Transcript Endeavouring to Build Networks of Tiny Devices David Culler Computer Science Division U.C. Berkeley www.cs.berkeley.edu/~culler.

Endeavouring to Build Networks
of Tiny Devices
David Culler
Computer Science Division
U.C. Berkeley
www.cs.berkeley.edu/~culler
Background
• Q1: design principles for Extremely Diverse
system architectures?
– immense services (Millennium, Ninja)
– tiny devices
appln as graph of state machines
concurrency intensive, variation in load, robustness
reactive
 tiny devices became “eyes and ears” of
ubiquitous computing
become source of control as well
4/2001
TinyOS
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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
• Low-power Wireless Communication
I SDQ SD
• Imagine, all sorts of chips
that are connected to the
physical world and to
cyberspace!
4/2001
PLL
TinyOS
baseband
filters
mixer
LNA
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Current One-Inch Networked Sensor
• 1” x 1.5” motherboard
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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
stackable expansion connector
» all ports, i2c, pwr, clock…
• Several sensor boards
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4/2001
basic protoboard
tiny weather station (temp,light,hum,press)
vibrations (2d acc, temp, LIGHT)
accelerometers
magnetometers
TinyOS
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TinyOS Approach
• Stylized programming model with extensive static
information
– Program = graph of TOS components
– TOS component = command/event interface + behavior
• Rich expression of concurrency
– Events propagate across many components
– Tasks provide internal concurrency
• Regimented storage management
• Very simple implementation
• Broad range of alternative execution mechanisms
• For More see http://tinyos.millennium.berkeley.edu
4/2001
TinyOS
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Tiny OS Concurrency Framework
Messaging Component
– frame per component, shared stack, no
heap
• Very lean multithreading
• Efficient Layering
TinyOS
internal thread
Internal
State
TX_pack
et_done
(success
RX_pack
)et_done
(buffer)
• Constrained Storage Model
4/2001
msg_rec(type, data)
msg_sen
d_done)
Commands,
Event Handlers
Frame (storage)
Tasks (concurrency)
init
Power(mode)
TX_packet(buf)
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init
• Component:
Events
send_msg
(addr,
type, data)
– constrained two-level scheduling
model: threads + events
Commands
power(mode)
• Scheduler + Graph of
Components
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application
Application = Component Graph
Route map
router
sensor appln
packet
Radio Packet
byte
Radio byte
bit
Active Messages
RFM
4/2001
Serial Packet
UART
Temp
photo
SW
HW
ADC
clocks
TinyOS
Example: ad hoc, multi-hop
routing of photo sensor
readings
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DARPA-esq demo
• UAV drops nodes along road,
– hot-water pipe insulation for package
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Nodes self configure into linear network
Calibrate magnetometers
Each detects passing vehicle
Share filtered sensor data with 5 neighbors
Each calculates estimated direction & velocity
Share results
As plane passes by,
– joins network
– upload as much of missing dataset as possible from each node when
in range
• 7.5 KB of code!
4/2001
TinyOS
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Cory Energy Monitoring/Mgmt System
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50 nodes on 4th floor
5 level ad hoc net
30 sec sampling
250K samples to database over 6 weeks
4/2001
TinyOS
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Energy Monitoring Network Arch
20-ton
chiller
sensor net
GW
control net
GW
GW
802-11
PC
modbus
PC
MYSQL
telegraph
scada term
UCB power
monitor net
4/2001
Browser
TinyOS
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Directions
• Systems technology: long-term management
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integrate new MAC and rate control (Alec Woo)
in situ network programming (Rob Szewczyk)
node query scheme (Sam Madden)
implicit discovery (Phil Levi)
signal strength adaptation
telegraph
• Power management
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Battery monitoring and adaptation
current and voltage sensors
non-intrusive load monitoring
integrate with broader sensor net
alert response
TinyOS
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Emerging “de facto” tiny system
• Feb. bootcamp
– 40 people
– UCB, UCLA, USC, Cornell,
Rutgers, Wash.,
– LANL, Bosch, Accenture,
Intel, crossbow
• Several groups actively developing around
tinyOS on “rene” node
• Concurrency framework has held up well.
• Next generation(s) selected as DARPA networked
embedded system tech (NEST) open platform
• Smaller building blocks for ubicomp
4/2001
TinyOS
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NEST Program Structure – evolution
Challenge Application
composition services
coordination
synthesis
services
services
Composition
Platform
SWOpen
platform
HW platform
sensors processing communication
actuators
initial low-power
wireless storage
year
Open Platform
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100+ tiny devices for alg. dev.
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TinyOS
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HW Platforms
• Current: SmartDust MacroMOTE => Renes =>
• Phase 1: 6 months => algorithm studies
– Mote++, MEMS sensors, TinyOS
– more microcontroller
» atmega163 => 2x storage
» atmega103 => 128K flash, 4k ram
» TIMSP430 => 60k flash, 2k ram, HW *, ...
» many subtle factors
– RFM with “ASH” 100 kb/s
» too early for bluetooth
– 100+ nodes for < 20K$
• Phase 2: 30 months => composition of alg’s
– ARM-power, Bluetooth physical
– integrated system
– OS??
4/2001
TinyOS
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SW Platform
• Tiny event-driven component OS
– allows NEST abstractions to emerge and each level
• Language-based robustness and optimization
– eg., critical path and jitter analysis
– inter-component transformations
– narrow interface with simple IDL
• Tiny networking
– power-aware appln-specific ad hoc routing, MAC, transmission
control
– in network aggregation
– in situ programming
• Algorithm building blocks
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Local multicast
event-driven reception
intelligent pruning of retransmission
non-blocking execution
TinyOS
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Programming Environment & Tools
• Provide support for: event-driven programming,
composition, debugging & visualization in the
small (node) and large (collection)
• Emulation => simulation => real devices
– identical APIs, range of visibility, and reality
• Debugging and visualization tools
– geared toward many interacting nodes & event-centric
development
• Application-Specific Virtual Machines
– analogous to query-plan vs query-processing engine
• FSM-based programming abstractions
• Macrocomputing
4/2001
TinyOS
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FSM-based Software Approach
• Fundamentally, we are not computing, we are
moving data intelligently
– threads are a computing abstraction, FSMs are a protocol
abstraction
use FSMs as the base then add some computing
• natural high concurrency
• natural handling of events, exceptions, and the
environment
• tools for understanding stability (e.g markov
models, game theory, control theory)
• composition is separate from creation
– late bind the callee in a separate step called "composition"
4/2001
TinyOS
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Macrocomputing
• Program a large, unstructured collection in
aggregate
– Single program, multiple data
» but errors and probabilistic behavior
» unstructured collection
– “global” variables that reflect collections
» need to handle error propagation
– scatter/gather for collections?
– online query processing?
• multi-WEbS abstractions
4/2001
TinyOS
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Security
• Individual nodes may be compromised, but hard
to get large fraction of nodes.
• Attacks introduce another form of unreliability in
the data.
• Lightweight encryption/decryption,
authentication.
• Novel protocols to support aggregate
operations, eg., broadcast, w/o shared root key
• Resilient aggregation
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TinyOS
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Resilient Aggregators
• operate in the face of faulty nodes, intermittent
communication, and security attacks
– ex max is not resilient, nine-tile is.
• develop algebra of resilient aggregators
• Random sampling as implementation
• foundation for security model
– easy to attack a node
– hard to attack large fraction of the nodes
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TinyOS
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Simulation
• Large-scale NEST simulator
– very large number of small nodes
– integrated with event-driven OS design for efficiency
– checkpointing
• Adversarial simulation mode
– Detecting “composition” bugs and scaling bugs
• Target failure: search for bugs
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test race conditions automatically
pick orders that consume resources
more efficient than random-walk testing
simulator is an adversary…
guided search
• Hybrid simulator/testbed
4/2001
TinyOS
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Test-bed Kits
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in situ programming/upgrade and debugging
synchronized logging (trace extraction)
passive monitoring
data collection
4/2001
TinyOS
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Challenge Applications
active markers
• sequence of
applications
obstacles
– interactive spaces
– flock of model cars
UAVs
– Multi-agent pursuit-
evasion
• also environmental
monitoring
– stunt ranch “whole canopy
ecophysiology” with UCLA
4/2001
evader
TinyOS
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Closed-loop at many levels
• Within a node
– behavior adapts to available energy, physical measurements,
network condition
• Across the network
– discovery and routing, transmission rate and schedule
– adopting roles,
• Within the middleware components
– synchronization, scheduling
• On the vehicle
– direction, stability, probabalistic map building
• Among the vehicles
– competitive, hidden markov decision processes
4/2001
TinyOS
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New building blocks for Ubicomp
4/2001
TinyOS
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New Collaboration
• Intel Berkeley Lablet
Extreme Interconnected Systems (XIS) lab
4/2001
TinyOS
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