1. Multi-Channel MAC Protocol for Multi-Hop Wireless Networks: Handling Multi-Channel Hidden Node Problem Using Snooping Myunghwan Seo, Yonggyu Kim, and Joongsoo Ma Information and Communications University IEEE Milcom 2008

2. Outline Introduction Multi-channel MAC protocol Performance evaluation Conclusion

3. Introduction Improve throughput Utilizing Multi-channel… However, multi-channel Multi-channel hidden node problem

4. Introduction- Multi-channel Hidden Node Problem C D Control Channel RTS(2) A→B CTS(2) B→A Data A → B RES AB 1 2 RTS(2) D→C CTS(2) C→D RES Data Channel 1 Data C → D ACK D→C Data Channel 2 2 Data D → C collision x Operation on CH x

5. Introduction-DCA C D Control Channel RTS(2) A→B CTS(2) B→A Data A → B RES AB 1 2 RTS(1) D→C CTS(1) C→D RES Data Channel 1 Data C → D ACK D→C Data Channel 2 1 Data D → C x Operation on CH x

6. Introduction-DCA C D Control Channel RTS (1) A→B CTS (1) B→A Data A → B RES AB 1 1 RTS (1) C→D CTS (1) D→C RES Data Channel 1 Data C → D ACK D→C Data Channel 2 Data D → C x Operation on CH x

7. Introduction

8. Goal Avoid multi-channel hidden node problem Utilizing multiple channels to increase the capacity of wireless network

9. Assumption Two half-duplex radios A control radio and a data radio The control radio is tuned to a fixed control channel Data radio switch in data channels When the data radio is idle, it is used to snoop data channels

10. Multi-channel MAC protocol DCSS (Dynamic Channel Selection with Snooping) DCSS Channel Usage Monitoring Data Channel Snooping Data Channel Selection and Data Transmission

11. DCSS - Channel Usage Monitoring S D 4 3 Node S 10 20 31 41 50 10 20 30 41 50 Channel Usage Table Node D ‘0’ means that channel is idle and ‘1’ means that channel is busy. x Operation on CH x

12. DCSS - Data Channel Snooping S D 4 3 Node S 11 21 3 n/a 4 50 11 21 31 4 50 Snooping Table Node D 2 1 2 1 ‘0’ means that channel is idle and ‘1’ means that channel is busy. Data Radio Node S CH1CH2CH3 CH4CH5 Snooping Time 4 or 15 μ Channel Switching Time 95 μ CH1 x Operation on CH x

13. DCSS - Data Channel Selection and Data Transmission SD 4 3 2 1 2 1 Node S 10 20 31 41 50 10 20 30 41 50 Node D 11 21 3n/a 4 50 11 21 31 4 50 10 20 30 40 51 10 20 30 40 51 NOR = = UsageFreeSnoopingUsageFreeSnooping Control Channel RTS (5) S→D CTS (5) D→S Data 5 Channel Data S → D ACK D→S SIFS RES Data 4 Channel Busy Channel Switching Time

14. Example C D Control Channel RTS (2) A→B CTS (2) B→A Data A → B RES AB 1 2 RTS (1) C→D CTS (1) D→C RES Data Channel 1 Data C → D ACK D→C Data Channel 2 Data D → C x Operation on CH x

15. Performance evaluation Parameter Value Simulator Ns-2 Number of Channel 6 (1 control and 5 data) Channel rate 2 Mbps Simulated area 1000m x 1000m Transmission range 250 m Carrier sensing range 500 m Snooping range 500 m Traffic type UDP Traffic load 1 ∼ 35 Mbps for the single-hop scenario and 0.1 ∼ 3.5 Mbps for the multi-hop scenario Packet size 1024 and 2048 bytes Snooping time per channel 15 μs Carrier sensing time of DCA-CS 15 μs Channel switching time 95 μs Simulation time 100 seconds

16. Performance evaluation- Single-hop 20 pairs 、 randomly No routing required and no congestion

17. Performance evaluation- Single-hop

20. Performance evaluation- Multi-hop 40 nodes 、 randomly 10 nodes as source Apply AODV to find routing paths

21. Performance evaluation- Multi-hop

22. Conclusion DCSS is simple and effectively to avoids collisions. Increasing throughput of DCSS is much better than DCA and DCA-CS in both scenarios. Decreasing delay of DCSS is much better than DCA and DCA-CS in both scenarios.

23. Thank you