Wireless Sensor Networks (WSNs)

1. Accurate Emulation of Wireless Sensor Networks Hejun Wu Joint work with Qiong Luo, Pei Zheng*, Bingsheng He, and Lionel M. NiDepartment of Computer ScienceThe Hong Kong University of Science & Technology, China *Arcadia University, USA

2. Wireless Sensor Networks (WSNs) Proxy User Client Sink Sensor mote

3. Wireless Sensor Networks (WSN) Proxy User Client Sink Sensor mote Query

4. Wireless Sensor Networks (WSN) Proxy User Client Sink Sensor mote Query Result

5. Motivation of VMNet • Substitute for sensor nodes in research • Easy to handle • Low price • A realistic & controllable environment • Debugging • Testing • Evaluating Performance • Parameter setting and validation for • Simulation • Modeling

6. VMNet architecture VMNet architecture

7. Virtual mote Virtual main board Real mote binary code Virtual CPU Virtual clock EM (Emulation Manager) Virtual socket Virtual UART( In Virtual Sink) Virtual sensor board Virtual radio frequency module Components in a VM

8. To VRFM Collision signal to VRFM From VRFM Bits Delay Module Bit error Module Collision Module UDP packet to other VMs via LAN Queue Control messages To/From Network Manager (NM) UDP packet from other VMs via LAN Virtual Radio Channel

9. Key Features of VMNet • Open architecture • Easy to transform to other WSN hardware emulation • Detailed emulation • CPU instructions • Operations of the components • CPU, Sensor and Radio • Accurate running status logs • Accurate time emulation • Granularity: microsecond level • power consumption evaluation

10. Open architecture design • Conflict between generality & accuracy • Generality is desirable • Ability to emulate various WSNs • Accuracy • Close to the specified target WSN • Highly modularized structure of a VM • Ensures the reusability • Virtual socket in a VM • Uniform interface between modules

11. Virtual mote Virtual main board Real mote binary code Virtual CPU Virtual clock EM (Emulation Manager) Virtual socket Virtual UART( In Virtual Sink) Virtual sensor board Virtual radio frequency module Highly modularized structure

12. Performance Evaluation on Applications of WSNs • Based on the fact that • Operation and time can be deduced by • Instructions executed by the CPU in a sensor mote • An instruction always takes constant time • VMNet approach in performance evaluation • Logging and reporting • Operations and time

13. Logging in VMNet • The operations : • VMNet logs • Running states • the operations of each component (e.g. III) • CPU clocks • describe the start time and end time The operations of components A fraction of a VMNet log

14. Conclusion • Detailed emulation • Useful for many areas in a WSN • Architecture, OS, and sensor network query processing. • Provides • parameter and validation for simulation & modeling • Performance evaluation • Especially valuable for query processing • Query Optimization: • choose a query plan with minimum energy and time cost • Query processor benchmark study

15. Future Work • Power consumption evaluation • Work in progress • Scalability • Mobile WSN emulation • Graphical Interface for VMNet • In the near future • Use multiple PCs to emulate a WSN