Extreme Networked Systems:

Large Self-Organized Networks

of Tiny Wireless Sensors

David Culler Computer Science Division

U.C. BerkeleyIntel Research @ Berkeley

www.cs.berkeley.edu/~culler

8/8/2001 EECS Visions 2

Emerging Microscopic Devices

• CMOS trend is not just Moore’s law

• Micro Electical Mechanical Systems (MEMS)– rich array of sensors are becoming cheap and tiny

• Imagine, all sorts of chips that are connected to the physical world and to cyberspace! LNA

mixerPLL basebandfilters

I Q

• Low-power Wireless Communication

8/8/2001 EECS Visions 3

Disaster Management

Circulatory Net

What can you do with them?

• Embed many distributed devices to monitor and interact with physical world

• Network these devices so that they can coordinate to perform higher-level tasks.

=> Requires robust distributed systems of hundreds or thousands of devices.

Habitat Monitoring

Condition-based

maintenance

8/8/2001 EECS Visions 4

Getting started in the small

• 1” x 1.5” motherboard– ATMEL 4Mhz, 8bit MCU, 512 bytes RAM, 8K pgm flash– 900Mhz Radio (RF Monolithics) 10-100 ft. range– ATMEL network pgming assist– Radio Signal strength control and sensing– I2C EPROM (logging)– Base-station ready (UART)– stackable expansion connector

» all ports, i2c, pwr, clock…

• Several sensor boards– basic protoboard– tiny weather station (temp,light,hum,prs)– vibrations (2d acc, temp, light)– accelerometers, magnetometers, – current, acoustics

8/8/2001 EECS Visions 5

A Operating System for Tiny Devices?

• Traditional approaches– command processing loop (wait request, act, respond)

– monolithic event processing

– bring full thread/socket posix regime to platform

• Alternative– provide framework for concurrency and modularity

– never poll, never block

– interleaving flows, events, energy management

– allow appropriate abstractions to emerge

8/8/2001 EECS Visions 6

Appln = graph of event-driven components

RFM

Radio byte

Radio Packet

UART

Serial Packet

ADC

Temp photo

Active Messages

clocks

bit

by

tep

ac

ke

t

Route map router sensor appln

ap

pli

ca

tio

n

HW

SW

Example: ad hoc, multi-hop routing of photo sensor readings

8/8/2001 EECS Visions 7

Pushing Scale

8/8/2001 EECS Visions 8

Re-explore networking

• Fundamentally new aspects in each level– encoding, framing, error handling

– media access control

– transmission rate control

– discovery, multihop routing

– broadcast, multicast, aggregation

– active network capsules (reprogramming)

– security, network-wide protection

• New trade-offs across traditional abstractions– density independent wake-up

– proximity estimation

– localization, time synchronization

• New kind of distribute/parallel processing

8/8/2001 EECS Visions 9

Larger Challenges

• Security / Authentication / Privacy

• Programming support for systems of generalized state machines

– language, debugging, verification

• Simulation and Testing Environments

• Programming the unstructured aggregates

• Resilient Aggregators

• Understanding how an extreme system is behaving and what is its envelope

– adversarial simulation

• Constructive foundations of self-organization

8/8/2001 EECS Visions 10

To learn more

• http://www.cs.berkeley.edu/~culler

• http://tinyos.millennium.berkeley.edu/

• http://webs.cs.berkeley.edu/

• http://ninja.cs.berkeley.edu/

8/8/2001 EECS Visions 11

Characteristics of the Large• Concurrency intensive

– data streams and real-time events, not command-response

• Communications-centric

• Limited resources (relative to load)

• Huge variation in load

• Robustness (despite unpredictable change)

• Hands-off (no UI)

• Dynamic configuration, discovery– Self-organized and reactive control

• Similar execution model (component-based events)

• Complimentary roles (eyes/ears of the grid)

• Huge space of open problems

...and Small