The Tenet Architecture for Tiered Sensor Networks Ben Greenstein, Jeongyeup Paek Omprakash Gnawali,...
-
Upload
ashlynn-peters -
Category
Documents
-
view
218 -
download
1
Transcript of The Tenet Architecture for Tiered Sensor Networks Ben Greenstein, Jeongyeup Paek Omprakash Gnawali,...
The Tenet Architecture for Tiered Sensor Networks
Ben Greenstein, Jeongyeup PaekOmprakash Gnawali, Ki-Young Jang, August Joki, Marcos Vieira,
Deborah Estrin, Ramesh Govindan, Eddie Kohler
2
The Problem
■ Sensor data fusion within the network• … can result in energy-efficient implementations
■ But implementing collaborative fusion on the motes for each application separately• … can result in fragile systems that are hard to program,
debug, re-configure, and manage.
■ We learnt this the hard way, through many trial deployments
3
An Aggressive Position
■ Why not design systems without sensor data fusion on the motes?
■ A more aggressive position: Why not design an architecture that prohibits collaborative data fusion on the motes?
■ Questions:• How do we design this architecture?
• Will such an architecture perform well?
No more on-mote collaborative fusion
4
Tiered Sensor Networks
MotesLow-power, short-range radiosContain sensing and actuation
Masters32-bit CPUs (e.g. PC, Stargate)Higher-bandwidth radiosLarger batteries or powered
Enable flexible deployment of dense instrumentation
Provide greater network capacity, larger spatial reach
Many real-world sensor network deployments are tiered
■ Real world deployments at,• Great Duck Island (UCB, [Szewczyk,`04]),
• James Reserve (UCLA, [Guy,`06]),• Exscal project (OSU, [Arora,`05]),• …
Future large-scale sensor network deployments will be tiered
5
Tenet Principle
Multi-node data fusion functionality and multi-node application logic should be implemented only in the master tier. The cost and complexity of implementing this functionality in a fully distributed fashion on motes outweighs the performance benefits of doing so.
Aggressively use tiering to simplify system !
6
and may return responses
Tenet Architecture
Motes process data,
No multi-node fusion at the mote tier
Masters control motes
Applications run on masters, and masters task motes
7
What do we gain ?
■ Simplifies the application development• Application writers do not need to write or debug
embedded code for the motes– Applications run on less-constrained masters
■ Enables significant code re-use across applications• Simple, generic, and re-usable mote tier
– Multiple applications can run concurrently with simplified mote functionality
• Robust and scalable network subsystem– Networking functionality is generic enough to support various types
of applications which improves network re-usability
8
■ More bits communicated than necessary? ■ Communication over longer hops?
Challenges
Fusion
■ Not an issue• Typically the diameter of the mote
tier will be small
• Can compensate by more aggressive processing at the motes
■ In most deployments, there is a significant temporal correlation • Mote-local processing can
achieve significant compression
■ … but little spatial correlation • Little additional gains from mote tier
fusion
■ Mote-local processing provides most of the aggregation benefits.
The cost will be small…
9
System Overview
Tasking Subsystem Networking Subsystem
TaskingLanguage
Task ParserTasklets and
RuntimeReliable
TransportRouting
Task Dissemination
Tenet System
How to disseminate tasks and deliver responses?
How to express tasks?
10
Tasking Subsystem
Tasking Subsystem Networking Subsystem
TaskingLanguage
TaskParser
Tasklets and Runtime
ReliableTransport
RoutingTask
Dissemination
Tenet System
■ Goals• Flexibility: Allow many applications to be implemented• Efficiency: Respect mote constraints• Generality: Avoid embedding application-specific functionality• Simplicity: Non-expert users should be able to develop applications
11
Tasking Language
■ Linear data-flow language allowing flexible composition of tasklets• A tasklet specifies an elementary sensing, actuation, or data processing
action
• Tasklets can have several parameters, hence flexible
• Tasklets can be composed to form a task– Sample(500ms, REPEAT, ADC0, LIGHT) Send()
■ No loops, branches: eases construction and analysis• Not Turing-complete: aggressively simple, but supports wide range of
proposed applications
Data-flow style language natural for sensor data processing
12
Classes of Tasklets
■ System• Reboot• Get• Send
■ Task Manipulation• Issue (Wait, Alarm)• DeleteTaskIf• DeleteActiveTaskIf
■ Sensor/Actuator• Sample• Actuate
■ Data Manipulation• Arithmetic• Comparison• Logical• Bitwise• Statistics• DeleteAttributeIf
■ Miscellaneous• Storage• Count / Constant
13
Task Compositions…
■ CntToLedsAndRfm
■ SenseToRfm
■ With time-stamp and seq. number
■ Get memory status for node 10
■ If sample value is above 50, send sample data, node-id and time-stamp
Wait Count Lights Send
Sample Send
CountStampTime SendSample
MemStats SendAddress NEQ(10) DeleteIf
Sample LT(50) DeleteATaskIf Address StampTime Send
14
How many Tenet tasks can a mote run at the same time?
+
Memory is the constraint, and task complexity matters!
Memory Usage (~5KB heap)
Sample(1) Send 110Bytes
Sample(1)Stamp Time
CAGSDASend 180Bytes
Sample(40) Send 190Bytes
tasksClassify
AmplitudeGather
StatisticsDelete
AttributeSample(1) SendStampTime26
ClassifyAmplitudeSample(1) SendStamp
Time tasks, or31 Sample(1) Send tasks38
Wait StampTime
MemoryStats
NextHop Send task1 Network Monitoring
tasksn Sensing Application
(…on Tmote Sky motes)
15
Overview of Networking Subsystem
Tasking System Networking Subsystem
TaskingLanguage
TaskParser
Tasklets and Runtime
Tenet System
■ Goals• Scalability and robustness• Generality: Should support diverse application needs
ReliableTransport
RoutingTask
Dissemination
16
Task Dissemination
■ Reliably flood task from any master to all motes• Uses the master tier for dissemination
• Per-active-master cache with LRU replacement and aging
17
Reliable Transport
■ Delivering task responses from motes to masters• Works transparently across the two tiers
■ Three different types of transport mechanism for different application requirements• Best-effort delivery (least overhead)
• End-to-end reliable packet transport
• End-to-end reliable stream transport
18
Putting it all together…
19
Application Case Study: PEG
■ Goal• Compare performance with an
implementation that performs in-mote multi-node fusion
■ Pursuit-Evasion Game• Pursuers (robots) collectively
determine the location of evaders, and try to corral them.
20
Mote-PEG vs. Tenet-PEG
Pursuer
Evader Detected
Re-task the motesTask the motes
Evader
Pursuer
Evader Detected
Evader
Leader Election
Leader
Mote-PEGTenet-PEG
21
Error in Position Estimate Reporting Message Overhead
PEG Results-1
0
0.1
0.2
0.3
0.4
0.5
Fra
ctio
n of
Rep
orts
0 1 2 3 4 5 6
Positional Error
Mote-PEGTenet-PEG
Comparable positional estimate error
Comparable reporting message overhead
0
50
100
150
200
250
300
350
400
msg
/min
Mote-PEG Tenet-PEG
minavgmax
22
PEG Results-2
Latency is nearly identical
A Tenet implementation of an application can perform as well as an implementation with
in-mote collaborative fusion
23
NW
Real-world Tenet deployment on Vincent Thomas Bridge
570 ft
120 ft
30 ft
Mote
Master
Ran successfully for 24 hours100% reliable data deliveryDeployment time: 2.5 hours
Total sensor data received: 860 MB
24
Interesting Observations
Fundamental modeagrees with previouslypublished measurement
Faulty sensor!
Consistent modesacross sensors
25
Related Work
■ Architecture• SNA [Culler,`05], [Polastre,`05], Internet [Saltzer, `84], …
■ Virtual Machine• Mate [Levis,`02], …
■ Tasking Library• VanGo [Greenstein,`06], SNACK [Greenstein,`04]
■ Task Dissemination• Deluge [Hui,`04], Trickle [Levis,`04], …
■ Reliable Transport• RMST [Stann,`03], Wisden [Xu,`04], …
■ Routing• ESS [Guy,`06], Centroute [Stathopoulos,`05], …
26
Conclusion
ApplicationsSimplifies application development
Networking SubsystemRobust and scalable network
Tasking SubsystemRe-usable generic mote tier
Simple, generic and re-usable system
27
Software Available Soon…
■ Master tier• Cygwin
• Linux Fedora Core 3
• Stargate
■ Mote tier• TelosB
• MicaZ
http://tenet.usc.edu
Thank you!