12/5/2006 - updated WSN Mote- MCU & Sensor Hardware 1 ECET 581 Wireless Sensor Networks Infrastructure Establishment November 28, 2006 Fall 2006 lin

12/5/2006 - updated12/5/2006 - updated WSN Mote- MCU & Sensor HardwareWSN Mote- MCU & Sensor Hardware 11

ECET 581ECET 581 Wireless Sensor NetworksWireless Sensor Networks

Infrastructure EstablishmentInfrastructure EstablishmentNovember 28, 2006November 28, 2006

Fall 2006Fall 2006http://www.etcs.ipfw.edu/~linhttp://www.etcs.ipfw.edu/~lin

References: References: **Ch 4 Infrastructure Establishment of the book: "Wireless Sensor Networks **Ch 4 Infrastructure Establishment of the book: "Wireless Sensor Networks

- An Information Processing Approach," by Feng Zhao and Leonidas - An Information Processing Approach," by Feng Zhao and Leonidas Guibas, from Morgan Kaufmann/Elsevier inc, 2004Guibas, from Morgan Kaufmann/Elsevier inc, 2004

** Ch 9 Network Position and Synchronization Services and Ch 10 Energy ** Ch 9 Network Position and Synchronization Services and Ch 10 Energy Management of the book: Principles of Embedded Networked System Management of the book: Principles of Embedded Networked System Design, by Gregory and William Kaiser, from Cambridge University Design, by Gregory and William Kaiser, from Cambridge University PressPress

**TMote Sky Web site: **TMote Sky Web site: www.moteiv.comwww.moteiv.com


Infrastructure EstablishmentInfrastructure Establishment

Topology ControlTopology Control ClusteringClustering Time SynchronizationTime Synchronization

• Clock and Communication DelaysClock and Communication Delays• Interval MethodsInterval Methods• Reference BroadcastsReference Broadcasts

Localization and Localization ServicesLocalization and Localization Services• Ranging TechniquesRanging Techniques• Range-based Localization Algorithms Range-based Localization Algorithms • Location ServicesLocation Services


Topology ControlTopology Control

ApplicationsApplications• Military surveillanceMilitary surveillance• Emergency responseEmergency response• Scientific explorationScientific exploration

Neighborhood DiscoveryNeighborhood Discovery• Execute a neighbor-nodes discovering protocolExecute a neighbor-nodes discovering protocol

Topology Discovery – build routing pathTopology Discovery – build routing path Radio power of the nodesRadio power of the nodes Local topographyLocal topography Other conditionsOther conditions IssuesIssues

• Setup radio range to minimize energy usageSetup radio range to minimize energy usage• Remains connected and satisfies other desirable Remains connected and satisfies other desirable

communication propertiescommunication properties• Determines CTR (critical transmitting range)Determines CTR (critical transmitting range)


Topology ControlTopology Control

Determines CTR (critical transmitting range)Determines CTR (critical transmitting range)• Geometric Random Graph (GRM) TheoryGeometric Random Graph (GRM) Theory

Related Issues Related Issues • Link Quality Indicator – LQI (packet reception ratio)Link Quality Indicator – LQI (packet reception ratio)• Received Signal Strength Indicator - RSSIReceived Signal Strength Indicator - RSSI• Coverage rangeCoverage range• Optimal transmit power adjustment (transmission power Optimal transmit power adjustment (transmission power

control)control)• Adaptive transmitting range control (models, temporal Adaptive transmitting range control (models, temporal

and LQI, RSSI)and LQI, RSSI)• CC1000/CC2420 RF Radio Hardware: CC1000/CC2420 RF Radio Hardware:

Transmitter/Receiver, dBm)Transmitter/Receiver, dBm)


RF TransceiversRF Transceivers TI-ChipconTI-Chipcon

• CC1000CC1000• CC2420CC2420


Tmote Sky - RSSI valuesTmote Sky - RSSI values

Ref: Ref: http://www.moteiv.com/community/Reading_RSSIhttp://www.moteiv.com/community/Reading_RSSI_values_from_Tmote_Sky_values_from_Tmote_Sky

Read a incoming packet and store the Read a incoming packet and store the signal strength in thesignal strength in the• TOS_Msg structureTOS_Msg structure

Read the signal in the absence of the Read the signal in the absence of the incoming packetsincoming packets• NoiseNoise• Source interference : 802.11 networks, Source interference : 802.11 networks,

Microwave ovensMicrowave ovens



• Modifying CC2420RadioC.ncModifying CC2420RadioC.nc

implementation { ... components new CC2420ResourceC() as CmdRSSI; ... CC2420ControlM.CmdRSSI -> CmdRSSI; }



• Modifying CC2420ControlM.nc to provide extra Modifying CC2420ControlM.nc to provide extra ADC interfaceADC interface

• Use an additional ResourceUse an additional Resource

provides { provides { ... ... interface ADC as RSSI; interface ADC as RSSI; ... } ... } uses { uses { ... ... interface ResourceCmd as CmdRSSI; interface ResourceCmd as CmdRSSI; ... ... } }


Tmote Sky - RSSI valuesTmote Sky - RSSI valuesimplementation { implementation { ... ... async command result_t RSSI.getData() { async command result_t RSSI.getData() { call CmdRSSI.deferRequest();call CmdRSSI.deferRequest(); return SUCCESS; return SUCCESS; } } event void CmdRSSI.granted(uint8_t rh) { event void CmdRSSI.granted(uint8_t rh) { uint16_t data; uint16_t data; data = call HPLChipcon.read(rh, CC2420_RSSI); data = call HPLChipcon.read(rh, CC2420_RSSI); call CmdRSSI.release(); call CmdRSSI.release(); data += 0x7f; data &= 0x00ff; data += 0x7f; data &= 0x00ff; signal RSSI.dataReady(data); signal RSSI.dataReady(data); } } async command result_t RSSI.getContinuousData() async command result_t RSSI.getContinuousData()

{ return FALSE; { return FALSE; }}


Power Management IssuesPower Management Issues TMote Sky Typical Operating ConditionsTMote Sky Typical Operating Conditions


Power Management IssuesPower Management Issues A pair of AA batteries – 2400 mA-hours of A pair of AA batteries – 2400 mA-hours of

capacitycapacity Mote’s Current:Mote’s Current:

• Sleeping – 21 µASleeping – 21 µA• Active – 23 mAActive – 23 mA

Sampling period Td = 30 sec, 4 sec active Sampling period Td = 30 sec, 4 sec active timetime

Battery Life Battery Life Life = 2400/(4/Td)*23 +((Td-4)/Td)*0.21) Life = 2400/(4/Td)*23 +((Td-4)/Td)*0.21)

= 738 hr, or 30 days= 738 hr, or 30 days


Radio Transmit Power and Radio Transmit Power and Frequency – CC2420Frequency – CC2420

Ref: Ref: http://www.moteiv.com/community/Change_radio_transmit_http://www.moteiv.com/community/Change_radio_transmit_power_and_frequencypower_and_frequency

Change frequency at compile timeChange frequency at compile time • Valid channels - 11 to 26Valid channels - 11 to 26• Default channel – 11Default channel – 11• Env Variable setup: Export CC2420_CHANNEL=12Env Variable setup: Export CC2420_CHANNEL=12• Makefile inclusion: CC2420_CHANNEL=12Makefile inclusion: CC2420_CHANNEL=12

Change transmit power at compile timeChange transmit power at compile time• Preprocessor Directive: CC2420_DEF_RFPOWERPreprocessor Directive: CC2420_DEF_RFPOWER• CFLAGS = -DCC2420_DEF_RFPOWER=x make moteCFLAGS = -DCC2420_DEF_RFPOWER=x make mote• Power Index x: 1 through 31Power Index x: 1 through 31• 1 == -25 dBm1 == -25 dBm• 31 == 0 dBm31 == 0 dBm


Radio Transmit Power and Radio Transmit Power and Frequency – CC2420Frequency – CC2420

Change power or frequency at run timeChange power or frequency at run time• Command result_t TunePreset(uint8_t rh, Command result_t TunePreset(uint8_t rh,

uint8_t channel);uint8_t channel);• Command result_t TSetRFPower(uint8_t rh, Command result_t TSetRFPower(uint8_t rh,

uint8_t power);uint8_t power);• rh optionsrh options

RESOURCE_NONE: for automatic resource schedulingRESOURCE_NONE: for automatic resource scheduling CC2420ResourceC componentCC2420ResourceC component

• channelchannel One of the valid 802.15.4 present channel: 11 – 26One of the valid 802.15.4 present channel: 11 – 26 Freq = 2405 + 5(k-11) MHz, k = 11, 12, .., 26Freq = 2405 + 5(k-11) MHz, k = 11, 12, .., 26

• Power: 1 to 31Power: 1 to 31


ClusteringClustering

Manual/Self-organizingManual/Self-organizing Support routing and data aggregationSupport routing and data aggregation Hierarchical structures Hierarchical structures

• Multiple clustersMultiple clusters• Cluster heads (higher ID nodes – Unique ID)Cluster heads (higher ID nodes – Unique ID)• Gateways – cluster nodesGateways – cluster nodes• Long range communication – Cluster headsLong range communication – Cluster heads• Fault toleranceFault tolerance

Within a ClusterWithin a Cluster• Simple protocol for Simple protocol for

BroadcastingBroadcasting RoutingRouting

• Time or frequency division multiplexing can be reused across Time or frequency division multiplexing can be reused across the non-overlapping clustersthe non-overlapping clusters

• Monitoring nodes healthMonitoring nodes health


Time SynchronizationTime Synchronization

Time SynchronizationTime Synchronization• Issues: Issues:

Time-based sensor reading (moving objects)Time-based sensor reading (moving objects) Ultrasonic, radio signalsUltrasonic, radio signals Detection time comparison? Accuracy, sync.Detection time comparison? Accuracy, sync. Inter-node distance estimation Inter-node distance estimation Local/global clock synchronization methodsLocal/global clock synchronization methods


Time Synchronization Time Synchronization (cont.)(cont.)

Clock and Communication DelaysClock and Communication Delays• Hardware clock Hardware clock

Perfect clock - dC(t)/dt = 1Perfect clock - dC(t)/dt = 1 Skewed clock – drifted due to temperature, humidity, Skewed clock – drifted due to temperature, humidity,

etc [ 1- etc [ 1- δδ ≤ dC(t)/dt ≤ 1+ ≤ dC(t)/dt ≤ 1+ δδ; ; δ≈δ≈1010-6-6]]

• Latency in the ChannelLatency in the Channel Send timeSend time Access timeAccess time Propagation timePropagation time Receive timeReceive time



Move clock reading around the network Move clock reading around the network and perform temporal comparisonsand perform temporal comparisons

Intervals between events durationIntervals between events duration• Event times -> Time Intervals (mapping) Event times -> Time Intervals (mapping) • Time stamps – real timeTime stamps – real time• Time differencesTime differences• Temporal reasoning (more important than the Temporal reasoning (more important than the

exact time)exact time)• 1- 1- δδi ≤ i ≤ ΔΔCi/Ci/ΔΔt ≤ 1+ t ≤ 1+ δδii

ΔΔCi – local durationCi – local duration Time in senderTime in sender Time in receiverTime in receiver



Interval Methods – Time Sync Interval Methods – Time Sync ProtocolProtocol• Low-overheadLow-overhead• Scalable with network size changesScalable with network size changes• Can accommodate topology changesCan accommodate topology changes• Short-lived connectionShort-lived connection


Tmote Sky – Measure Elapse TimeTmote Sky – Measure Elapse Time

Elapse time: time between eventsElapse time: time between events• LocalTime interfaceLocalTime interface• 3 basic time precisions: Components3 basic time precisions: Components

CounterMilliC - MillisecondCounterMilliC - Millisecond Counter32khzC - 30 µs (32 kHz)Counter32khzC - 30 µs (32 kHz) CounterMicroC - MicrosecondCounterMicroC - Microsecond



LocalTime interfaceLocalTime interfaceinterface LocalTime<precision_tag> { interface LocalTime<precision_tag> {

async command uint32_t get(); }async command uint32_t get(); } Example Code:Example Code:configuration MyAppC { configuration MyAppC {

{ {

implementation { implementation {

components MyAppP; components MyAppP;

components CounterMilliC; components CounterMilliC;

MyAppP.LocalTime -> CounterMilliC; MyAppP.LocalTime -> CounterMilliC;

} }



Example Code:Example Code: module MyAppP { module MyAppP { uses interface LocalTime<TMilli>; uses interface LocalTime<TMilli>; } } implementation { implementation { task void some_task() { task void some_task() { // ... // ... t = call LocalTime.get(); t = call LocalTime.get(); // ... // ... } } } }


Time Synchronization – Reference Time Synchronization – Reference Broadcast System (RBS)Broadcast System (RBS)

Major Sources of Time Sync. ErrorsMajor Sources of Time Sync. Errors• Send timeSend time – clock propagation through node – clock propagation through node

OS and radio transmitterOS and radio transmitter• Access timeAccess time – due to multiple access protocol – due to multiple access protocol• Propagation timePropagation time - due to transmission through - due to transmission through

the multihop physical medium, queuing delays the multihop physical medium, queuing delays caused by congestioncaused by congestion

• Receive timeReceive time – receive path in the radio and – receive path in the radio and variable delays in interrupting the OSvariable delays in interrupting the OS



Problems with time comparison protocolsProblems with time comparison protocols• Long delays/Multihop routesLong delays/Multihop routes• Mapping time become uselessMapping time become useless

Assume that all radios are within range of Assume that all radios are within range of a single transmitter, many of these delays a single transmitter, many of these delays are mitigatedare mitigated

Reference Broadcasts Protocol – Reference Broadcasts Protocol – Objectives of Tim SyncObjectives of Tim Sync• Reduce delays and delay uncertaintyReduce delays and delay uncertainty• Establish the relative time among different Establish the relative time among different

clocks, while allowing the individual clocks to clocks, while allowing the individual clocks to run freelyrun freely



SenderSender• Send a sync reference packet (message)Send a sync reference packet (message)• The send and access times – unknown and variable, but The send and access times – unknown and variable, but

are the same for every radio that hears any particular are the same for every radio that hears any particular message broadcastmessage broadcast

• Negligible propagation time for single radio hopNegligible propagation time for single radio hop ReceiversReceivers

• Receive the same the packet Receive the same the packet • Record TOA in their own time frame Record TOA in their own time frame • Receive time Receive time

The only significant source of errorThe only significant source of error Due to the variability among the receiversDue to the variability among the receivers A sequence of broadcasts – reduce error A sequence of broadcasts – reduce error

• Exchange info among themselvesExchange info among themselves Receiver know the relative to each other, rather than to the Receiver know the relative to each other, rather than to the

broadcasting nodebroadcasting node



SenderSender• Send a sync reference packet (message)Send a sync reference packet (message)• The send and access times – unknown and variable, but The send and access times – unknown and variable, but

are the same for every radio that hears any particular are the same for every radio that hears any particular message broadcastmessage broadcast

• Negligible propagation time for single radio hopNegligible propagation time for single radio hop ReceiversReceivers

• Receive the same the packet Receive the same the packet • Record TOA in their own time frame Record TOA in their own time frame • Receive time Receive time

The only significant source of errorThe only significant source of error Due to the variability among the receiversDue to the variability among the receivers A sequence of broadcasts – reduce error A sequence of broadcasts – reduce error

• Exchange info among themselvesExchange info among themselves Receiver know the relative to each other, rather than to the Receiver know the relative to each other, rather than to the

broadcasting nodebroadcasting node


Localization and Localization Localization and Localization ServicesServices

Provide info about the world – highly Provide info about the world – highly localized in space and/or timelocalized in space and/or time

ApplicationsApplications• Static nodesStatic nodes• Mobile nodesMobile nodes• Location and time infoLocation and time info

Target trackingTarget tracking Habitat monitoringHabitat monitoring

How about the addition of GPS?How about the addition of GPS?• Landmark nodesLandmark nodes• Outside onlyOutside only


Localization and Localization Localization and Localization Services Services (cont.)(cont.)

Ranging TechniquesRanging Techniques• Received Signal Strength (RSS) – RF signal Received Signal Strength (RSS) – RF signal

estimationestimation• Distance estimation Distance estimation

Send/Receive Power calculationSend/Receive Power calculation• Source signal strength, attenuated laws, RSSSource signal strength, attenuated laws, RSS• Square law (not linear) – received power and distance Square law (not linear) – received power and distance

relationshiprelationship TOA (Time of Arrival)TOA (Time of Arrival)

• Time measurement (sender -> receiver)Time measurement (sender -> receiver)• Synchronized sender and receiver timeSynchronized sender and receiver time

TDOA (Time Difference of Arrival) at two receiversTDOA (Time Difference of Arrival) at two receivers• Estimate the difference in distances between the two Estimate the difference in distances between the two

receivers and the senderreceivers and the sender


Localization and Localization Localization and Localization Services Services (cont.)(cont.)

Range-based Localization Algorithms Range-based Localization Algorithms Location ServicesLocation Services

Documents

12/5/2006 - updated WSN Mote- MCU & Sensor Hardware 1 ECET 581 Wireless Sensor Networks Infrastructure Establishment November 28, 2006 Fall 2006 lin