QoS Provisionings in Intelligent Vehicular Networks

QoS Provisionings in Intelligent Vehicular Networks

Xi ZhangNetworking and Information Systems LaboratoryDepartment of Electrical & Computer Engineering

Texas A&M UniversityCollege Station, Texas, USA

This research is supported in part by the U.S. NSF CAREER Award under Grant ECS-0348694

August 3, 2012

Seminar at Institute of Network Coding, The Chinese University of Hong Kong

Seminar at INC/CUHK Xi Zhang Texas A&M University, ECE Dept.

Outline

Background and motivation of ITS Intelligent vehicular networks

DSRC/802.11 p/ WAVE (protocols) Challenges and QoS requirements

QoS provisionings in vehicle-to-vehicle (V2V) communications Clustering-based multi-channel

communications architecture Conclusions and future work

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ITS Background and Motivations: Costs and Problems of Moving Vehicles

Safety: 6 Million crashes, 41,000 fatalities in U.S. per year ($150 Billion)

Congestions: 3.5 B hours delay, 5.7 Billion gal. wasted fuel per year in U.S. ($65 Billion)

Pollutions: produce > 50% hazardous air pollutants in U.S.; contributes up to 90% of the carbon monoxide (CO) in space air of urban area

< 0.5 Million

0.5 - 1M1M - 3M

> 3M

Source: 2005 Annual Urban Mobility Report (http://mobility.tamu.edu)Texas Natural Resource Conservation Commission (http://www.tnrcc.state.tx.us/air)

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4


What is ITS – Solutions ?

Intelligent transportation systems (ITS) encompass a broad range of wireless and wire line communications-based information and electronics technologies.

ITS improves transportation safety and mobility and enhances American productivity through the integration of advanced communications technologies into the transportation infrastructure and in vehicles.

Quoted from Research and Innovative Technology Administration (RITA) of U.S. DOT

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Examples of the Traditional ITS Technologies

Many infrastructure based ITS technologies are already in use traditionally: Variable vehicles speed limits Adaptive signal timing systems Speed activated curve-warning systems

(e.g., GPS, or road-side signal signs)

Modern Intelligent Vehicular Networks – Our Focus

Empowered/driven by Information Technology, especially High-speed broadband Wireless and Wired Communications Tech.

GOAL: increase the safety, efficiency, and convenience of the transportation system.

Communications link between vehicles on the road, and between vehicles and the roadside infrastructure

ITS Architectures


Vehicle to Vehicle Communications

Vehicle to Infrastructure Communications

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(Highway admin/driver)

(fleet manager)

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International Efforts/Standards

US EU JapanRF bands 75 MHz bandwidth

5.850-5.925 GHz range at 5.9GHz7 channels (each 10 MHz)

20 MHz at 5.9GHz allocation by 2010

20 MHz at 5.8 GHz allocation since 1997

Political Environments

USDOT10 State DOTsMajor Car Manufacturers IEEE and ASTM

Strong political support by the EU and most Nations’ Governments

Rollout of infrastructure for vehicle safety communications ongoing

Activities/Projects Vehicle Infrastructure Integration

Car2Car Communications ConsortiumCOM eSafety

SmartwayASV-4

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Def.: Common Techniques/Terms/Devices

V2I: Vehicle to Infrastructure V2V: Vehicle to Vehicle V2R: Vehicle to Roadside unit DSRC: Dedicated Short Range

Communications

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V2I Communications/Applications

Vehicle to Infrastructure Probe Data Trip Path Data Transaction Data (e.g., E-Payment)

Infrastructure to Vehicle Advisory Message Data Localized Map Data (safety) Signal Phase & Timing Data Position Corrections Transaction Data (e.g., E-Payment)

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V2V Communications

Vehicle to Vehicle Heartbeat Data (periodic vehicle info

renew) Intersection-crossing assistance blind spot warning lane switch assistance do-not-pass warning control loss warning

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Introduction of DSRC for V2V (our focus) and V2I

History On December 17, 2003 the FCC adopted a Report and

Order establishing licensing and service rules for the Dedicated Short Range Communications (DSRC) Service in the Intelligent Transportation Systems (ITS) Radio Service in the 5.850-5.925 GHz band (10 MHz centered at 5.9 GHz band point).

What is it? The DSRC Service involves V2V and V2I

communications, Help protect the safety of the traveling public. It can

save lives by warning drivers of an impending dangerous condition or event in time to take corrective or evasive actions.

The band is also eligible for use by non-public safety entities for commercial or private DSRC operations.

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Frequency (GHz)

5.85

0

5.85

5

5.86

0

5.86

5

5.87

0

5.87

5

5.88

0

5.88

5

5.89

0

5.89

5

5.90

0

5.90

5

5.91

0

5.91

5

5.92

0

5.92

5

5.82

5

5.83

0

5.83

5

5.84

0

5.84

5

US Spread Spectrum Allocation

Uplink

Downlink

CH 184CH 178 CH 180

US DSRC Allocation

CH 182CH 176 CH172

5.9 GHz DSRC “7- BAND PLAN” with 10 MHz for each CHANNEL

CH 174

//

IntersectionsControl Veh-Veh

Dedicated Public Safety

Short Rng ServiceMed Rng Service

Shared Public Safety/Private

//

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DSRC/802.11p/WAVE Protocols

DSRC (Dedicated Short Range Communications) ASTM Standard E2213-03, based on IEEE 802.11a Name of the 5.9 GHz Band allocated for the ITS

communications IEEE 802.11p

Based on ASTM Standard E2213-03 Currently draft standard

WAVE (Wireless Access in Vehicular Environments) Mode of operation used by IEEE 802.11 devices to

operate in the DSRC band Specified by IEEE 1609 standards

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Challenges in Vehicular Networks

Network layer

MAC layer

Physical layer

Security and privacy

Vehicular environment

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PHY Layer

Multi-path channels May destroy the orthogonality of channels

High relative speed between vehicles or between vehicles and RSU Doppler Spread

Coherence BW vs. carrier BW if >, then frequency selective fading

Coherence time vs. packet length Should be longer than a packet for fading corrections

Wireless channel modeling for vehicular environment

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Network Layer

Vehicle’s high mobility Time-varying topology

Neighboring discovery Neighbors change in a short time

Network connectivity Depends on highway traffic

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Security and Privacy Concerns OBU addresses are randomized

prevents vehicles from being tracked Authenticated RSU application

announcements Prevents WLAN from receiving the fake

message Link level encryption

prevents overhearings Authentication

Public key infrastructure (PKI)

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QoS Requirements

Safety Messages: Bounded Delay

Hop by hop (e.g., collision warning between neighboring vehicles in V2V)

End to end (e.g., accident-ahead-warning) Jitter (e.g., voice communications) Successful delivery Rate

Non-Safety Messages Non-real-time traffic Throughput Connection Opportunity Packet error rate

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MAC Layer

High relative-speed Fast establish time Short connection time (esp. for V2I)

Handoff issues Power control Hidden terminal problem Reliable and timely delivery of

safety messages

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(II) V2V: Our Proposed Scheme: Clustering-Based Multi-Channel V2V Scheme (1)

Aims at supporting QoS for timely delivery of real-time data and increasing the throughput for non-real-time traffics over V2V-based VANET.

Integrates the clustering algorithm with both the contention-free and contention-based MAC protocols under the DSRC architecture.

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(II) V2V: Our Proposed Scheme: Clustering-Based Multi-Channel V2V Scheme (2)

Handles three tasks: Cluster-membership management Real-time traffic delivery Non-real-time data communications

Complies with the DSRC 7-channel band plan

Incorporates with IEEE 802.11p Each vehicle is equipped with two

sets of transceivers, that is, it can work on two separated channels simultaneously.

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Overview of our proposed scheme

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Scheme structure diagram

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Due to the highly mobility of the vehicle networks, even the well designed clustering algorithm cannot guarantee the stability of the cluster topology.

Cluster-head vehicles may malfunction due to the unreliable wireless channel or crash failure.

We divide the vehicle’s states into two types in terms of functionality Cluster-head Cluster-member

The vehicle’s states

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The Intra-Cluster Coordination and Communication Protocol In the Cluster Range Control (CRC) channel, time

is partitioned into regular time intervals (TDMA frame) with the equal-length of T, called “repetition period”.

The repetition period consists of TDMA upstream period and downstream period

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Notations/Variables Defs. : the average gap between the

leading vehicle and the following vehicle

: the average length of the vehicle

: the cluster radius : the number of lanes The length of time slot assigned to (taken

by) each member (vehicle) within a cluster is

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Timely safety message delivery

The TDMA scheme can guarantee that each vehicle within a cluster has a chance to transmit data in every T time unit.

Denote the updating interval of safety messages by , the channel rate by R, and the packet length of safety message by

The condition (delay bound) for the timely delivery of the safety messages is:

(delay-bound) and min BW is:

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The Inter-Cluster Communication Protocol

Two types of traffics on two separate channels between clusters The real-time safety messages over

Inter-Cluster-Control Channel The non-real-time traffic over Inter-

Cluster-Data Channel

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Delay QoS Modeling (1) The transmission delay of the safety

messages is the most important performance metric.

The delay of a safety message from a cluster-member vehicle to another cluster-member vehicle in the neighboring cluster consists of 3 parts:

Delay of transmitting the consolidated safety message from a cluster-head to its neighboring cluster-head

Delay for a safety message to be sent from a cluster-member to its cluster-head

Delay for the cluster-member vehicle in the neighboring cluster to receive the safety message from its cluster-head

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Delay Modeling (2)

The TDMA nature of the Intra-Cluster Coordination and Communication Protocol ensures that

(upstream) and (down)

The maximum total delay The maximum allowable delay for

CH-to-CH communications for vehicle i

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Delay Modeling (3)

Recall that the inter-cluster communication protocol is based on IEEE 802.11 over ICC channel.

Three types of vehicles can send safety messages over ICC channel, i.e., consolidated safety messages by cluster-head, non-consolidated safety messages by quasi-cluster-head and quasi-cluster-member.

Now we use the mature IEEE 802.11 models to investigate the delay for CH-to-CH communications.

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Hidden terminal set

Bi: the set of broadcast receivers for vehicle iHi: the set of hidden terminals for vehicle i

L I

L C

B road cast A re a

H id d e n T erm inal H id d en T erm inal

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Transmission probability (802.11)

For the saturation network, the probability, , that a given cluster-head i attempts to send a safety message is

For the non-saturation network, the probability that cluster-head i attempts to send a safety message is

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Delay

On average, each node successfully transmits one packet during the cycle time of this regenerative process, which includes: the back-off time, E[bi] the successful transmission time, E[mi] the channel busy time, E[ei]

Thus, the average delay is

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Successful delivery rate The probability pi that the cluster-

head i successfully broadcast to all neighbors can be derived as follows using algebra:

When the contention window goes to infinity, we can get its limit:

36Parameters in analyses/simulations


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Tradeoff between delay and delivery rate for safety messages

0.965

0.97

0.975

0.98

0.985

0.99

0.995

1

1.005

Contention window size (CW)

Suc

cess

ful d

eliv

ery

rate

of s

afet

y m

essa

ges

(p)

0

0.01

0.02

0.03

0.04

0.05

0.06

0.07

0.08

Del

ay o

f saf

ety

mes

sage

am

ong

CH

veh

icle

s in

sec

ond

(s)p

p'

s

Delay bound

Max allowable CW

CW*

Delay-QoS gain

S(CW*)

10 100 1000

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Summary

Introduced the background of ITS Discussed the challenges and QoS

requirements in intelligent vehicular networks Proposed the clustering-based multi-channel

communications architecture Conducted delay QoS Modeling for safety

messages transmissions Analyzed the trade-off between delay and

delivery rate

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Future Work

Future work Applying cognitive radio technology to

improve the spectrum utilization in V2V and V2I networks

Extending the effective capacity theory to vehicular networks

Applying more complicated network coding technique in vehicular networks

Furthering the investigation of the privacy issue and its impact on QoS in ITS

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Thanks for your participation!!

http://www.ece.tamu.edu/[email protected]

Documents

QoS Provisionings in Intelligent Vehicular Networks