Network and Systems Laboratory nslab.ee.ntu.edu.tw 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 2010 Presenter: SY
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Prabal Dutta , Stephen Dawson-Haggerty, Yin Chen, Chieh -Jan (Mike) Liang, and Andreas Terzis
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 2010 Presenter: SY. Outline. Introduction A-MAC primitive Implementation - PowerPoint PPT Presentation
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Network and Systems Laboratorynslab.ee.ntu.edu.tw
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
A sender-initiated MAC:Sender triggers communications by transmitting a data
Receiver
Sender Listen D
DListen
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Low-power listening (LPL) with a sender-initiated MAC
Preamble DSender
Receiver D
Tlisten Noise
Overhearing/noise adds significant unpredictability to node lifetime
Network and Systems Laboratorynslab.ee.ntu.edu.tw
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A receiver-initiated MAC:Receiver triggers exchange by transmitting a probe
Receiver
Sender PListen D
P D
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Receiver-initiated services -- benefitsHandle hidden terminals better than sender-initiated
ones
Support asynchronous communication w/o long-preambles
Support extremely low duty cycles or high data rates
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)
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Receiver-initiated services -- drawbacksProbe (LPP) is more expensive than channel sample (LPL)
Baseline power is higher
Frequent probe transmissionsCould congest channel & increase latencyCould disrupt ongoing communicationsChannel usage scales with node density rather than
traffic
Services use incompatible probe semanticsMakes concurrent use of services difficultSupporting multiple, incompatible probes increases
power
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The probe incompatibility mess
Probes use hardware acknowledgementsProbes do not use hardware acknowledgementsProbes include only receiver-specific dataProbes include sender-specific data tooProbes include contention windowsProbes do not include contention windows
Pollcast
RI-MACLPP
Backcast
Network and Systems Laboratorynslab.ee.ntu.edu.tw
Is it possible to design a general-purpose,
yet efficient, receiver-initiated link layer?
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Network and Systems Laboratorynslab.ee.ntu.edu.tw
Most consequential decision a low-power MAC makes:stay awake or go to sleep?
Preamble DTX
RX D
Tlisten Noise
TX
RX
P
P
DATA
DATA
Listen
Sender-Initiated: Channel Sampling
Receiver-Initiated: Channel Probing
P10
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Solving the synchronization problem with BackcastA link-layer frame exchange in which:
A single radio PROBE frame transmission Triggers zero or more identical ACK frames Transmitted with tight timing tolerance So there is minimum inter-symbol interference And ACKs collide non-destructively at the receiver
P ATX
RX P A
P ATXYou sh
ould be skeptica
l that th
is idea might
work
P. Dutta, R. Musaloiu-E., I. Stoica, A. Terzis, “Wireless ACK Collisions Not Considered Harmful”,HotNets-VII, October, 2008, Alberta, BC, Canada
M. Demirbas, O. Soysal, and M. Hussain,“A Single-Hop Collaborative Feedback Primitive for Wireless Sensor Networks”,INFOCOM’08, April , 2008, Phoenix, AZ
Backcast degrades when path delay differences exceeds approximately 500 ns (500 ft free space)
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Network and Systems Laboratorynslab.ee.ntu.edu.tw
A-MAC single channel PDR degrades with high node density and high probe frequency
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S
RS
S
CollisionDomain
S S
S S S S
S
SSSS
S S
S S
S
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ConclusionBackcast provides a new synchronization primitive
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