25-07-2012, 09:55 AM
Wireless Sensor Networks
WirelessSensorNetChap04.pdf (Size: 1.88 MB / Downloads: 25)
INTRODUCTION
Smart environments represent the next evolutionary development step in building, utilities, industrial, home, shipboard, and transportation systems automation. Like any sentient organism, the smart environment relies first and foremost on sensory data from the real world. 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; this is captured in biological systems by the distinction between exteroceptors and proprioceptors. PDABSC(Base Station Controller, Preprocessing)BSTWirelessSensorMachine MonitoringMedical MonitoringWireless SensorWirelessData Collection NetworksWireless(Wi-Fi 802.11 2.4GHzBlueToothCellular Network, -CDMA, GSM)PrinterWireland(Ethernet WLAN, Optical)Animal MonitoringVehicle MonitoringOnlinemonitoringServertransmitterAny where, any time to accessNotebookCellular PhonePCShip MonitoringWireless Sensor NetworksRovingHumanmonitorData Distribution NetworkManagement Center(Database large storage, analysis)Data Acquisition Network
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.
COMMUNICATION NETWORKS
The study of communication networks can encompass several years at the college or university level. To understand and be able to implement sensor networks, however, several basic primary concepts are sufficient.
Network Topology
The basic issue in communication networks is the transmission of messages to achieve a prescribed message throughput (Quantity of Service) and Quality of Service (QoS). QoS can be specified in terms of message delay, message due dates, bit error rates, packet loss, economic cost of transmission, transmission power, etc. Depending on QoS, the installation environment, economic considerations, and the application, one of several basic network topologies may be used.
Power Management
With the advent of ad hoc networks of geographically distributed sensors in remote site environments (e.g. sensors dropped from aircraft for personnel/vehicle surveillance), there is a focus on increasing the lifetimes of sensor nodes through power generation, power conservation, and power management. Current research is in designing small MEMS (microelectromechanical systems) RF components for transceivers, including capacitors, inductors, etc. The limiting factor now is in fabricating micro-sized inductors. Another thrust is in designing MEMS power generators using technologies including solar, vibration (electromagnetic and electrostatic).
Network Structure and Hierarchical Networks
Routing tables for distributed networks increase exponentially as nodes are added. An n mesh network has nm links, and there are multiple paths from each source to each destination. Hierarchical network structures simplify routing, and also are amenable to distributed signal processing and decision-making, since some processing can be done at each hierarchical layer. m
It has been shown [Lewis and Abdallah 1993] that a fully connected network has NP-hard complexity, while imposing routing protocols by restricting the allowed paths to obtain a reentrant flow topology results in polynomial complexity. Such streamlined protocols are natural for hierarchical networks.
WIRELESS SENSOR NETWORKS
Sensor networks are the key to gathering the information needed by smart environments, whether in buildings, utilities, industrial, home, shipboard, transportation systems automation, or elsewhere. Recent terrorist and guerilla warfare countermeasures require distributed networks of sensors that can be deployed using, e.g. aircraft, and have self-organizing capabilities. In such applications, running wires or cabling is usually impractical. A sensor network is required that is fast and easy to install and maintain.
IEEE 1451 and Smart Sensors
Wireless sensor networks satisfy these requirements. 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, and standard control protocols and network interfaces [IEEE 1451 Expo, 2001].
WirelessSensorNetChap04.pdf (Size: 1.88 MB / Downloads: 25)
INTRODUCTION
Smart environments represent the next evolutionary development step in building, utilities, industrial, home, shipboard, and transportation systems automation. Like any sentient organism, the smart environment relies first and foremost on sensory data from the real world. 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; this is captured in biological systems by the distinction between exteroceptors and proprioceptors. PDABSC(Base Station Controller, Preprocessing)BSTWirelessSensorMachine MonitoringMedical MonitoringWireless SensorWirelessData Collection NetworksWireless(Wi-Fi 802.11 2.4GHzBlueToothCellular Network, -CDMA, GSM)PrinterWireland(Ethernet WLAN, Optical)Animal MonitoringVehicle MonitoringOnlinemonitoringServertransmitterAny where, any time to accessNotebookCellular PhonePCShip MonitoringWireless Sensor NetworksRovingHumanmonitorData Distribution NetworkManagement Center(Database large storage, analysis)Data Acquisition Network
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.
COMMUNICATION NETWORKS
The study of communication networks can encompass several years at the college or university level. To understand and be able to implement sensor networks, however, several basic primary concepts are sufficient.
Network Topology
The basic issue in communication networks is the transmission of messages to achieve a prescribed message throughput (Quantity of Service) and Quality of Service (QoS). QoS can be specified in terms of message delay, message due dates, bit error rates, packet loss, economic cost of transmission, transmission power, etc. Depending on QoS, the installation environment, economic considerations, and the application, one of several basic network topologies may be used.
Power Management
With the advent of ad hoc networks of geographically distributed sensors in remote site environments (e.g. sensors dropped from aircraft for personnel/vehicle surveillance), there is a focus on increasing the lifetimes of sensor nodes through power generation, power conservation, and power management. Current research is in designing small MEMS (microelectromechanical systems) RF components for transceivers, including capacitors, inductors, etc. The limiting factor now is in fabricating micro-sized inductors. Another thrust is in designing MEMS power generators using technologies including solar, vibration (electromagnetic and electrostatic).
Network Structure and Hierarchical Networks
Routing tables for distributed networks increase exponentially as nodes are added. An n mesh network has nm links, and there are multiple paths from each source to each destination. Hierarchical network structures simplify routing, and also are amenable to distributed signal processing and decision-making, since some processing can be done at each hierarchical layer. m
It has been shown [Lewis and Abdallah 1993] that a fully connected network has NP-hard complexity, while imposing routing protocols by restricting the allowed paths to obtain a reentrant flow topology results in polynomial complexity. Such streamlined protocols are natural for hierarchical networks.
WIRELESS SENSOR NETWORKS
Sensor networks are the key to gathering the information needed by smart environments, whether in buildings, utilities, industrial, home, shipboard, transportation systems automation, or elsewhere. Recent terrorist and guerilla warfare countermeasures require distributed networks of sensors that can be deployed using, e.g. aircraft, and have self-organizing capabilities. In such applications, running wires or cabling is usually impractical. A sensor network is required that is fast and easy to install and maintain.
IEEE 1451 and Smart Sensors
Wireless sensor networks satisfy these requirements. 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, and standard control protocols and network interfaces [IEEE 1451 Expo, 2001].