Getting Things Done on Computational RFIDs with Energy-Aware - - PowerPoint PPT Presentation

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Getting Things Done on Computational RFIDs with Energy-Aware - - PowerPoint PPT Presentation

Jun 23, 2023 193 likes •556 views

HotPower 08 Getting Things Done on Computational RFIDs with Energy-Aware Checkpointing and Voltage-Aware Scheduling Benjamin Ransford , Shane Clark, Mastooreh Salajegheh, Kevin Fu Department of Computer Science University of

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SLIDE 1

Getting Things Done ☑

  • n Computational RFIDs

with Energy-Aware Checkpointing and Voltage-Aware Scheduling

Benjamin Ransford, Shane Clark, Mastooreh Salajegheh, Kevin Fu Department of Computer Science University of Massachusetts Amherst

HotPower ’08

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SLIDE 2

HotPower ’08 — Ben Ransford —

Scenario: RFID Sensor Network

2 Photos: Impinj, M. W. Moss Ltd., reinforcedearth.com

  • Maintenance-free
  • Batteryless nodes
  • RF power harvesting
  • Try to do public-key

crypto.

[HotNets ’08]

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SLIDE 3

HotPower ’08 — Ben Ransford —

Scenario: RFID Sensor Network

2 Photos: Impinj, M. W. Moss Ltd., reinforcedearth.com

  • Maintenance-free
  • Batteryless nodes
  • RF power harvesting
  • Try to do public-key

crypto.

[HotNets ’08]

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SLIDE 4

HotPower ’08 — Ben Ransford —

Scenario: RFID Sensor Network

2 Photos: Impinj, M. W. Moss Ltd., reinforcedearth.com

  • Maintenance-free
  • Batteryless nodes
  • RF power harvesting
  • Try to do public-key

crypto.

[HotNets ’08]

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SLIDE 5

HotPower ’08 — Ben Ransford —

The next 15 minutes

  • 1. Batteryless computing with

computational RFID (CRFID)

  • 2. Obstacles to computing on harvested energy
  • Fluctuating supply, power loss
  • 3. Mementos: s/w for getting things done
  • Checkpointing, program reordering

3

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SLIDE 6

HotPower ’08 — Ben Ransford —

Batteries constrain design.

Big & heavy relative to circuits. Must be replaced or recharged. Energy density slooooowly increasing.

(1991: 204 Wh/l ... 2005: 514 Wh/l)

photos: Duracell, Micro-Tools.com, Crossbow 4

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SLIDE 7

HotPower ’08 — Ben Ransford —

How can we do useful computation without a battery?

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SLIDE 8

HotPower ’08 — Ben Ransford —

How can we do useful computation without a battery?

Focus on energy harvesting.

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SLIDE 9

HotPower ’08 — Ben Ransford —

Perils of RF harvesting

  • Devices become dependent on energy supply
  • Unpredictable supply
  • Fluctuating voltage
  • Frequent loss of power/state

6 Photo: Lois Elling

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SLIDE 10

HotPower ’08 — Ben Ransford —

Today’s batteryless computers

Photos: thisismoney.co.uk, TI

must finish in one energy lifecycle non-programmable circuitry

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smart card RFID tag

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SLIDE 11

HotPower ’08 — Ben Ransford —

Computational RFID

  • Modern ultra-low-power (1.5µA sleep, 600µA

active) programmable microcontroller

  • von Neumann architecture
  • RAM, flash memory

e.g. (new term) WISP No battery... RF harvesting.

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[IEEE TIM ’08]

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SLIDE 12

HotPower ’08 — Ben Ransford —

Computational RFID

  • Modern ultra-low-power (1.5µA sleep, 600µA

active) programmable microcontroller

  • von Neumann architecture
  • RAM, flash memory

e.g. (new term) WISP No battery... RF harvesting.

8

[IEEE TIM ’08]

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SLIDE 13

HotPower ’08 — Ben Ransford —

Reader

Power + Query Static ID

0x3C6B23A4

RFID: Computational RFID:

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SLIDE 14

HotPower ’08 — Ben Ransford —

Reader

Power + Query Static ID

0x3C6B23A4

Reader

Power + Query Results of computation or sensing

0x1234CAFE

RFID: Computational RFID:

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SLIDE 15

HotPower ’08 — Ben Ransford —

Perils of RF harvesting

  • Devices become dependent on energy supply
  • Unpredictable supply
  • Fluctuating voltage
  • Frequent loss of power/state

10 Photo: Lois Elling

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SLIDE 16

HotPower ’08 — Ben Ransford —

Perils of RF harvesting

  • Devices become dependent on energy supply
  • Unpredictable supply
  • Fluctuating voltage
  • Frequent loss of power/state

10 Photo: Lois Elling

We can address these.

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SLIDE 17

HotPower ’08 — Ben Ransford —

Getting things done

Major goal: help programs on CRFIDs make forward progress despite fluctuating voltage and constant interruption.

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SLIDE 18

HotPower ’08 — Ben Ransford —

Our system: Mementos

  • Designed to aid forward progress.
  • Execution checkpointing (suspend, resume)
  • Program reordering

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SLIDE 19

HotPower ’08 — Ben Ransford —

Our system: Mementos

  • Designed to aid forward progress.
  • Execution checkpointing (suspend, resume)
  • Program reordering

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  • Frequent loss of power/state
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SLIDE 20

HotPower ’08 — Ben Ransford —

Our system: Mementos

  • Designed to aid forward progress.
  • Execution checkpointing (suspend, resume)
  • Program reordering

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  • Frequent loss of power/state
  • Fluctuating voltage
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SLIDE 21

HotPower ’08 — Ben Ransford —

Checkpointing

  • Idea: save state to flash before dying
  • Problem: flash writes consume significant

energy when it’s least available.

  • Flash vs. register: 400x more energy
  • Flash vs. memory: 40x more energy

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  • Frequent loss of power/state
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SLIDE 22

HotPower ’08 — Ben Ransford —

Checkpointing

  • Compile time static analysis:
  • Compute per-block energy estimates
  • Run time:
  • CRFID checks own voltage
  • Dynamic checkpointing decision

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SLIDE 23

HotPower ’08 — Ben Ransford —

Energy estimation

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Platform-specific energy profile Annotated instruction stream at compile time

label1: MOV R11, R12 1 nJ ADD R12, R8 1 nJ (Flash write) 461 nJ JMP label2

  • ...

...

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SLIDE 24

HotPower ’08 — Ben Ransford —

e.g.: modexp

  • Halve 32-bit exponent, square 32-bit base
  • No checkpointing: dies before finishing

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SLIDE 25

HotPower ’08 — Ben Ransford —

e.g.: modexp

  • Halve 32-bit exponent, square 32-bit base
  • No checkpointing: dies before finishing

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SLIDE 26

HotPower ’08 — Ben Ransford —

e.g.: modexp

  • Halve 32-bit exponent, square 32-bit base
  • No checkpointing: dies before finishing

16

  • Checkpoint halfway through:
  • Save base, exp., accumulated result

after 15 iterations; die before finishing

  • Restore from checkpoint; 17 more

iterations; complete.

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SLIDE 27

HotPower ’08 — Ben Ransford —

Program reordering

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  • Observations:
  • Some operations require higher voltage
  • Voltage tends to decline during each

device lifecycle

  • Microcontrollers don’t like continuously

varying voltage (PLL logic limitations)

  • Fluctuating voltage
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SLIDE 28

HotPower ’08 — Ben Ransford —

Program reordering

  • Static analysis at compile time
  • Estimate energy requirements
  • Derive dependency graph
  • Must not violate program semantics!

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SLIDE 29

HotPower ’08 — Ben Ransford —

Program reordering

  • Voltage declines: reorder independent code

chunks at compile time to execute high-V

  • ps when voltage is high

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  • Min. Required Voltage
  • Min. Required Voltage

Before After Flash write block

I1 I2 I3 I4 I5 I4 I1 I2 I3 I5

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SLIDE 30

HotPower ’08 — Ben Ransford —

Program reordering

  • Smaller timescale: adaptively reschedule

program chunks at run time to avoid logjams

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Voltage Run queue

{

These never get to run!

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SLIDE 31

HotPower ’08 — Ben Ransford —

Challenges

  • Predicting program behavior is hard.
  • Balance checkpointing behavior:
  • How much state to save
  • How often to checkpoint
  • Program reordering:
  • Finding dependencies can be hard

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SLIDE 32

HotPower ’08 — Ben Ransford —

Physical barriers

  • Can’t harvest RF energy at arbitrary

distances (current prototypes: ≤ 10 m)

  • Diode drop limits energy harvesting

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SLIDE 33

HotPower ’08 — Ben Ransford —

CRFID applications

  • Medical implants [Oakland ’08]
  • RFID Sensor Networks [HotNets ’08]
  • Computation in inaccessible locations.

fragile hazardous

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SLIDE 34

HotPower ’08 — Ben Ransford —

Future developments

  • Our work:
  • Fully implement checkpointing, reordering
  • Device profiling
  • CRFIDs:
  • Intel Research competition

(Google intel wisp challenge)

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SLIDE 35

HotPower ’08 — Ben Ransford —

Summary

  • Computational RFIDs: general-purpose

batteryless computers

  • Mementos for forward progress
  • Checkpointing to cope with constant

power interruptions

  • Program reordering to cope with

fluctuating voltage

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SLIDE 36

HotPower ’08 — Ben Ransford —

Applications? Challenges? Alternatives?

ransford@cs.umass.edu

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