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P-MAC A Cross-Layer Duty Cycle MAC ProtocolTowards Pipelining for Wireless Sensor Networks

P-MAC A Cross-Layer Duty Cycle MAC ProtocolTowards Pipelining for Wireless Sensor Networks. Jae Weon Choi Graduate School of Convergence IT. Asynchronous MAC protocol.

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P-MAC A Cross-Layer Duty Cycle MAC ProtocolTowards Pipelining for Wireless Sensor Networks

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  1. P-MACA Cross-Layer Duty Cycle MAC ProtocolTowards Pipelining for Wireless Sensor Networks Jae Weon Choi Graduate School of Convergence IT

  2. Asynchronous MAC protocol • [S-MAC] Medium Access Control with Coordinated Adaptive Sleeping for Wireless Sensor Networks (IEEE Transactions on Networking 2004) • RMAC: a routing-enhanced duty-cycle MAC protocol for wireless sensor networks (INFOCOM 2007) • P-MAC: A Cross-Layer Duty Cycle MAC Protocol Towards Pipelining for Wireless Sensor Networks (ICC 2011)

  3. Motivation • Limited Battery supply • Implemented Duty Cycling Mechanism (Wake/Sleep) (S-MAC) • S-MAC has packet latency problem • Delay = (#hops – 0.5) * T • RMAC mitigated packet latency • Implementing Routing is problematic • P-MAC requires no extra routing mechanism • Grade level Division according to logical hop distance

  4. RMAC • 3 operation cycle (SYNC, DATA, SLEEP) • Use pioneer frame (PION) to schedule when to wake up for sleep period

  5. P-MAC Characteristic • Grade Division • Variation of RTS/CTS • 3 Types of Period • Predefined Ladder Pattern • Scheduled according to Grade • No extra Synchronizing period

  6. Grade Division • Grade Division through logical Hop distance

  7. P-MAC’s RTS/CTS • Instead of ‘Next Hop Address’, P-MAC’s RTS has Grade information. • Any low grade(Receiving) node that hear RTS can reply with CTS • Contention Window is also used when a node replies with CTS

  8. 3 Types of Period • Send/Receive Data Period = 2CW + 2DIFS + 2SIFS + durRTS + durCTS + durDATA + durACK • SLEEP Period = sleep_factor * [Send/Receive Data] (sleep_factor need to at least be 2) • Cycle Duration = (sleep_factor + 2) * [Send/Receive Data] (sleep_factor + 2) is called cycle coefficient.

  9. Predefined Scheduling • Schedule Setup is done when grade division takes place • Tg = Time needed to finish Grading process • durGRADE = transmission duration of Grade message • i = grade • If i%(sleep_factor + 2) = 0, the node enters RECEIVE DATA Period at (Tg – i*durGrade) • If i%(sleep_factor + 2) = 1, the node enters SEND DATA Period at (Tg – i*durGrade) • If i%(sleep_factor + 2) >= 2, the node enters SLEEP Period at (Tg – i*durGrade)

  10. No Extra Synchronization Period • P-MAC’s Frame each contains relative start time of the current period. • And if the drift become great enough, when a node receive the frame, it will adjust its schedule

  11. Simulation • OPNET Modeler • Two Ray Ground Radio • Single omnidirectional antenna • Same as RMAC • Number of Hops the PION can be forwarded in data period • Same Length of Duty Cycle • Nodes has been already synchronized • Routing is assigned for RMAC, except for middle nodes, in that case, it randomly pick one from two nodes • Grading is only done once, and its overhead was not consider in the comparison with RMAC

  12. Simulation

  13. Latency Evaluation • 1 to 24 nodes were tested with 1 packet for every 10 second • RMAC increase much faster, because it has to wait for next Data period • RMAC experience less latency around 4th hop count • 7 hop count is maximum forwarded hop count for RMAC

  14. Power Consumption Evaluation • First Scenario • 1 packet for every 10 second with simulation time of 1200 second • Traffic load varying from 0 packet to 120 packets • Second Scenario • Fixed Traffic load • Simulation time Varies (400s, 800s, 1200s, 1600s, 2000s)

  15. Throughput Evaluation • Setting • 24 hops topology with 1200 second simulation time • Data input interval Varies from 1 packet / 10s to 1 packet / 1s • Throughput is measured in terms of the average number of packets successfully received by the sink per second • Due to limit in capability of data forwarding, RMAC underperform • At 1 packet / 3s, P-MAC reaches its peak and stabilize power consumption

  16. Conclusion • P-MAC uses Grade Division to rout the packet • P-MAC utilize RTS/CTS to deal with contention • Communication overhead can be significantly reduced • P-MAC achieves better performance in terms of energy efficiency, latency reduction and throughput improvement

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