Wireless Sensor Networks

Smart Environments: Technologies, Protocols, and Applicationsed. D.J. Cook and S.K. Das, John Wiley, New York, 2004.

B.Devi8986402207.06.2010

Introduction

Communication Networks

Network Topology Communication Protocols and Routing Power Management Network Structure Historical Development and Standards

Wireless sensor networks IEEE 1451 and Smart Sensors Transducers and Physical Transduction Principles Sensors for Smart Environments Commercially Available Wireless Sensor Systems

Signal processing and decision making Building and Home Automation Conclusion

Synopsis

INTRODUCTION

Sensory data comes from multiple sensors of different modalities in distributed locations.

The smart environment needs information about its surroundings as well as about its internal workings

The challenges in the hierarchy of: Detecting the relevant quantities, monitoring and collecting the data, assessing and evaluating the information, formulating meaningful user displays, and performing decision-making and alarm functions are enormous.

The information needed by smart environments is provided by Distributed Wireless Sensor Networks, which are responsible for sensing as well as for the first stages of the processing hierarchy.

The study of wireless sensor networks is challenging in that it requires an enormous breadth of knowledge from an enormous variety of disciplines.

In this we outline communication networks, wireless sensor networks and smart sensors, physical transduction principles, commercially available wireless sensor systems, signal processing and decision-making, and finally some concepts for home automation.

COMMUNICATION NETWORKS

Network Topology

Communication Protocols and Routing

The topics of communication protocols and routing are complex and require much study. Some basics useful for understanding sensor nets are presented here.

HeadersSwitching Multiple Access Protocols Flow Control Routing Fixed routing schemes Adaptive routing schemes Deadlock and Livelock Open Systems Interconnection Reference Model (OSI/RM)

Open Systems Interconnection Reference Model (OSI/RM)

Power Management

MEMS power generator MEMS fabrication layout of power generator

Multicast Systems

Multicast routing improves efficiency and reduces message path length

Network Structure

Historical Development and Standards

Ethernet

Token Ring

Gigabit Ethernet

Client-Server networks

Peer-to-Peer networking

Peer-to-Peer Computing

802.11 Wireless Local Area Network

Bluetooth

Home RF

WIRELESS SENSOR NETWORKS

Desirable functions for sensor nodes include:

Ease of installation

Self-identification

Self-diagnosis

Reliability

Time awareness for coordination with other nodes

Some software functions and DSP

Standard control protocols

Network interfaces

Basic architecture of IEEE 1451

A general model of a smart sensor [IEEE 1451 Expo, Oct. 2001]

Transducers and Physical Transduction Principles

A transducer is a device that converts energy from one domain to another. In our application, it converts the quantity to be sensed into a useful signal that can be directly measured and processed.

Sensory Transducer

Sensory transduction may be carried out using physical principles, some of here

Mechanical Sensors include :

The Piezoresistive Effect

The Piezoelectric Effect

Tunneling Sensing

Capacitive Sensors

Magnetic and Electromagnetic Sensors include:

Magnetic Field Sensors

Eddy-Current Sensors

Thermal Sensors

Thermo-Mechanical Transduction

Thermocouples

Resonant Temperature Sensors

Sensors for Smart Environments

Commercially Available Wireless Sensor Systems

Berkeley Crossbow Motes

Microstrain Wireless Sensors

SIGNAL PROCESSING AND DECISION-MAKING

The IEEE 1451 Smart Sensor includes basic blocks for signal conditioning (SC), digital signal processing (DSP).

Signal conditioning (SC): SC is performed using electronic circuitry, which may conveniently be built using standard VLSI fabrication techniques in situ with MEMS sensors.

Digital signal processing (DSP): Sensor fusion is important in a network of sensors of different modalities. A distributed vehicle/personnel surveillance network might include seismic, acoustic, infrared motion, temperature, and magnetic sensors. The standard DSP tool for combining the information from many sensors

Building and Home Automation

Smart Home Networks

CONCLUSION

A wireless sensor network (WSN) consists of spatially distributed autonomous sensors to cooperatively monitor physical or environmental conditions, such as temperature, sound, vibration, pressure, motion or pollutants.

The development of wireless sensor networks was motivated by military applications such as battlefield surveillance.

They are now used in many industrial and civilian application areas, including industrial process monitoring and control, machine health monitoring, environment and habitat monitoring, healthcare applications, home automation, and traffic control.