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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 trafficsuch 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
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Car APDF = 0.8
Car BPDF = 0.5
Forwarding Node choose
FOUR BROADCASTING STRATEGIES
Location-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-BASED112/04/18
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Target
Forwarding Node choose
Car Bwants to turn right
Car A
FOUR BROADCASTING STRATEGIES
Neighbor-basedA 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
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Target
Forwarding Node choose
Car B
Car ACollect the information of neighbors
FOUR BROADCASTING STRATEGIES
Cluster-basedNodes 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-BASED112/04/18
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Cluster-Header
Cluster-Header
Gateway-Node
Forwarding Node choose
SYSTEM ARCHITECTURE
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SYSTEM ARCHITECTURE
Our 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
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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
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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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23Time division in the CRC channel
THE INTRACLUSTER COORDINATION AND COMMUNICATION PROTOCOL
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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
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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 EVALUATIONS112/04/18
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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
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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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