1. Jingbin Zhang( 張靜斌 ) †, Gang Zhou †, Chengdu Huang ‡, Sang H. Son †, John A. Stankovic † TMMAC: An Energy Efficient Multi- Channel MAC Protocol for Ad Hoc Networks † University of Virginia ‡ University of Illinois IEEE International Conference on Communications 2007 (ICC 2007)

2. Outline Introduction Proposed Protocol – TMMAC Schedule Transmission Dynamic ATIM Window Adjustment Simulation Conclusion

3. Introduction IEEE 802.11 is designed for single channel access However, multiple channels can be used – Enhance network throughput IEEE 802.11a  12 channels IEEE 802.11b  3 channels 3

4. Introduction – Related Work Multi-channel MAC for ad hoc networks: handling multi-channel hidden terminal using a single transceiver J. So and N. Vaidya MobiHoc 2004 Time Beacon Interval

5. Introduction – Related Work Time Beacon Interval

6. Introduction – Related Work Time Beacon Interval ATIM WindowCommunication Window Beacon Interval Time

7. Proposed Protocol The authors present a TDMA based Multi- channel MAC protocol (TMMAC) – Single transceiver – Data transmission are scheduled – Dynamically adjust ATIM window

8. TMMAC -- Architecture Time Beacon Interval ATIM WindowCommunication Window Beacon Interval Time Communication Window

9. TMMAC Four types of packets are used for negotiation: – ATIM – ATIM-ACK (ATIM-Acknowledgement) – ATIM-RES (ATIM-Reservation) – ATIM-BRD (ATIM-Broadcast)

10. TMMAC During the negotiation, the transmission pair decide – Which channels – Which time slots

11. TMMAC -- DATA structures Two data structures used in TMMAC – Channel Usage Bitmap (CUB) – Channel Allocation Bitmap (CAB)

12. TMMAC -- DATA structures Channel Usage Bitmap (CUB) – Each node need to maintain – Transmitted with ATIM packets

13. TMMAC -- DATA structures Channel Allocation Bitmap (CAB) – Not need to maintain – Transmitted with ATIM-ACK, ATIM-RES ATIM- BRD packets – Telling the neighboring nodes which channels and which time slots are allocated by the current negotiation

14. TMMAC -- Unicast Negotiation AB ACUBs CUB 1 01000…0 CUB 2 10010…0 …00100…1 CUB M 10100…0 ATIM(CUBs, M) BCUBs CUB 1 00010…0 CUB 2 10010…0 …11100…0 CUB M 00001…0 OR

15. TMMAC -- Unicast Negotiation AB ACUBs CUB 1 01000…0 CUB 2 10010…0 …00100…1 CUB M 10100…0 ATIM(CUBs, M) BCUBs CUB 1 00010…0 CUB 2 10010…0 …11100…0 CUB M 00001…0 OR A&BCUBs CUB 1 01010…0 CUB 2 10010…0 …11100…1 CUB M 10101…0

16. TMMAC -- Unicast Negotiation AB A&BCUBs CUB 1 01010…0 CUB 2 10010…0 …11100…1 CUB M 10101…0 ATIM-ACK(CABs) BCABs CUB 1 00000…0 CUB 2 01101…0 …00000…0 CUB M 00000…0 ATIM-RES(CABs)

17. TMMAC -- CUBs update AB BCABs CUB 1 00000…0 CUB 2 01101…0 …00000…0 CUB M 00000…0 ACUBs CUB 1 01000…0 CUB 2 10010…0 …00100…1 CUB M 10100…0 BCUBs CUB 1 00010…0 CUB 2 10010…0 …11100…0 CUB M 00001…0 ACUBs CUB 1 01101…0 CUB 2 11111…0 …01101…1 CUB M 11101…0 BCUBs CUB 1 01111…0 CUB 2 11111…0 …11101…0 CUB M 01101…0

18. TMMAC -- CUBs update AB BCABs CUB 1 00000…0 CUB 2 01101…0 …00000…0 CUB M 00000…0 CCUBs CUB 1 10100…0 CUB 2 00010…1 …01100…0 CUB M 11001…0 C CCUBs CUB 1 10100…0 CUB 2 01111…1 …01100…0 CUB M 11001…0

19. TMMAC -- Broadcast Negotiation Randomly selects the time slots, in which all the channels are not used by any of its neighbors yet S SCUBs CUB 1 01000…0 CUB 2 10010…0 …00100…1 CUB M 10100…0 ATIM-BRD(CABs) SCUBs CUB 1 00000…0 CUB 2 00001…0 …00000…0 CUB M 00000…0

20. TMMAC -- Broadcast Negotiation In broadcast negotiation, – The time slot must all channels are free – It is more difficult to allocate time slots To alleviate that problem, – Within a single node Boradcast packets first – Within multiple nodes Broadcast packets use a small backoff window

21. TMMAC -- Data packets transmission In the ith time slot, – Have packets to send or receive First switch to the negotiated channel Transmits or waits for the data packet – No packets to send or receive Go into doze

22. TMMAC -- Dynamic ATIM window adjustment Use a finite set of ATIM window sizes {ATIM 1,...,ATIM i,ATIM i+1,...,ATIM m }, – ATIM 1 = minimal ATIM window size – ATIM m = maximal ATIM window size – ATIM i+1 - ATIM i = l slot

23. TMMAC -- Dynamic ATIM window adjustment In TMMAC, each node adjusts its ATIM window size dynamically – Allowing different nodes to have different ATIM window sizes When a node is sending an ATIM control packet, it piggybacks its ATIM window size for the next beacon interval

24. TMMAC -- Dynamic ATIM window adjustment To avoid collisions between ATIM control packets and data packets in the default channel – The default channel is never used for data communication in the time slots before ATIM m

25. TMMAC -- Dynamic ATIM window adjustment When node A wants to send a packet to node B – A know B’s ATIM window size A decide whether the negotiation can be finished within min{A’s ATIM window,B’s ATIM window } – Else A decide whether the negotiation can be finished within ATIM 1

26. TMMAC -- Rules for Dynamic ATIM window adjustment Use the information whether all the available bandwidth in the communication window is scheduled for data communication

27. TMMAC -- Rules for Dynamic ATIM window adjustment All the slot times in the communication window are scheduled – Decrease the ATIM window by one level Time ATIM windowCommu windowATIM windowCommu window Time Beacon Interval DecreaseAll in used

28. TMMAC -- Rules for Dynamic ATIM window adjustment Not all the slot times are scheduled – Can negotiate Time ATIM windowCommu windowATIM windowCommu window Time Beacon Interval DecreaseNot all in usedCan negotiate

29. TMMAC -- Rules for Dynamic ATIM window adjustment Not all the slot times are scheduled – Cannot negotiate Time ATIM windowCommu windowATIM windowCommu window Time Beacon Interval Increase Not all in used Can’t negotiate

30. Simulation -- Parameters ParametersValues SimulatorGloMoSim Length of time frame (beacon interval)100 ms Number of channels3 Data rate2 Mbps Network area size1000m*1000m Randomly deployed200 nodes Packet size512Bytes Max ATIM window size31.43 ms Min ATIM window size8.57 ms Channel switch delay80 μs Max time synchronization error0.1 ms Simulation result20 trials Simulation time50s

31. Simulation Evaluation of Dynamic ATIM Window Adjustment Number of packets transmitted vs. ATIM window size

32. Simulation Evaluation of Dynamic ATIM Window Adjustment Number of packets transmitted vs. ATIM window size

33. Simulation Performance and System Loads Aggressive throughputEnergy consumption per packet

34. Conclusion The authors present the TMMAC protocol – Energy efficient – Single transceiver – Support broadcast – Dynamically adjust ATIM window From performance evaluation, TMMAC achieve – Higher throughput – Less energy consumption

35. Thank you Thank you