1 / 50

A sender-initiated MAC: Sender triggers communications by transmitting a data

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 at ETH Zurich.

celina
Download Presentation

A sender-initiated MAC: Sender triggers communications by transmitting a data

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript


  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 at ETH Zurich

  2. A sender-initiated MAC:Sender triggers communications by transmitting a data Sender Listen D Receiver D Listen

  3. Low-power listening (LPL) with a sender-initiated MAC D Receiver Tlisten Preamble D Noise Sender Overhearing/noise adds significant unpredictability to node lifetime

  4. A receiver-initiated MAC:Receiver triggers exchange by transmitting a probe Sender Listen P D Receiver P D

  5. 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 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)

  6. 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 • Channel usage scales with node density rather than traffic • Services use incompatible probe semantics • Makes concurrent use of services difficult • Supporting multiple, incompatible probes increases power

  7. The probe incompatibility mess Pollcast Backcast • 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 LPP RI-MAC

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

  9. 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

  10. Asynchronous network wakeup 1 2 4 3 5 Listen P D Listen Node 1 D D P D Listen P Listen P Listen P D Node 2 P D Listen P D Node 3 P D Listen P D Node 4 P D Node 5 PFN? frame collision PFP?

  11. Wait, not so fast! Node 5 might receive a response • Power capture: One response has a sufficiently higher power than the sum of the others… and it arrives first • Delay capture: One response frame arrives some time before the remaining ones… and its power is higher than the sum of the others • Message-in-Message capture: Like power capture, but the highest power frame arrives in the middle of another frame transmission and radio detects elevated energy… and the radio does continuous preamble detection • These are a lot of caveats…

  12. Solving the synchronization problem with Backcast • A 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 You should be skeptical that this idea might work P A TX P A RX P A TX P. Dutta, R. Musaloiu-E., I. Stoica, A. Terzis, “Wireless ACK Collisions Not Considered Harmful”, HotNets-VII, October, 2008, Alberta, BC, Canada

  13. Outline • Introduction • Motivation • What is A-MAC? • Protocol overview • Synchronization using Backcast • Contention using binary exponential backoff • Communications using multichannel transfers • How is it used? • How well does it work? • How much does it cost? • What are its limitations?

  14. 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

  15. A-MAC’s 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

  16. A-MAC’s parallel multichannel data transfersuse control, data (1), and data (2) channels Sender 1 Listen P P A DATA Receiver 1 P P A DATA Sender 2 Listen P P A DATA Receiver 2 P P A DATA

  17. Outline • Introduction • Motivation • What is A-MAC? • How is it used? [Lacking hardware support] • Unicast • Broadcast • Pollcast • Wakeup • How well does it work? • How much does it cost? • What are its limitations?

  18. 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

  19. 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

  20. 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

  21. 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 M. Demirbas, O. Soysal, and M. Hussain, “A Single-Hop Collaborative Feedback Primitive for Wireless Sensor Networks”, INFOCOM’08, April , 2008, Phoenix, AZ

  22. Outline • Introduction • Motivation • What is A-MAC? • How is it used? • How well does it work? • Backcast • A-MAC • How much does it cost? • What are its limitations?

  23. Setup Methodology Platform: Telos mote Protocol: IEEE 802.15.4 Radio: Texas Instruments CC2420 Experiment 8 responder nodes Connect w/ splitter/attenuator Turned on sequentially Transmit 100 packets 125 ms inter-packet interval Log RSSI: received signal strength LQI: chip correlation rate ARR: ACK reception rate Evaluating Backcast: equal-power, equal-path delay

  24. As the number of colliding ACKsgoes from one to eight… Median RSSI increases logarithmically Median LQI remains nearly constant but is more left-tailed ACK reception rate stays practically constant But, for two nodes, LQI exhibits outliers and a lower median

  25. Backcast scales to a large number of nodes

  26. The effect of interference on idle listening:Sampling, Probing, and Backcast Background noise/traffic/noise in an office environment Channel 18 Channel 26 Sampling Sampling Probing Probing Backcast Backcast

  27. Idle listening cost skyrockets under heavy interference

  28. A-MAC offers modest incast performance R S S S S Collision Domain

  29. A-MAC supports multiple parallel unicast flows S R S R S R Collision Domain

  30. A-MAC wakes up the network fasterand more efficiently than LPL (Flash) flooding Fewer Packets Faster Wakeup LPL (Flash) LPL (Flash) A-MAC A-MAC

  31. A-MAC wakeup works well at low duty cycles Tprobe = 4,000 ms Pavg = 63 µW Iavg = 21 µA N = 59 “Wakeup Latency” is normalized to the probe interval

  32. Supporting the Collection Tree Protocol (CTP),A-MAC beats LPL on nearly every figure of merit R S S S S S S N = 59 Tdata = 60 s Tprobe = 500 ms S S

  33. Outline • Introduction • Motivation • What is A-MAC? • How is it used? • How well does it work? • How much does it cost? • What are its limitations?

  34. Energy cost of A-MAC primitives:probe, receive, transmit, and listen

  35. With hardware support, probes would cost at least 40% less energy 0. Sleep 1: Start Radio (41 µJ) 2: Ld Prb (61 µJ) 3: Ld Done (23 µJ) 4: Prb Alarm (6 µJ) 5: Start TX (56 µJ) 6: ACK Timer (30 µJ) 7: ACK T’out (26 µJ) 8: Stop Radio (9 µJ) 9: Stopped (13 µJ) 0 1 2 3 4 5 6 7 8 9 35

  36. The cost of a Backcast can be less than 1 ms(for IEEE 802.15.4) RXTX turnaround time: 192 µs Max data packet 4.256 ms Sender P A DATA Receiver P A DATA ACK transmission time 352 µs

  37. Outline • Introduction • Motivation • What is A-MAC? • How is it used? • How well does it work? • How much does it cost? • What are its limitations? • Backcast • A-MAC

  38. Backcast Limitations • Protocol support (802.15.4 supports) • Superposition semantically valid for modulation scheme • Auto ACK with tight timing • ACK frames are identical • Radio support (CC2420 supports) • Broadcast auto ACKs • Multicast auto ACKs • Multiple MAC addresses for interface • Auto ACKs based on SRC address filtering • Auto ACKs based on DST address filtering • Other factors (Not necessarily an issue) • Propagation delay  ΔRTT < ½ symbol time • ACK frames do not cancel at PHY layer • Security  Easy to spoof

  39. Backcast degrades when path delay differences exceeds approximately 500 ns (500 ft free space)

  40. A-MAC single channel PDR degrades with high node density and high probe frequency S S S S S S S S S S S S R S S S S S S S Collision Domain

  41. 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

  42. Acknowledgements

  43. Questions? Comments? Discussion?

  44. Backup Slides

  45. A-MAC’s synchronization primitive P A Sender P A Receiver P A Sender ACK transmission Probe transmission A P ACK reception Probe reception A P

  46. The Query/Response exchange can be mapped to“acknowledged anycast” semantics 1 2 4 3 5 src=<doesn’t matter> dst=broadcast Node 5 asks all of it neighbors, “should one wake up?” To which, Nodes 2, 3, and 4 all respond, “Yes” (everyone sends back the same response) • A node • Broadcasts (or multicasts) a query packet • Waits to see whether the packet is ACK’ed • By at least one of its neighboring nodes • And stays awake if an ACK is received • But goes to sleep otherwise • And the frame collision is like a multicast “ACK implosion” ACK

  47. Backcast using a link-layer DATA/ACK frame exchange Receiver D A Sender D A • Many wireless standards use link-layer automatic ACKs • IEEE 802.11 a/b/g • IEEE 802.15.4 • The DATA/ACK frame turnaround time is tightly-controlled • Creates conditions favorable for power and delay capture • But what should the destination address be? • 802.11 a/b/g: DON’T ACK broadcast or multicast frames • 802.15.4: Standard is fuzzy on ACK-ing broadcast frames • We play with the SRC and DST addresses to get around this

  48. 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

  49. 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

  50. 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 M. Demirbas, O. Soysal, and M. Hussain, “A Single-Hop Collaborative Feedback Primitive for Wireless Sensor Networks”, INFOCOM’08, April , 2008, Phoenix, AZ

More Related