mr eze sen zora chapter 1

8/18/2019 Mr Eze Sen Zora Chapter 1

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BASICS OF SENSOR NETWORKS

1

Sensor Networks © 2014: Dr. H. K. Verma

Dr. H. K. Verma

Distinguished Professor (EEE)

Sharda University, Greater Noida

(Formerly: Deputy Director and Professor of Instrumentation

Indian Institute of Technology Roorkee)


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CONTENTS


1. Industrial Data Networks

2. LAN Topologies

3.

Device Level Networks

4. 7-Layer OSI Model of Communication System

5.

Networking of Sensors


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3

!

Communication among computers/ servers/ work-

stations

! Communication between computer and peripherals

!

Communication between computer and intelligent

instruments

! Communication among field devices (Factory-floor or

field communications) using: " Transducer networks or Sensor networks, or" Field-device networks or Device-level networks, or

" Sensor and actuator networks, or" Factory-wide networks

Industrial Data Communications


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Hierarchy of Industrial Data Networks

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FD FD FD FD

ServerPC

Enterprise – levelnetwork

(LAN / WAN)Control Terminal Control Terminal

Device-level network(LAN/PAN)

FD: Field Device (Sensor / Actuator/etc.)

Control – levelnetwork

(LAN)Industrial Controller/PLC/RTU

Workstation


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Data Networks in Industry

!

Enterprise NetworkNetwork of the PCs, workstations and servers in Offices

and the control terminals (PCs) in Control Room.

!

Control-Level Network Network of the control-terminals (PCs) and industrial

controllers (PLCs), which are either in Control Room oron Factory Floor.

! Device-Level Network

Network of a controller/PLC/RTU in Control Room with

its field devices (Sensors, Actuators, etc.) on FactoryFloor.


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LAN Topologies

! Basic Topologies

1. Point-to-Point2. Multipoint

! Multipoint Topologies

1. Bus2. Ring

3.

Star4. Tree5. Mesh


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Bus (or Multidrop)Topology

S t a t i o n

s

BusData flow

T

Tap

!

Bus is a linear transmission medium

! Data flow is bidirectional

! Stations connected through taps taken from bus

! Terminator (T) absorbs signal, thus avoids echos

T



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Ring (or Loop)Topology

!

Nodes (computers) are connected in tandem (series) to form closed loop! Data flows through nodes (computers)

! Data flow is unidirectional

! Each node acts as a repeater

! It receives a data on one link and transmits bit-by-bit on other link



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Star Topology

! Network comprised of many point-to-point circuits! Central node: Hub or switch! Hub: Operates in broadcasting mode! Switch: Operates as frame-switching device

Central node


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Tree Topology

Headend

Branches

Data flow

T

Tap

! Generalization of bus topology

! Each branch may have further branches

T

T

Data flow

Data flow

10Sensor Networks © 2014: Dr. H. K. Verma



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Mesh (or Fully Connected) Topology

! Each station has a bidirectional link to every other station

! Less traffic problems, high reliability, high security

! Large no. of links: n(n-1)/2 links for n nodes

! Each station must have n-1 I/O ports


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Device–Level Wired Network


Control – level network

(Ethernet)

FD FD FD FD

Device-level network

Industrial Controller/PLC/RTU



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FD FD FD

Device–Level Wireless Network


Device-level network

Control – level network

(Ethernet)


Industrial Controller/PLC/RTU

Access Point



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Special Requirements of Device Level Networks

!

Low latency or small end-to-end delay

! Low bandwidth or data rate

! High data security

!

High network security

! Low power consumption or long battery life(for wireless networks only)

T h l i /P t l



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Technologies/Protocolsfor Device-Level Networks

Technologies/Protocolsfor Wired Networks

! RS422

! RSR485

!

MODbus

! Foundation Fieldbus

! HART

! CAN

! LON

! BACNet

Technologies/Protocolsfor Wireless Networks

! Zigbee

!

Wi-Fi

! Bluetooth

! Wireless Fieldbus



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7-Layer OSI Model of Communication Systems

! Open System Interconnection model

! Prepared and issued by International Standards Organization

! Reference model of communication systems

! Defines functions of a communication system in 7 layers

!

For use as reference or model to identify and classify the

various functions of a given communication system

! Not a standard or set of prescriptions for a communication

system to adhere to

! For any communication system, layers 1 and 7 are

essential, while some middle layers may be absent

! A communication protocol or standard may not define all

the 7 layers, it may define as few as one layer.


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Data Transfer Between Systems

Application Layer

Presentation Layer

Session Layer

Transport Layer

Network Layer

Data-Link Layer

Physical Layer

Application Layer

Presentation Layer

Session Layer

Transport Layer

Network Layer

Data-Link Layer

Physical Layer



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Functions of Seven Layers

Application Layer

Presentation Layer

Session Layer

Transport Layer

Network Layer

Data-Link Layer

Physical Layer

Signal

Application Programs

Data Presentation(Encryption, Compression, Data Formatting)

Inter-Application Dialogues

Addressing

Network Routing

Medium Access Control, Frame Format

Comm. Medium, Connectors,Data-to-Signal Conversion,



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Networking of Sensors

Four Situations:

Situation A – Ordinary Sensor + SC + MPU + Interface

Situation B – Network Sensor

Situation C – Smart Sensor + Custom Interface

Situation D – Smart Sensor + IEEE 1451 Interface


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Situation A: Ordinary Sensor+SC+MPU+Interface

Ordinarysensor

Network

SC ADC !pComm.

interface

Advantage ! Flexibility

Disadvantages ! Cumbersome

! Only expert can do! Expensive

Comm.port

ROM

RAM


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Situation B: Network Sensor

Smartnetwork

sensor

Network

Comm. port

Advantages ! Simple

! Fast! No expertise required

Disadvantage ! No flexibility of network protocol


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Situation C: Smart Sensor + Custom Interface

Smart

sensorNetworkADC MPU

Customcom

interface

Comm.

port

Advantage ! No SC required

Disadvantages ! Cumbersome

! Only expert can do


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S N k © 2014 D H K V

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Situation D: Smart Sensor + IEEE1451 Interface

Smartsensor

NetworkSTIM NCAP

IEEE 1451–Compliant

Advantages ! No SC required

! Flexibility of network protocol

Disadvantage ! Needs STIM & NCAP

mr eze sen zora chapter 1

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