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Implementing Software on Resource-Constrained Mobile Sensors: Experience with Impala and ZebraNet

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Implementing software on resource constrained mobile sensors experience with impala and zebranet l.jpg

Implementing Software on Resource-Constrained Mobile Sensors: Experience with Impala and ZebraNet

Ting Liu

Christopher M. Sadler

Pei Zhang

Margaret Martonosi

Depts. Of Electrical Engineering and Computer Science

Princeton University


Slide2 l.jpg

ZebraNet: Fusing Mobile Computing and Sensor Systems

Tracking node with CPU, FLASH, radio and GPS

Data

Store-and-forward communications

Data

Base station (car or plane)

Data

Data


Slide3 l.jpg

Applications

Impala

Hardware

Middle ground

Software Design Rationales

Question One: System Layering

Single

Software System

Layer 6

Layer 5

Layer 4

Layer 3

Layer 2

Layer 1

Monolithic approach:

Layered approach:

Software modularity

Layering overhead


Slide4 l.jpg

Applications

Impala

Hardware

Middle ground

Software Design Rationales

Question Two: Middleware Weight

Applications

Applications

Super-middleware

Mini-Middleware

Hardware

Hardware

Limited services:

Overloaded services:

application simplicity

Middleware overhead


Slide5 l.jpg

Impala Overview

Application modularity, simplicity, adaptivity and repairability

Adapter

Updater

Operation

Scheduler

Event

Filter

Network

Support

  • Software adaptation for sensor network performance

  • Software update for sensor network deployment

  • Operation scheduling for regular operations

  • Event handling for irregular events

  • Network support for sensor network communications


Slide6 l.jpg

This Paper

Application modularity, simplicity, adaptivity and repairability

Adapter

Updater

Operation

Scheduler

Event

Filter

Network

Support

PPoPP 2003:

This Paper:

Operation, event, network

Adaptation and update

Implemented on ZebraNet node

Prototyped on iPAQs


Roadmap l.jpg

Roadmap

  • Hardware design and constraints

  • Problem 1: Complex hardware realities Solution: Layers and interfaces

  • Problem 2: Miscellaneous system activities Solution: Operation scheduling and event handling

  • Problem 3: Special communication needs Solution: Messages models

  • Problem 4: Limited communication resources Solution: Networking strategies

  • Conclusions


Hardware design and constraints l.jpg

Microcontroller

TI MSP430F149

16-bit RISC

2KB RAM

60KB ROM

8MHz/32KHz dual clock

FLASH

ATMEL AT45DB041B

4Mbit

78 days data capacity

SPI

667Kbps

USART

38.4Kbps

Radio

MaxStream 9Xstream

902-928MHz

19.2Kbps over-the-air

0.5-1mile transmit range

GPS

µ-blox GPS-MS1E

10-20s position fix time

USART

38.4Kbps

5V

3.3V

Power supplies

Charging circuits

Solar modules

Hardware Design and Constraints

Power Measurement (4.0V applied)

  • Memory constraint

  • Energy constraint

  • Device access constraint

  • Radio packet size constraint

  • GPS sensing time constraint

  • FLASH storage constraint


Problem 1 complex hardware realities solution layers and interfaces l.jpg

Application 1

Application 2

Application 3

Application 4

Asynchronous Network Transmission

GPS Data Event Handler

Application Timer Event Handler

Protected FLASH Access

Network Packet Event Handler

Application Timer Control

Network Send Done Event Handler

System Clock Time Read

Adapter

Updater

Operation

Scheduler

Event

Filter

Network

Support

GPS Data Event

Access and Control to All Devices

Radio Packet Event

Timer Event

CPU

Radio

GPS

FLASH

Timer

WDT

Problem 1: Complex Hardware Realities Solution: Layers and Interfaces


Memory footprint of impala layers l.jpg

Memory Footprint of Impala Layers


Problem 2 misc system activities solution regular operation scheduling l.jpg

Problem 2: Misc System Activities Solution: Regular Operation Scheduling

  • GPS-aided operation synchronization

  • Prohibited simultaneous device operations

  • Non-trivial radio wake-up time

  • Potentially long GPS sensing time

  • Stringent energy budget

1

2

7

8

4

5

3

6

Networking Period

Sleep Period

GPS Sensing Period

1

5

CPU wake up/Radio, FLASH power on

GPS power on

2

6

Radio transmitting / receiving start

GPS sensing time

3

7

Network communication time

GPS power off / FLASH power on

4

8

Radio power off/FLASH power off

CPU sleep / FLASH power off


Operation scheduling overhead l.jpg

Operation Scheduling Overhead


Problem 2 misc system activities solution cont handling irregular events l.jpg

Problem 2: Misc System Activities Solution (cont.): Handling Irregular Events

Issue One: Event Abstraction

Issue Two: Concurrency

Abstract Application Events

Short / atomic hardware interrupts

Impala

Idle

Long / preemptive software events

Miscellaneous Hardware Interrupts

Issue Three: Event Prioritization

High Priority Events

Event

Handler

Event

Signaler

Low Priority Events


Problem 3 special communication needs solution message models and sessions l.jpg

Problem 3: Special Communication Needs Solution: Message Models and Sessions

  • Peer discovery or data

  • 1 to 32KB

  • One, more or unlimited destinations

  • Data from FLASH or RAM

  • Acknowledgment or not

  • Connectionless

  • Asynchronous

Sensor

data

ACK

Reliable Unicast

Sensor

Sensor

data

data

ACK

Unreliable Broadcast

Reliable Multicast


Problem 4 limited comm resources solution unified mac transport control l.jpg

Problem 4: Limited Comm Resources Solution: Unified MAC &Transport Control

  • MAC: round-robin timeslots (w/ GPS-aided time synchronization)

  • Transport control: detect packet loss and retransmit

  • Unified: reduce data copy and overhead across protocol layers

B acks packet 1-8 C acks packet 1-4 D silent

B acks packet 9-16 C acks packet 1-4 D acks packet 9-16

B acks packet 1-8 C acks packet 1-4 D acks packet 1-8

A

B

C

D

A

B

C

D

A

B

C

D

A gives up C and sends packet 9-16

A sends packet 1-8 to B, C, and D

A sends packet 1-8


Zebranet status and next steps l.jpg

ZebraNet Status and Next Steps

  • Status

    • January, 2004: 7 test collars deployed on zebras in Kenya. First data received: 1/19/2004

  • Next Steps

    • Refine collar design; switch to lower-energy GPS, merge Impala software update code into final collars


Conclusions l.jpg

Conclusions

  • Propose and implement Impala middleware model

  • Solutions for hardware constraints and app req

  • Concrete experience with real system and application

Applications

Simple layering and rich services

Impala

Hardware


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