Densidad de tráfico

Per

cent

age

of p

acke

ts re

ceiv

ed a

t des

tinat

ion

area

Unicast: GPSRUnicast: SAR (more-lanes path)Unicast: SAR (shortest path)Broadcast: CBF



• Proposal that improves unicast traffic density based routing protocols– Performance close to broadcasting CBF– Significantly reduces channel congestion

Crossnet 2008




• Vehicle to Infrastructure communications– Winning technology? UMTS, WiMAX, DVB,…

� Reusing infrastructure or new road side units deployed?� Vehicle Infrastructure Integration: 57 RSUs deployed in Detroit test site

– WiMax: 28 sites / Wireline: 21 sites / 3G: 5 sites / Canopy: 2 sites / WiFi: 1 site

– Challenging scenario for efficient handovers and heterogeneous wireless networking

32Research ‘Testbed’ towards 4G Systems

Crossnet 2008



• What do we know about 4G?– IP-based– New radio interfaces: LTE…– New transmission techniques: MIMO…– Heterogenous wireless networking: CRRM…– Multi-hop cellular: fixed and mobile

Crossnet 2008




• Research challenges in the development of mobile ad-hoc relaying 4G technologies– Relaying cooperation– Robust and delay tolerant networking

� Communications reliability� Contextual communications� Peer-to-peer channel effects

– Minimise channel congestion and interference� Contextual communications

Crossnet 2008




35Conclusions

• Wireless vehicular communications offer a great potential to improve traffic safety and efficiency

• Need for intelligent and contextual communication protocols to ensure the communications reliability and the system’s scalability

• Wireless vehicular communications research represents a good testbed for future 4G mobile relaying multi-hop cellular networks


University Miguel Hernández, www.uwicore.umh.esIEEE WiVeC 2007

36

Thank you for your attention

This work was supported in part by the Spanish Ministerio de Fomento under the project T39/2006, by the Generalitat Valenciana under research grant BFPI06/126 and by the University Miguel Hernández under the 2005 Young Researcher Award received by Dr. Javier Gozalvez.

www.uwicore.umh.es

Documents

Wireless Vehicular Communications Challenges and Impact on 4G Research