TTDD: A Two-tier Data Dissemination Model for Large-scale Wireless Sensor Networks

1. TTDD: A Two-tier Data Dissemination Model for Large-scale Wireless Sensor Networks Haiyun Luo, Fan Ye, Jerry Cheng, Songwu Lu, Lixia Zhang UCLA Computer Science Department Presenter: Tylor

2. Road Map • Introduction • TTDD • Grid construction • Two-tier query and data forwarding • Grid maintenance • Performance evaluation • Discussion • Conclusion

3. Introduction • Sensor network applications • Environmental/eco-system monitoring • Health care • Elevator, Presence detection, … etc • Basic problem • Source • Sink • But how? ?

4. Introduction • Design Consideration • Energy efficiency • Reliability • Short delay • New challenge • Mobility • Two-tier data dissemination (TTDD) • Efficient data dissemination in large-scale wireless sensor networks with sink mobility

5. Road Map • Introduction • TTDD • Grid construction • Two-tier query and data forwarding • Grid maintenance • Performance evaluation • Discussion • Conclusion

6. Two-tier Data Dissemination • Assumption • Static sensor nodes (except the sinks) • Location-aware • Each node is aware of its own location • Mission-aware

7. Road Map • Introduction • TTDD • Grid construction • Two-tier query and data forwarding • Grid maintenance • Performance evaluation • Discussion • Conclusion

8. Grid Construction • Once detection of a stimulus, source divides the network into a grid of cells

9. Grid Construction • Determination of grid points α : cell size (X, Y) : location of source (Xi, Yi) : location of grid points • Source sends a data announcement message to four adjacent grid points using simple greedy geographic forwarding (GF)

10. Grid Construction • A node is closer to the grid point than all its neighbors If the distance is less than α/ 2 this node becomes dissemination node Else drop the message End • Dissemination node stores some information • The location of the grid point it is serving • Upstream dissemination node’s location • The grid is built on a per-source basis

11. Road Map • Introduction • TTDD • Grid construction • Two-tier query and data forwarding • Grid maintenance • Performance evaluation • Discussion • Conclusion

12. Two-tier Query and Data Forwarding • Two-tier • The lower tier is within the local grid of the sink’s current location • The higher tier is made of the dissemination nodes • Sink floods the query locally to find a (immediate) dissemination node

13. Query Forwarding and Data Forwarding • Each dissemination node stores the location of the downstream dissemination node

14. Trajectory Forwarding • The primary agent (PA) • The immediate agent (IA) • Initially PA and IA are the same sensor nodes

15. Road Map • Introduction • TTDD • Grid construction • Two-tier query and data forwarding • Grid maintenance • Performance evaluation • Discussion • Conclusion

16. Grid maintenance • The failure of sensor nodes • Upstream information duplication • Dissemination nodes • Timeout at the sink • Immediate dissemination nodes • Primary agent • Immediate agent • There is also a timer for the grid state

17. Road Map • Introduction • TTDD • Grid construction • Two-tier query and data forwarding • Grid maintenance • Performance evaluation • Discussion • Conclusion

18. Simulation Setups • ns-2.1b8a • 4 sources, 4 sinks • Mobility model • Random way point • Sink’s speed 10 m/s • 5-sec pause time • Local flooding range • 1.3 α

19. Reachability v.s. Sink Mobility (4 srcs, 4 sinks) • The capability of handling mobility

20. Increasing energy consumption • Sink’s local flooding queries • The high-tier grid forwarding effectively localizes the impact of sink mobility

21. Reachability v.s. Node Failures(4 srcs, sinks, 10m/s) • 15% randomly-chosen nodes fail at 20 seconds

22. Reduced data packet delivery • Repair of failed dissemination nodes

23. TTDD v.s DD Static sinks

24. No dissemination node serves for the sink Collisions Reachability v.s. Sink #

25. Less energy consumption when more than 2 srcs Location estimation High data rate Less energy consumption in 1 or 2 srcs Exploratory data Query aggreagation Energy v.s. Sink #

26. Longer data path In cases of multiple sources Data path overlap Delay v.s. Sink #

27. Road Map • Introduction • TTDD • Grid construction • Two-tier query and data forwarding • Grid maintenance • Performance evaluation • Discussion • Conclusion

28. Energy v.s. cell sizes(1 src, 1 sink, 10m/s) • The energy first decreases • Less energy is required to build a grid with larger cell size • The energy increases later • Local query flooding consumes more energy in larger cells • The decision of α depends on the mobility patterns of the sink

29. Conclusion • TTDD • Efficient data dissemination is large-scale sensor fields • Local floodings minimize the overall network load and the amount of energy to maintain data-forwarding paths • Sources and sinks cooperate to accomplish efficient data delivery to mobile sinks

30. Pros and cons • Pros • The idea is similar to GSM architecture which efficiently locates the mobility of user • Simple and work well • Cons • The grid structure which is built on a per-source basis may consume too much energy when the location of sources change frequently • The assumption of static nodes in the network and the poor failure recovery mechanism