The Design Space of Wireless Sensor Networks

1. The Design Space of Wireless Sensor Networks Xin-Xian Liu 2005 03 22

2. Outline • Background • Performance Metrics • Sensor Network Architecture • Design Space • Conclusion

3. Background • Initial research into WSN was mainly motivated by military application • A de facto definition of WSN as a large-scale, ad hoc, multihop, tiny, resource-constrained

4. Sensor network

5. The components of a sensor node

6. Performance Metrics • Energy efficiency / system lifetime • Latency • Accuracy • Fault-tolerance • Scalability

7. Sensor Network Architecture • The network protocol is responsible for supporting all communication between the sensors and the observer • The performance of the protocol will be highly influenced by the network dynamics and by the specific data delivery model employed

8. Communication Models • Communication within a sensor network can be classified into two categories • Application communication • Infrastructure communication • Application communication is related to the transfer of sensed data with the goal of informing the observer about the phenomena

9. Communication Models • Within application communication, there are two models: • Cooperative • Non-cooperative

10. Communication Models • Infrastructure communication refers to the communication needed to configure, maintain and optimize operation • In sensor networks, an initial phase of infrastructure communication is needed to set up the network

11. Data Delivery Models • Sensor networks can be classified in terms of the data delivery required by the application interest as: • Continuous • Event-driven • Observer-initiated • hybrid

12. Data Delivery Models • Continuous • The sensors communicate their data continuously at a prespecified rate • Event-driven • The sensors report information only if an event of interest occurs • Observer-initiated • The sensors only report their results in response to an explicit request from the observer

13. Data Delivery Models • The actual flow of data packets between the sensors and the observer • Flooding • Unicast • Multicast

14. Network Dynamics Models • The approach to construct and maintain a path between observer and phenomenon will differ depending on the network dynamics, which we classify as • Static sensor networks • Dynamic sensors networks

15. Static Sensor Networks • In static sensor networks, there is no motion among communication sensor, the observer and the phenomenon

16. Dynamic Sensor Networks • In dynamic sensor networks, either the sensors themselves, the observer, or the phenomenon are mobile • Dynamic sensor networks can be further classified by considering the motion of the components • Mobile observer • Mobile sensors • Mobile phenomena

17. Design Space • We informally characterize each of the dimension and, where appropriate, identify property classes in order to support a coarse-grained classification of sensor network application

18. Design Space • Deployment • Random vs. Manual • One-time vs. Iterative • Mobility • Immobile vs. Partly vs. All • Occasional vs. Continuous • Active vs. Passive

19. Design Space • Cost • The cost of a single device may vary from hundreds of Euros to a few cents • Size • The form factor of a single sensor node may vary from the size of a shoebox to a microscopically small particle

20. Design Space • Resources and Energy • Varying size and cost constrains directly result in corresponding varying limits on the energy available, as well as on computing, storage and communication resources • We partition sensor nodes roughly into four classes based on their physical size • brick, matchbox, grain, and dust

21. Design Space • Heterogeneity • Homogeneous vs. Heterogeneous • Communication Modality • Radio vs. Light vs. Inductive vs. Capacitive vs. Sound • Infrastructure • Infrastructure vs. Ad Hoc

22. Design Space • Network Topology • Single-hop vs. Star vs. Networked Start vs. Tree • Coverage • Sparse vs. Dense vs. Redundant • Connectivity • Connected vs. Intermittent vs. sporadic

23. Design Space • Network Size • The network size may vary from a few nodes to thousands of sensor nodes or even more • Lifetime • Depending on the application, the required lifetime of a sensor network may range from some hours to several years

24. Design Space • Other QoS Requirement • Depending on the application, a sensor network must support certain QoS aspects such as • Real-time • Robustness • Tamper-resistance • Eavesdropping resistance

25. Conclusion • Clearly, a single hardware platform will most likely not be sufficient to support the wide range of possible applications • A modular approach, where the individual components of a sensor node can easily exchanged

26. References [1] S. Tilak, N. B. Abu-Ghazaleh, and W. Heinzelman, “A Taxonomy of Wireless Micro-Sensor Network Models,”MR2C, vol. 6, no. 2, Arp.2002, pp. 28-36 [2] Kay Romer and Friedemann Mattern, ETH Zurich, “The Design Space of Wireless Sensor Networks,” IEEE Communications Magazine, pp.54-61,December 2004