指導教授：許子衡 教授 報告學生：馬敏修 2010/5/31 1

1.Introduction 2.Multi-Channel MAC Protocol 3.CMMP(Clustering-Based Multi-Channel MAC Protocol ) 4.Evaluation and Analysis 5.Conclusions 2010/5/31 2

IEEE p WAVE(Wireless Access in the Vehicular Environment) defines amendments to IEEE To improve V2V communication efficiency have studied MAC (Medium Access Control) and network algorithm based on MANET (Mobile Ad-hoc Network) and VANET (Vehicle Ad-hoc Network). 2010/5/31 3

The VANET contains the location of every node on the road from GPS (Global Positioning System). VANET has more frequent path loss, a shorter link life- time, and lower packet throughput Wireless LAN that is using CSMA/CA in the vehicular environment procedure accompany by frequent collisions 2010/5/31 4

Multi-channel MAC protocol based on cluster head for contention free considering a feature of VANET Cluster head manages the channel status table of cluster and periodically broadcasts CUL (Channel Usage List) in control channel. Each station transmits RCA (Request Channel Assignment) to cluster head to get an allocation of data channel in control channel. 2010/5/31 5

1. For the single-channel, the biggest data size which can be handled will be restrained by the channel wide. 2. Much lower normalized propagation delay will be caused in multichannel than in the single-channel. 3. When the multichannel is used, the QoS (Quality of Service) can be achieved much easily than single- channel 2010/5/31 6

In the simple multichannel media access control protocol, all the other nodes which use different channels will be caused the deafness phenomenon as the failure of the RTS/CTS (Request To Send / Clear to Send) transmission. 2010/5/31 7

In DCA(Dynamic Channel Assignment), one control channel and N data channels are assigned, each node should check whether the data channel is available for the data transmission In order to check the available of the data channel, each node should maintain two kinds of tables such as CUL(Current Usage List) and FCL(Free Channel List). 2010/5/31 8

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Single channel media access control protocol has the weak points of the restrain of the biggest data handle quantity, a lack of the QoS Because of the frequently transmit packet of the DCA’s RTS/CTS, and the overhead caused by the data update, the network efficiency be reduced. The same as the DCA, CMMP also uses the control channel and data channel separately. 2010/5/31 10

Control channel be operated the TDMA based on contention method as follows 1. A cluster member node transmits the RCA (Request Channel Assignment) packet to the cluster header in order to compete with other nodes to use the channel 2. The cluster member node will check the CUL which is broadcasted by the cluster header periodically to check the available channel 2010/5/31 11

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If the data wants to be transmitted, the RCA packet will be transmitted to the cluster header If the RCA is received from its cluster header successfully, cluster header will update its CUL and transmit it to the cluster member periodically. If there is no data wants to be transmitted or receive the RCA failed, it will wait when it receives the CUL each time. 2010/5/31 13

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Used the QualNet version 3.9 Use the basic highway model in the vehicle environment In order to check the performance of the media access control in the continuously data transmit stations, CBR (Constant Bit Rate) is used Support the multi-channel, the frequency has been divided into 6 channels The basic layer setting, it is followed the IEEE p 2010/5/31 16

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Improving network performance in a vehicle environment with multi-channel media access control of the cluster- based algorithm was proposed According to the allocated channel numbers, loss of channel and contention or collision node, we confirmed that MAC transmission delay has decreased more than 60% and it also has increased more than 30% for total transmission ratio 2010/5/31 20