1. Mohamed Elhawary Computer Science Department Cornell University PERCOM 2008 Zygmunt J. Haas Electrical and Computer Engineering Department Cornell University

2. Outline Introduction The Busy Tone Multi Channel Protocol (BTMC) Simulation Conclusion

3. Introduction Wireless ad hoc network To increase the capacity multi-channel 802.11 a → 12 802.11 b → 3 The protocols designed for the multi channel environment To solve the hidden terminal problem How the channel rendezvous is done

4. Introduction This is the first MAC protocol With a single packet radio per node That does not require synchronization or a dedicated control channel Does not cause network partitioning

5. Motivation Solve the hidden terminal problem in multi-channel. No synchronization. We do not want to have a control channel that can get saturated. All channels can be used for data or control exchange

6. Goal To propose a new distributed multi-channel MAC protocol The Busy Tone Multi Channel Protocol (BTMC) To increase the capacity

7. MAC protocol To use a set of k hash functions; h0, h1,…, hk-1, A channel number from 0 to m-1 where m is the channel environment was described before in previous works number of channels available Nodes are aware of MAC addresses of each other and have the same set of the hash functions

8. MAC protocol ABCE D Ch 1 Ch 2 Ch 3 Ch 4 hash function : A {2, 1, 3, 1, 2} B {1, 4, 2, 1, 3} C {4, 3, 2, 1, 2} D {3, 2, 1, 4, 1} E {1, 4, 3, 4, 2} A E D B C

9. MAC protocol A E D B C ABCE D Ch 1 Ch 2 Ch 3 Ch 4 hash function : A {2, 1, 3, 1, 2} B {1, 4, 2, 1, 3} C {4, 3, 2, 1, 2} D {3, 2, 1, 4, 1} E {1, 4, 3, 4, 2}

10. MAC protocol A E D C ABCE D Ch 1 Ch 2 Ch 3 Ch 4 hash function : A {2, 1, 3, 1, 2} B {1, 4, 2, 1, 3} C {4, 3, 2, 1, 2} D {3, 2, 1, 4, 1} E {1, 4, 3, 4, 2} B RTS

11. MAC protocol E D C Ch 4 A B RTS A B 2τ+γ2τ+γ idle CTS DATA Variable definitions: δ: data packet transmission time γ: RTS/CTS transmission time τ: maximum one way propagation delay td: busy tone detection delay E 2τ + δ + td searches for the next free channel

12. MAC protocol A E D C ABCE D Ch 1 Ch 2 Ch 3 Ch 4 hash function : A {2, 1, 3, 1, 2} B {1, 4, 2, 1, 3} C {4, 3, 2, 1, 2} D {3, 2, 1, 4, 1} E {1, 4, 3, 4, 2} B RTS

13. MAC protocol E D C Ch 4 A B RTS A B 2τ+γ2τ+γ Not idle Busy tone E

14. MAC protocol E D C ABCE D Ch 1 Ch 2 Ch 3 Ch 4 A B RTS wait 2τ + 2δ hash function : A {2, 1, 3, 1, 2} B {1, 4, 2, 1, 3} C {4, 3, 2, 1, 2} D {3, 2, 1, 4, 1} E {1, 4, 3, 4, 2} Variable definitions: δ: data packet transmission time γ: RTS/CTS transmission time τ: maximum one way propagation delay td: busy tone detection delay

15. MAC protocol E D C ABCE D Ch 1 Ch 2 Ch 3 Ch 4 A B RTS hash function : A {2, 1, 3, 1, 2} B {1, 4, 2, 1, 3} C {4, 3, 2, 1, 2} D {3, 2, 1, 4, 1} E {1, 4, 3, 4, 2}

16. MAC protocol E D C Ch 4 A B RTS A B 2τ+γ2τ+γ Variable definitions: δ: data packet transmission time γ: RTS/CTS transmission time τ: maximum one way propagation delay td: busy tone detection delay

17. MAC protocol A C D B E

18. Experimental results

21. Conclusion We proposed a new multi channel MAC protocol in ad hoc network To use one packet radio per node It has a low overhead Future work We want to test the effect of using more sophisticated hash functions To save power like in the IEEE 802.11 specifications