Date post: | 15-Jan-2016 |
Category: |
Documents |
View: | 213 times |
Download: | 0 times |
Sys
temsW
irel
ess
EmBedded
Distributed System Design from a Sensor
Net Perspective
David Culler
1/28/2004 Sensor Net Day 2
Sys
temsW
irel
ess
EmBedded
Moore’s Law – 2x stuff per 1-2 yr
1/28/2004 Sensor Net Day 3
Sys
temsW
irel
ess
EmBedded
Bell’s Law – new computer class per 10 years
year
log
(p
eo
ple
pe
r c
om
pu
ter)
streaming informationto/from physical world
Number CrunchingData Storage
productivityinteractive
• 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
1/28/2004 Sensor Net Day 4
Sys
temsW
irel
ess
EmBedded
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
1/28/2004 Sensor Net Day 5
Sys
temsW
irel
ess
EmBedded
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.net
Networking
Services
Crossbow
1/28/2004 Sensor Net Day 6
Sys
temsW
irel
ess
EmBedded
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.eduLifetime and Scale
Sample Rate & Precision
Mobility & Disconnection
1/28/2004 Sensor Net Day 7
Sys
temsW
irel
ess
EmBedded
Resolving The Systems Challenge
applications
service
network
system
architecture
data mgmt
Monitoring & Managing Spaces and Things
technology
MEMSsensing Power
Comm. uRobotsactuate
Miniature, low-power connections to the physical world
Proc
Store
1/28/2004 Sensor Net Day 8
Sys
temsW
irel
ess
EmBedded
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
Application
Routers
1/28/2004 Sensor Net Day 9
Sys
temsW
irel
ess
EmBedded
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
1/28/2004 Sensor Net Day 10
Sys
temsW
irel
ess
EmBedded
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
StorePower Mgmt
Phy
Link
Network
Transport
nbr
mac
Broadcast Collect
Aggregate
Scheduler
Data proc.
Neighborhoods
AS Virtual Machine
Timesynch
Localize
1/28/2004 Sensor Net Day 11
Sys
temsW
irel
ess
EmBedded
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
1/28/2004 Sensor Net Day 12
Sys
temsW
irel
ess
EmBedded
Example Radio Cells
1/28/2004 Sensor Net Day 13
Sys
temsW
irel
ess
EmBedded
Discovery & Routes formation
0
112
2
2
22
1/28/2004 Sensor Net Day 14
Sys
temsW
irel
ess
EmBedded
Behavior over Time
70-100%
Est. Link Quality
40-70%
0- 40%
Tree Depth
1
2
3
1/28/2004 Sensor Net Day 15
Sys
temsW
irel
ess
EmBedded
What is connectivity?
• CS: Ability to correctly receive a large fraction of transmitted packets
• EE: Signal-to-noise ratio exceeds some threshold
1/28/2004 Sensor Net Day 16
Sys
temsW
irel
ess
EmBedded
The Amoeboed “cell”
Signal
Noise
Distance
1/28/2004 Sensor Net Day 17
Sys
temsW
irel
ess
EmBedded
Which node do you route through?
1/28/2004 Sensor Net Day 18
Sys
temsW
irel
ess
EmBedded
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
1/28/2004 Sensor Net Day 19
Sys
temsW
irel
ess
EmBedded
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, “21st 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, ….