26-03-2011, 02:24 PM
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Overview of WSN
The sensor nodes, which have sensing, data processing, communication components forms the heart of the sensor networks. Wireless sensor networks were originally developed for military applications such as battlefield surveillance.
However WSN are now being used in many civilian application areas. A sensor node can be visualized as a small computer having basic interfaces and components. These devices are used to monitor physical or environmental conditions such as heat, temperature, or other events, at different locations. The size of the sensor node can be as small as a grain of dust and the cost can be as low as few cents.
A WSN consists of a large number of tiny, low power, cheap sensor nodes having sensing, data processing, communication components. It has not only the ability to sense some phenomena in the interested region but also the network features, thereby representing an improvement over the traditional sensor system.
Components of Sensor nodes
A sensor nodes consists of the following components
1. Processing unit with limited memory and processing power.
2. Sensors along with analog to digital converters for the data.
3. Transmitting device which is usually a radio
4. Power source in the form of a battery.
There can be more components which are optional and are included in a sensor node based on the target application. We will talk briefly on these optional components in the latter sections.
A sensor network consists of a number of sensor nodes having data sensing, data processing and transmission capabilities. The sensor nodes are characterized by small size, low-power, and low cost with communication capabilities over short distances. The communication rage varies from 10-15m. None of the existing algorithms or protocols is well suited to address the requirements of sensor networks.
Design factors
The different design aspects that need to be taken into consideration while designing architecture for a WSN application.
Power consumption/management
Power management techniques can greatly reduce the power consumed by sensor nodes. TDMA is usefull for power saving since a node can sleep between its assingned time slots and wake up only when its need to send or receive messages during its time slot. If a node fails, new routes need to be formed to address the topology changes. This might require more power and hence design of power aware algorithms becomes an important aspect.
Lifetime Maximization
Sensor node lifetime is highly dependent on the battery lifetime. A node might be left unattended for months or years. Hence, the maximum node lifetime needs to be considered before deployment of a sensor node
Fault tolerance
The failure of a sensor node should not affect the overall behavior of sensor network. Thus fault tolerance becomes an important aspects. The fault tolerance of a sensor node can be modeled using poisson distribution.
Self organization
A sensor network should self-organize itself once the different sensor nodes randomly distributed in a region wake up. Hence efficient MAC protocols and algorithms needs to be chosen to achieve self-organization.
Scalability
The number of sensor nodes in a sensor network can grow to huge numbers. All the new algorithms and protocols developed need to work even when the number of sensor nodes increases.
Cost
The cost of a sensor node has to be kept very low and should be less than 1 dollar so that the sensor nodes could be deployed.
Network topology
The different network topologies are available are star, ring, bus, tree, fully connected and mesh network. The power consumed in a sensor network increases as the square of the distance between source and destination, it is recommended to use networks with multiple nodes like a mesh configuration.]
Environments
Sensor nodes can be deployed in a different geographical areas like in a home, on the top of a building, at the bottom of an ocean or in a military battlefield. The area in which the sensor node will be deployed needs to be considerd to make it more robust.
Transmission Media
The transmission medium could be radio, infrared or optical media. Most of the hardware for sensor node has RF circuitry. Infrared communication is robust to interference from other devices and also these transceivers are cheaper and easier to build.
Middleware
Design of middleware primitives between hardware and software becomes an important aspects while designing architecture for sensor nodes, This mainly depends on the target application.
Overview of WSN
The sensor nodes, which have sensing, data processing, communication components forms the heart of the sensor networks. Wireless sensor networks were originally developed for military applications such as battlefield surveillance.
However WSN are now being used in many civilian application areas. A sensor node can be visualized as a small computer having basic interfaces and components. These devices are used to monitor physical or environmental conditions such as heat, temperature, or other events, at different locations. The size of the sensor node can be as small as a grain of dust and the cost can be as low as few cents.
A WSN consists of a large number of tiny, low power, cheap sensor nodes having sensing, data processing, communication components. It has not only the ability to sense some phenomena in the interested region but also the network features, thereby representing an improvement over the traditional sensor system.
Components of Sensor nodes
A sensor nodes consists of the following components
1. Processing unit with limited memory and processing power.
2. Sensors along with analog to digital converters for the data.
3. Transmitting device which is usually a radio
4. Power source in the form of a battery.
There can be more components which are optional and are included in a sensor node based on the target application. We will talk briefly on these optional components in the latter sections.
A sensor network consists of a number of sensor nodes having data sensing, data processing and transmission capabilities. The sensor nodes are characterized by small size, low-power, and low cost with communication capabilities over short distances. The communication rage varies from 10-15m. None of the existing algorithms or protocols is well suited to address the requirements of sensor networks.
Design factors
The different design aspects that need to be taken into consideration while designing architecture for a WSN application.
Power consumption/management
Power management techniques can greatly reduce the power consumed by sensor nodes. TDMA is usefull for power saving since a node can sleep between its assingned time slots and wake up only when its need to send or receive messages during its time slot. If a node fails, new routes need to be formed to address the topology changes. This might require more power and hence design of power aware algorithms becomes an important aspect.
Lifetime Maximization
Sensor node lifetime is highly dependent on the battery lifetime. A node might be left unattended for months or years. Hence, the maximum node lifetime needs to be considered before deployment of a sensor node
Fault tolerance
The failure of a sensor node should not affect the overall behavior of sensor network. Thus fault tolerance becomes an important aspects. The fault tolerance of a sensor node can be modeled using poisson distribution.
Self organization
A sensor network should self-organize itself once the different sensor nodes randomly distributed in a region wake up. Hence efficient MAC protocols and algorithms needs to be chosen to achieve self-organization.
Scalability
The number of sensor nodes in a sensor network can grow to huge numbers. All the new algorithms and protocols developed need to work even when the number of sensor nodes increases.
Cost
The cost of a sensor node has to be kept very low and should be less than 1 dollar so that the sensor nodes could be deployed.
Network topology
The different network topologies are available are star, ring, bus, tree, fully connected and mesh network. The power consumed in a sensor network increases as the square of the distance between source and destination, it is recommended to use networks with multiple nodes like a mesh configuration.]
Environments
Sensor nodes can be deployed in a different geographical areas like in a home, on the top of a building, at the bottom of an ocean or in a military battlefield. The area in which the sensor node will be deployed needs to be considerd to make it more robust.
Transmission Media
The transmission medium could be radio, infrared or optical media. Most of the hardware for sensor node has RF circuitry. Infrared communication is robust to interference from other devices and also these transceivers are cheaper and easier to build.
Middleware
Design of middleware primitives between hardware and software becomes an important aspects while designing architecture for sensor nodes, This mainly depends on the target application.
