Multi-channel MAC protocol
for
cognitive wireless mesh network
Advisor：Wei-Yeh Chen
Student：王璽農
M. Yu, L. Huang, H. Chen , “Multi-channel MAC protocol
for cognitive wireless mesh network, “IWASID 2008. IEEE
CNF, vol.20-23, no.10, Aug 2008, pp.203-206.
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Outline
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Introduction
The principle of cognitive radio
MMAC of wireless mesh network
CWMN-MMAC
 Assumptions
 Data & Time structure
Simulation & analysis
Conclusion
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Introduction
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With the flourishing development of wideband
wireless communication, the number of mobile
users grows rapidly, and data transmission rate of
wideband wireless communication get higher and
higher.
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But as some theory, the increasing requirement of
communication system in wireless spectrum
resource results in scarcity of spectrum.
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It has become a bottleneck of the development of
wireless communication, and cognitive radio
comes out resolving this problem.
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Base on spectrum sensing of cognitive radio, we
apply it in multi-channel MAC protocol of
wireless mesh network, and propose a new multichannel MAC protocol for cognitive wireless mesh
network in this paper.
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CWMN= Cognitive Wireless Mesh Network
MMAC= Multi-channel MAC
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PU & SU
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Primary User or licensed user
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Those who get license and have the right to use the
spectrum in law.
Secondary User or unlicensed user

Those who do not get license but need to use the licensed
spectrum temporarily.
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The principle of cognitive radio
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A great principle of cognitive radio is when SU
access to licensed channel, it can not influence the
ordinary using of PU.
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When SU detect the licensed channel which is not used
by PU, it can be share to use the channel.
Once PU reuse the channel, all of SU must quit the
communication of the channel.
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MMAC of wireless mesh network
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As a typical MMAC in WMN don’t have specific
control channel.
Every node is equipped a single half-duplex
transceiver, a PCL and all synchronized.
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It is called the Preferable Channel List.
It records the usage of channels inside the transmission
range of the node.
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The channels are categorized into 3 states.

High-This channel has already been selected by the
node for use.
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Medium-This channel has not yet been taken for use in
the transmission range of the host.

Low-This channel is already taken by at least one of
nodes immediate neighbors.
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CWMN-MMAC Assumptions
1.
N +1 channels are available and all channels
have the same bandwidth.
2.
Nodes know how many channels can be used
previously.
3.
None of these channels overlap, so packet
transmitted over different channels doesn’t
interfere with each other.
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4.
5.
One of channels is a control channel. It’s not in
the licensed band, so it will not be interfered by
PU.
Every host has a half-duplex transceiver, and it
can switch channel dynamically.
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6.
The period of PU is longer than the beacon
interval of this protocol. When PU active, it can
be detected in a beacon interval, minimize the
interfering to the PU.
7.
Every node is synchronized strictly, they start
and end beacon interval at the same time.
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CWMN-MMAC Data structure
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Every node has two data structures. The first is
called Primary users Spectral State (PSS), and the
other is PCL.
PSS is the PUs’ usage state in the current channel
which is detected by SUs.
 No PU is active on channel n (SIP [n] = 0)
 A PU is active on channel n (SIP [n] = 1)
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CWMN-MMAC Time structure
競爭視窗 檢測視窗
ATIM視窗
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Simulation & Analysis
數據控制通道流量
1Mbps
數據通道數量(N)
4
數據封包
512Bytes
間隔長度
100ms
交涉視窗的時槽
50 (=802.11 FHSS)
交涉視窗的間隔
20ms
傳輸率
100% & 10%
模擬時間
40s
100個節點隨機分布在500*500的區域內
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100%負載的傳輸量與ATIM
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10%負載的傳輸量與ATIM
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Conclusion
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CWMN-MMAC可以將未使用的頻譜動態分配
給SU，提高頻譜資源利用率。
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他們僅使用一個收發器，可以降低設備價格。
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必須是PU不在使用中為前提，而問題是ATIM
並未做一個詳細解釋。
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