TinyOSTinyOS

By Morgan LeiderBy Morgan Leider

CS 411CS 411

with Mike Rowewith Mike Rowe

BackgroundBackground

Created at UCBerkeleyCreated at UCBerkeleyUsed by over 500 groupsUsed by over 500 groups tinyos.nettinyos.netUsesUses

Habitat MonitoringHabitat MonitoringShooter LocalizationShooter LocalizationPursuer-EvaderPursuer-Evader

Design FeaturesDesign Features

Cross-layer controlCross-layer controlStatic Resource allocationStatic Resource allocationSnooping & scheduled communicationSnooping & scheduled communication

Design RequirementsDesign Requirements

Work with current and future designsWork with current and future designsAllow diverse implementation of operating Allow diverse implementation of operating

system services and applicationssystem services and applicationsSupport varying hardwareSupport varying hardwareAddress the unusual challenges of sensor Address the unusual challenges of sensor

networksnetworks

HardwareHardware

Motes-small resource constrained Motes-small resource constrained computing nodescomputing nodes

Mica motesMica motesRadio capable of 40KbpsRadio capable of 40Kbps4Mhz processor4Mhz processor1-4k of ram1-4k of ramUp to 128K of storageUp to 128K of storage32Khz external clock32Khz external clock

General code infoGeneral code info

TinyOS requires 400 bytes for core OSTinyOS requires 400 bytes for core OSSupportsSupports

Event-driven executionEvent-driven executionFlexible concurrency modelFlexible concurrency model

TasksTasksEventsEvents

Component oriented application designComponent oriented application designApps use only the components they needApps use only the components they need

LanguageLanguage

Written in nesCWritten in nesCAn extension of CAn extension of CStripped downStripped downNo function pointersNo function pointersStatic Static

No dynamic memory allocationNo dynamic memory allocationCall-graph fully known at run timeCall-graph fully known at run time

Writing in nesCWriting in nesC

Everything is a componentEverything is a componentModule – application code, implements Module – application code, implements

interfacesinterfacesConfigurations – connect interfacesConfigurations – connect interfaces

All components use modular interfacesAll components use modular interfacesGroup commands and events togetherGroup commands and events togetherBi-directional interfaces to support Bi-directional interfaces to support

hardware interruptshardware interrupts

Writing in nesCWriting in nesC

Discourage sharing of dataDiscourage sharing of dataAsynchronous operation with interruptsAsynchronous operation with interruptsSynchronous operation with tasksSynchronous operation with tasksMake event code atomicMake event code atomicOptimizesOptimizes

Inlines small functionsInlines small functionsEleminates unreachable codeEleminates unreachable code

Reduces cpu usage by 30% and code size by 10%Reduces cpu usage by 30% and code size by 10%

TinyOS featuresTinyOS features

Multi-hop communicationMulti-hop communicationTree-based collectionTree-based collection Intra-network routingIntra-network routingDisseminationDissemination

Broadcast – everyone transmits onceBroadcast – everyone transmits onceEpidemic – send when needed, snoopEpidemic – send when needed, snoop

TinyOS FeaturesTinyOS Features

SchedulingSchedulingTimed listening and communicationTimed listening and communicationReduces collisionsReduces collisionsExtends LifeExtends Life

SynchronizationSynchronizationTime-stamped messagesTime-stamped messagesExternal ClockExternal ClockAccurate to within +/- 1 msAccurate to within +/- 1 ms

Flexible Power SchedulingFlexible Power Scheduling

Idle listening costs tons of powerIdle listening costs tons of powerProvides communication schedules for Provides communication schedules for

local nodeslocal nodesTree based topologyTree based topologyAdaptive slotted communication schedule Adaptive slotted communication schedule

used to route packetsused to route packetsAllows for global routing schedulesAllows for global routing schedulesBase/root nodes have higher duty cyclesBase/root nodes have higher duty cycles

Node States + ReservationsNode States + Reservations

SendingSendingReceivingReceivingAdvertisement – receive from parent node Advertisement – receive from parent node

with available reservation slotwith available reservation slotTransmit pending – send reservation Transmit pending – send reservation

requestrequestReceive pending – receive a reservation Receive pending – receive a reservation

request from childrequest from child IdleIdle

Effects of Power SchedulingEffects of Power Scheduling

High efficiency AA battery gives about 221 High efficiency AA battery gives about 221 hours or 9 days of operation without power hours or 9 days of operation without power management.management.

1274 hours or 53 days of operation with 1274 hours or 53 days of operation with power schedulingpower scheduling

Can be increased even moreCan be increased even more

Trickle – A TinyOS componentTrickle – A TinyOS component

““A self-regulating algorithm for code A self-regulating algorithm for code propagation and maintenance in wireless propagation and maintenance in wireless sensor networks”sensor networks”Designed with 3 principlesDesigned with 3 principles

Low maintenance – scalable and infrequent data Low maintenance – scalable and infrequent data exchangesexchanges

Rapid propagation – must be able to update every Rapid propagation – must be able to update every node in a network within 2 minsnode in a network within 2 mins

Scalability – handle few to hundreds of neighbors, Scalability – handle few to hundreds of neighbors, don’t rely on mapped info because wireless don’t rely on mapped info because wireless networks changenetworks change

Trickle’s (Polite Gossip)Trickle’s (Polite Gossip)

Periodically broadcast code summaries to local Periodically broadcast code summaries to local neighborsneighbors

Stay quiet if another neighbor has broadcast Stay quiet if another neighbor has broadcast identical code summaryidentical code summary

Older summaries result in broadcast of an Older summaries result in broadcast of an updateupdate

Newer summaries result in request for updateNewer summaries result in request for update Few seconds of operation an hourFew seconds of operation an hour Prevents network floodingPrevents network flooding

Trickle’s CodeTrickle’s Code

Requires only 11 bytes of state on nodeRequires only 11 bytes of state on nodeBroadcasts and listens every interval I for Broadcasts and listens every interval I for

time Ttime TTransmission time is T/2Transmission time is T/2

Max of 2 transmissions every interval iMax of 2 transmissions every interval iTransmissions suppress other broadcastsTransmissions suppress other broadcastsEach node has a 1/(num of local node/ Each node has a 1/(num of local node/

max 75) chance of broadcastingmax 75) chance of broadcasting

Trickle’s CodeTrickle’s Code

If over 75 neighbors, collisions begin to If over 75 neighbors, collisions begin to happenhappen512/75 or 1024/75 chance of broadcasting512/75 or 1024/75 chance of broadcasting

Does not have overhead of discovering Does not have overhead of discovering and maintaining local groupsand maintaining local groups

Trickle’s BenefitsTrickle’s Benefits

Traditionally – have to rebroadcast all Traditionally – have to rebroadcast all code to entire network if a node code to entire network if a node disconnects for a whiledisconnects for a while

Trickle – local distribution where neededTrickle – local distribution where neededTremendous power savingsTremendous power savings

1 bit broadcasted costs 1000 cpu cycles of 1 bit broadcasted costs 1000 cpu cycles of powerpower

64k file costs days worth of operation time64k file costs days worth of operation time

TinyDB – A TinyOS componentTinyDB – A TinyOS component

Problems with databases in wireless Problems with databases in wireless networksnetworksFrequency of queriesFrequency of queriesRelevance of a node’s dataRelevance of a node’s dataOrder of query samplesOrder of query samples Is a sample worth processing? Is a sample worth processing?

TinyDB featuresTinyDB features

Query optimizationQuery optimizationDo work on motes to reduce broadcast sizeDo work on motes to reduce broadcast sizeEliminate recursive queriesEliminate recursive queries

Identification of similar or unchanged infoIdentification of similar or unchanged infoAbility to specify sampling rate and Ability to specify sampling rate and

minimum sampling rateminimum sampling rateDynamic adjustment of sampling rate Dynamic adjustment of sampling rate

based upon power and minimum specified based upon power and minimum specified lifetimelifetime

Deluge – A variant of TrickleDeluge – A variant of Trickle

Trickle is designed for single packet Trickle is designed for single packet disseminationdissemination

Deluge designed to handle large data Deluge designed to handle large data objectsobjects

Deluge FeaturesDeluge Features

Message suppressionMessage suppressionRobust asymmetric link creationRobust asymmetric link creation

Get rid of bad and find new neighborsGet rid of bad and find new neighborsDynamic advertisement rate adjustmentDynamic advertisement rate adjustmentMinimize collisions in node cellsMinimize collisions in node cellsSpatial multiplexing allows parallel Spatial multiplexing allows parallel

transfers of datatransfers of data

How Deluge worksHow Deluge works

Divides data objects into fixed-size pagesDivides data objects into fixed-size pagesBroadcasts all pages, in orderBroadcasts all pages, in orderMust receive 1 page before can start the Must receive 1 page before can start the

nextnext16 bit cyclic redundancy checks 16 bit cyclic redundancy checks Updates OS by pageUpdates OS by pageCapable of catching up nodes with only Capable of catching up nodes with only

local communicationlocal communication

ConclusionsConclusions

TinyOS is a highly customizable and TinyOS is a highly customizable and adaptable operating system.adaptable operating system.

Used by hundreds of reported groups.Used by hundreds of reported groups.Open source.Open source.Dozens of modules available for download Dozens of modules available for download

for free at tinyos.netfor free at tinyos.net

Any Questions?Any Questions?