Sensor Networks & TinyDB

Author: Roman KolcunSupervisor: Julie A. McCann

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Index

Sensor Motes Sensor Networks Real world deployments TinyDB

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What a Sensor Can Sense?

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What a Sensor Can Sense?

Temperature Humidity Acceleration Noise Light Magnetic Field Gravity Pressure

Heart Rate Motion Toxins Nutrients Glucose Level Oxygen Level Hormones Proteins

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Sensor Mote

CPU ?

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Sensor Mote

CPU 4 MHz 8 bit ATmega 128L, RISC

Memory ?

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Sensor Mote

CPU 4 MHz 8 bit ATmega 128L, RISC

Memory 128KB Program Flash Memory 4KB RAM 512KB Flash – serial access, max. 10-100k rewritten

Wireless ?

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Sensor Mote

CPU 4 MHz 8 bit ATmega 128L, RISC

Memory 128KB Program Flash Mem. 4KB RAM 512KB Flash – serial access, max. 10-100k rewritten

Wireless IEEE 802.15.4 - 2.4GHz 250kbps 70 – 100m outdoor, 20 – 30m indoor

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Beastie – Imperial

8k bytes Flash program memory 1k byte SRAM 512 bytes EEPROM 4MHz FM radio at 434.65MHz 10kbps maximum data rate (run at 5kbps as

standard) Maximum range 500m

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1 mm3 Sensor

Designed at Michigan University Measures pressure in an eye every 15 minutes Average Power Consumption 15 nW To charge batteries:

10 hours of artificial light

1.5 hours of sun light

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Power Consumption

Typically supplied by small batteries 1000 – 3000 mAh 1 mAh – 1 milliamp current for 1 hour Power = Watts (W) = Amps (A) * Volts (V) Energy = Joules (J) = W * time

Power consumption Processor: 8mA active, <15μA sleep Radio: 19.7mA receive, 11 – 17.4mA xmit,

~20ms/packet Sensor: 1μA – 100's mA, 1μs – 1s to sample

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Example

Battery: 1000mAh How long a node can last and how much data

can a node receive?

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Example

Battery: 1000mAh How long a node can last and how much data

can a node receive?

1000mAh / 19.7mA = ~50.7h50.7h = 182 741s * 250kbps = ~5.7MB

in real world approx. half of it = 2.85MB

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Example

Battery: 1000mAh Sense 1 value every 30 seconds, receive 1

packet and send 1 packet. How long will battery last?

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Example

Battery: 1000mAh Sense 1 value every 30 seconds, receive 1

packet and send 1 packet. How long will battery last?

8+29*0.015+1+19.7*0.02+13*0.02 = = ~10mA/30s = ~ 0.3363 mA/s1000mAh = 3 600 000 mAs / 0.3363 = ~124 days

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Sensor Networks - Problems

Lossy, Ad-hoc radio communication Really lossy radio communication Node / link failures Severe power constraints Asymmetric links – if I can hear you, it does not

mean you can hear me Interference Hidden node problem

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Sensor Networks

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Sensor Networks

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Sensor Networks - Problems

Duty cycling Time synchronization Node / link failure

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Duty Cycling

… zzz … … zzz …

timewake-up period

epoch time

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Real World Deployments

Great Duck Island temperature relative humidity infra-red termophile

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Real World Deployments

Golden Gate Bridge vibrations temperature

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Redwood

Humidity vs. Time

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45

55

65

75

85

95

Rel

Hu

mid

ity (

%)

101 104 109 110 111

Temperature vs. Time

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13

18

23

28

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7/7/039:40

7/7/0313:11

7/7/0316:43

7/7/0320:15

7/7/0323:46

7/8/033:18

7/8/036:50

7/8/0310:21

7/8/0313:53

7/8/0317:25

7/8/0320:56

7/9/030:28

7/9/034:00

7/9/037:31

7/9/0311:03

Date

Tem

pera

ture

(C

)

36m

33m: 11132m: 110

30m: 109,108,107

20m: 106,105,104

10m: 103, 102, 101

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Imperial Deployment

Mobile Node (Mule) Experiment

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Other Deployments

Monitoring Space environmental and habitat monitoring (Duck Island,

Redwood Trees) precision agricultures climate control surveillance intelligent alarms

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Other Deployments (cont.)

Things structural monitoring ecophysiology condition based maintenance (plane, bridges,

buildings, pipes) medical diagnostics terrain mapping

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Other Deployments (cont.)

Interactions with things and encompassing space monitoring wildlife habitats disaster management emergency response ubicomp process flow

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Motivations for TinyDB

Create an application which measures temperature. Make an average of temperatures over 15°C.

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Motivations for TinyDB

Create an application which measures temperature. Make an average of temperatures over 15°C.

How would you change the application to make an average of temperatures over 20°C ?

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Motivations for TinyDB

Create an application which measures temperature. Make an average of temperatures over 15°C.

How would you change the application to make an average of temperatures over 20°C ? Recode the application and manually update every

node. Think about it while programming the application

and let it accept commands from the basestation Use TinyDB

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TinyDB

Supports a subset of Stream SQL Whole network could be seen as ”sensor” table Query syntax:

SELECT <aggregates>, <attributes>[FROM {sensors} | {buffer}][WHERE <predicates>][GROUP BY <expression>][SAMPLE INTERVAL <const> | ONCE][INTO buffer][TRIGGER ACTION <command>]

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TinyDB

Example:SELECT light, magFROM sensorsWHERE light > c1AND mag > c2SAMPLE INTERVAL 1s[FOR 3600s]

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TinyDB

Example:SELECT light, magFROM sensorsWHERE light > c1AND mag > c2SAMPLE INTERVAL 1s

E(sampling mag) » E(sampling light)

1500 μJ vs 90 μJ

In which order the predicates should be evaluated?

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TinyDB

Do we need to notify all sensors in the network?

SELECT lightFROM sensorsWHERE node_id > 20SAMPLE INTERVAL 10s

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What if the Result Depends on More than One Node?

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What if the Result Depends on More than One Node? (cont.)

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What We Do

Adjust power transmission in order to minimise interference using game theory

Duty-cycling Time synchronization Mules In-network data processing (joining data & data

filtering)

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References

[1] Decentralised & Volatile Self-Adaptive,Self Organising WSNs by Julie A. McCann[2] Implementation and Research Issues in Query Processing for Wireless Sensor Networks by Wei Hong & Sam Madden[3] Modelling the Golden Gate Bridge using Wireless Sensor Networks by Guilherme Rocha, Shamim Pakzad and Bin Yu[4] http://www.coa.edu/greatduckisland.htm – College of the Atlantic – Great Duck Island Project

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Where You Can Find Us

Julie A. McCann: jamm@doc.ic.ac.uk Roman Kolcun: rk1208@doc.ic.ac.uk Lab: Huxley Building, 563