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Design and Evaluation of an Efficient Receiver-Initiated Link Layer for Low-Power Wireless Networks

This paper presents a novel receiver-initiated MAC protocol designed to enhance communication efficiency in low-power wireless networks. By allowing receivers to trigger exchanges rather than relying on senders, the proposed approach addresses significant limitations of existing sender-initiated systems, such as handling hidden terminals and facilitating asynchronous communication without lengthy preambles. The paper discusses various mechanisms including wakeup signals, discovery methods, and support for multipoint communication, leading to a versatile and energy-efficient link layer suitable for dynamic traffic loads.

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Design and Evaluation of an Efficient Receiver-Initiated Link Layer for Low-Power Wireless Networks

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  1. Design and Evaluation of a Versatile and Efficient Receiver-Initiated Link Layer for Low-Power Wireless Prabal Dutta, Stephen Dawson-Haggerty, Yin Chen, Chieh-Jan (Mike) Liang, and Andreas Terzis Sensys’10 HIgh Performance Computing & Systems LAB

  2. Motivation • A sender-initiated MAC:Sender triggers communications by transmitting a data Sender Listen D Receiver D Listen http://hipe.korea.ac.kr

  3. Motivation • Low-power listening (LPL) with a sender-initiated MAC D Receiver Tlisten Preamble D Noise Sender Overhearing/noise adds significant unpredictability to node lifetime http://hipe.korea.ac.kr

  4. Motivation • A receiver-initiated MAC:Receiver triggers exchange by transmitting a probe Sender Listen P D Receiver P D http://hipe.korea.ac.kr

  5. Motivation • Low-power, receiver-initiated servicesoffer many benefits over sender-initiated ones • Handle hidden terminals better than sender-initiated ones • Support asynchronous communication w/o long-preambles • Support many low-power services • Wakeup (“LPP”, Musaloiu-E. et al., IPSN’08) • Discovery (“Disco”, Dutta et al., Sensys’08) • Unicast (“RI-MAC”, Sun et al., Sensys’08) • Broadcast (“ADB”, Sun et al., Sensys’09) • Pollcast (“Pollcast”, Demirbas et al., INFOCOM’08) • Anycast (“Backcast”, Dutta et al., HotNets’08) http://hipe.korea.ac.kr

  6. Motivation • Low-power, receiver-initiated MACs face a number of drawbacks as well • Probe (LPP) is more expensive than channel sample (LPL) • Baseline power is higher • Frequent probe transmissions • Could congest channel & increase latency • Could disrupt ongoing communications • Services use incompatible probe semantics • Makes concurrent use of services difficult • Supporting multiple, incompatible probes increases power http://hipe.korea.ac.kr

  7. Motivation • The probe incompatibility mess Pollcast Backcast LPP RI-MAC • Probes use hardware acknowledgements • Probes do not use hardware acknowledgements • Probes include only receiver-specific data • Probes include sender-specific data too • Probes include contention windows • Probes do not include contention windows http://hipe.korea.ac.kr

  8. Motivation • RI-MAC B B DATA B T Wake up Wake up DATA B B R • Transmitter(T) wakes up and waits for the intended receiver • Receive a beacon from intended receiver(R), the transmitter starts DATA transmission • Receiver acknowledges the DATA with another beacon (B) RI-MAC: A Receiver-Initiated Asynchronous Duty Cycle MAC Protocol for Dynamic Traffic Load in Wireless Sensor Networks

  9. Motivation • RI-MAC The BW field in the beacon specifies the back-off window size, senders should use when they contend for them medium

  10. Motivation

  11. Motivation • Pollcast • singlehop collaborative feedback primitive • Using a pollcast, a node can take a quick poll from its neighborhood by asking all nodes with a certain property to reply • Poll phase • Vote phase A Singlehop Collaborative Feedback Primitive for Wireless Sensor Networks(INFOCOM 08’)

  12. Motivation

  13. Motivation • Low Power Probing(LPP) Koala: Ultra-Low Power Data Retrieval in Wireless Sensor Networks(IPSN ‘08)

  14. Motivation

  15. Motivation • Backcast Wireless ACK Collisions Not Considered Harmful(In Proceedings of the Seventh Workshop on Hot Topics in Networks)

  16. Motivation

  17. Motivation Is it possible to design a general-purpose, yet efficient, receiver-initiated link layer?

  18. Motivation • Most consequential decision a low-power MAC makes:stay awake or go to sleep? Sender-Initiated: Channel Sampling D RX Tlisten Preamble D Noise TX Receiver-Initiated: Channel Probing Listen P DATA TX P P DATA RX http://hipe.korea.ac.kr

  19. A-MAC Overview • A-MAC: An 802.15.4 receiver-initiated link layer RXTX turnaround time: 192 µs Max data packet 4.256 ms Sender Listen P P A DATA Receiver P P A DATA ACK transmission time 352 µs http://hipe.korea.ac.kr

  20. A-MAC Contention mechanism Sender Listen P A D P-CW BO Receiver P A D P-CW D Sender Listen P A D P-CW D Backcast frame collision http://hipe.korea.ac.kr

  21. A-MAC • Unicast DST=0x0002 SRC=0x0001 SEQ=0x23 MAC=0x8002 MAC=0x8002 Node 1 (Sender) Listen P A D P Listen P A D P-CW BO Node 2 (Receiver) D P L P A D P-CW D P A DST=0x8002 SRC=0x0002 DST=0x8002 SRC=0x0002 ACK=0x0023 FRM=0x0001 MAC=0x8002 Node 3 (Sender) Listen P A D P-CW D Backcast frame collision http://hipe.korea.ac.kr

  22. A-MAC • Broadcast DST=0x0002 SRC=0x0001 SEQ=0x23 auto-ack=on addr-recog=off off off on off D D D A A A Listen P P Listen P P Listen P P TX 1 D P A P RX 2 DST=0x8002 SRC=0x0002 DST=0x8002 SRC=0x0002 ACK=0x0023 FRM=0x0001 P P A D RX 3 Backcast P P A D RX 4 Backcast Backcast http://hipe.korea.ac.kr

  23. A-MAC • Wakeup Listen P A Listen Node 1 A A P A Listen P Listen P Listen P A Node 2 DST=0xFFFF SRC=0x0002 P A Listen P A Node 3 P A Listen P A Node 4 P A Node 5 Backcast http://hipe.korea.ac.kr

  24. A-MAC • Pollcast MAC=0x8765 Node 1 (Sender) A Event Pred Listen P A P+Pred Node 2 (Receiver) Event Pred P+Pred A Listen P A DST=0xFFFF SRC=0x0002 PRED=elephant MAC=0x8765 DST=0x8765 DST=0xFFFF SRC=0x0002 PRED=elephant MAC=0x8765 Node 3 (Sender) Event Pred Listen P+Pred A P A Backcast http://hipe.korea.ac.kr

  25. Evaluation • Backcast • Platform: Telos B • Protocol: IEEE 802.15.4 • Location: office building (typical RF environment) • Experiment • 94 nodes within radio range of initiator • Programmed to automatically ack all probes • 94 nodes are turned on one after another • After turn on, 500 frames are transmitted at 125ms intervals http://hipe.korea.ac.kr

  26. Evaluation • Backcast scales to a large number of nodes http://hipe.korea.ac.kr

  27. Evaluation • Effect of interference http://hipe.korea.ac.kr

  28. Evaluation • incast performance R S S S S Collision Domain

  29. Evaluation • multiple parallel unicast flows S R S R S R Collision Domain

  30. Evaluation • Wakeup Fewer Packets Faster Wakeup LPL (Flash) LPL (Flash) A-MAC A-MAC

  31. Evaluation • single channel PDR degrades with high node density S S S S S S S S S S S S R S S S S S S S Collision Domain

  32. Conclusion • Backcast provides a new synchronization primitive • Common abstraction underlying many protocols • Can be implemented using a DATA/ACK frame exchange • Works even with a 8, 12, 94 colliding ACK frames • Faster, more efficient, and more robust than LPL, LPP • A-MAC augments Backcast to implement • Unicast • Broadcast • Network wakeup • Robust pollcast • Results show • Higher packet delivery ratios • Lower duty cycles • Better throughput (and min/max fairness) • Faster network wakeup • Higher channel efficiency http://hipe.korea.ac.kr

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