Multi-channel MAC protocol for cognitive wireless mesh network

1. Multi-channel MAC protocol forcognitive 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.

2. Outline • Introduction • The principle of cognitive radio • MMAC of wireless mesh network • CWMN-MMAC • Assumptions • Data & Time structure • Simulation & analysis • Conclusion

3. Introduction • 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.

4. But as some theory, the increasing requirement of communication system in wireless spectrum resource results in scarcity of spectrum. • It has become a bottleneck of the development of wireless communication, and cognitive radio comes out resolving this problem.

5. Base on spectrum sensing of cognitive radio, we apply it in multi-channel MAC protocol of wireless mesh network, and propose a new multi-channel MAC protocol for cognitive wireless mesh network in this paper. • CWMN= Cognitive Wireless Mesh Network • MMAC= Multi-channel MAC

6. PU & SU • Primary User or licensed user • 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.

7. The principle of cognitive radio • A great principle of cognitive radio is when SU access to licensed channel, it can not influence the ordinary using of PU. • 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.

8. MMAC of wireless mesh network • 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. • It is called the Preferable Channel List. • It records the usage of channels inside the transmission range of the node.

9. The channels are categorized into 3 states. • High-This channel has already been selected by the node for use. • 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.

10. CWMN-MMAC Assumptions • N +1 channels are available and all channels have the same bandwidth. • Nodes know how many channels can be used previously. • None of these channels overlap, so packet transmitted over different channels doesn’t interfere with each other.

11. 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.

12. 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. • Every node is synchronized strictly, they start and end beacon interval at the same time.

13. CWMN-MMAC Data structure • 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)

14. CWMN-MMAC Time structure 競爭視窗 檢測視窗 ATIM視窗

15. Simulation & Analysis

16. 100%負載的傳輸量與ATIM

17. 10%負載的傳輸量與ATIM

18. Conclusion • 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。 • 他們僅使用一個收發器，可以降低設備價格。 • 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。