1. CONTENTION FREE MAC PROTOCOL BASED ON PRIORITY IN UNDERWATER ACOUSTIC COMMUNICATION Hui-Jin Cho, Jung-Il Namgung, Nam-Yeol Yun, Soo-Hyun Park, Chang- Hwa Kim and Young-Sun Ryuh IEEE Oceans 2011 Speaker : Chuan-Heng, Chi

2. Outline Introduction Related work Goals Proposed MAC protocol Network environment PR-MAC Simulation Conclusion

3. Introduction The world's oceans cover over 70 % of its surface Underwater Wireless Sensor Networks (UWSNs)

4. Introduction Underwater sensor network technology can be applied in many fields Data acquisition Underwater exploration Unattended environmental monitoring systems Prevention of natural disasters Military purpose

5. Introduction The battery cannot be recharged in simple way How to reduce the energy consumption is importance Sensor

6. Introduction Transmission rate WSN: 3 x 10 8 m/s UWSN: 1500 m/s Propagation delay A B BA

7. Introduction Problem Long propagation delay RTS CTS DATA RTS CTS A B C

8. Related work Slotted FAMA RTS CTS DATA RTS CTSDEFERS TRANSMISSIONS A B C Maximum Propagation Delay+CTS

9. Goals We propose appropriate MAC Protocol for underwater acoustic communications Minimizing conflicts Reducing energy loss

10. Proposed MAC protocol We propose the Priority Reservation MAC (PR-MAC) protocol Long propagation delay Minimizing the conflict Energy loss

11. Network environment Assumption Time synchronization of each node is conducted before Each node’s ID assumed to be unique

12. PR-MAC DBACE A’s neighbors : B,C B’s neighbors : A,D C’s neighbors : A,E D’s neighbors : B E’s neighbors : C

13. PR-MAC Random access period (R1) Transmission cycle period (C1)(C2)(Cn) Transmission cycle period Slot reservation periodData transmission period ‧‧‧‧‧ Random access period (R2) time ‧‧‧‧‧

14. PR-MAC Random access period Every node waits for random backoff time to broadcast own information (include node ID, RSSI, Power status) DBACE A B C D E A A AC C CE E B B B D D C C C B B B Random access period (contention) Active mode Random access period (R1) Transmission cycle period (C1)(C2)(Cn) ‧‧‧‧‧ Random access period (R2) time A A AC C C B B B

15. PR-MAC Priority decision DBACE AAA C C C EE B B B A B C D E A A AC C CE E B B B D D C C C B B B A A AC C C B B B AA D D E D E C B D B D E C 12354

16. PR-MAC Random access period (R1) Transmission cycle period (C1)(C2)(Cn) Transmission cycle period Slot reservation periodData transmission period ‧‧‧‧‧ Random access period (R2) time ‧‧‧‧‧

17. Slot reservation period Data transmission period Transmission cycle period (contention free) A A A A B C D E (A,2) C C C (C,10) E DBACE E (E,2) (no data) B B B (B,6) A A E rx-rx collision from A,E B B B C C C Active mode Sleep mode PR-MAC Transmission cycle period Slot reservation periodData transmission period time ‧‧‧‧‧

18. Simulation ParameterValue Transmission range1km Data rate1kbps Network size10km×10km Nodes20~200 Reservation message packet size100 bits Data packet size3000 bits Reservation slots1 sec Data slots4 sec

19. Simulation UASN-MAC Transmission cycle period Slot reservation periodData transmission period time ‧‧‧‧‧ Competitive method

20. Simulation UWAN-MAC

21. Simulation

24. Conclusion In this paper, we proposed PR-MAC protocol suitable for underwater acoustic communication minimizing collision reducing energy consumption