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Introduction To Wireless Sensor Networks. Wireless Sensor Networks.
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Wireless Sensor Networks A wireless sensor network is a collection of nodes organized into a cooperative network. Each node consists of processing capability may contain multiple types of memory have an RF transceiver, have a power source (e.g., batteries and solar cells), and accommodate various sensors.
Communication Network A communication network is composed of nodes, each of which has computing power and can transmit and receive messages over communication links, wireless or cabled.
Basic Network Topologies • Star Topology • Ring Topology • Bus Topology • Tree Topology • Fully Connected Networks • Mesh Networks
Star Topology All nodes of the star topology are connected to a single hub node. The hub requires greater message handling, routing, and decision-making capabilities than the other nodes. If a communication link is cut, it only affects one node. However, if the hub is incapacitated the network is destroyed.
Ring Topology In the ring topology all nodes perform the same function and there is no leader node. Messages generally travel around the ring in a single direction. However, if the ring is cut, all communication is lost.
Bus Topology In the bus topology, messages are broadcast on the bus to all nodes. Each node checks the destination address in the message header, and processes the messages addressed to it.
Tree Topology In Tree Topology there will be a root node and the root node has two branches. Each branch may again contains branches and so on.
Fully-connected Network In a fully connected Network when additional nodes are added, the number of links increases exponentially.
Mesh Network Mesh networks are regularly distributed networks that generally allow transmission only to a node’s nearest neighbors. The nodes in these networks are generally identical. Mesh nets can be good models for large-scale networks of wireless sensors that are distributed over a geographic region.
Communication Network continue … A single network may consist of several interconnected subnets of different topologies. Networks are further classified as Local Area Networks (LAN), e.g. inside one building, or Wide Area Networks (WAN), e.g. between buildings.
Wireless Sensor Networks A wireless sensor network (WSN) is a wireless network consisting of spatially distributed autonomous devices using sensors to cooperatively monitor physical or environmental conditions, such as temperature, sound, vibration, pressure, motion or pollutants, at different locations.
Wireless Sensor Networks continue … The development of wireless sensor networks was originally motivated by military applications such as battlefield surveillance. However, wireless sensor networks are now used in many civilian application areas, including environment and habitat monitoring, healthcare applications, home automation, and traffic control.
P O W E R Sensors Storage Processor Radio WSN device schematics Sensor Node • Networks of typically small, battery-powered, wireless devices. • On-board processing, • Communication, and • Sensing capabilities.
P O W E R Sensors Storage Processor Radio WSN device schematics Sensor Node continue … In addition to one or more sensors, each node in a sensor network is typically equipped with a radio transceiver or other wireless communications device, a small microcontroller, and an energy source, usually a battery.
Sensor Node continue …
Sensor Node continue …
Antenna Interface electronics, radio and microcontroller Soil moisture probe Mote Communications barrier Sensor Network Server Sensor field Gateway Internet
Computer Revolution Original IBM PC (1981) MICAZ Mote (2005) 4.77 MHz 4 MHz 16-256 KB RAM 128 KB RAM 160 KB Floppies 512 KB Flash ~ $6K (today) ~ $35 ~ 64 W ~14 mW 25 lb, 19.5 x 5.5 x 16 inch 0.5 oz, 2.25 x 1.25 x 0.25 inch
Sensor Network Server Watershed Sensor field Gateway Internet
Network Model for WSN A wireless sensor network consists of hundreds or thousands of low cost nodes which could either have a fixed location or randomly deployed to monitor the environment. The flowing of data ends at special nodes called base stations (sometimes they are also referred to as sinks).
Network Model for WSN continue … A base station links the sensor network to another network (like a gateway) to disseminate the data sensed for further processing. Base stations have enhanced capabilities over simple sensor nodes since they must do complex data processing.
Network Model for WSN continue … This justifies the fact that bases stations have workstation/laptop class processors, and of course enough memory, energy, storage and computational power to perform their tasks well.
Usage of Sensor Networks Environmental Observation: Sensor networks can be used to monitor environmental changes. An example could be water pollution detection in a lake that is located near a factory that uses chemical substances. Sensor nodes could be randomly deployed in unknown and hostile areas and relay the exact origin of a pollutant. Other examples include forest fire detection, air pollution and rainfall observation in agriculture.
Usage of Sensor Networks continue … Military Monitoring: Military uses sensor networks for battlefield surveillance; sensors could monitor vehicular traffic, track the position of the enemy.
Usage of Sensor Networks continue … Building Monitoring: Sensors can also be used in large buildings or factories monitoring climate changes. Thermostats and temperature sensor nodes are deployed all over the building’s area. In addition, sensors could be used to monitor vibration that could damage the structure of a building.
Usage of Sensor Networks continue … Healthcare: Sensors can be used in biomedical applications to improve the quality of the provided care. Sensors are implanted in the human body to monitor medical problems like cancer and help patients maintain their health.
