1. Systems Wireless EmBedded Distributed System Design from a Sensor Net Perspective David Culler

2. Systems Wireless EmBedded 1/28/2004Sensor Net Day2 Moore’s Law – 2x stuff per 1-2 yr

3. Systems Wireless EmBedded 1/28/2004Sensor Net Day3 Bell’s Law – new computer class per 10 years year log (people per computer) streaming information to/from physical world Number Crunching Data Storage productivity interactive Enabled by technological opportunities Smaller, more numerous and more intimately connected Ushers in a new kind of application Ultimately used in many ways not previously imagined

4. Systems Wireless EmBedded 1/28/2004Sensor Net Day4 Making it happen Move the research from ‘simulations of imagined problems’ to ‘experience with real ones’  open, widely used HW/SW “close enough” platform Pilot applications that show how it might change the way we do science and engineering  Focus the technology advance  Set the bar on capability Tackle the new computer systems challenges due resource constraints, scale, & embedment  Fundamentally simpler, more robust software structures

5. Systems Wireless EmBedded 1/28/2004Sensor Net Day5 Open Experimental Platform to Catalyze a Community Small microcontroller - 8 kb code, - 512 B data Simple, low-power radio - 10 kb EEPROM (32 KB) Simple sensors WeC 99 “Smart Rock” Mica 1/02 NEST open exp. platform 128 KB code, 4 KB data 50 KB radio 512 KB Flash comm accelerators - DARPA NEST Dot 9/01 Demonstrate scale - Intel Rene 11/00 Designed for experimentation -sensor boards -power boards DARPA SENSIT, Expeditions TinyOS www.tinyos.netNetworkingServices Crossbow

6. Systems Wireless EmBedded 1/28/2004Sensor Net Day6 Example uses Env. Monitoring, Conservation biology,... –Precision agriculture, land conservation,... –built environment comfort & efficiency... –alarms, security, surveillance, treaty verification... Civil Engineering: structures response –condition-based maintenance –disaster management –urban terrain mapping & monitoring Interactive Environments –context aware computing, non-verbal communication –handicap assistance »home/elder care »asset tracking Integrated robotics CENS.ucla.edu Lifetime and Scale Sample Rate & Precision Mobility & Disconnection

7. Systems Wireless EmBedded 1/28/2004Sensor Net Day7 Resolving The Systems Challenge applications service network system architecture data mgmt Monitoring & Managing Spaces and Things technology MEMS sensing Power Comm. uRobots actuate Miniature, low-power connections to the physical world Proc Store

8. Systems Wireless EmBedded 1/28/2004Sensor Net Day8 Traditional Systems Well established layers of abstractions Strict boundaries Ample resources Independent Applications at endpoints communicate pt-pt through routers Well attended User System Physical Layer Data Link Network Transport Network Stack Threads Address Space Drivers Files Application Routers

9. Systems Wireless EmBedded 1/28/2004Sensor Net Day9 by comparison... Highly Constrained resources –processing, storage, bandwidth, power Applications spread over many small nodes –self-organizing Collectives –highly integrated with changing environment and network –communication is fundamental Concurrency intensive in bursts –streams of sensor data and network traffic Robust –inaccessible, critical operation Unclear where the boundaries belong –even HW/SW will move => Provide a framework for: Resource-constrained concurrency Defining boundaries Appl’n-specific processing and power management allow abstractions to emerge

10. Systems Wireless EmBedded 1/28/2004Sensor Net Day10 Example 1: Rethinking Across Layers Appln Specific VM Routing –Bcast –Aggregate operation –Epidemic Dissemination Sleep Neighborhood –Link estimation –Table mgmt –Reflected tuples MAC –Backoff –Collision –Recovery –TimeStamp Phy –Energy –Sampling Watchdog analog Digital ??? Clocks Timers Flash Store Power Mgmt Phy Link Network Transport nbr mac Broadcast Collect Aggregate Scheduler Data proc. Neighborhoods AS Virtual Machine Timesynch Localize

11. Systems Wireless EmBedded 1/28/2004Sensor Net Day11 Example 2: Multihop Routing Necessity for low-power operation at scale Discover connectivity graph Determine routing subgraph relative to traffic pattern Route data hop-by-hop

12. Systems Wireless EmBedded 1/28/2004Sensor Net Day12 Example Radio Cells

13. Systems Wireless EmBedded 1/28/2004Sensor Net Day13 Discovery & Routes formation 0 1 1 2 2 2 2 2

14. Systems Wireless EmBedded 1/28/2004Sensor Net Day14 Behavior over Time 70-100% Est. Link Quality 40-70% 0- 40% Tree Depth 1 2 3

15. Systems Wireless EmBedded 1/28/2004Sensor Net Day15 What is connectivity? CS: Ability to correctly receive a large fraction of transmitted packets EE: Signal-to-noise ratio exceeds some threshold

16. Systems Wireless EmBedded 1/28/2004Sensor Net Day16 The Amoeboed “cell” Signal Noise Distance

17. Systems Wireless EmBedded 1/28/2004Sensor Net Day17 Which node do you route through?

18. Systems Wireless EmBedded 1/28/2004Sensor Net Day18 What does this mean? Always routing through nodes “at the hairy edge” –Wherever you set the threshold, the most useful node will be close to it The underlying connectivity graph changes when you use it –More connectivity when less communication –Discovery must be performed under load

19. Systems Wireless EmBedded 1/28/2004Sensor Net Day19 Deeper questions Localized algorithms: Distributed computation where each node performs local operations and communicates within some neighborhood to accomplish a desired global behavior –D. Estrin, “21 st Century Challenges…” It takes energy to maintain ‘structure’ from local interactions. How much? –To maintain a routing tree? –To aggregate? –To disseminate info? Compression / reliability, ….