2014 1029 adaptive dissmination of safety data among vehicles

Adaptive dissemination of safety data among vehicles

Chisalita, I.、Shahmehri, N.

Personal, Indoor and Mobile Radio Communications, 2006 IEEE 17th International Symposium on

11-14 Sept. 2006

KUAN-YU, CHEN

stu9458@gmail.com

Outline

• Introduction

– Challenge

• Related work

• Protocol overview

• Basic safety messages dissemination

• Evaluation

• Concluding remarks

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Introduction(1/3)

• An adaptive approach to dissemination of safety data among vehicles.

• Support the driver in dangerous traffic situations.

• Avoid the occurrence of such situations(collision warning and collision avoidance).

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Introduction(2/3)

• Challenge

– Specific properties of the traffic environment.

– The strict requirements of safety applications.

• Vehicles that are not in each other communication range may need to exchange data.

– Forwarding information.

• Vehicles that send their data may not be aware of the receivers that will make use of it

– Filtering of information.2014/10/29 4

Introducton(3/3)

• The protocol makes use of contextual informationfor sustaining inter-vehicle communication adaptable to the current traffic situation.

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Related work(1/4)

• Three main area about communication

– Group membership in vehicular networks

– Medium access control(MAC) schemes

– Traffic data dissemination.

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Related work(2/4)

• Various routing protocols have been proposed for data dissemination in ad-hocnetworks

• Protocols are less applicable to safety vehicular communication.

• Require the establishment of routes to a given destinations.

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Related work(3/4)

• Protocols followed a reactive approach, where notifications are sent when vehicles detect hazards in traffic.

• Takes a proactive approach where vehicles are regularly informed about the traffic situation.

• Used for predicting the occurrence of dangerous situations.

• e.g. Vehicle suddenly breaks down.

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Related work(4/4)

• DSRC (Dedicated Short Range Communication)

– Specifies the MAC layer, the link layer and the radio layer for vehicular communication systems.

– Vehicle-to-road 、Vehicle-to-vehicle

– Augment DSRC functionality when providing safety services.

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Outline

• Introduction

– Challenge

• Related work

• Protocol overview

• Basic safety messages dissemination

• Evaluation

• Concluding remarks

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Protocol overview(1/7)

Problem

• A large number of communicating hosts may

tend to exchange data.

• Produce a heavy load on the communication channel.

• Difficulties in accessing the transmission medium and packet collisions.

• Apply two techniques for controlling the

dissemination of safety information.

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First(1/2)

• Define an organization of the vehicles in virtual clusters

– limited in space and in composition.

• Research in traffic safety has indicated that a vehicle can not extensively benefit by having data about a large number of vehicles.

• imposed a 300 meters as the cluster size.

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First(2/2)

• Impact of the cluster size on the communication performance.

– maximum number of members is 20.

• The data is importance.(remain)

– The sender be registered in cluster.

• If this does not happen, the data describing the respective vehicle is removed.

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Second

• An anonymous context-based broadcast.

• Receivers need to determine the data if they are the intended destination of this data.

• Context-based filtering.

– Based on a set of rules defined using research results in crash analyses.

– Guidelines for developing active safety systems

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Protocol overview(2/7)

• Basic Safety Messages (BSM)

Host identity Message sequence number

Message type Vehicle velocity

Vehicle positions(Two consecutive indications)

Vehicle heading

Vehicle status and size Road identity*

Road type* Road slipperiness*

Speed limit* Number of members

Cluster members identities Other information

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Protocol overview(3/7)

• send error

– BSMs are issued at regular time intervals.

– BSM can not be transmitted and a new one is generated, the older BSM is removed and the new one is inserted into the buffer.

• Forwarded

– Same cluster may not directly receive data about each other.

– Packet collision, shadowing or medium access

– Filtering

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Protocol overview(4/7)

• VA runs a matching algorithm to determine if these hosts may have interest in VB’s data.

– The process ends if such a host if found.

VB

VA

Host

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Protocol overview(5/7)

• Produces a peak-load on the channel and can reduce communication performance

• Before forwarding a BSM, a host waits an amount of time randomly selected between 0 and the transmission rate of BSMs.

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Protocol overview(6/7)

• Filtering and forwarding.

– Using a context-based technique.

• Traffic Postulates

– P1: The vehicles in close proximity have important data. Their number is limited

– P2: Vehicles in front and behind traveling on the same road and in the same direction have data of interest.

– P3: Vehicles coming from an opposite direction can constitute a danger on undivided roads.

– P4: Vehicles can collide if they arrive at an intersection at the same time.

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Protocol overview(7/7)

• Inclusion rule

– (I1) The Euclidean distance between sender and receiver is less than SAT ± ΔD. (ΔD is a hysterezisthreshold)

• Regular rules

– (R1)The sender and the receiver are traveling on the same road AND have similar heading.

– (R2) The sender and the receiver are on the same undivided road AND have different headings AND the sender is ahead of the receiver.

– (R3) The sender and the receiver are traveling on different roads AND a route contention is detected.

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Outline

• Introduction

– Challenge

• Related work

• Protocol overview

• Basic safety messages dissemination

• Evaluation

• Concluding remarks

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Basic safety messages dissemination(1/3)

• Providing vehicles with up-to-date traffic information in a regular manner can be performed using two approaches.

• First

– The constant rate approach, where BSMs are sent at fixed regular intervals.

– The analysis indicated a rate of 10 BSMs/second as appropriate

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Basic safety messages dissemination(2/3)

• Second

– Adaptive approach

– General enough as to accommodate a large diversity of situations.

– Velocities of the vehicles and the traffic density.

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Basic safety messages dissemination(3/3)

• vehicles velocity

– Residential areas, 30 to 50 km/h

– On country roads, 70 to 100 km/h

– Highway, 100 to 150 km/h

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Evaluation(1/10)

• GloMoSim v2.3

• Evaluation

– BSMs delivery delay

– packet collisions

– send errors

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Evaluation(2/9)

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Evaluation(3/10)

• BSMs delivery delay– The efficiency of information filtering was

measured by the information filtering rate.

– the ratio between accepted BSMs and received BSMs.

• packet collisions– The collisions were normalized with the number

of BSMs correctly received.

• send errors– Number of BSMs issued by a host.

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Evaluation(4/10)

• System bandwidth,10 - 2000 kbps.

• Communication service area or cluster size, 50 - 600 m.

• Network load, 6 – 20 vehicles/km/lane.

• Vehicles mobility, 10 - 40 m/s.

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Evaluation(5/10)

Propagation model Two-ray

Channel AWGN and Rician fading

Radio model Based on IEEE 802.11

Frequency 2.4GHz and 5.9 GHz

MAC scheme Non-persistent CSMA

Transmission Power 12 dBm (i.e.～317m range)

BSM size 112 bytes

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Evaluation(6/10)

• BSMs delay as a function of load density

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Evaluation(7/10)

• Packet collisions as a function of mobility

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Evaluation(8/10)

• Information filtering rate under mobility

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Evaluation(9/10)

• Send errors as a function of load density

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Evaluation(10/10)

• The extended version of the protocol considerably outperformed the basic version in most of the tests.

• Areas of improvements

– Efficient information filtering.

– Forwarding techniques.

– Better MAC schemes.

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Concluding remarks(1/2)

• Propose a protocol that makes use of contextual information for controlling thevehicular communication.

• Future work will focus on improvements of the protocol.

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Concluding remarks(2/2)

• The development of a prototype system using on-market devices (e.g. 802.11 WLAN cards or DSRC transceivers when these will be available) is intended.

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