vision for sensor networks
DESCRIPTION
Vision for Sensor Networks. CSE 291 Chien Spring 2003 April 8, 2003. Course Logistics. Friday meeting time 1230-150, SSB 106 (only irregularly, including this Friday) Web site emerging Information being added regularly Initial paper presentation signups and paper summaries - PowerPoint PPT PresentationTRANSCRIPT
Vision for Sensor Networks
CSE 291 Chien
Spring 2003
April 8, 2003
CSE 291 Sensor Networks – 4/8/2003
Course Logistics
• Friday meeting time» 1230-150, SSB 106 (only irregularly, including this Friday)
• Web site emerging» Information being added regularly» Initial paper presentation signups and paper summaries» Lectures available» Projects (still coming)
CSE 291 Sensor Networks – 4/8/2003
Paper Summaries
• Evaluations of the papers are due after we cover them in class. Each should be less than a page long (don't write a novel) and should follow this rough format:
» Title and Authors of paper » One sentence summary of the paper (the problem(s) it addresses and how) » Summary of key or important ideas in the paper (why are we reading this
anyway?) » How does the paper substantiate the importance of those ideas (brief
summary of logical argument and evidence) » One or two important flaws or limitations in the paper (be explicit) » How relevant is this work today and/or what future research does it
suggest?
• The evaluations should be turned in to Prof Chien’s office at the end of each week, on Friday before 5pm. If the door is closed, these can be put under the door.
CSE 291 Sensor Networks – 4/8/2003
Today’s Papers
• D. Estrin, D. Culler, K. Pister, and G. Sukhatme, Connecting the Physical World with Pervasive Networks , IEEE Pervasive Computing, pp. 59-69, January-March 2002.
• Which largely subsumes» D. Estrin, R. Govindan, J. Heidemann and S. Kumar,
Next Century Challenges: Scalable Coordination in Sensor Networks, International Conference on Mobile Computing and Networks (MobiCOM '99), August 1999, Seattle, Washington.
• J. M. Kahn, R. H. Katz, and K. S. J. Pister, Next Century Challenges: Mobile Networking for "Smart Dust" , In International Conference on Mobile Computing and Networks (MobiCOM '99), August 1999, Seattle, Washington.
CSE 291 Sensor Networks – 4/8/2003
First…
• D. Estrin, D. Culler, K. Pister, and G. Sukhatme, Connecting the Physical World with Pervasive Networks , IEEE Pervasive Computing, pp. 59-69, January-March 2002.
CSE 291 Sensor Networks – 4/8/2003
Vision of Ubiquity
• Capability to go anywhere and be anyplace• Out of the machine room, backpack…• Away from the power supplies… (or near)• Away from the infrastructure… (or near)• … can’t require a crushing effort…
CSE 291 Sensor Networks – 4/8/2003
Vision of Invisibility
• Not seen…» Systems that are small…» Systems that are unobtrusive…» Systems that are intuitive to use… interfaces that don’t
require training
• Invisibility is coupled with pervasive for utility
CSE 291 Sensor Networks – 4/8/2003
Deep Integration with the Physical World
• Today’s computers are “blind, deaf, dumb”» Limited sensory input» Limited interaction» Either disconnected, offline or primarily input processing, etc.
• Embedded systems are the exception to this, but historically have limited networking
• Sensor networks are the superexception to this» Focused on the physical world» Data acquisition, computation, and action» Closely coupled sensing and actuation» The real “autonomic computing systems” ??
CSE 291 Sensor Networks – 4/8/2003
Major System Challenges
• Large numbers of elements• Limited physical access• Extreme environmental conditions
• => demand a fundamental reexamination of familiar layers of abstraction, hardware, algorithms
• Suggestion: these are a radically different kind of computing system
CSE 291 Sensor Networks – 4/8/2003
Scale
• # of sensors: 10’s to millions• Size of sensors (cubic feet to millimeters)• Spatial and temporal sampling rates (miles to mm’s
and days to ms)• Capability (sensors, power, compute, communicate)• Compose and evolve as a system at scale
• Question: what computing systems do we have that span these ranges? Are they one kind?
CSE 291 Sensor Networks – 4/8/2003
Limited Access
• Unwired, unpowered, limited networking (cost)• Physically remote or harsh enviroments• Limited human intervention support/administration• Resource limited
• What are characteristics of our longest running, reliable systems, and techniques?
CSE 291 Sensor Networks – 4/8/2003
Extreme Dynamics
• Activity in the physical world happens in bursts» Animals are built for this (adrenaline, fear-flight, hunt, taste,
smell, etc.)» Static network -> things passing, evolving» Mobile network -> things encountered» Dynamic range of sensory input is orders of magnitude
• Systems must have passive vigilance, efficient triggering, and rapid transformation to high levels of concurrency and effectiveness.
• Not quite “lazy computing”, or something analogous?
CSE 291 Sensor Networks – 4/8/2003
Breadth
• Variable design structure – static, dynamic, regular and irregular
• Single sensor type/mode, multiple, single application and multiple-application
• Static or mobile – fast and slow change• Autonomy and limited access
» Degree of human involvement in both decision-making/control as well as maintenance of system
CSE 291 Sensor Networks – 4/8/2003
State of the Art
• … rambling discussion of some current research activities…» Small devices increasing in environmental awareness and
networking capability» Evolving radio, silicon technology enabling sensor networks» Maturing software environments
CSE 291 Sensor Networks – 4/8/2003
State of the Art (cont.)
• Outline of several specific challenges (not comprehensive)» Sensing and actuation – control loops and variable delays» Localization as a key challenge and foundation for coupling
with the physical world» Self configuration – and reconfiguration
CSE 291 Sensor Networks – 4/8/2003
Some “throw ins”
• Data centric architecture and “directed diffusion” (we’ll discuss later)
• Tiered (hierarchical) architectures» Different capabilities, heterogeneity
• Frontier for almost any CS subdiscipline is in this area
CSE 291 Sensor Networks – 4/8/2003
Discussion
• What kind of systems are really being discussed?• How do they differ fundamentally from those more
familiar?• How do they differ qualitatively/parametrically?• Are the systems being discussed a single class?
Multiple classes?• What areas are likely to be extensions of current
areas? Which are likely to be revolutionarily new?• Is the frontier for your CS subdiscipline in this area?
CSE 291 Sensor Networks – 4/8/2003
Second…
• J. M. Kahn, R. H. Katz, and K. S. J. Pister, Next Century Challenges: Mobile Networking for "Smart Dust" , In International Conference on Mobile Computing and Networks (MobiCOM '99), August 1999, Seattle, Washington.
CSE 291 Sensor Networks – 4/8/2003
Mobile Networking for “Smart Dust”
• Smart dust can be small enough to» Remain suspended in air» Buoyed by air currents» Sensing and communicating for hours and days on end
• “Exploring the limits of size and power consumption in autonomous sensor nodes”
• Interestingly, macro-scale systems have achieved this capability today…
CSE 291 Sensor Networks – 4/8/2003
Smart Dust
• “Mote”, as in dust Motes• Integrated
» MEMS sensors» Signal processing and
control circuitry» Power source and solar
cells» Laser diode and MEMS
mirror for active optical» Retroreflector and optical
receiver for passive
• 1-2 mm in dimension, autonomous system
CSE 291 Sensor Networks – 4/8/2003
Some Technology Limits
• Objective: 1mm3 sensors
• How much energy can we consume?
• Batteries -> ~1 Joule / 1mm3
• For a lifetime of 1 day» -> 10 microwatts average (NOT milliwatts!)» Augmenting with solar power limited to 2x» Artificial lighting 1.001x» Energy scavenging all well below solar
CSE 291 Sensor Networks – 4/8/2003
What does this mean?
• There are fundamental limits to what can be consumed (resources) by these systems in particular deployment/connection modes» Energy consumed per unit time (average)» Energy consumed in a burst, and cluster of bursts» Data communicated (probably)» Operations computed (?)
• Do these limits naturally partition sensor network systems? Is this a continuum or a discontinuity?
CSE 291 Sensor Networks – 4/8/2003
Low Power Techniques
• Clearly at a premium in these systems» E.g. 2x efficiency => 2x more STUFF can get done or 2x
LIFETIME or 2x reduction in COST» Intelligent control of hardware subsystems» Intelligent control of software and application activities» Intelligent design and implementation of systems for power
efficiency
• In particular, power-efficient techniques for communication which due to radios is dramatically more expensive than computation
CSE 291 Sensor Networks – 4/8/2003
Free space Networking
• Base station architecture, based on cheap video and imaging circuits• Many sensors transmit simultaneously• Power efficiency per bit is dramatically higher
» Active (LEDs), passive cornercube retroreflector (MEMS) for interrogation, demonstrated kb/s
• Reading an electronic panel
CSE 291 Sensor Networks – 4/8/2003
Specific Functions
• Parallel Read out » Synchronized sample of the space and smart dust
• Demand Access» Passive monitoring, triggered activation and sensing
• Controlled probing rates
• => the benefits of centralized control
CSE 291 Sensor Networks – 4/8/2003
Limitations
• Line of sight» Direct optical communication to BTS ideal» Multihop possible, but limited» Increases bandwidth densities, but decreases connectivity
• Link Directionality» Can focus interrogation subset of “viewable” sensors» Limits mote visibility and connectivity to a hemisphere» Interesting connectivity, routing, and interlaced network
challenges
CSE 291 Sensor Networks – 4/8/2003
Discussion
• How is this vision different/similar to that of Culler/Estrin?
• What are the advantages of this type of networking approach? Disadvantages?
• Power, line of sight, orientation, how do applications differ in their needs for these things?
• How does a technological underpinning like this affect the “architecture” of a sensor network system?
CSE 291 Sensor Networks – 4/8/2003
Next Time
• Friday, April 11 in SSB 106• Detailed overview of current/emerging sensor
network hardware» Ember Networks Platform (Ryan Wu) » Crossbow Platform (Berkeley Motes) (Johanz Ammerlahn)
• We will update the web links to specific documents, but not until late today
• Don’t forget your first set of paper summaries are due Friday at 5pm.