指導教授：許子衡 教授
報告學生：馬敏修
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1.Introduction
2.Multi-Channel MAC Protocol
3.CMMP(Clustering-Based Multi-Channel MAC
Protocol )
4.Evaluation and Analysis
5.Conclusions
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 IEEE 802.11p WAVE(Wireless Access in the Vehicular
Environment) defines amendments to IEEE 802.11
 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).
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 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
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 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.
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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 singlechannel
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 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.
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 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).
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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.
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 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
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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.
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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 802.11p
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 Improving network performance in a vehicle environment
with multi-channel media access control of the clusterbased 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
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