Smart Dust

1. Smart Dust Embedded Computing Seminar Noam Sapiens

2. Outline • What is smart dust? • Characteristics • Applications • Military • Commercial • Requirements and restrictions • Analysis of smart dust communication • General architecture and design • What we have today • Would like to have • References

3. What is Smart Dust? Large scale networks of wireless sensors for various applications • The three key capabilities of smart dust are: • Sensory capabilities • Processing capabilities • Communication capabilities

4. Smart dust characteristics • A system is made of one or a few base stations (interrogators) and as many smart dust motes as possible or required • Ubiquitous – sensors of different types • Very task/application oriented design and performance • Wireless communication • Self-organizing, self-optimizing, self-configuring, self-sustaining. • Very small (should be under 1mm3) • Low power consumption • Easy to deploy • Based on current or very near future components

5. Military and Space applications • Internal and external spacecraft monitoring • Meteorological and seismological monitoring in difficult terrain and environments • Land/space communication • Chemical/biological environment sensing • Meteorological sensing – for better aiming of guns and artillery • Autonomous vehicles external aid

6. Surveillance • Sensors minefield e.g. smart clear tracks on borders • Urban engagement (cont. DARPA funding in 2005) • Motion detection and enemy numbers • Bunker/building mapping • Peace time/treaty monitoring • Intelligence in hostile areas/behind enemy lines • Transportation monitoring and traffic mapping • Missile hunting • Monitoring soldier vitals and injury • Pursuit aid

7. Unmanned pursuit Integration of several smart dust experiments • Aerial smart dust deployment in the area of interest – ground and air • Sensors: • Each mote has motion detectors and a small CMOS camera • Some motes has GPS • Computation: • Image processing for target distinction • Communication: • Ad-hoc networking • Relative localization Energy tradeoff Local coordinate system Northwestern university UC Berkeley and MLB Co.

8. UC Berkley PEG (pursuit-evasion game) experiment • 200 sensors network • One aerial and three ground unmanned vehicles – pursuers • One ground unmanned – evader • Pursuers are interrogators of the sensor network deployed • Sensor networks roles: • Provide complete monitoring of the environment, overcoming the limited sensing range of on board sensors • Relay secure information to the pursuers to design and implement an optimal pursue strategy • Provide guidance to pursuers, when GPS or other navigation sensors may fail UC Berkeley

9. Experiment block diagram Sensor Network EvaderDynamics Pursuer PursuerDynamics GPS Evader motionestimator Pursuit Strategy Tracking control

10. Commercial applications • Games and sports • Traffic monitoring • Inventory control • Security • Identification and tagging • Predictive maintenance • Product quality control • Industrial facilities • Vehicles and systems • Appliances • Agriculture

11. Building management • Energy management • Temperature control • Lighting control • Fire systems • Smart office spaces • Computer interface • Virtual keyboard • 3D virtual sculpturing • Health, medicine and wellness • Handicap aid

13. Requirements • Perform a specific task according to the application • Sense as defined by the task profile (different types of detectors – will not be discussed in this talk) • Perform basic computations – digitization, noise filtering, DSP, FFT, image processing, decision making, localization, etc… • Establish ad-hoc communication in a physical environment • Base station communication and peer to peer • Ranges between a few meters (between motes) and over a km (motes to base station) • Multi-hop routing (if required) • Self configuration and optimization

14. Restrictions • Mote volume will not exceed 1mm3 • A single mote is probably restricted to few sensory capabilities • Energy restrictions • Battery ≈ 1J/mm3 (about 10W for a day) • Capacitors ≈ 1mJ/mm3 • Solar cells ≈ 1J/day (sun) or ≈1mJ/day (room light) • Vibrations ≈ 0.4-30W (depends on amplitude and frequency) • Thermopile ≈ 0.4-2W @ 25-37C • Very low cost motes (enable large scale distribution) • No science fiction technologies

15. Analysis of smart dust communication RF vs. Optical • RF – radio frequency • MHz – hundreds of GHz  1mm – 100s meters wavelength • Technologies: • Bluetooth • Cell phones (GSM, CDMA, etc.) • RFID • Optical • 100THz – 1PHz  0.3 - 1.6 wavelength • Lasers and LEDs

16. RF • Pros • Well developed technologies • Multiplexing techniques: TDMA, FDMA, CDMA. • Does not require line of sight • Not much affected by the environment • Cons • Antenna size (has to be at least ¼ of the wavelength) • Complex circuitry (modulation/demodulation, bandpass filters, etc.) • Energy consumption (approx. 100nJ/bit)

17. Optical • Pros • Low energy consumption (<1nJ/bit) • High data rates • Small aperture, very directional (localization) • Spatial division multiplexing • Cons • Very directional • Line of sight • Atmospheric turbulence, weather and environmental conditions dependent

18. General smart dust mote architecture - optical

19. MEMs controlled corner cube retro-reflector • Perfectly aligned corner cube reflects light at the exact same direction of incidence • MEMs control of one of the corner cube side’s alignment enables modulation • Energy consumption of about 1pJ/bit @ 1kb/sec • Range up to 1km UC Berkeley

20. Smart dust active transmitter • Incorporates a laser, lens and a MEM steering mirror • 1mrad transmission • Data rate of approx. 5Mb/sec • Energy consumption depends on distance and detector size 1mW at 1mrad laser is 40 times brighter than 100W light bulb

21. SEM view Laser diode MEM mirror Lens Optical view UC Berkeley

22. Experimental results • Beam steering at kHz rates • Steering in approx 1str ≈ 60X 60 5.2 km Berkeley Marina 15.3 km Coit Tower 300m Link test 14W laser 8mW laser

23. The base station • Hand held • Binoculars • Palm • Cell phone • Laptop computer • Command center • Unmanned vehicle (land, sea, air) • Autonomous systems

24. Base station architecture range Quarter-wave Filter Polarizing Plate Beam Splitter Lens Camera Smart dust Beam Laser Expander Mirror Optical interrogation – principles of operation For example:FOV=17mX17mCMOS is 256X256, 432pixelsRange = 2kmfLens=20cmSpatial resolution = 6.6cm2 Space division multiplexing

25. Airborne base station example UC Berkeley and MLB Co.

26. Challenges for mobile networking for smart dust • Line of sight requirement • Link directionality • Parallel readout and cross talk • Trade-offs • Revisit rates

27. Line of sight requirement • Optical communication requires photons from the transmitter reach the receiver – photons travel in straight lines • Line of sight is not the only way of making the photons arrive at a desired location: • Diffuse reflections – low energy, wide spread (the entire FOV) and low contrast with the environment (especially with interrogating beam) • Non fixed smart dust systems - line of sight could be achieved intermittently • Ad hoc multi-hop routing Cannot work with passive communication, very small SNR Latency Algorithms Latency Reliability

28. Link directionality General • Motes are unaware of neighbors location • Base station can disseminate location information to motes Passive links • A corner cube retro-reflector angle of acceptance is 10-20 • Placing multiple corner cubes • Placing the corner cube and the receiver on a MEM mount – signal maximization • Increase mote density – high probability for communication with at least some motes in the area of interest

29. Active links • Mote receiver is omnidirectional within a hemisphere • Enables mote attention without aiming • No source identification • Making the receiver directional (by adding a lens) and connecting its directionality to the transmitter will enable communication automatically to the source • Requires aiming • Solved by increasing the density of motes • In a static system, identification could be saved in mote memory • Difference between receiver and transmitter angular spreads leads to non-reciprocal linking

30. Parallel readout and crosstalk • The network architecture of smart dust enables space division multiplexing in the base station • There are as many channels as there are pixels in the CMOS camera of the base station • If the interrogating beam is divergent enough several motes could be ready simultaneously • A base station will not distinguish between motes in the same space equivalent pixel • TDMA could be incorporated in the architecture – modulation of the interrogating beam could establish a clock for synchronization • Demand access method (as in cellular and satellite networks) could be implemented as well – a mote sends an active short pulse to the base station will receive attention by the interrogation beam of the base station

31. Trade-offs SNR – signal to noise ratio, governs the probability for bit error Pt – average transmitter power A – receiver area N0 – receiver inherent noise B – bit rate r – the distance between the transmitter and receiver  - beam divergence

32. Revisit rate • Revisit rate should be application specific • Use of AI – learning system • Frequent revisits to areas in which changes happen most rapidly • Could be based on human judgment or automatic • Could be based on the demand access method

33. What we have today www.dust-inc.com www.xbow.com • Different markets • Airborne systems – monitoring, camera stability, unmanned… • Marine • Land vehicles • Environment • Mote price ~100$ • Kit price (8-12 motes) ~ 2000$ • Building management • Industrial monitoring • Security

34. Would like to have capabilities (a partial list) • Miniaturization of available smart dust and extreme price reduction • Possibility of optical pre-processing and optical circuits • Incorporate the concept of smart dust societies – integration of different types of smart dust • Requires more robust network protocols • Requires better definition of mote task • Enables complex systems easy distribution • Enables smaller and cheaper motes

35. Multi wavelength VCSEL arrays will enable smart dust WDM capabilities • Beam quality control (divergence) – for easier scanning • Electro-optic instead of MEMs • Higher bit rate (will be required for very large networks) • Lower energy (about 20pJ/bit @ 10Mb/sec) • Active smart dust – interfaces, robotic capabilities and motion Rocket chip UCSD

36. References • JM Kahn, RH Katz & KSJ Pister, “Emerging challenges: mobile networking for smart dust”, J. of Comm. and Net. 2 pp.188-196 (2000) • Y Song, “Optical Communication Systems for Smart Dust”, M.Sc. Thesis, Virginia polytechnic institute and state university, 2002 • The following urls: • http://www.darpa.mil/ • http://robotics.eecs.berkeley.edu/~pister/SmartDust/ • http://www-bsac.eecs.berkeley.edu/archive/users/warneke-brett/SmartDust/index.html • http://www.xbow.com/ • http://www.dust-inc.com/ • http://chem-faculty.ucsd.edu/sailor/research/highlights.html • http://www.nanotech-now.com/smartdust.htm

37. thank you for your time