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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
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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
Motivation • A sender-initiated MAC:Sender triggers communications by transmitting a data Sender Listen D Receiver D Listen http://hipe.korea.ac.kr
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
Motivation • A receiver-initiated MAC:Receiver triggers exchange by transmitting a probe Sender Listen P D Receiver P D http://hipe.korea.ac.kr
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
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
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
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
Motivation • RI-MAC The BW field in the beacon specifies the back-off window size, senders should use when they contend for them medium
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’)
Motivation • Low Power Probing(LPP) Koala: Ultra-Low Power Data Retrieval in Wireless Sensor Networks(IPSN ‘08)
Motivation • Backcast Wireless ACK Collisions Not Considered Harmful(In Proceedings of the Seventh Workshop on Hot Topics in Networks)
Motivation Is it possible to design a general-purpose, yet efficient, receiver-initiated link layer?
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
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
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
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
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
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
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
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
Evaluation • Backcast scales to a large number of nodes http://hipe.korea.ac.kr
Evaluation • Effect of interference http://hipe.korea.ac.kr
Evaluation • incast performance R S S S S Collision Domain
Evaluation • multiple parallel unicast flows S R S R S R Collision Domain
Evaluation • Wakeup Fewer Packets Faster Wakeup LPL (Flash) LPL (Flash) A-MAC A-MAC
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
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