Lokale Netzstrukturen

(1)

Lokale Netzstrukturen

Einführung

(2)

Motivation

SS 2017 Lokale Netzstrukturen ‐Einführung 2

(3)

Moore’s Law

(4)

Exploiting Moore‘s Law wrt. Scale

one mainframe for many desktop PC for one many devices for one

Size Number

4

(5)

How to Network many Devices?

• Small (and possibly mobile devices)  wireless networking

• “Classical” wireless Networking uses base stations

–

Example: Wireless LAN

–

Example: Mobile Phones

• Why always relying on an infrastructure?

–

Less maintenance cost without relying on an infrastructure

–

Rapid installation of a network if infrastructure is used

–

Communication would be for free

–

Not involving a far away base station may even save communication bandwidth

• Try to construct a network without infrastructure, using networking abilities of the participants

• Simplest example: Laptops in a conference room – a single‐hop ad hoc network

• More sophisticated example: multihop ad‐hoc networks

(6)

Ad‐Hoc Networking Examples

• Factory floor automation

 Disaster recovery

 Car-to-car

communication

ad hoc ad hoc



Military networking: Tanks, soldiers, …



Finding out empty parking lots in a city, without asking a server



Search-and-rescue in an avalanche



Personal area networking (watch, glasses, PDA, medical appliance, …)



Rooftop networks



…

Lokale Netzstrukturen ‐Einführung

SS 2017 6

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The Wireless Sensor Network Idea

Sensor Node Sensor Network

(8)

Example: Environmental Monitoring

Example: Great Duck Island, Berkeley, Culler et al.

SS 2017 8

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Example: Precision Agriculture

• Example: LOFAR project

– Fighting Phytophtora using micro‐climate

– Temperature and relative humidity

(10)

Example: Forest‐Fire Detection

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(11)

Example: Exploration of Unknown Territory

Example: CotsBots, Berkeley, Pister et al.

(12)

Example: Traffic Telematics

Image source: www.whnet.com/4x4/telematics.html Lokale Netzstrukturen ‐Einführung

SS 2017 12

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More Examples

Building Automation

Home Automation

Industrial Automation

Logistics

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Die Idee der drahtlosen Sensor‐Aktuator‐Netze

Beispiel Gebäudeautomatisierung

Generell: Aktoren in den Beispielanwendungen von Sensornetzen

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(15)

Idee: Mobile autonome Roboter‐Sensor‐Netze

Beispiel: Überwachung eines kontaminierten Gebietes

Beispiel: Exploration von unerforschtem

schwer zugänglichem Gebiet

(16)

Idee: Kombinierte mobile Roboter‐ und Sensor‐(Aktuator)‐Netze

Mobile Roboter als drahtlose Support‐Knoten oder Data‐Mules

Mobile Roboter für Deployment und Maintenance von drahtlosen Sensor‐

(Aktuator)‐Netzen

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Herausforderungen

(18)

Drahtlose Kommunikation = Unzuverlässige Kommunikation

LOS-Weg

NLOS-Weg



Typisches Fading‐Verhalten Hauptursache: Mehrwegeausbreitung

(19)

Hoher Pfadverlust  Multihop

(20)

Sender Receiver

Große Kollisionsdomänen  Multihop

(21)

Große Kollisionsdomäne  Broadcast‐Stürme

Redundante Übertragungen

Auslieferungsrate Kollisionen &

Netzdichte niedrig

hoch

(22)

Limitierender Faktor Batteriekapazität

(23)

Energie‐Effizienz  Multihop

10 m

1 nJoule/Bit

…

Bluetooth‐Beispiel



100m in einem Hop: 100nJ/Bit



100m in zehn Hops: 10nJ/Bit

Signalstärk e

100 m

100 nJoule/Bit

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Energieeffizienz  Schalf‐Wach‐Zyklen

P

_sleep

P

_active

t P

“Traditionelle” MAC-Verfahren:

P

_sleep

P

_active

t P

Ein ideales energieminimales MAC-Verfahren:

Power Consumption

Power Savings

TX/RX TX/RX TX/RX

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Energieeffizienz  In‐Network‐Processing

S3 Sink: compute

max(d1,d2,d3) S1

S2

send(d1)

send(d2)

send(d3)

S3 Sink

S1

S2

send(d1)

send(d2)

compute

m = max(d1,d2,d3) send(m)

Beispiel: Maximum‐Berechnung

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Energieeffizient und kleine Größe  Limitierte Ressourcen

BTNode

Mica2

Mica2Dot

Tmote Sky

Imote

Source: http://www.btnode.ethz.ch/Projects/SensorNetworkMuseum

Serial attached Flash in kB

Internal RAM in kB

Flash RAM in kB

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Energieeffizient und kleine Größe  Limitierte Ressourcen

CC1000 CC1021 CC2420 TR1000 XE1205

Bit Rate [kbps]

76.8 153.6 250 115.2 1.2 - 152.3

Sleep Mode [uA]

0.2 - 1 (osc.

core off)

1.8 (core off) 1 0.7 0.2

RX [mA] 9.3 (433MHz) / 11.8

(868MHz)

19.9 19.7 3.8 (115.2kbps)

14 TX Min [mA] 8.6 (-20dBm) 14.5 (- 20dBm)

8.5 (-25dBm) 33 (+5dBm)

TX Max [mA] 25.4 (+5dBm)

25.1 (+5dBm)

17.4 (0dBm) 12

(+1.5dBm)

62 (+15dBm)

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Mobilität

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Modellbildung

Modellierung einer einzigen Verbindung

(30)

Path Loss

d S _RX

S _RX =

(31)

Path Loss: A Geometric Explanation

(32)

Considering Attenuation

S _RX =

(33)

Further Effects

• Reflection & Refraction

• Diffraction

• Scattering

• Doppler Shift

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Log‐Distance Path Loss Model

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Considering Shadowing: Lognormal Model

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Modeling the Time Varying Nature

• Consider mobile sender receiver pair

• Modeling received signal strength as R.V. X

• Considering probability P[X · x] (the CDF)

• Example: Rayleigh Fading Model

– No line of sight

– Exponential distributed CDF

• Example: Ricean fading model

– Dominant line of sight – Ricean distributed CDF

SS 2017 Lokale Netzstrukturen ‐Einführung