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					                Application-Informed
                 Radio Duty-Cycling
                                        in a
               Re-taskable Multi-user
                  Sensing System


                          Omprakash Gnawali
                  Jongkeun Na and Ramesh Govindan
                                   April 15, 2009
The 8th ACM/IEEE International Conference on Information Processing in Sensor Networks
Low-power Sensornet Research

Approaches                   Systems
Application                  AppSleep, TinyDB

Network                      FPS, SPAN, GAF, ASCENT, MT, ETX,
                             Energy Routing Metrics
MAC                          S-MAC, T-MAC, B-MAC, STEM, X-MAC,
                             SCP-MAC, PAMAS, Piconet, Dozer, Koala
OS                           TinyOS Scheduler

Hardware                     Trio and Prometheus



                                                                          2

     Motivation   Overview    Task Analysis   Duty-cycling   Evaluation
                    Open Problem

• Duty-cycling system that
   – Adapts to the changing workload in a re-taskable
     sensornet
   – Supports concurrent tasks
   – Enables low latency data delivery
   – Provides reliable data delivery

• AEM simultaneously addresses these challenges


                                                                         3

     Motivation   Overview   Task Analysis   Duty-cycling   Evaluation
             Re-taskable Networks
• Deployments often serve multiple functions
• Multiple tasks
   – Sensor data collection
   – Network health monitoring

                                             James Reserve, Riverside, CA




                                                                              4

     Motivation   Overview   Task Analysis   Duty-cycling        Evaluation
                       AEM Goals
• Low duty-cycles and latency
• Supports
  – Re-tasking, concurrent tasks, reliable transport
• Robust to failures
• Transparent to applications




                                                                        5

    Motivation   Overview   Task Analysis   Duty-cycling   Evaluation
                 AEM Contributions
• Task analysis to characterize workload
• Workload information to tune duty-cycling
• Robust synchronized duty-cycling
  – Network and time synchronization failures
  – Link and network dynamics
  – Reliable data delivery
• Implementation and experimental evaluation

                                                                         6

    Motivation    Overview   Task Analysis   Duty-cycling   Evaluation
Tenet: A Re-taskable Network
                                         Applications run on masters,
                                           and masters task motes



                                             Motes process data,



                                            And return responses



                 Linear data-flow program
repeat(1s)->sample(LIGHT)->send(RELIABLE)
                                                                        7

 Motivation   Overview   Task Analysis    Duty-cycling   Evaluation
                            AEM Overview
            wait(2)repeat(10s)sample(LIGHT)send()

datasched(start=2, period=10s)

                                                                analysis Master
                                                           Task Analysis at master



                                                          Setup schedules at motes
              [on=2]                  [on=2]


                                                          Data delivery from motes

                                                 [on=2]

                         [on=2]
   [on=2]                                                                            8

            Motivation    Overview   Task Analysis   Duty-cycling    Evaluation
          Task Analysis - Key Idea
• Analyze Tenet task to infer traffic profile
• Send the profile parameters with the task
• Nodes use this information to setup duty-
  cycles


   repeat(1s)->sample(LIGHT)->send(RELIABLE)

                        Data every second

                                                                         9

     Motivation   Overview   Task Analysis   Duty-cycling   Evaluation
     Task Analysis Overview

                                                       Tenet App
 repeat(1s)->sample(LIGHT)->
   send(RELIABLE)

                                                        Analyze
 repeat(1s)->sample(LIGHT)->
   send(RELIABLE),
 offset=0x1234, period=1
                                                        Rewrite
 datasched(0x1234,1)->
   repeat(1s)->sample(LIGHT)->
   send(RELIABLE)
                                                  Disseminate

                                                                       10

Motivation   Overview   Task Analysis   Duty-cycling      Evaluation
             Periodic Collection

             repeat(1s)->sample(LIGHT)->send()


•    No start time specified
•    Periodicity – 1s
•    Data generation and processing – sample LIGHT
•    One sample per packet




                                                                      11

Motivation     Overview   Task Analysis   Duty-cycling   Evaluation
                     Task Analysis
•   Task sections
      1.   Synchronization                        wait(0x1234)->
      2.   Periodicity                            repeat(1s)->
      3.   Data generation and processing         sample(LIGHT)->
      4.   Packing                                pack(20)->
      5.   Send                                   send(RELIABLE)

•   Rewrite
    datasched(0x1234,20s)->wait(0x1234)->
      repeat(1ms)->sample(LIGHT)->..


                                                                          12

     Motivation   Overview    Task Analysis   Duty-cycling   Evaluation
                            AEM Overview
            wait(2)repeat(10s)sample(LIGHT)send()

datasched(start=2, period=10s)

                                                           Task Analysis at Master



                                                          Setup schedules at motes
              [on=2]                  [on=2]


                                                          Data delivery from motes

                                                 [on=2]

                         [on=2]
   [on=2]                                                                            13

            Motivation     Overview   Task Analysis   Duty-cycling    Evaluation
          Duty-cycling Overview
• Coordinated Sleep scheduling
  – No separate transmit or receive slots
• Two types
  – Control Schedules
     • Network sets it up
     • Routing, dissemination, time synchronization
  – Data Schedules
     • Setup in response to a task
     • Data, retx, ack
                                                                        14

    Motivation   Overview   Task Analysis   Duty-cycling   Evaluation
                  Elastic Frames
• Frame Parameters




                                                     Pkt event
  – Start time
  – Quiet time                                                   TX RXRX
• Every TX or RX
  extends the frame


                                       Radio State
• Handles Transients                                 On
  – Topology
  – Link                                             Off
  – Data
                                                                     Time
                                                                                    15

    Motivation   Overview   Task Analysis             Duty-cycling     Evaluation
                    Data Schedule
• Data Packets




                                              Radio State
   – Task response                                          On
   – Retransmissions
   – ACKs
                                                            Off
• Globally synchronous start
  time                                                            Time
• Elastic end time
• Multiple schedules possible
   – Multiple tasks

                                                                               16

      Motivation   Overview   Task Analysis   Duty-cycling        Evaluation
    Schedules Across Nodes


       C                          C


                   B              B

                                        On
A                                 A     Off
                                                                    17

Motivation   Overview   Task Analysis   Duty-cycling   Evaluation
                      Schedules on a Node
    On
Radio




                                                                              Task1
        Off
                                       Time
                                                                              Task2


                                                                         Control


                                                                      Combined

                                                                                  18

              Motivation   Overview   Task Analysis   Duty-cycling   Evaluation
                                   AEM Recap
            wait(2)periodic(10s)sample(LIGHT)send()

datasched(start=2, period=10s)

                                                                 Task Analysis



                                                              Setup Schedules
               [on=2]                  [on=2]


                                                                 Data Delivery

                                                  [on=2]

                          [on=2]
   [on=2]                                                                           19

             Motivation     Overview   Task Analysis   Duty-cycling    Evaluation
             AEM Implementation



      Tenet Applications                           Tasking Library
                                            Reliable
     Mote Tasking Library
                                           Transport            Time Platform
                                                       TRD
                                                                Sync Drivers
  AEM: Transport
Reliable Task Analysis/Rewrite              Routing
                          Time
                    TRD
                          Sync
     Routing
Reliable Transport                           AEM: Control/Data Frames
                          Time
                    TRD
                          Sync
     Routing

                                                                                20

      Motivation   Overview      Task Analysis   Duty-cycling      Evaluation
                       Evaluation
• Test if AEM meets its design goals
• Experiments on a testbed demonstrate
  – Low duty-cycle and latency
  – Supports Tenet features
     • dynamic workloads
     • End-to-end reliable transport
  – Robustness

             100% data delivery in all experiments

                                                                        21

    Motivation   Overview   Task Analysis   Duty-cycling   Evaluation
                   Experiment Setup
•   40 Tmotes on Tutornet
•   One master
•   Up to 4-hop paths
•   Comparisons with BoX-MAC (LPL)
    – Default settings
• Typical task
    – repeat(2mins)->sample(LIGHT)->send(RELIABLE)



                                                                          22

      Motivation   Overview   Task Analysis   Duty-cycling   Evaluation
    Duty-cycle Performance




                    Low duty-cycle with AEM                         23

Motivation   Overview   Task Analysis   Duty-cycling   Evaluation
     Dynamic Task Insertion
                 Task1        Task2       Task1          Task2
                 inject       inject      stop           stop




              AEM adapts to dynamic workload                             24

Motivation   Overview     Task Analysis   Duty-cycling      Evaluation
                  Robustness
                         Task                 20 nodes
                                              deactivated




                 AEM is robust to network failures                  25

Motivation   Overview   Task Analysis   Duty-cycling   Evaluation
                  Conclusion
• Application-informed Energy Management
  – Transparently tailors duty-cycling to applications
  – Supports Tenet features such as dynamic tasking
    and reliable transport
  – No low-level knobs or static assumptions
• Future directions
  – Batched workloads
  – Ultra-low radio duty-cycles
  – Energy-management of other resources
                                                         26

				
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