Cluster-Based Multi-Channel Communications Protocols in Vehicle Ad Hoc Networks

IEEE Wireless Communications october2006, vol.13 No. 5指導老師：童曉儒 教授報告人：張益瑞

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Outline INTRODUCTION SYSTEM ARCHITECTURE FUNCTIONS AND DESIGNS OF

PROTOCOLS THE CLUSTER CONFIGURATION

PROTOCOL THE INTRACLUSTER COORDINATION AND

COMMUNICATION PROTOCOL SIMULATION EVALUATIONS CONCLUSIONS

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INTRODUCTION(1/2)

What is DSRC(Dedicated Short Range Communication)?

V2V-based VANETs and V2R-based VANETs.

The data transmitted over the VANETs can be classified into the real-time traffic and the non-real-time traffic.

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DSRC DSRC/802.11p

The standard of 802.11p is based on IEEE 802.11a PHY layer and IEEE 802.11 MAC layer Seven 10 MHz channels at 5.9GHz one control channel and six service channels

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Vehicle to vehicle

Service channel

Service channel

Control channel Intersection

CH 172 CH 174 CH 182CH 180CH 178CH 176 CH 184

5.855

5.925

5.915

5.905

5.895

5.885

5.875

5.865

Frequency (GHz)

Optionally combined service channels

V2V-BASED VANETS AND V2R-BASED VANETS

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THE DATA TRANSMITTED OVER THE VANETS real-time traffic

such as safety messages and video/audio signals

non-real-time trafficsuch as e-maps and

road/vehicle-traffic/weather information

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INTRODUCTION(2/2) Our proposed scheme mainly consists of

following three core protocols. Cluster Configuration Protocol Intracluster Coordination and

Communication Protocol Intercluster Communication Protocol

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SYSTEM ARCHITECTURE

Four Broadcasting Strategies1. Probability-based2. Location-based 3. Neighbor-based4. Cluster-based

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FOUR BROADCASTING STRATEGIES

1. Probability-based: A given PDF determines the decision, for

example depending on the number of copies a node has received.

The strategy is often dynamic.

PDF = probability distribution function

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PROBABILITY-BASED 112/04/24

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Car APDF = 0.8

Car BPDF = 0.5

Forwarding Node choose

FOUR BROADCASTING STRATEGIESLocation-based

The selection criterion is the amount of additional area that would be covered by enabling a node to forward.

Some proposal also computes position prediction as useful input information.

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LOCATION-BASED112/04/24

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Target

Forwarding Node choose

Car Bwants to turn right

Car A

FOUR BROADCASTING STRATEGIESNeighbor-based

A node is selected depending on its neighbors status (for instance, the status concerns how a neighbor is connected to the network).

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NEIGHBOR-BASED 112/04/24

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Target

Forwarding Node choose

Car B

Car ACollect the information of neighbors

FOUR BROADCASTING STRATEGIESCluster-based

Nodes are grouped in clusters represented by an elected cluster-head. Only cluster-heads forward packets.

Nodes in the same cluster share some features (e.g., relative speed in VANETs).

Reclustering on-demand or periodically.

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CLUSTER-BASED112/04/24

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Cluster-Header

Cluster-Header

Gateway-Node

Forwarding Node choose

SYSTEM ARCHITECTURE 112/04/24

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SYSTEM ARCHITECTUREOur proposed scheme handles the

following three tasksCluster-membership managementReal-time traffic (such as safety messages delivery)Non-real-time data communications (such

as e-maps download, movies download, etc.)

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SYSTEM ARCHITECTURE 112/04/24

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有限狀態機 ( FINITE STATE MACHINE, FSM) 在現實中，有許多事情可以用有限個狀態來表達。 紅綠燈運作的原理相當簡單，從一開始綠燈，經過一段時間後，將變為黃燈，再隔一會兒，就會變成紅燈，如此不斷反覆。

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FUNCTIONS AND DESIGNS OF PROTOCOLS We use the Finite State Machine (FSM) Each vehicle operates under one and

only one of the following four states at any given time:

cluster-head (CH)quasi-cluster-head (QCH)cluster-member (CM)quasi-cluster-member (QCM)

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FUNCTIONS AND DESIGNS OF PROTOCOLS 112/04/24

22Finite state machine of our proposed scheme. T1 and T2 represent Transceiver 1 and Transceiver 2

THE INTRACLUSTER COORDINATION AND COMMUNICATION PROTOCOL

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THE INTRACLUSTER COORDINATION AND COMMUNICATION PROTOCOL 112/04/24

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Tt = 分時多工時間區段N = 叢集內群組成員gap = 平均車間距離v = 平均車輛長度Lc = 半徑Nlane = 位於公路上的車道數量

THE INTRACLUSTER COORDINATION AND COMMUNICATION PROTOCOL 112/04/24

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T = repetition period( 重複期間，預設為 200ms)R = channel rateTsafety = 更新安全訊息的間隔時間Hsafety = 安全訊息的 packet size ，預設為200bytes

SIMULATION EVALUATIONS 實驗情境設定

環境：單向 3 線道進入時間： 2100 秒，變異數： 180 秒平均速率： 35m/s ，變異數： 15m2 / s2

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SIMULATION EVALUATIONS 實驗工具： Matlab 參數設定： 車距： 25m 車長： 5m 車內半徑： 150m 車間半徑： 400ms 接收時間： 150ms 發送時間： 50ms 安全訊息封包大小： 200bytes

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SIMULATION EVALUATIONS112/04/24

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The performance of three protocols against non-real-time traffic arrival rate: a) Probability of safety-message-delivery failure; and b) aggregate throughput of non-real-time traffics. The size of the non-real-time traffic packet is 512 bytes.

SIMULATION EVALUATIONS 112/04/24

29Channel busy rates of the seven different channels. The size of the non-real-time traffic packet is 512 bytes and the packet arrival rate of the non real-time traffic is 200packets/sec/vehicle.

CONCLUSIONS Reduce data-congestion Support QoS for real-time delivery of safety

messages High throughput

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