1. Analyzing Multi-channel MAC Protocols for Underwater Sensor Networks Presenter: Zhong Zhou

2. Outline Introduction Related work System model and analysis Performance evaluation Conclusions

3. Introduction Underwater sensor networks (UWSN) – Long propagation delay – High error rate MAC protocols for UWSN – Single-channel MAC R-MAC et. al – Multi-channel MAC Previous work shows higher throughput

4. Related work Multi-channel MAC for terrestrial networks – Multi-channel with Aloha – Multi-channel with RTS/CTS – Split phase Multi-channel MAC for UWSN – Multi-channel with Aloha – Multi-channel with RTS/CTS To our best knowledge, No work analyzes multi-channel MAC for UWSN !

5. Contributions Analyze two generalized multi-channel protocols – Random channel allocation – RTS/CTS based channel allocation Tight upper bound and lower bound Comparison of Multi-channel protocols

6. Assumptions(1)

7. Assumptions(2)

8. Multi-channel with Aloha

9. Multi-channel with RTS/CTS

10. Analysis for Multi-channel with Aloha The probability of successfully transmitting a packet is

11. Analysis for Multi-channel with Aloha Because the input traffic is assumed to be a poisson process for every node

12. Analysis for Multi-channel with Aloha And then, we can get

13. Analysis for Multi-channel with Aloha

14. Optimal bandwidth allocation between control and data channel can be written as: And we can get:

15. Analysis for Multi-channel with RTS/CTS Analyzing the control channel – Previous work shows that the completion time of successfully RTS/CTS exchanged can be accurately modeled by a poisson process Its collision probability can be written as : The net traffic to the data channels is :

16. Problems with data channels

17. Analyzing the data channels Markov chain can no longer model the system as it does in the terrestrial networks Three stochastic processes interacts – Packet arriving process – Channel allocation process – Packet leaving process Instead of investigating the system itself, we try to find its upper bound and lower bound!

18. Basic virtual system (1) We discrete the system and confine the collision to every 2t area

19. Basic virtual system (2) The lengths of the collision region for every packet in both systems are same. since the input is the same poisson process, the performance of these two system are the same

20. Lower bound system the available channel set of every packet will keep the same as that in the beginning of a slot. The channels that are released can be reused during this slot in the original virtual system. However, this will not happen in the confined system. They are only available to the packets in the next slot. Compared to the original virtual system, the number of available channels for every packet in every slot is smaller because the released channels in this slot will not be available to the packets in the same slot any more. this confined system will have higher collision probability than the original virtual system. It can be served as the lower bound of the original virtual system.

21. Upper bound system the release of channels occurs at the beginning of a slot and thus these channels are available to all packets in this slot. Compared with the original virtual system, the number of the available channels for every packet in one slot will be larger because all released channels will be available for all packets in the slot. this revised system must have lower collision probability and can be served as the upper bound of the original virtual system

22. Solving upper bound and lower bound systems The upper bound and lower bound systems can be accurately modeled by Markov chain and we can calculate its performance

23. Performance evaluation Simulation setting – Fully connected network with 50 nodes – Propagation delay : 0.3s – Data packet: 200 bytes – Control packet: 10bytes – Data channels: 16. – Overall bandwidth: 17kbps

24. Simulation results Optimal bandwidth for multi-channel with Aloha

25. Upper bound and lower bound

26. Comparisons Effects of number of channels

27. Effects of input traffic

28. Effects of the length of data packets

29. Effects of propagation delay

30. Conclusions We analyze two general multi-channel protocols for UWSN We compare these two protocols with different network parameters Simulation results show that our theoretical result are quite accurate

31. Future work Explore more complicated multi-channel MAC protocols Investigate multi-channel protocols in multi- hop UWSN environments.