1 / 27

CMPE 259

CMPE 259. Sensor Networks Katia Obraczka Winter 2005 Topology Control. Announcements. What’s topology control?. What’s topology control?. When nodes are deployed, how do they organize into a network? Neighbor-discovery protocol. If neighborhood is sparse, use all neighbors.

shlomo
Download Presentation

CMPE 259

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. CMPE 259 Sensor Networks Katia Obraczka Winter 2005 Topology Control

  2. Announcements

  3. What’s topology control?

  4. What’s topology control? • When nodes are deployed, how do they organize into a network? • Neighbor-discovery protocol. • If neighborhood is sparse, use all neighbors. • What if neighborhood is dense? • Use a subset of neighbors. • How?

  5. Approaches to topology control • Adjust transmit power. • Turn nodes on/off.

  6. ASCENT

  7. ASCENT: scenario • Ad hoc deployment. • Energy limitations. • Arbitrarily large scale. • Unattended operation. • Assume CSMA.

  8. ASCENT: goals • Self-organization of nodes into topology that allows sensing coverage and communication under tight energy constraints.

  9. ASCENT: approach • Nodes turn themselves on/off depending on assessment of operating conditions. • Neighborhood density. • Data loss.

  10. State diagram After Tt Test Active Nbors<NT And Loss>LT or Help Nbors > NT or Loss > After Tp Passive Sleep After Ts

  11. In “test” state: • Signaling (e.g., neighbor announcements). • After Tt, goes to “active”. • Or, if before Tt, number of neighbors>NT or average data loss (Tt) > average data loss (T0), go to “passive”.

  12. In “passive” state: • After Tp, go to “sleep”. • If neighborhood is sparse loss > LT or “help” from “active” neighbor, go to “test”.

  13. In “sleep”: • Turn off radio. • After Ts, go to “passive”.

  14. In “active”: • Node does routing and forwarding. • Sends “help” if data loss > LT. • Stays on until runs out of battery!

  15. Considerations • Why passive and test states? • Why once in active, a node runs until battery dies? • How to set parameters? • NT, LT. • Tt, Tp, Ts.

  16. Neighborhood and loss • Node is neighbor if directly connected and link packet loss < NLS. • NLS is adjusted according to node’s number of neighbors. • Average loss date uses data packets only. • Packet is lost if not received from any neighbors.

  17. Performance evaluation • Modeling, simulation, experimentation. • Metrics: • Packet loss. • Delivery ratio. • Energy efficiency. • Lifetime. • Time till 90% of transit nodes die.

  18. Results • From the paper…

  19. PEAS

  20. PEAS • Probing Environment, Adaptive Sleeping. • “Extra” nodes are turned off. • Nodes keep minimum state. • No need for neighborhood-related state. • PEAS consiers very high node density and failures are likely to happen.

  21. Bi-modal operation • Probing environment. • Adaptive sleeping.

  22. PEAS state diagram Working No reply for probe Wakes up Probing Sleeping Hears probe reply.

  23. Probing • When node wakes up, enters probing mode. • Is there working node in range? • Broadcasts PROBE to range Rp. • Working nodes send REPLY (randomly scheduled). • Upon receiving REPLY, node goes back to sleep. • Adjusts sleeping interval accordingly. • Else, switches to working state.

  24. Considerations • Probing range is application-specific. • Robustness (sensing and communication) versus energy-efficiency. • Location-based probing as a way to achieve balance between redundancy and energy efficiency. • Randomized sleeping time. • Better resilience to failure. • Less contention. • Adaptive based on “desired probing rate”.

  25. More considerations… • Multiple PROBEs (and multiple REPLIES) to compensate for losses. • Multiple PROBEs randomly spread over time. • Multiple working nodes in the neighborhood. • Favor “oldest” one. • Nodes with fixed transmit power. • Deployment density.

  26. Evaluation • Simulations. • Simulated failures: failure rate and failure percentage. • Metrics: • Coverage lifetime. • Delivery lifetime.

  27. Results • With and without failures. • From the paper…

More Related