1 A System for Simulation, Emulation, and Deployment of Heterogeneous Wireless Sensor Networks Lewis Girod, Thanos Stathopoulos, Nithya Ramanathan, Jeremy Elson, Eric Osterweil, Tom Schoellhammer, Deborah Estrin CENS, UCLA Presented by David G. Watson Friday, July 16, 2004

2 Heterogeneous Systems ● What hardware platform to use for sensor networks? – Motes – most scalable platform to support long battery lifetimes – Microservers – most capable platforms that can be readily deployed ● Authors contend that both are necessary: – Many cheap mote-like devices – A few powerful microserver devices ● They have developed a software platform to support both types of device

3 Current Simulation Platforms ● TOSSIM – Simulates motes running TinyOS code ● EmSim – Simulates microservers ● Neither one is sufficient to simulate a heterogeneous system

4 Simulating Heterogeneous Systems ● EmTOS: an extension to EmStar – Enables a complete NesC/TOS app to run unmodified under EmStar – Can be used either for deployment or simulation

5 HostMote Protocol ● To communicate with real motes, EmStar uses the HostMote protocol – Works over a serial connection – Failure-tolerant – supports hot-swap of motes ● HostMote can be used for other things as well: – Debugging – motes can transport messages to microserver – Configuration – reports status of connected mote

6 Microserver Participation in Mote Networks Microservers can take part in MoteNets in several ways: ● As a serial gateway: attached mote relays data to microserver over serial connection ● Re-implement or port NesC application on microserver platform ● Use EmTOS and extend NesC code under EmStar

7 Modes of Heterogeneous Simulation Four modes in which the ESS application may be run under EmTOS

8 EmTOS Emulation Modes ● Emulation Mode – all physical motes run Transceiver app – programs are run on simulation host ● Real Mode – all motes run natively – concentrator is run on the simulation machine ● Hybrid Mode – some motes run Transceiver, some run real code – concentrator runs on sim machine, as do some motes

9 Performance Analysis ● Comparing Timer Jitter between EmTOS and Mica2 – Case 1: One timer, 200ms – Case 2: 3 timers: 100ms, 200ms, 500ms – Case 3: 200ms timer, 120ms timer with 20s task ● Timer Jitter Scaling in EmSim – Ran 3 previous experiments at different scales ● Comparative Packet Latency in EmTOS – Ran tests comparing Ping times between EmTOS and real motes

10 Comparative Timer Jitter Top row is Mica2, Bottom row is EmTOS

11 Timer Jitter Scaling

12 Round Trip Time

13 Future Work ● Determine how TimeWarp affects fidelity at scale ● See if Kernel 2.6 can improve scalability ● Fix the ESS application using the EmTOS tools ● Use an EmView Gateway to funnel real data into analysis and visualization tools