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AN ADAPTIVE MAC PROTOCOL FOR WIRELESS SENSOR NETWORKS

AN ADAPTIVE MAC PROTOCOL FOR WIRELESS SENSOR NETWORKS. Wen-Hwa Liao, Hsiao-Hsien Wang, and Wan-Chi Wu PIMRC ’ 07. Outline. Introduction Related work Asynchronous MAC(AMAC) protocol Simulation Conclusion. Introduction.

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AN ADAPTIVE MAC PROTOCOL FOR WIRELESS SENSOR NETWORKS

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  1. AN ADAPTIVE MAC PROTOCOL FOR WIRELESS SENSOR NETWORKS Wen-Hwa Liao, Hsiao-Hsien Wang, and Wan-Chi Wu PIMRC’07

  2. Outline • Introduction • Related work • Asynchronous MAC(AMAC) protocol • Simulation • Conclusion

  3. Introduction • In WSNs, the sensors are used to sensing , calculating, and transmitting data. • Each sensor equips with battery and works individually. • The power of sensor is supplied by battery.

  4. Introduction • Because of technical limitations, the power carried by sensor is very limited. • To replace battery is very time consuming and costly process. • There are a lot of researches on energy saving. • Ex: • Hardware • Operating mechanism

  5. Introduction - motivation • The sleeping mechanism is one of the most effective energy saving method. • In order to conserve energy, the sensor turns its antenna off when it doesn’t have to transmit data. • Because the topology of WSNs may change frequently, the saving mechanism should be distributed and self-organized.

  6. Related work - SMAC • Each sensor has its fixed wake-up schedule. • The sensor exchanges their schedules by broadcasting it to all its immediate neighbors. Schedule Sleep Sleep Listen Listen Time W. Ye, J. Heidemann, and D. Estrin, “An Energy-Efficient MAC Protocol for Wireless Sensor Networks,” IEEE INFOCOM , 2002.

  7. Related work - SMAC B’s schedule B A A Sleep Sleep Listen Listen Time B Sleep Sleep Listen Listen

  8. Related work - PMAC • Sensor generates sleeping schedule based on its own traffic periodically. • Pattern string • Bit 1 indicates wake-up • Bit 0 means sleep • Period • N time slots • The sensor also exchanges their schedules by broadcasting it to all its immediate neighbors. • TDMA system T. Zheng, S. Radhakrishnan, and V. Sarangan, “PMAC: An Adaptive Energy-Efficient MAC Protocol for Wireless Sensor Networks,” IEEE International Parallel and Distributed Processing Symposium (IDPDS), 2005.

  9. Related work –PMAC schedule • Time is divided into super time frames (STF) STF STF STF Period i+2 Period i Period i+1 Time PRTF PETF W 0 1 0 0 1 0 … N slots Exchange the schedule of i+2

  10. Related work - PMAC • δ is a predefine threshold. • The time slot in a period will be repeated, if pattern is small than the size of period N • Schedule is composed of sleep-wakeup pattern • Ex: • 1, 011, 021, 041, ···0m1, 0m01, for m ≤δ • 1,01,001,00001 ,δ=4 • 0δ02 1, 0δ03 1, ···0N−1 1. for δ≤m ≤N • 0401,04001 δ=4

  11. Pattern:001 m= 2 Pattern:00001 m =4 Pattern:000001 m =5 Update Pattern PRTF PETF 0 W 0 0 0 0 1 … 6 slots Time Related work - PMAC • δ=4 , N=6 Update Pattern PRTF PETF 0 W 0 1 0 0 1 … 6 slots Time

  12. Related work - PMAC • The drawback of PMAC • Sensor is necessary to exchange it own schedule for neighbor discovery. • PMAC is required to achieve clock synchronous.

  13. Related work –quorum based • Asynchronous method r1 r2 c1 c2 Host A Host B R. Zheng, J. C. Hou, and L. Sha, “Asynchronous Wakeup for Ad Hoc Networks,”ACM International Symposium on Mobile Ad Hoc Networking & Computing (Mobihoc), 2003.

  14. AMAC –goal • Design a hybrid protocol • time asynchronous schedule • Quorum system • traffic-aware schedule • PMAC

  15. AMAC -modify pattern string to adapt to quorum • Problem with PMAC between quorum • The original Pattern is not compatible • Ex: • Original pattern • 001

  16. AMAC -modify pattern string to adapt to quorum • Replace the original sleep-wakeup string bit • 1 => 111…1 =>1n • 0 => 000…1 =>0n-11

  17. AMAC - modify pattern string to adapt to quorum • Origin PMAC pattern • (000..)m-11 • Exchange to new pattern • {(0n-11)(0n-11) (0n-11)}m-1 1n • 1N represents selected column in quorum • The other 0n-11 forms the selected row in quorum n r m c

  18. AMAC –traffic aware • Total time slot is also N slots • N=n*m • Pattern • (0n-11) 1n

  19. Pattern 000001 111111 Pattern 000101 000101 111111 AMAC –different size

  20. Simulation • 100 sensors nodes • Duty cycle 100 time slots • Execution time 1000~10000 time slot • Schedule pattern is re-adjusted after 100 time slots

  21. Simulation

  22. Simulation

  23. Simulation

  24. Simulation

  25. Conclusion • AMAC • has good adaptation ability • doesn’t need time synchronous

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