1. A Cooperative Multi-Channel MAC Protocol for Wireless Networks IEEE Globecom 2010 Devu Manikantan Shila, Tricha Anjali and Yu Cheng Dept. of Electrical and Computer Engineering, Illinois Institute of Technology, Chicago, USA

2. Outline Introduction Goals The Proposed MAC Protocol Simulation Conclusion

3. Introduction How to provide robust communication over fading channels is a crucial challenge in wireless networks ◦ cooperative communications achieve spatial diversity and thereby reduce the negative effects of fading on wireless channels

4. Introduction Deploying cooperative relays in large-scale wireless networks lead to : ◦ An elevated level of interference  Degraded throughput  Higher packet losses Multiple channel ◦ mitigate the wireless interference

5. Goals Designing a protocol ◦ Integrate the capabilities of both cooperative communications and multiple channels into wireless networks

6. The Proposed MAC Protocol CoopMC MAC protocol ◦ There are C channels in the network ◦ Each node (source, destination and relay) is equipped with two half-duplex interface ◦ Cooperative link  Direct path  Relay path ◦ Assume that each source node is aware of the best helper nodes

7. The Proposed MAC Protocol Data Structures in CoopMC design ◦ Each node maintains  Neighbor-table (Ntable)  Find a best helper node to assist the communication  Good Channel State Information  Minimum interfering neighbors  Channel-table (CTable)  Counter that indicates the number of neighbors that have planned to utilize the channel

8. The Proposed MAC Protocol Based on the existing Multichannel MAC protocol (MMAC) ◦ Control phase  Pre-defined channel ◦ Data phase

9. The Proposed MAC Protocol Channel negotiation during the Control Phase ◦ If the channel is busy  Sender should wait until the channel is idle plus a DIFS time period SenderDestination Relay 1. Carry sense

10. The Proposed MAC Protocol Channel negotiation during the Control Phase ◦ If the channel is idle for a DIFS time period and has completed the required backoff process 2. send CTU(CTable) SenderDestination Relay

11. The Proposed MAC Protocol Channel negotiation during the Control Phase ◦ A helper node cannot cooperate  Channel is busy due to other transmissions  Helper node has already agreed to serve another transmission 3. send CTU-R(CTable) SenderDestination Relay

12. The Proposed MAC Protocol Channel negotiation during the Control Phase ◦ Destination selects two channels based on the CTables at sender, relay and itself 4. send CTU-ACK(1,2) SenderDestination Relay 1 2

13. The Proposed MAC Protocol Channel negotiation during the Control Phase ◦ Destination selects two channels based on the CTables at sender, relay and itself 4. send CTU-ACK(1,2) SenderDestination Relay 1 2 1 1 2

14. The Proposed MAC Protocol Channel negotiation during the Control Phase 5. send CTU-RES(1) SenderDestination Relay 1 2

15. The Proposed MAC Protocol Channel negotiation during the Control Phase ◦ If the CTUR-RES packet is not heard, the sender and destination switch to direct transmission mode in the D ATA Phase 5. send CTU-RES(1) SenderDestination Relay 1 2 6. send CTUR-RES(1,2)

16. Example Control phase

17. Example Data phase SenderDestination Relay 1 2 1 Channel 2

18. Simulation NS-2 simulator ◦ A grid of 40 wireless nodes located in 1000x1000(m) ◦ Bit rate of channel is 2Mbps ◦ Transmission range of each node is 250m ◦ Randomly select the source and destination pairs ◦ Traffic flow adopted UDP/CBR

19. Simulation Assume that sufficient number of relay nodes are present in the network Packet size is 1000 bytes. The beacon interval is set to 150ms and control phase duration as 32ms

20. Simulation Aggregate Throughput vs. Packet Arrival Rate

21. Simulation Sensitivity of models to wireless errors

22. Simulation Impact of Channels on Throughput

23. Conclusion The auther proposed a cooperative multi- channel (CoopMC) MAC protocol ◦ Allocates each cooperative transmission, dynamically, onto a different channel. The simulation results ◦ Greatly reduce the interference in cooperative wireless network ◦ Provide an enhanced performance

24. Thanks for your attention