1 / 16

DESYNC: Self-Organizing Desynchronization and TDMA on Wireless Sensor Networks

DESYNC: Self-Organizing Desynchronization and TDMA on Wireless Sensor Networks. Julius Degesys , Ian Rose, Ankit Patel and Radhika Nagpal IPSN 2007 20073648 황재호. Contents. Introduction Desynchronization Algorithm Desync -TDMA Experiment Conclusion. Introduction.

belita
Download Presentation

DESYNC: Self-Organizing Desynchronization and TDMA on Wireless Sensor Networks

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. DESYNC: Self-Organizing Desynchronization and TDMA on Wireless Sensor Networks Julius Degesys, Ian Rose, Ankit Patel and RadhikaNagpal IPSN 2007 20073648 황재호

  2. Contents • Introduction • Desynchronization Algorithm • Desync-TDMA • Experiment • Conclusion

  3. Introduction • Synchronization: Sometimes desirable to perform tasks at the same time • [Werner-Allen et al - SenSys ‘05, • Maróti et al - SenSys ’04, etc.] • Perfect Desynchronization: Other times, want even distribution • No two are happening at the same time • Perfect round-robin schedule

  4. ? How do we get from a random start to desynchronization? Introduction - framework Single node periodically “fires” by broadcasting a message A typical starting configuration (random) A system in desynchronization

  5. Desynchronization Algorithm(1) DESYNC Algorithm: • Record firing times of phase neighbors • Compute the average • When back neighbor fires, jump towards the average Jump corresponds to a mote advancing or delaying its timer

  6. Desynchronization Algorithm(2)

  7. Remove 1 Add 3 Desynchronization Algorithm(3)

  8. Desynchronization Algorithm(4) • Completely distributed • No central authority • No time synchronization • Simple! • 10s of lines of code • Constant memory • Self-healing • Robust to disturbances • Addition/Removal of nodes

  9. Desync-TDMA(1) • Time Division Multiple Access (TDMA) • Protocol for broadcast channel sharing, where nodes divide time into equal slots, and each node “owns” a slot Nice Properties • Collision-free message transmission • Fair allocation of bandwidth • High bandwidth coverage in high load 1 3 2 5 4 1 2 3 4 5 1 2 3 4 5 … …

  10. Desync-TDMA(2) • DESYNC-TDMA Algorithm: • Define slots at midpoints of firings from the round before Slot Properties • Non-overlapping • Full bandwidth coverage • Well-defined (regardless of state) • Can always send • Fairness over time

  11. Centralized • Negotiate slot schedules • Time synchronization required • Not Adaptive • Limited addition/removal of nodes • Can waste bandwidth • Complicated • Separate phases, maintain neighbor identities, etc. Desync-TDMA(3) Traditional TDMA DESYNC-TDMA Decentralized Self-adapting Simple

  12. All-to-all network Eavesdropping Base Experiment(1) Metrics Throughput Message loss Comparisons TDMA (Theoretical) CSMA (Default TinyOS) Hybrid (Z-MAC) • Traffic Model • Nodes always try to send data whenever possible Period = 1 sec

  13. …but throughput is still high and near-constant System is not yet desynchronized Experiment(2) 40 1 35 0.8 30 25 0.6 Average Desync Error (ms) Normalized Throughput 20 0.4 15 10 0.2 5 0 0 Measured capacity: 62.8 kbps

  14. The “distance” from desynchronization may spike But total throughput is only slightly affected (~10% = O(1/n)) Experiment(3) In a network of 8 nodes, one is removed, and 45 seconds later, 3 are added -1 +3

  15. Experiment(4) Setup: 20-node all-to-all network, 10 sending

  16. Conclusion & Future Work Contributions • Self-organizing TDMA schedule • Desynchronization • Can generalize (e.g. ADCs, traffic intersections) • Round-robin scheduling or periodic tasks Future Work • Multi-hop TDMA • Simulations give evidence for convergence • Doesn’t solve hidden terminal problem

More Related