system architecture of networked sensor platforms and sensor networks applications

System Architecture of Networked Sensor Platforms

andSensor Networks Applications

Wireless sensor networksWireless sensor networks (WSN) consists of group of sensor (WSN) consists of group of sensor

nodes to perform distributed sensing task using wireless nodes to perform distributed sensing task using wireless

medium.medium.

CharacteristicsCharacteristics- low-cost, low-power, lightweight- low-cost, low-power, lightweight

- densely deployed- densely deployed

- prone to failures- prone to failures

- two ways of - two ways of deploymentdeployment: randomly, pre-determined or engineered: randomly, pre-determined or engineered

ObjectivesObjectives-- Monitor activitiesMonitor activities- Gather and fuse information- Gather and fuse information

- Communicate with global data processing unit- Communicate with global data processing unit

Introduction

– Recent sensor networks research involves almost all the layers and can Recent sensor networks research involves almost all the layers and can

be categorized into the following three aspects: be categorized into the following three aspects: [Akyildiz+2002, [Akyildiz+2002,

Elson+2002]:Elson+2002]:

Energy Efficiency: Energy Efficiency:

small devices, limited amount of energy, essential to prolong system small devices, limited amount of energy, essential to prolong system

lifetimelifetime

Scalability: Scalability:

deployment of thousands of sensor nodes, low-costdeployment of thousands of sensor nodes, low-cost

Locality: Locality:

smallest networks cannot depend on having global statessmallest networks cannot depend on having global states

Introduction

– Traditional mechanisms of exploring the network (analysis and Traditional mechanisms of exploring the network (analysis and

simulation) are not satisfied for exploring such a large-scale, dynamic simulation) are not satisfied for exploring such a large-scale, dynamic

and resource-constrained networks due to their difficulties to modeling and resource-constrained networks due to their difficulties to modeling

every aspect of the system as a wholeevery aspect of the system as a whole

– For example, energy consumption model of the hardware platforms, For example, energy consumption model of the hardware platforms,

including sensing, computation and communication, is not fully including sensing, computation and communication, is not fully

considered and overly-simplified assumptions have been madeconsidered and overly-simplified assumptions have been made

– Application-specific property of WSN makes the existing research Application-specific property of WSN makes the existing research

mechanisms even harder to obtain meaningful results mechanisms even harder to obtain meaningful results

– Therefore, the demand to build a platform is increasing; e.g., Berkeley’s Therefore, the demand to build a platform is increasing; e.g., Berkeley’s

motes and MANTISmotes and MANTIS

Why Sensor Platforms?

– Compared to analysis and simulation techniques, designing a system Compared to analysis and simulation techniques, designing a system

platform has the following advantages:platform has the following advantages:

Provides genuine executive environment: various proposed Provides genuine executive environment: various proposed

algorithms can be exactly evaluated; good way to examine existing algorithms can be exactly evaluated; good way to examine existing

design principles and discover new ones under different design principles and discover new ones under different

configurationsconfigurations

More attention can be focused on the application-layerMore attention can be focused on the application-layer

A real system platform can accelerate the pace of research and A real system platform can accelerate the pace of research and

developmentdevelopment

Why Sensor Platforms?

– Constructing a platform for WSN falls into the area of embedded system Constructing a platform for WSN falls into the area of embedded system

development which usually consists of developing environment, development which usually consists of developing environment,

hardware and software platforms.hardware and software platforms.

1.1. Hardware PlatformHardware Platform

Consists of the following four components:Consists of the following four components:

a) Processing Unita) Processing Unit

Associates with small storage unit (tens of kilo bytes order) and Associates with small storage unit (tens of kilo bytes order) and

manages the procedures to collaborate with other nodes to carry out themanages the procedures to collaborate with other nodes to carry out the

assigned sensing taskassigned sensing task

b) Transceiver Unitb) Transceiver Unit

Connects the node to the network via various possible transmissionConnects the node to the network via various possible transmission

medias such as infra, light, radio and so onmedias such as infra, light, radio and so on

General WSN System Architecture


c) Power Unitc) Power Unit

Supplies power to the system by small size batteries which makes the Supplies power to the system by small size batteries which makes the

energy a scarce resourceenergy a scarce resource

d) Sensing Unitsd) Sensing Units

Usually composed of two subunits: sensors and analog-to-digitalUsually composed of two subunits: sensors and analog-to-digital

Converters (ADCs). The analog signal produced by the sensors areConverters (ADCs). The analog signal produced by the sensors are

converted to digital signals by the ADC, and fed into the processing unitconverted to digital signals by the ADC, and fed into the processing unit

e) Other Application Dependent Componentse) Other Application Dependent Components

Location finding system is needed to determine the location of sensor Location finding system is needed to determine the location of sensor

nodes with high accuracy; mobilizer may be needed to move sensor nodes with high accuracy; mobilizer may be needed to move sensor

nodes when it is required to carry out the tasknodes when it is required to carry out the task




Figure 1: The components of a sensor nodeFigure 1: The components of a sensor node [Akyildiz+2002][Akyildiz+2002]

2.2. Software PlatformSoftware Platform

Consists of the following four components:Consists of the following four components:

a) Embedded Operating System (EOS)a) Embedded Operating System (EOS)

Manages the hardware capability efficiently as well as supportsManages the hardware capability efficiently as well as supports

concurrency-intense operations. Apart from traditional OS tasks such asconcurrency-intense operations. Apart from traditional OS tasks such as

processor, memory and I/O management, it must be real-time to rapidlyprocessor, memory and I/O management, it must be real-time to rapidly

respond the hardware triggered events, multi-threading to handle respond the hardware triggered events, multi-threading to handle

concurrent flows concurrent flows

b) Application Programming Interface (API)b) Application Programming Interface (API)

A series of functions provided by OS and other system-level components A series of functions provided by OS and other system-level components

for assisting developers to build applications upon itselffor assisting developers to build applications upon itself



c) Device Driversc) Device Drivers

A series of routines that determine how the upper layer entities A series of routines that determine how the upper layer entities

communicate with the peripheral devicescommunicate with the peripheral devices

d) Hardware Abstract Layer (HAL)d) Hardware Abstract Layer (HAL)

Intermediate layer between the hardware and the OS. Provides uniformIntermediate layer between the hardware and the OS. Provides uniform

interfaces to the upper layer while its implementation is highly dependentinterfaces to the upper layer while its implementation is highly dependent

on the lower layer hardware. With the use of HAL, the OS and on the lower layer hardware. With the use of HAL, the OS and

applications easily transplant from one hardware platform to anotherapplications easily transplant from one hardware platform to another




Figure 2: The software platform for WSNFigure 2: The software platform for WSN

3.3. System Development EnvironmentSystem Development Environment

Provides various of tools for every stage of software development over Provides various of tools for every stage of software development over

the specific hardware platformthe specific hardware platform

a) Cross-Platform Developmenta) Cross-Platform Development

Generally, an embedded system unlike PC and does not have the ability Generally, an embedded system unlike PC and does not have the ability

of self-development. The final binary code run on that system, termed asof self-development. The final binary code run on that system, termed as

target system, will be generated on the PC, termed as host system, by target system, will be generated on the PC, termed as host system, by

cross-platform compilers and linkers, and download the resulted image cross-platform compilers and linkers, and download the resulted image

via the communication port onto the target systemvia the communication port onto the target system


3.3. System Development EnvironmentSystem Development Environment

Provides various of tools for every stage of software development over Provides various of tools for every stage of software development over

the specific hardware platformthe specific hardware platform

b) Debug Techniquesb) Debug Techniques

Due to the difficulties introduced by cross-platform development mode, Due to the difficulties introduced by cross-platform development mode,

the debug techniques become critical for the efficiency of software the debug techniques become critical for the efficiency of software

production. For this reason, many chips on the system provide the production. For this reason, many chips on the system provide the

on-chip debugger, such as JTAF, to reduce the development time.on-chip debugger, such as JTAF, to reduce the development time.


– Motes are tiny, self-contained, battery powered computers with radio Motes are tiny, self-contained, battery powered computers with radio

links, which enable them to communicate and exchange data with one links, which enable them to communicate and exchange data with one

another, and to self-organize into ad hoc networksanother, and to self-organize into ad hoc networks

– Motes form the building blocks of wireless sensor networksMotes form the building blocks of wireless sensor networks

– TinyOS TinyOS [TinyOS][TinyOS], component-based runtime environment, is designed to , component-based runtime environment, is designed to

provide support for these motes which require concurrency intensive provide support for these motes which require concurrency intensive

operations while constrained by minimal hardware resourcesoperations while constrained by minimal hardware resources

Berkeley Motes [Hill+ 2000]

Figure 3: Berkeley MoteFigure 3: Berkeley Mote

Hardware PlatformHardware Platform

– Consists of Consists of

o micro-controller with internal flash program memory micro-controller with internal flash program memory

o data SRAMdata SRAM

o data EEPROMdata EEPROM

o a set of actuator and sensor devices, including LEDsa set of actuator and sensor devices, including LEDs

o a low-power transceivera low-power transceiver

o an analog photo-sensoran analog photo-sensor

o a digital temperature sensora digital temperature sensor

o a serial porta serial port

o a small coprocessor unita small coprocessor unit




Figure 4: The schematic for representative network sensor platformFigure 4: The schematic for representative network sensor platform


– The The processing unitprocessing unit

o MCU (ATMEL 90LS8535), an 8-bit architecture with 16-bit addressesMCU (ATMEL 90LS8535), an 8-bit architecture with 16-bit addresses

o provides 32 8-bit general registers and runs at 4 MHz and 3.0 Vprovides 32 8-bit general registers and runs at 4 MHz and 3.0 V

o has 8 KB flash as the program memory and 512 Bytes of SRAM as has 8 KB flash as the program memory and 512 Bytes of SRAM as

the data memorythe data memory

o MCU is designed such that the processor cannot write to instruction MCU is designed such that the processor cannot write to instruction

memory; the prototype uses a coprocessor to perform this functionmemory; the prototype uses a coprocessor to perform this function

o the processor integrates a set of timers and counters which can be the processor integrates a set of timers and counters which can be

configured to generate interrupts at regular time intervalsconfigured to generate interrupts at regular time intervals

o three sleep modes: three sleep modes: idleidle (shuts off the processor), (shuts off the processor), power downpower down (shuts (shuts

off everything, but the watchdog and asynchronous interrupt logic off everything, but the watchdog and asynchronous interrupt logic

necessary to wake up), necessary to wake up), power savepower save (keep asynchronous timer on) (keep asynchronous timer on)



– The The sensing unitssensing units

o contains two sub-components: photo sensor and temperature sensorcontains two sub-components: photo sensor and temperature sensor

o photo sensorphoto sensor represents an analog input device with simple control represents an analog input device with simple control

lines which eliminate power drain through the photo resistor when not lines which eliminate power drain through the photo resistor when not

in usein use

o temperature sensor temperature sensor (Analog Devices AD7418) represents a large (Analog Devices AD7418) represents a large

class of digital sensors which have internal A/D converters and class of digital sensors which have internal A/D converters and

interface over a standard chip-to-chip protocol (the synchronous two-interface over a standard chip-to-chip protocol (the synchronous two-

wire Iwire I22C protocol with software on the micro-controller synthesizing C protocol with software on the micro-controller synthesizing

the Ithe I22C master over general I/O pins. There is no explicit arbiter and C master over general I/O pins. There is no explicit arbiter and

bus negotiations are carried out by the software on the micro-bus negotiations are carried out by the software on the micro-

controllercontroller



– The The transceiver unittransceiver unit

o consist of an RF Monolithics 916.50 MHz transceiver (TR1000), consist of an RF Monolithics 916.50 MHz transceiver (TR1000),

antenna, and a collection of discrete components to configure the antenna, and a collection of discrete components to configure the

physical layer characteristics such as signal strength and sensitivityphysical layer characteristics such as signal strength and sensitivity

o operates in an ON-OFF key mode at speeds up to 19.2 Kbpsoperates in an ON-OFF key mode at speeds up to 19.2 Kbps

o control signals configure the radio to operate in either transmit, control signals configure the radio to operate in either transmit,

receive, or power-off modereceive, or power-off mode

o the radio contains no buffering, so each bit must be serviced by the the radio contains no buffering, so each bit must be serviced by the

controller on timecontroller on time

o the transmitted value is not latched by the radio, so the jitter at the the transmitted value is not latched by the radio, so the jitter at the

radio input is propagated into the transmission signalradio input is propagated into the transmission signal



– The The transceiver unittransceiver unit is an Energizer CR2450 lithium battery rated at is an Energizer CR2450 lithium battery rated at

575 mAh575 mAh

– The The other auxiliary other auxiliary components include:components include:

The coprocessorThe coprocessor

o represents a synchronous bit-level device with byte-level supportrepresents a synchronous bit-level device with byte-level support

o MCU (AT09LS2343, with 2KB instruction memory, 128 bytes of MCU (AT09LS2343, with 2KB instruction memory, 128 bytes of

SRAM and EEPROM) that uses I/O pins connected to an SPI SRAM and EEPROM) that uses I/O pins connected to an SPI

controller where SPI is a synchronous serial data link, providing high controller where SPI is a synchronous serial data link, providing high

speed full-duplex connections (up to 1 Mbit) between peripheralsspeed full-duplex connections (up to 1 Mbit) between peripherals

o the sensor can be reprogrammed by transferring data from the the sensor can be reprogrammed by transferring data from the

network into the coprocessor’s 256 KB EEPROM (24LC256)network into the coprocessor’s 256 KB EEPROM (24LC256)

o can be used as a gateway to extra storage by the main processorcan be used as a gateway to extra storage by the main processor




The serial portThe serial port

o represents a synchronous bit-level device with byte-level controller represents a synchronous bit-level device with byte-level controller

supportsupport

o uses I/O pins that are connected to an internal UART controlleruses I/O pins that are connected to an internal UART controller

o in transmit mode, the UART takes a byte of data and shifts it out in transmit mode, the UART takes a byte of data and shifts it out

serially at a specified intervalserially at a specified interval

o in receive mode, it samples the input pin for a transition and shifts in in receive mode, it samples the input pin for a transition and shifts in

bits at a specified interval from the edgebits at a specified interval from the edge

o interrupts are triggered in the processor to signal completion of the interrupts are triggered in the processor to signal completion of the

eventsevents




Three LEDsThree LEDs

o represent outputs connected through general I/O ports; they may be represent outputs connected through general I/O ports; they may be

used to display digital values or statusused to display digital values or status

Software PlatformSoftware Platform

– based on Tiny Micro-Threading Operating System (TinyOS) which is based on Tiny Micro-Threading Operating System (TinyOS) which is

designed for resource-constrained MEMS sensorsdesigned for resource-constrained MEMS sensors

– TinyOS adopts an event model so that high levels of concurrency can be TinyOS adopts an event model so that high levels of concurrency can be

handled in a small amount of spacehandled in a small amount of space

– A stack-based threaded approach would require that stack space be A stack-based threaded approach would require that stack space be

reserved for each execution contextreserved for each execution context

Berkeley Motes [Hill+ 2000, TinyOS]


– A complete system configuration consists of a tiny A complete system configuration consists of a tiny schedulerscheduler and a graph and a graph

of of componentscomponents

– A component has four interrelated parts: a set of A component has four interrelated parts: a set of

o a set of command handlersa set of command handlers

o a set of event handlersa set of event handlers

o an encapsulated fixed-size framean encapsulated fixed-size frame

o Bundle of simple tasksBundle of simple tasks

– tasks, commands and event handlers execute in the context of the frame tasks, commands and event handlers execute in the context of the frame

and operate on its stateand operate on its state

– each component declares the commands it uses and the events it signalseach component declares the commands it uses and the events it signals

– these declarations are used to compose the modular components in a these declarations are used to compose the modular components in a

per-application configurationper-application configuration



– the composition process creates layers of components where higher-level the composition process creates layers of components where higher-level

components issue commands to lower-level components and lower-level components issue commands to lower-level components and lower-level

components signal events to the higher-level componentscomponents signal events to the higher-level components

FramesFrames

– fixed-size and statistically allocated which allows us to know memory fixed-size and statistically allocated which allows us to know memory

requirements of a component at a compile time -- prevents overhead requirements of a component at a compile time -- prevents overhead

associated with dynamic allocationassociated with dynamic allocation

CommandsCommands

– non-blocking requests made to lower level componentsnon-blocking requests made to lower level components

– typically, a command will deposit request parameters into its frame and typically, a command will deposit request parameters into its frame and

conditionally post a task for later executionconditionally post a task for later execution



CommandsCommands

– can invoke lower commands, but it must not wait for longcan invoke lower commands, but it must not wait for long

– must provide feedback to its caller by returning status indicating whether it must provide feedback to its caller by returning status indicating whether it

was successful or notwas successful or not

Event handlersEvent handlers

– Invoked to deal with hardware events, either directly or indirectlyInvoked to deal with hardware events, either directly or indirectly

– The lowest level components have handlers connected directly to The lowest level components have handlers connected directly to

hardware interrupts which may be external interrupts, timer events, or hardware interrupts which may be external interrupts, timer events, or

counter eventscounter events

– An event handler can deposit information into its frame, post tasks, signal An event handler can deposit information into its frame, post tasks, signal

higher level events or call lower level commandshigher level events or call lower level commands



Event handlersEvent handlers

– in order to avoid cycles in the command/event chain, commands cannot in order to avoid cycles in the command/event chain, commands cannot

signal eventssignal events

– both signals and events are intended to perform a small, fixed amount of both signals and events are intended to perform a small, fixed amount of

work, which occurs within the context of their component’s statework, which occurs within the context of their component’s state

TasksTasks

– perform the primary workperform the primary work

– atomic entities with respect to other tasks, run to completion and can be atomic entities with respect to other tasks, run to completion and can be

preempted by eventspreempted by events

– can call lower level commands, signal higher level events, and schedule can call lower level commands, signal higher level events, and schedule

other tasks within a componentother tasks within a component



TasksTasks

– run-to-completion semantics make it possible to allocate a single stack run-to-completion semantics make it possible to allocate a single stack

that is assigned to the currently executing task which is essential in that is assigned to the currently executing task which is essential in

memory constrained systemsmemory constrained systems

– allows to simulate concurrency within each component, since tasks allows to simulate concurrency within each component, since tasks

execute asynchronously with respect to the eventsexecute asynchronously with respect to the events

– must never block or spin wait, otherwise, they will prevent progress in must never block or spin wait, otherwise, they will prevent progress in

other componentsother components

Task schedulerTask scheduler

– Utilizes a bounded size scheduling data structure to schedule various Utilizes a bounded size scheduling data structure to schedule various

tasks base on FIFO, priority-based or deadline-based policy which is tasks base on FIFO, priority-based or deadline-based policy which is

dependent on the requirements of the applicationdependent on the requirements of the application




Figure 5: The schematic for the architecture of TinyOSFigure 5: The schematic for the architecture of TinyOS

– MANTISMANTIS ( (MMultimodultimodAAl system for l system for NNeeTTworks of works of IIn-situ wireless n-situ wireless SSensors) ensors)

provides a new multi-threaded embedded operating system integrated provides a new multi-threaded embedded operating system integrated

with a general-purpose single-board hardware platform to enable flexible with a general-purpose single-board hardware platform to enable flexible

and rapid prototyping of wireless sensor networksand rapid prototyping of wireless sensor networks

– the key design goals of MANTIS are the key design goals of MANTIS are

o ease of useease of use, i.e., a small learning curve that encourages novice , i.e., a small learning curve that encourages novice

programmers to rapidly prototype sensor applicationsprogrammers to rapidly prototype sensor applications

o flexibilityflexibility such that expert researchers can continue to adapt and such that expert researchers can continue to adapt and

extend the hardware/software system to suit the needs of advanced extend the hardware/software system to suit the needs of advanced

researchresearch

MANTIS [Abrach+ 2003]

– MANTIS OS is called MOSMANTIS OS is called MOS

o MOS selects its model as classical structure of layered multi-MOS selects its model as classical structure of layered multi-

threaded operating systems which includes multi-threading, threaded operating systems which includes multi-threading,

preemptive scheduling with time slicing, I/O synchronization via preemptive scheduling with time slicing, I/O synchronization via

mutual exclusion, a standard network stack, and device driversmutual exclusion, a standard network stack, and device drivers

o MOS choose a standard programming language that the entire MOS choose a standard programming language that the entire

kernel and API are written in standard C. This design choice not only kernel and API are written in standard C. This design choice not only

almost eliminates the learning curve, but also accrues many of the almost eliminates the learning curve, but also accrues many of the

other benefits of a standard programming language, including cross-other benefits of a standard programming language, including cross-

platform support and reuse of a vast legacy code base. C also eases platform support and reuse of a vast legacy code base. C also eases

development of cross-platform multimodal prototyping environments development of cross-platform multimodal prototyping environments

on X86 PCson X86 PCs



– MANTIS hardware nymph’s design was inspired by the Berkeley MICA an MANTIS hardware nymph’s design was inspired by the Berkeley MICA an

MICA2 Mote architectureMICA2 Mote architecture

– MANTIS Nymph is a single-board design, incorporating the micro-MANTIS Nymph is a single-board design, incorporating the micro-

controller, analog sensor ports, RF communication, EEPROM, and serial controller, analog sensor ports, RF communication, EEPROM, and serial

ports on one dual-layer 3.5 x 5.5 cm printed circuit boardports on one dual-layer 3.5 x 5.5 cm printed circuit board

– the Nymph is centered around the AMTEL ATmega128(L) MCU, including the Nymph is centered around the AMTEL ATmega128(L) MCU, including

interfaces for two UARTs, an SPI bus, an Iinterfaces for two UARTs, an SPI bus, an I22C bus, and eight analog-to-C bus, and eight analog-to-

digital converter channels. It provides additional 64KB EEPROM external digital converter channels. It provides additional 64KB EEPROM external

to MCU in addition to 4KB EEPROM included in MCUto MCU in addition to 4KB EEPROM included in MCU

– the unit is powered either by batteries or an AC adapter, and a set of three the unit is powered either by batteries or an AC adapter, and a set of three

on-board LEDs are included to aid in the debugging process. It is designed on-board LEDs are included to aid in the debugging process. It is designed

to hold a 24mm diameter lithium ion coin cell battery (CR2477), but any to hold a 24mm diameter lithium ion coin cell battery (CR2477), but any

battery in the range of 1.8V to 3.6V can be connectedbattery in the range of 1.8V to 3.6V can be connected



– in order to facilitate rapid prototyping in research environment, the Nymph in order to facilitate rapid prototyping in research environment, the Nymph

has solderless plug connections for both analog and digital sensors, which has solderless plug connections for both analog and digital sensors, which

eliminates the external sensor board for many applicationseliminates the external sensor board for many applications

– each connector provides lines for ground, power and sensor signal, each connector provides lines for ground, power and sensor signal,

allowing basic sensors such as photo sensors or complex devices such allowing basic sensors such as photo sensors or complex devices such

as infrared an ultra sounds receivers to be connected easilyas infrared an ultra sounds receivers to be connected easily

– the Chipcon CC1000 radio was chosen to handle wireless the Chipcon CC1000 radio was chosen to handle wireless

communication. It supports four carrier frequency bands (315, 433, 868, communication. It supports four carrier frequency bands (315, 433, 868,

and 915 MHz) and allows for frequency hopping which is useful for multi-and 915 MHz) and allows for frequency hopping which is useful for multi-

channel communication. It is one of the lowest power commercial radios channel communication. It is one of the lowest power commercial radios

and allows MOS to optimize the radio to further reduce the power and allows MOS to optimize the radio to further reduce the power

consumptionconsumption



– for additional modules, the Nymph includes JTAG interface which allows for additional modules, the Nymph includes JTAG interface which allows

the user to easily download code to the hardware. This addition eliminates the user to easily download code to the hardware. This addition eliminates

a need for separate programming board, simplifying the process of a need for separate programming board, simplifying the process of

reprogramming the nodes while reducing the cost of overall system. As reprogramming the nodes while reducing the cost of overall system. As

added benefit, the JTAG port allows the user to single-step through code added benefit, the JTAG port allows the user to single-step through code

on the MCU and also supports the remote shellon the MCU and also supports the remote shell

– the Nymph uses one of the UARTs to supply a serial port (RS232) for the Nymph uses one of the UARTs to supply a serial port (RS232) for

connection to a PC while the second one is used as an interface to the connection to a PC while the second one is used as an interface to the

optional GPS unitoptional GPS unit

– MAX3221 RS232 serial chip is used and may be set in three different MAX3221 RS232 serial chip is used and may be set in three different

power saving modes: power-down, receive only and shut downpower saving modes: power-down, receive only and shut down




Figure 6: MANTIS NymphFigure 6: MANTIS Nymph


– MANTIS OS (MOS) adheres to classical layered multi-threaded designMANTIS OS (MOS) adheres to classical layered multi-threaded design

– top application and API layers show a simple C API which promotes the top application and API layers show a simple C API which promotes the

ease of use, cross-platform portability, and reuse of a large installed code ease of use, cross-platform portability, and reuse of a large installed code

basebase

– in lower layers of MOS, it adapts the classical OS structures to achieve in lower layers of MOS, it adapts the classical OS structures to achieve

small memory footprintsmall memory footprint

System APIsSystem APIs

– MANTIS provides comprehensive System APIs for I/O and system MANTIS provides comprehensive System APIs for I/O and system

interactioninteraction

– the choice of C language API simplifies cross-platform support and the the choice of C language API simplifies cross-platform support and the

development of a multimodal prototyping environmentdevelopment of a multimodal prototyping environment



System APIsSystem APIs

– since MANTIS System API is preserved across both physical sensor since MANTIS System API is preserved across both physical sensor

nodes as well as virtual sensor nodes running on X86 platforms, the same nodes as well as virtual sensor nodes running on X86 platforms, the same

C code developed for MANTIS sensor Nymphs with AMTEL MCU can be C code developed for MANTIS sensor Nymphs with AMTEL MCU can be

compiled to run on X86 PCs with little or no alterationcompiled to run on X86 PCs with little or no alteration

Kernel and SchedulerKernel and Scheduler

– design of MOS kernel resembles classical UNIX-style schedulersdesign of MOS kernel resembles classical UNIX-style schedulers

– The services provided are subset of POSIX threads, most notably priority-The services provided are subset of POSIX threads, most notably priority-

based thread scheduling with round-robin semantics within a priority levelbased thread scheduling with round-robin semantics within a priority level

– binary (mutex) and counting semaphores are also supportedbinary (mutex) and counting semaphores are also supported

– the goal of the kernel design is to implement these familiar services in an the goal of the kernel design is to implement these familiar services in an

efficient manner for resource-constrained environment of a sensor nodeefficient manner for resource-constrained environment of a sensor node



Network StackNetwork Stack

– focused on efficient use of limited memory, flexibility, and conveniencefocused on efficient use of limited memory, flexibility, and convenience

– implemented as one or more user-level threadsimplemented as one or more user-level threads

– different layers can be implemented in different threads, or all layers in the different layers can be implemented in different threads, or all layers in the

stack can be implemented in one threadstack can be implemented in one thread

– the tradeoff is between performance and flexibilitythe tradeoff is between performance and flexibility

– designed to minimize memory buffer allocation through layersdesigned to minimize memory buffer allocation through layers

– the data body for a packet is common through all layers within a threadthe data body for a packet is common through all layers within a thread

– the headers for a packet is variably-sized and are pre-pended to the single the headers for a packet is variably-sized and are pre-pended to the single

data bodydata body

– designed in a modular manner with standard APIs between each layers, designed in a modular manner with standard APIs between each layers,

thereby allowing developers easily modify or replace layer modulesthereby allowing developers easily modify or replace layer modules



Device DriversDevice Drivers

– Adopts the traditional logical/physical partitioning with respect to device Adopts the traditional logical/physical partitioning with respect to device

driver design for the hardwaredriver design for the hardware

– The application developer need not to interact with the hardware to The application developer need not to interact with the hardware to

accomplish a given taskaccomplish a given task




Figure 7: MANTIS OS ArchitectureFigure 7: MANTIS OS Architecture

System DevelopmentSystem Development

– application developers need to be able to prototype and test applications application developers need to be able to prototype and test applications

prior to distribution and physical deployment in the fieldprior to distribution and physical deployment in the field

– during deployment, in-situ sensor nodes need to be capable of being both during deployment, in-situ sensor nodes need to be capable of being both

dynamically reprogrammed and remotely debuggeddynamically reprogrammed and remotely debugged

– in order to facilitates these issues, MANTIS identifies and implements in order to facilitates these issues, MANTIS identifies and implements

three key advanced features for expert users of general-purpose sensor three key advanced features for expert users of general-purpose sensor

systemssystems

o multimodal prototyping environmentmultimodal prototyping environment

o dynamic reprogrammingdynamic reprogramming

o remote shell and commander serverremote shell and commander server



Multimodal Prototyping EnvironmentMultimodal Prototyping Environment

– Provides a framework for prototyping diverse applications across Provides a framework for prototyping diverse applications across

heterogeneous platformsheterogeneous platforms

– A key requirement of sensor systems is the need to provide a prototyping A key requirement of sensor systems is the need to provide a prototyping

environment to test sensor networking applications prior to deploymentenvironment to test sensor networking applications prior to deployment

– Postponing testing of an application until after its deployment across a Postponing testing of an application until after its deployment across a

distributed sensor network can incur severe consequencesdistributed sensor network can incur severe consequences

– MANTIS prototyping environment extends beyond simulation to provide MANTIS prototyping environment extends beyond simulation to provide

larger framework for development of network management and larger framework for development of network management and

visualization applications as virtual nodes within a MANTIS networkvisualization applications as virtual nodes within a MANTIS network

o MANTIS has property of enabling an application developer to test MANTIS has property of enabling an application developer to test

execution of the same C code on both virtual sensor nodes and later execution of the same C code on both virtual sensor nodes and later

on in-situ physical sensor nodes on in-situ physical sensor nodes




o Seamlessly integrates virtual environment with the real deployment Seamlessly integrates virtual environment with the real deployment

network such that both virtual and physical nodes can co-exit and network such that both virtual and physical nodes can co-exit and

communicate with each other in the prototyping environmentcommunicate with each other in the prototyping environment

o Permits a virtual node to leverage other APIs outside of the MANTIS Permits a virtual node to leverage other APIs outside of the MANTIS

API, e.g., a virtual node with the MANTIS API could be realized as a API, e.g., a virtual node with the MANTIS API could be realized as a

UNIX X windows application that communicates with other rendering UNIX X windows application that communicates with other rendering

or database APIs to build visualization and network management or database APIs to build visualization and network management

applicationsapplications





Figure 8: Multimodal prototyping integrates both virtual and physical sensorFigure 8: Multimodal prototyping integrates both virtual and physical sensornodes across heterogeneous X86 and AMTEL sensor platformsnodes across heterogeneous X86 and AMTEL sensor platforms


Dynamic ReprogrammingDynamic Reprogramming

– Sensor nodes should be remotely reconfigurable over a wireless multi-hop Sensor nodes should be remotely reconfigurable over a wireless multi-hop

network after being deployed in the field. Since sensor nodes may be network after being deployed in the field. Since sensor nodes may be

deployed in inaccessible areas and may scale to thousands of nodes, this deployed in inaccessible areas and may scale to thousands of nodes, this

simplifies management of the sensor networksimplifies management of the sensor network

– MOS achieves dynamic reprogramming in several granularities: re-flashing MOS achieves dynamic reprogramming in several granularities: re-flashing

the entire OS; reprogramming of a single thread; and changing of variables the entire OS; reprogramming of a single thread; and changing of variables

within a threadwithin a thread

– Another useful feature would be the ability to remotely debug a running Another useful feature would be the ability to remotely debug a running

thread. MOS provides a remote shell that enables a user to login and thread. MOS provides a remote shell that enables a user to login and

inspect the sensor node’s memoryinspect the sensor node’s memory

– MOS includes two programming modes (simpler and more advanced) in MOS includes two programming modes (simpler and more advanced) in

order to overcome the difficulty of reprogramming the networkorder to overcome the difficulty of reprogramming the network




– The The simpler programmingsimpler programming mode is similar to that used in many other mode is similar to that used in many other

systems and involves a direct communication with a specific MANTIS nodesystems and involves a direct communication with a specific MANTIS node

– On a Nymph, this would be accomplished via a serial port: the user simply On a Nymph, this would be accomplished via a serial port: the user simply

connects the node to a PC and opens the MANTIS shellconnects the node to a PC and opens the MANTIS shell

– Upon reset, MOS enters a boot loader that checks for communication from Upon reset, MOS enters a boot loader that checks for communication from

the shell. At this point, the node will accept a new code image, which is the shell. At this point, the node will accept a new code image, which is

downloaded from the PC over the direct communication linedownloaded from the PC over the direct communication line

– From the shell, the user has the ability to inspect and modify the node’s From the shell, the user has the ability to inspect and modify the node’s

memory directly as well as spawn threads and retrieve debugging memory directly as well as spawn threads and retrieve debugging

information including thread status, stack fill, and other statistics from OSinformation including thread status, stack fill, and other statistics from OS

– The boot loader transfers control to the MOS kernel on command from the The boot loader transfers control to the MOS kernel on command from the

shell, or at a startup if the shell is not presentshell, or at a startup if the shell is not present




– The more The more advanced programmingadvanced programming mode is used when a node is already mode is used when a node is already

deployed, and does not require direct access to the nodedeployed, and does not require direct access to the node

– The spectrum of dynamic reprogramming of in-situ sensor networks ranges The spectrum of dynamic reprogramming of in-situ sensor networks ranges

from fine grained reprogramming to complete reprogramming from fine grained reprogramming to complete reprogramming

– MOS has a provision for reprogramming any portion of the node up to and MOS has a provision for reprogramming any portion of the node up to and

including the OS itself while the node is deployed in the fieldincluding the OS itself while the node is deployed in the field

– This is accomplished through the MOS dynamic reprogramming interfaceThis is accomplished through the MOS dynamic reprogramming interface



Remote Shell and Commander ServerRemote Shell and Commander Server

– MOS includes the MANTIS Command Server (MCS) which is MOS includes the MANTIS Command Server (MCS) which is

implemented as an application threadimplemented as an application thread

– From any device in the network equipped with a terminal, the user may From any device in the network equipped with a terminal, the user may

invoke the command server client (also referred to as the shell) and log in invoke the command server client (also referred to as the shell) and log in

to either a physical node (e.g., on a Nymph or Mica board) or a virtual node to either a physical node (e.g., on a Nymph or Mica board) or a virtual node

running as a process on a PCrunning as a process on a PC

– MCS listens on a network port for commands and replies with the results, MCS listens on a network port for commands and replies with the results,

in a manner similar to RPCin a manner similar to RPC

– The shell gains the ability to control a node remotely through MCSThe shell gains the ability to control a node remotely through MCS



Remote Shell and Commander ServerRemote Shell and Commander Server

– The user may alter the node’s configuration settings, run or kill programs, The user may alter the node’s configuration settings, run or kill programs,

display the thread table and other OS data, inspect and modify the node’s display the thread table and other OS data, inspect and modify the node’s

data memory, and call arbitrary user-defined functions data memory, and call arbitrary user-defined functions

– The shell is powerful debugging tool since it allows the user to examine The shell is powerful debugging tool since it allows the user to examine

and modify the state of any node, without requiring physical access to the and modify the state of any node, without requiring physical access to the

nodenode


IntroductionIntroduction

– Habitat and environmental monitoring represent essential class of sensor Habitat and environmental monitoring represent essential class of sensor

network applications by placing numerous networked micro-sensors in an network applications by placing numerous networked micro-sensors in an

environment where long-term data collection can be achievedenvironment where long-term data collection can be achieved

– The sensor nodes perform filtering and triggering functions as well as The sensor nodes perform filtering and triggering functions as well as

application-specific or sensor-specific data compression algorithms thru application-specific or sensor-specific data compression algorithms thru

the integration of local processing and storagethe integration of local processing and storage

– The ability to communicate allows nodes to cooperate in performing The ability to communicate allows nodes to cooperate in performing

tasks such as statistical sampling, data aggregation, and system health tasks such as statistical sampling, data aggregation, and system health

and status monitoringand status monitoring

– Increased power efficiency assists in resolving fundamental design Increased power efficiency assists in resolving fundamental design

tradeoffs, e.g., between sampling rates and battery lifetimestradeoffs, e.g., between sampling rates and battery lifetimes

Wireless Sensor Networks for Habitat Monitoring [Mainwaring+ 2002]


– The sensor nodes can be reprogrammed or retasked after deployment in The sensor nodes can be reprogrammed or retasked after deployment in

the field by the networking and computing capabilities providedthe field by the networking and computing capabilities provided

– Nodes can adapt their operation over time in response to changes in the Nodes can adapt their operation over time in response to changes in the

environmentenvironment

– The application context helps to differentiate problems with simple and The application context helps to differentiate problems with simple and

concrete solutions from open research areasconcrete solutions from open research areas

– An effective sensor network architecture and general solutions should be An effective sensor network architecture and general solutions should be

developed for the domaindeveloped for the domain

– The impact of sensor networks for habitat and environmental monitoring The impact of sensor networks for habitat and environmental monitoring

is measured by their ability to enable new applications and produce new is measured by their ability to enable new applications and produce new

resultsresults



– This paper develops a specific habitat monitoring application, but yet a This paper develops a specific habitat monitoring application, but yet a

representative of the domainrepresentative of the domain

– It presents a collection of requirements, constraints and guidelines that It presents a collection of requirements, constraints and guidelines that

serve as a basis for general sensor network architectureserve as a basis for general sensor network architecture

– It describes the core components of the sensor network for this domain– It describes the core components of the sensor network for this domain–

hardware and sensor platforms, the distinct networks involved, their hardware and sensor platforms, the distinct networks involved, their

interconnection, and the data management facilitiesinterconnection, and the data management facilities

– The design and implementation of the essential network services – The design and implementation of the essential network services –

power management, communications, re-tasking, and node management power management, communications, re-tasking, and node management

can be evaluated in this contextcan be evaluated in this context


Habitat MonitoringHabitat Monitoring

– Researchers in the Life Sciences are concerned about the impacts of Researchers in the Life Sciences are concerned about the impacts of

human presence in monitoring plants and animals in the field conditionshuman presence in monitoring plants and animals in the field conditions

– It is possible that chronic human disturbance may adversely effect results It is possible that chronic human disturbance may adversely effect results

by changing behavioral patterns or distributionsby changing behavioral patterns or distributions

– Disturbance effects are of concern in small island situations where it may Disturbance effects are of concern in small island situations where it may

be physically impossible for researchers to avoid some impact on an be physically impossible for researchers to avoid some impact on an

entire populationentire population

– Seabird colonies are extreme sensitive to human disturbanceSeabird colonies are extreme sensitive to human disturbance

– Research in Maine [Anderson 1995], suggests that a 15 minute visit to a Research in Maine [Anderson 1995], suggests that a 15 minute visit to a

cormorant colony can result in up to 20% mortality among eggs and cormorant colony can result in up to 20% mortality among eggs and

chicks in a given breeding year. Repeated disturbance can lead to the chicks in a given breeding year. Repeated disturbance can lead to the

end of the colonyend of the colony


Habitat MonitoringHabitat Monitoring

– On Kent Island, Nova Scotia, research learned that Leach’s Storm Petrels On Kent Island, Nova Scotia, research learned that Leach’s Storm Petrels

are likely to desert their nesting burrows in case of disturbance during the are likely to desert their nesting burrows in case of disturbance during the

first two weeks of incubationfirst two weeks of incubation

– Sensor networks advances the monitoring methods over the traditional Sensor networks advances the monitoring methods over the traditional

invasive onesinvasive ones

– Sensors can be deployed prior to the breeding season or other sensitive Sensors can be deployed prior to the breeding season or other sensitive

period or while plants are dormant or the ground is frozen on small islets period or while plants are dormant or the ground is frozen on small islets

where it would be unsafe or unwise to repeatedly attempt field studieswhere it would be unsafe or unwise to repeatedly attempt field studies

– Sensor network deployment may be more economical method for Sensor network deployment may be more economical method for

conducting long-term studies than traditional personnel-rich methodsconducting long-term studies than traditional personnel-rich methods

– A “deploy ‘em and leave ‘em” strategy of wireless sensor usage would A “deploy ‘em and leave ‘em” strategy of wireless sensor usage would

decrease the logistical needs to initial placement and occasional servicingdecrease the logistical needs to initial placement and occasional servicing


Great Duck IslandGreat Duck Island

– The College of Atlantic (COA) is field testing in-situ sensor networks for The College of Atlantic (COA) is field testing in-situ sensor networks for

habitat monitoringhabitat monitoring

– Great Duck Island (GDI) is a 237 acre island located 15 km south of Great Duck Island (GDI) is a 237 acre island located 15 km south of

Mount Desert Island, MaineMount Desert Island, Maine

– At GDI, three major questions in monitoring the Leach’s Storm Petrel At GDI, three major questions in monitoring the Leach’s Storm Petrel

[Anderson 1995]:[Anderson 1995]:

1.1. What is the usage pattern of nesting burrows over the 24-72 hour What is the usage pattern of nesting burrows over the 24-72 hour

cycle when one or both members of a breeding pair may alternate cycle when one or both members of a breeding pair may alternate

incubation duties with feeding at sea?incubation duties with feeding at sea?

2.2. What changes can be observed in the burrow and surface What changes can be observed in the burrow and surface

environmental parameters during the course of the approximately 7 environmental parameters during the course of the approximately 7

month breeding season (April-October)?month breeding season (April-October)?


Great Duck IslandGreat Duck Island

3.3. What are the differences in the micro-environments with and without What are the differences in the micro-environments with and without

large numbers of nesting petrels?large numbers of nesting petrels?

– Presence/absence data is obtained through occupancy detection and Presence/absence data is obtained through occupancy detection and

temperature differentials between burrows with adult birds and burrows temperature differentials between burrows with adult birds and burrows

that contain eggs, chicks, or are emptythat contain eggs, chicks, or are empty

– Petrels will most likely enter or leave during the daytime; however, 5-10 Petrels will most likely enter or leave during the daytime; however, 5-10

minutes during late evening and early morning measurements are minutes during late evening and early morning measurements are

needed to capture the entry and exit timingsneeded to capture the entry and exit timings

– More general environmental differentials between burrow and surface More general environmental differentials between burrow and surface

conditions can be captured by records every 2-4 hours during the conditions can be captured by records every 2-4 hours during the

extended breeding season; whereas, the differences between “popular” extended breeding season; whereas, the differences between “popular”

and “unpopular” sites benefit from hourly samplingand “unpopular” sites benefit from hourly sampling


Great Duck Island RequirementsGreat Duck Island Requirements

1.1. Internet AccessInternet Access

– The sensor networks at GDI must be accessible via the Internet since the The sensor networks at GDI must be accessible via the Internet since the

ability to support remote interactions with in-situ networks is essentialability to support remote interactions with in-situ networks is essential

2.2. Hierarchical NetworkHierarchical Network

– Habitats of interest are located up to several kilometers away. A second Habitats of interest are located up to several kilometers away. A second

tier of wireless networking provides connectivity to multiple patches of tier of wireless networking provides connectivity to multiple patches of

sensor networks deployed at each of the areas.sensor networks deployed at each of the areas.

3.3. Sensor Network LongevitySensor Network Longevity

– Sensor networks that runs for several month from non-rechargeable Sensor networks that runs for several month from non-rechargeable

power sources would be desirable since studies at GDI can span multiple power sources would be desirable since studies at GDI can span multiple

field seasonsfield seasons



4.4. Operating off-the gridOperating off-the grid

– Every level of the network must operate with bounded energy suppliesEvery level of the network must operate with bounded energy supplies

– Renewable energy such as solar power may be available some locations, Renewable energy such as solar power may be available some locations,

disconnected operation is a possibilitydisconnected operation is a possibility

– GDI has enough solar power that run the application 24x7 with small GDI has enough solar power that run the application 24x7 with small

probabilities of service interruptions due to power lossprobabilities of service interruptions due to power loss

5.5. Management at-a-distanceManagement at-a-distance

– Remoteness of the field sites requires the ability to monitor and manage Remoteness of the field sites requires the ability to monitor and manage

sensor networks over the Internet. The goal is no on-site presence for sensor networks over the Internet. The goal is no on-site presence for

maintenance and administration during the field season, except for maintenance and administration during the field season, except for

installation and removal of nodesinstallation and removal of nodes



6.6. Inconspicuous operationInconspicuous operation

– It should not disrupt the natural processes or behaviors under studyIt should not disrupt the natural processes or behaviors under study

– Removing human presence from the study areas would eliminate a Removing human presence from the study areas would eliminate a

source of error and variation in data collection and source of disturbancesource of error and variation in data collection and source of disturbance

7.7. System behaviorSystem behavior

– Sensor networks should present stable, predictable, and repeatable Sensor networks should present stable, predictable, and repeatable

behavior at all times since unpredictable system is difficult to debug and behavior at all times since unpredictable system is difficult to debug and

maintainmaintain

– Predictability is essential in developing trust in these new technologies Predictability is essential in developing trust in these new technologies

for life scientistsfor life scientists



8.8. In-situ interactionsIn-situ interactions

– Local interactions are required during initial development, maintenance Local interactions are required during initial development, maintenance

and on-site visits and on-site visits

– PDAs can be useful in accomplishing these tasks – they may directly PDAs can be useful in accomplishing these tasks – they may directly

query a sensor, adjust operational parameters and so onquery a sensor, adjust operational parameters and so on

9.9. Sensors and samplingSensors and sampling

– The ability to sense light, temperature, infrared, relative humidity, and The ability to sense light, temperature, infrared, relative humidity, and

barometric pressure are essential set of measurementsbarometric pressure are essential set of measurements

– Additional measurements may include acceleration/vibration, weight, Additional measurements may include acceleration/vibration, weight,

chemical vapors, gas concentrations, pH, and noise levelschemical vapors, gas concentrations, pH, and noise levels



10.10. Data archivingData archiving

– Sensor readings must be achieved for off-line data mining and analysisSensor readings must be achieved for off-line data mining and analysis

– The reliable offloading of sensor logs to databases in the wired, powered The reliable offloading of sensor logs to databases in the wired, powered

infrastructure is essentialinfrastructure is essential

– It is desirable to interactively “drill-down” and explore sensors in near It is desirable to interactively “drill-down” and explore sensors in near

real-time complement log-based studies. In this mode of operation, the real-time complement log-based studies. In this mode of operation, the

timely delivery of sensor data is the keytimely delivery of sensor data is the key

– Nodal data summaries and periodic health-and-status monitoring also Nodal data summaries and periodic health-and-status monitoring also

requires timely delivery of the datarequires timely delivery of the data


System ArchitectureSystem Architecture

– A tiered architecture is developedA tiered architecture is developed

– The lowest level consists of the The lowest level consists of the sensor nodessensor nodes that perform general that perform general

purpose computing and networking as well as application-specific sensingpurpose computing and networking as well as application-specific sensing

– The sensor nodes may be deployed in dense patches and transmit their The sensor nodes may be deployed in dense patches and transmit their

data through the sensor network to the sensor network data through the sensor network to the sensor network gatewaygateway

– Gateway is responsible for transmitting sensor data from the Gateway is responsible for transmitting sensor data from the sensor patchsensor patch

through a local through a local transit networktransit network to the remote to the remote base stationbase station that provides that provides

WAN connectivity and data loggingWAN connectivity and data logging

– The base station connects to database replicas across the internetThe base station connects to database replicas across the internet

– At last, the data is displayed to researchers through a user interfaceAt last, the data is displayed to researchers through a user interface




Figure 1: System architecture for habitat monitoringFigure 1: System architecture for habitat monitoring


– The autonomous sensor nodes are placed in the areas of interest where The autonomous sensor nodes are placed in the areas of interest where

each sensor node collects environmental data about its immediate each sensor node collects environmental data about its immediate

surroundingssurroundings

– Since these sensors are placed close to the area of interest, they can be Since these sensors are placed close to the area of interest, they can be

built using small and inexpensive individual sensors – high spatial built using small and inexpensive individual sensors – high spatial

resolution can be achieved through dense deployment of sensor nodesresolution can be achieved through dense deployment of sensor nodes

– This architecture offers higher robustness compared to traditional This architecture offers higher robustness compared to traditional

approaches which use a few high quality sensors with complex signal approaches which use a few high quality sensors with complex signal

processingprocessing

– The computational module is a programmable unit that provides The computational module is a programmable unit that provides

computation, storage and bidirectional communication with other nodescomputation, storage and bidirectional communication with other nodes



– The computational module interfaces with the analog and digital sensors The computational module interfaces with the analog and digital sensors

on the sensor module, performs basic signal processing and dispatches on the sensor module, performs basic signal processing and dispatches

the data according to the needs of the applicationthe data according to the needs of the application

– Compared to traditional data logging systems, networked sensors offer Compared to traditional data logging systems, networked sensors offer

two main advantages: they can be re-tasked in the field and they can two main advantages: they can be re-tasked in the field and they can

communicate with the rest of the systemcommunicate with the rest of the system

– In-situ re-tasking gives researchers the ability to refocus their observations In-situ re-tasking gives researchers the ability to refocus their observations

based on the analysis of the initial results – initially, absolute temperature based on the analysis of the initial results – initially, absolute temperature

readings are desired, after a while, only significant temperature changes readings are desired, after a while, only significant temperature changes

exceeding a threshold may become more usefulexceeding a threshold may become more useful



– Individual sensor nodes communicate and coordinate with one another Individual sensor nodes communicate and coordinate with one another

– These nodes form a multi-hop network by forwarding each other’s These nodes form a multi-hop network by forwarding each other’s

messages and if needed, the network can perform in-network aggregation messages and if needed, the network can perform in-network aggregation

(e.g., relaying the average temperature across the region)(e.g., relaying the average temperature across the region)

– Eventually, data from each sensor needs to be propagated to the InternetEventually, data from each sensor needs to be propagated to the Internet

– The propagated data may be raw, filtered or processed dataThe propagated data may be raw, filtered or processed data

– Since direct wide area connectivity cannot be brought to each sensor path Since direct wide area connectivity cannot be brought to each sensor path

due to several reasons (e.g., cost of equipment, power, disturbance due to several reasons (e.g., cost of equipment, power, disturbance

created by the installation of the equipment in the environment), wide are created by the installation of the equipment in the environment), wide are

connectivity is brought to a connectivity is brought to a base stationbase station instead instead



– The base station may communicate with the sensor patch using a wireless The base station may communicate with the sensor patch using a wireless

LAN where each sensor patch is equipped with a LAN where each sensor patch is equipped with a gatewaygateway that can that can

communicate with the sensor network and provides connectivity to the communicate with the sensor network and provides connectivity to the

transit networktransit network

– The transit network may consist of a single hop link or series of networked The transit network may consist of a single hop link or series of networked

wireless nodes and each transit network design has different wireless nodes and each transit network design has different

characteristics with respect to expected robustness, bandwidth, energy characteristics with respect to expected robustness, bandwidth, energy

efficiency, cost and manageabilityefficiency, cost and manageability

– To provide data to remote end-users, the To provide data to remote end-users, the base stationbase station includes WAN includes WAN

connectivity and persistent data storage for the collection of sensor connectivity and persistent data storage for the collection of sensor

patchespatches



– It is expected that WAN connection will be wirelessIt is expected that WAN connection will be wireless

– The architecture needs to address the disconnection possibilitiesThe architecture needs to address the disconnection possibilities

– Each layer (sensor nodes, gateways, base stations) has some persistent Each layer (sensor nodes, gateways, base stations) has some persistent

storage to protect against data loss due to power outage as well as data storage to protect against data loss due to power outage as well as data

management servicesmanagement services

– At the sensor level, these will be primitive, taking the form of data loggingAt the sensor level, these will be primitive, taking the form of data logging

– The base station may provide relational database service while the data The base station may provide relational database service while the data

management at the gateways falls somewhere in betweenmanagement at the gateways falls somewhere in between

– When it comes to data collection, long-latency is preferable to data lossWhen it comes to data collection, long-latency is preferable to data loss

– Users interact with the sensor network in two waysUsers interact with the sensor network in two ways



– Remote users access the replica of the base station database Remote users access the replica of the base station database

– This approach assists on integration with data analysis and mining tools This approach assists on integration with data analysis and mining tools

while masking the potential wide area disconnections with the base while masking the potential wide area disconnections with the base

stationsstations

– On-site users may require direct interaction with the network and this can On-site users may require direct interaction with the network and this can

be accomplished with a small, PDA-sized device, referred to as be accomplished with a small, PDA-sized device, referred to as gizmogizmo

– Gizmo allows the user to interactively control the network parameters by Gizmo allows the user to interactively control the network parameters by

adjusting the sampling rates, power management parameters and other adjusting the sampling rates, power management parameters and other

network parametersnetwork parameters

– The connectivity between any sensor node and gizmo may or may not rely The connectivity between any sensor node and gizmo may or may not rely

on functioning on multi-hop sensor network routingon functioning on multi-hop sensor network routing


Implementation StrategiesImplementation Strategies

Sensor Network NodeSensor Network Node

– UC Berkeley motes are used as the sensor nodesUC Berkeley motes are used as the sensor nodes

– Mica uses a single channel, 916 MHz radio from RF Monolithics to Mica uses a single channel, 916 MHz radio from RF Monolithics to

provide bi-directional communication at 40 Kbps, an Atmel Atmega 103 provide bi-directional communication at 40 Kbps, an Atmel Atmega 103

microcontroller running at 4 MHz and 512 KB nonvolatile storagemicrocontroller running at 4 MHz and 512 KB nonvolatile storage

– A pair of conventional AA batteries and a DC boost converter provide the A pair of conventional AA batteries and a DC boost converter provide the

power source; however, other renewable energy sources can be usedpower source; however, other renewable energy sources can be used



Sensor BoardSensor Board

– The Mica Weather Board provides sensors that monitor changing The Mica Weather Board provides sensors that monitor changing

environmental conditions with the same functionality as a traditional environmental conditions with the same functionality as a traditional

weather stationweather station

– The Mica Weather Board includes temperature, photoresistor, barometric The Mica Weather Board includes temperature, photoresistor, barometric

pressure, humidity, and passive infrared (thermopile) sensorspressure, humidity, and passive infrared (thermopile) sensors


Table 1: Mica Weather BoardTable 1: Mica Weather Board


Sensor BoardSensor Board


Figure 2: Mica Hardware Platform: The Mica sensor node (left) with the MicaFigure 2: Mica Hardware Platform: The Mica sensor node (left) with the MicaWeather Board developed for environmental monitoring applicationsWeather Board developed for environmental monitoring applications


Energy BudgetEnergy Budget

– Typical habitat monitoring applications need to run for nine monthsTypical habitat monitoring applications need to run for nine months

– The application chooses how to allocate the energy budget between The application chooses how to allocate the energy budget between

sleep modes, sensing, local calculations and communicationssleep modes, sensing, local calculations and communications

– Since different nodes have different functions, they also have different Since different nodes have different functions, they also have different

power requirements, for instance, the nodes near the gateway may need power requirements, for instance, the nodes near the gateway may need

to forward all messages from a patch while a node in a nest may only to forward all messages from a patch while a node in a nest may only

need to report its own readingsneed to report its own readings

– When a set of power limited nodes exhaust their power supplies, the When a set of power limited nodes exhaust their power supplies, the

network can become disconnected and inoperablenetwork can become disconnected and inoperable

– There is a need to budget the power with respect to the energy There is a need to budget the power with respect to the energy

bottlenecks of the networkbottlenecks of the network



Energy BudgetEnergy Budget

– The baseline life time of the node is determined by the current draw in The baseline life time of the node is determined by the current draw in

the sleep statethe sleep state

– Minimizing power in sleep mode means turning off the sensors, the radio Minimizing power in sleep mode means turning off the sensors, the radio

and putting the processor into a deep sleep modeand putting the processor into a deep sleep mode


Table 2: Power required by various Mica operationsTable 2: Power required by various Mica operations


Sensor DeploymentSensor Deployment

– A wireless sensor network using Mica motes with Mica Weather Board A wireless sensor network using Mica motes with Mica Weather Board

has been deployed in July 2002has been deployed in July 2002

– Environmental protective packaging has been designed which minimally Environmental protective packaging has been designed which minimally

obstruct sensing functionalityobstruct sensing functionality


Figure 3: Acrylic enclosure used for deploying the Mica moteFigure 3: Acrylic enclosure used for deploying the Mica mote


Patch GatewaysPatch Gateways

– Usage of different gateway nodes directly affects the underlying available Usage of different gateway nodes directly affects the underlying available

transit networktransit network

– Two designs implemented: an 802.11b single hop with an embedded Two designs implemented: an 802.11b single hop with an embedded

Linux system and a single hop mote-to-mote networkLinux system and a single hop mote-to-mote network

– Initially, CerfCube [Cerfcube] which is a small StrongARM-based Initially, CerfCube [Cerfcube] which is a small StrongARM-based

embedded system to act as a sensor patch gateway, is chosenembedded system to act as a sensor patch gateway, is chosen

– Each gateway is equipped with a CompactFlash 802.11b adapterEach gateway is equipped with a CompactFlash 802.11b adapter

– Gateway use permanent storage of up to 1GBGateway use permanent storage of up to 1GB

– The mote-to-mote solution consisted of a mote connected to the base The mote-to-mote solution consisted of a mote connected to the base

station and a mote in the sensor patchstation and a mote in the sensor patch



Patch GatewaysPatch Gateways

– The differences between the mote and CerfCube include differentThe differences between the mote and CerfCube include different

o communication frequencycommunication frequency

o power requirements power requirements

o software componentssoftware components

– The mote’s MAC layer does not require bi-directional link like 802.11bThe mote’s MAC layer does not require bi-directional link like 802.11b

– In addition, the mote sends raw data with a small packet header (4 bytes) In addition, the mote sends raw data with a small packet header (4 bytes)

directly over the radio as opposed to overheads imposed by 802.11b and directly over the radio as opposed to overheads imposed by 802.11b and

TCP/IP connectionsTCP/IP connections



Base-station installationBase-station installation

– For achieve remote access, collection of sensor patches is connected to For achieve remote access, collection of sensor patches is connected to

the Internet through a wide-area linkthe Internet through a wide-area link

– On GDI, Internet connectivity is accomplished through a two-way satellite On GDI, Internet connectivity is accomplished through a two-way satellite

connection provided by Hughes and similar to DirecTV systemconnection provided by Hughes and similar to DirecTV system

– The satellite system is connected to a laptop which coordinates the The satellite system is connected to a laptop which coordinates the

sensor patches and provides a relational database servicesensor patches and provides a relational database service

Database Management SystemDatabase Management System

– The base station uses Postgres SQL database which stores time-The base station uses Postgres SQL database which stores time-

stamped readings from the sensors, health status of the individual stamped readings from the sensors, health status of the individual

sensors, and metadata (e.g., sensor locations)sensors, and metadata (e.g., sensor locations)



Database Management SystemDatabase Management System

– The GDI database is replicated every fifteen minutes over the wide-area The GDI database is replicated every fifteen minutes over the wide-area

satellite link to Postgres database in Berkeleysatellite link to Postgres database in Berkeley

User InterfacesUser Interfaces

– Many user interfaces can be implemented on top of the sensor databaseMany user interfaces can be implemented on top of the sensor database

– GIS systems provide a widely used standard for analyzing geographical GIS systems provide a widely used standard for analyzing geographical

data and most statistics and data analysis packages implement data and most statistics and data analysis packages implement

interfaces to relational databasesinterfaces to relational databases

– Number of web interfaces can be implemented to provide the ubiquitous Number of web interfaces can be implemented to provide the ubiquitous

interfaces to the habitat datainterfaces to the habitat data



– Focus is on issues related to dynamic sensor networks with mobile Focus is on issues related to dynamic sensor networks with mobile

nodes and wireless communication between themnodes and wireless communication between them

– In this system, the sensor nodes collars carried by the animals under In this system, the sensor nodes collars carried by the animals under

study; wireless ad hoc networking techniques are used to swap and store study; wireless ad hoc networking techniques are used to swap and store

data in a peer-to-peer manner and to pass it towards a mobile base data in a peer-to-peer manner and to pass it towards a mobile base

station that sporadically traverses the area to upload datastation that sporadically traverses the area to upload data

– Biology and biocomplexity research has been focused on gathering data Biology and biocomplexity research has been focused on gathering data

and observations on a range of species to understand their interactions and observations on a range of species to understand their interactions

and influences on each otherand influences on each other

– For example, how human development into wilderness areas affects For example, how human development into wilderness areas affects

indigenous species there; understand the migration patterns of wild indigenous species there; understand the migration patterns of wild

animals and how they may be affected by changes in weather patterns or animals and how they may be affected by changes in weather patterns or

plant life, by introduction of non-native species, and by other influencesplant life, by introduction of non-native species, and by other influences

Energy-Efficient Computing for Wildlife Tracking: Design Tradeoffs and Early Experiences with ZebraNet [Juang+ 2002]


– Finding and learning these details require long-term position logs and Finding and learning these details require long-term position logs and

other biometric data such as heart rate, body temperature, and frequency other biometric data such as heart rate, body temperature, and frequency

feedingfeeding

– Current wildlife tracking studies rely on simple technology, for example, Current wildlife tracking studies rely on simple technology, for example,

many studies rely on collaring a sample subset of animals with simple many studies rely on collaring a sample subset of animals with simple

VHF transmittersVHF transmitters

– Researchers periodically drive through and/or fly over an area with a Researchers periodically drive through and/or fly over an area with a

receiver antenna, and listen for pings from previously collared animalsreceiver antenna, and listen for pings from previously collared animals

– Once animal is found, its behavior can be observed and its observed Once animal is found, its behavior can be observed and its observed

position can be logged; however, there are limits to such studiesposition can be logged; however, there are limits to such studies

– First, data collection is infrequent and can miss many “First, data collection is infrequent and can miss many “interesting eventsinteresting events””



– Second, data collection is mostly limited to daylight hours, but animal Second, data collection is mostly limited to daylight hours, but animal

behavior and movements in night hours can be differentbehavior and movements in night hours can be different

– Third, data collection is impossible or very limited for secluded species Third, data collection is impossible or very limited for secluded species

that avoid human contactthat avoid human contact

– The most elegant trackers commercially available use GPS to track The most elegant trackers commercially available use GPS to track

position and use satellite uploads to transfer data to a base stationposition and use satellite uploads to transfer data to a base station

– These systems also suffer from several limitationsThese systems also suffer from several limitations

– First, at most a log of 3000 position samples can be logged and no First, at most a log of 3000 position samples can be logged and no

biometric databiometric data

– Second, since satellite uploads are slow and uses high power Second, since satellite uploads are slow and uses high power

consumption, they are done infrequently – this limits how often position consumption, they are done infrequently – this limits how often position

samples can be gathered without overflowing 3000-entry log storagesamples can be gathered without overflowing 3000-entry log storage



– Third, downloads of data from the satellite to the researchers are both Third, downloads of data from the satellite to the researchers are both

slow and expensive, therefore, constraining the amount of data collectedslow and expensive, therefore, constraining the amount of data collected

– Finally, these systems operate on batteries without recharge – when Finally, these systems operate on batteries without recharge – when

power is drained, the system become unusable unless it is retrieved, power is drained, the system become unusable unless it is retrieved,

recharged and re-deployedrecharged and re-deployed

– ZebraNetZebraNet project is building tracking nodes that include a low-power project is building tracking nodes that include a low-power

miniature GPS system with user-programmable CPU, non-volatile miniature GPS system with user-programmable CPU, non-volatile

storage for data logs, and radio transceivers for communicating either storage for data logs, and radio transceivers for communicating either

with other nodes or with a base stationwith other nodes or with a base station



– One of the key principles of ZebraNet is that the system should work in One of the key principles of ZebraNet is that the system should work in

arbitrary wilderness locations; no assumptions are made about the arbitrary wilderness locations; no assumptions are made about the

presence of of fixed antenna towers or cellular phone servicepresence of of fixed antenna towers or cellular phone service

– The system uses peer-to-peer data swaps to move the data around; The system uses peer-to-peer data swaps to move the data around;

periodic researcher drives bys and/or fly-overs can collect logged data periodic researcher drives bys and/or fly-overs can collect logged data

from several animals despite encountering relatively few within rangefrom several animals despite encountering relatively few within range

– Even though ad hoc sensor networks have been heavily studied, not Even though ad hoc sensor networks have been heavily studied, not

much has been published about the characteristics of mobile sensor much has been published about the characteristics of mobile sensor

networks with mobile base stations and very few studies focus on networks with mobile base stations and very few studies focus on

building real systemsbuilding real systems



– This paper has the following unique contributions:This paper has the following unique contributions:

o To the best knowledge of authors, this is the first study of mobile To the best knowledge of authors, this is the first study of mobile

sensor networks protocols in which the base station is also sensor networks protocols in which the base station is also mobilemobile. It . It

is presumed that researchers will upload data while driving or flying is presumed that researchers will upload data while driving or flying

by the regionby the region

o Zebra-tracking is a domain in which the node mobility models are Zebra-tracking is a domain in which the node mobility models are

unknown which makes it a research goal. Understanding how, when unknown which makes it a research goal. Understanding how, when

and why zebras undertake long-term migrations is the most essential and why zebras undertake long-term migrations is the most essential

biological question of this work. biological question of this work.

o ZebraNet’s data collection has communication patterns in which data ZebraNet’s data collection has communication patterns in which data

can be cooperatively passed towards a base stationcan be cooperatively passed towards a base station

o Energy tradeoffs are examined in detail using real system energy Energy tradeoffs are examined in detail using real system energy

measurements for ZebraNet prototype hardware in operationmeasurements for ZebraNet prototype hardware in operation



– Some of the interesting research questions to be explored are:Some of the interesting research questions to be explored are:

o How to make the communications protocol both effective and power-How to make the communications protocol both effective and power-

efficient?efficient?

o To what extent can we rely on ad hoc, peer-to-peer transfers in a To what extent can we rely on ad hoc, peer-to-peer transfers in a

sparsely-connected spatially-huge sensor network?sparsely-connected spatially-huge sensor network?

o How can we provide comprehensive tracking of a collection of How can we provide comprehensive tracking of a collection of

animals, even if some of the animals are reclusive and rarely are animals, even if some of the animals are reclusive and rarely are

close enough to humans to have their data logs updated directly?close enough to humans to have their data logs updated directly?

– This research work gives quantitative explorations of the design This research work gives quantitative explorations of the design

decisions behind some of these questionsdecisions behind some of these questions


ZebraNet Design GoalsZebraNet Design Goals

– The ZebraNet project is a direct and ongoing collaboration between The ZebraNet project is a direct and ongoing collaboration between

researchers in experimental computer systems and in wildlife biologyresearchers in experimental computer systems and in wildlife biology

– The wildlife biologists have determined the tracker’s overall design goals:The wildlife biologists have determined the tracker’s overall design goals:

o GPS position samples are taken every three minutesGPS position samples are taken every three minutes

o Detailed activity logs taken for three minutes every hourDetailed activity logs taken for three minutes every hour

o One year of operation without direct human intervention – that is, not One year of operation without direct human intervention – that is, not

counting on tranquilizing and re-collaring an animal more than once counting on tranquilizing and re-collaring an animal more than once

per yearper year

o No fixed base stations, antennas, or cellular service No fixed base stations, antennas, or cellular service

o A high success rate for A high success rate for eventuallyeventually delivering all logged data is delivering all logged data is

essential while latency is not as criticalessential while latency is not as critical

o For a zebra collar, a weight limit of 3-5 lbs is recommendedFor a zebra collar, a weight limit of 3-5 lbs is recommended


ZebraNet Design GoalsZebraNet Design Goals

– Ultimately, this detailed information may include several position Ultimately, this detailed information may include several position

estimates, temperature information, weather data, environmental data, estimates, temperature information, weather data, environmental data,

and body movements that will serve as signatures of behavior; however, and body movements that will serve as signatures of behavior; however,

in this initial system, the focus is only on position datain this initial system, the focus is only on position data

– Overall, the key goal is to deliver to researchers a very high fraction of the Overall, the key goal is to deliver to researchers a very high fraction of the

data collected over the months or years that the system is in operationdata collected over the months or years that the system is in operation

– Therefore, ZebraNet must be power-efficient, designed with appropriate Therefore, ZebraNet must be power-efficient, designed with appropriate

data log storage, and must be rugged to ensure reliability under tough data log storage, and must be rugged to ensure reliability under tough

environmental conditionsenvironmental conditions


ZebraNet Problem StatementZebraNet Problem Statement

– The biologists design goals need to be translated into the engineering The biologists design goals need to be translated into the engineering

task at handtask at hand

– Success rate at delivering position data to the researchers –data homing Success rate at delivering position data to the researchers –data homing

rate– should approach 100%rate– should approach 100%

– Weight limits on each node translate almost directly to computational Weight limits on each node translate almost directly to computational

energy limits since weight of the battery and solar panel takes bulk of the energy limits since weight of the battery and solar panel takes bulk of the

total weight of a ZebraNet node; therefore, collar and protocol design total weight of a ZebraNet node; therefore, collar and protocol design

decisions must manage the number and size of data transmissions decisions must manage the number and size of data transmissions

requiredrequired

– System design choices must be made that limit the range of System design choices must be made that limit the range of

transmissions since the required transmitter energy increases transmissions since the required transmitter energy increases

dramatically with the distance transmitteddramatically with the distance transmitted



– The amount of storage needed to hold position logs must be limited – if The amount of storage needed to hold position logs must be limited – if

many redundant copies are stored and swapped, the storage many redundant copies are stored and swapped, the storage

requirements can scale as requirements can scale as O(nO(n22))

– Although the energy cost of storage is small compared to that of Although the energy cost of storage is small compared to that of

transmissions, it is still necessary to develop storage-efficient designtransmissions, it is still necessary to develop storage-efficient design

– Due to limited transceiver, coverage and a base station only sporadically Due to limited transceiver, coverage and a base station only sporadically

available, ZebraNet must forward data through other nodes in peer-to-available, ZebraNet must forward data through other nodes in peer-to-

peer manner and store redundant copies of position logs in other tracking peer manner and store redundant copies of position logs in other tracking

nodesnodes

– Some of the key challenges in ZebraNet come from the spatial and Some of the key challenges in ZebraNet come from the spatial and

temporal scale of the systemtemporal scale of the system



– In terms of temporal scale, keeping a system running autonomously In terms of temporal scale, keeping a system running autonomously

months at a time is challenging; it requires tremendous design-time months at a time is challenging; it requires tremendous design-time

attention to both hardware and software reliabilityattention to both hardware and software reliability

– In terms of spatial scale, ZebraNet is also aggressive; it is the specific In terms of spatial scale, ZebraNet is also aggressive; it is the specific

intent of the system to operate over an area of hundreds or thousands of intent of the system to operate over an area of hundreds or thousands of

square square kilometerssquare square kilometers

– Due to the large distances involved and sparse sensor coverage, Due to the large distances involved and sparse sensor coverage,

energy/connectivity tradeoffs become keyenergy/connectivity tradeoffs become key



– These challenges mentioned here tackles several open problems:These challenges mentioned here tackles several open problems:

– ZebraNet protocol promises good communication behavior on mobile ZebraNet protocol promises good communication behavior on mobile

sensors forwarding data towards a mobile base stationsensors forwarding data towards a mobile base station

– ZebraNet explores design issues for sensors that are more coarse-ZebraNet explores design issues for sensors that are more coarse-

grained than many prior sensor proposals. Larger the weight limits grained than many prior sensor proposals. Larger the weight limits

and storage budgets allow researchers to consider different protocols and storage budgets allow researchers to consider different protocols

with improved leverage for sparsely-connected, physically-with improved leverage for sparsely-connected, physically-

widespread sensorswidespread sensors


[Abrach+ 2003] H. Abrach, S. Bhatti, J. Carlson, H. Dai, J. Rose, A. Sheth, B. Shucker, J, Deng and R. Han, MANTIS: System Support for MultimodAl NeTworks of In-Situ Sensors, 2nd ACM International Workshop on Wireless Sensor Networks and Applications (WSNA 2003), September 2003.

[Akyildiz+ 2002] I. F. Akyildiz, W. Su, Y. Sankarasubramaniam, and E. Cayirci, A Survey on Sensor Networks, IEEE Communications Magazine, Vol. 40, No. 8, pp. 102-114, August 2002.

[Anderson 1995] J.G.T. Anderson, Pilot survey of mid-coast Maine seabird colonies: an evaluation of techniques, Bangor, ME, 1995. Report to the State of Maine Dept. of Inland Fisheries and Wildlife.

[Cerfcube] Cerfcube embedded StrongARM system, http://www.intrinsys.com/products/cerfcube

[Elson+ 2002] J. Elson and K. Romer, Wireless Sensor Networks: A New Regime for Time Synchronization, First Workshop on Hot Topics in Networks (Hotnets-I), Princeton, USA, October 2002.

[Hill+ 2000] J. Hill, R. Szewczyk, A. Woo, S. Hollar, D. Culler, and K. Pister, System Architecture Directions for Networked Sensors, Architectural Support for Programming Languages and Operating Systems (ASPLOS) 2000.

[Juang+ 2002] P. Juang, H. Oki, Y. Wang, M. Martonosi, L-S Peh, and D. Rubenstein, Energy-Efficient Computing for Wildlife Tracking: Design Tradeoffs and Early Experiences with ZebraNet, ACM SIGARCH Computer Architecture News, vol. 30, no. 5, December 2002 .

[Mainwaring+ 2002] A. Mainwaring, J. Polastre, R. Szewczyk, D. Culler, and J. Anderson, Wireless Sensor Networks for Habitat Monitoring, 1st ACM International Workshop on Wireless Sensor Networks and Applications (WSNA 2002), Atlanta, Georgia, September 28, 2002.

[TinyOS] TinyOS: a component-based OS for the networked sensor regime.

References

system architecture of networked sensor platforms and sensor networks applications

Documents

system lifetimescalability

group of sensor nodes

location of sensor nodes

mantiswhy sensor platforms

sensor node akyildiz

hardware platforms

smallest networks

energy efficiency