More Related Content
Similar to wireless sensor network
wireless sensor network
- 1. Unit-2 Sensor Network-Introduction & Architecture Dr.DEEPA.D AsstProfessor Electronics and communication R.M.K College of Engineering and Technology
- 2. What is asensor A sensor is a tiny electronic device that measures physical input from its environment and converts it into data that can be interpreted by either a human or a machine. senorPhysical qty observable qty
- 3. Wireless Sensor Networks(WSNs) can be defined as a self-configured and infrastructure less wireless networks to monitor physical or environmental conditions, such as temperature, sound, vibration, pressure, motion or pollutants A sink or base station acts like an interface between users and the network. One can retrieve required information from the network by injecting queries and gathering results from the sink. A wireless sensor network contains hundreds of thousands of sensor nodes. The sensor nodes can communicate among themselves using radio signals.
- 4. A wireless sensornode is equipped with sensing and computing devices, radio transceivers and power components. The individual nodes in a wireless sensor network (WSN) are inherently resource constrained: they have limited processing speed, storage capacity, and communication bandwidth. After the sensor nodes are deployed, they are responsible for self-organizing an appropriate network infrastructure often with multi-hop communication with them.
- 5. Challenges for WirelessSensor Network Characteristic requirements Type of service :The service type rendered by a conventional communication network is evident – it moves bits from one place to another. A WSN is expected to provide meaningful information and/or actions about a given task Quality of Service : Delay or minimum bandwidth are irrelevant when applications are tolerant to latency or the bandwidth fault Tolerance: To tolerate node failure, redundant deployment is necessary, using more nodes than would be strictly necessary if all nodes functioned correctly.
- 6. lifetime: WSNmust operate at least for a given mission time or as long as possible. Hence, the lifetime of a WSN becomes a very important figure of merit. Evidently, an energy-efficient way of operation of the WSN is necessary. Scalability Since a WSN might include a large number of nodes, the employed architectures and protocols must be able scale to these numbers. Wide range of densities : In a WSN, the number of nodes per unit area – the density of the network – can vary considerably. Different applications will have very different node densities. Programmability:These nodes should be programmable, and their programming must be changeable during operation when new tasks become important
- 7. Maintainability :Asboth the environment of a WSN and the WSN itself change (depleted batteries, failing nodes, new tasks), the system has to adapt. It has to monitor its own health and status to change operational parameters or to choose different tradeoffs
- 8. Required mechanisms Torealize these requirements, innovative mechanisms for a communication network have to be found, as well as new architectures, and protocol concepts. A particular challenge here is the need to find mechanisms that are sufficiently specific to the idiosyncrasies of a given application to support the specific quality of service, lifetime, and maintainability requirements
- 9. Required mechanisms Multihop:A direct communication between a sender and a receiver of WSN is difficult for long distance since it needs high transmission power. The use of intermediate nodes as relays can reduce the total required power. Energy-efficient operation: To support long lifetimes, energy- efficient operation is a key technique. Energy-efficient data transport between two nodes and energy- efficient computation of a requested information are to be used.
- 10. Auto-configuration: AWSN has to configure its operational parameters autonomously, independent of external configuration. Collaboration and in-network processing: In some applications, a single sensor node is not able to decide whether an event has happened. Several sensor nodes have to collaborate to detect an event and only the joint data of many sensors provides enough information. Information is processed in the network itself in various forms to achieve this collaboration.
- 11. Data centric: Address-centric: Transferof data between two specific devices, each with one network address as in traditional communication networks. In WSN, where nodes are deployed redundantly to protect against node failures the identity of the node supplying data is not important. Importance is given only to the data. Hence a data-centric paradigm is necessary in designing WSN.
- 12. Locality: Nodes which arevery limited in resources like memory, should limit the state of information processing with their direct neighbors only. This will allow the network to scale to large numbers of nodes without having to rely on powerful processing at each single node. .
- 13. 1.6 Enabling technologiesfor wireless sensor networks MINIATURIZATION OF HARDWARE:. Smaller sizes in chips have driven down the power consumption of the basic components of a sensor node such as microcontrollers and memory chips, the radio modems, responsible for wireless communication, have become much more energy efficient Reduced chip size and improved energy efficiency is accompanied by reduced cost, which is necessary to make redundant deployment of nodes affordable .
- 14. Enabling technologies forwireless sensor networks Processing and communication: Communication between sensor nodes is the most energy consuming operation The primary objective of protocols is to minimize energy consumption for communication. For efficiently communicate between sensor nodes, medium access control (MAC) should be designed to minimize energy consumption. Another major communication method in WSNs is broadcasting. A broadcast protocol for WSNs must be designed to minimize the factors of energy waste, such as redundant transmissions of identical broadcast packets and collisions.
- 15. Enabling technologies forwireless sensor networks Sensing equipment: It is difficult to generalize because of the vast range of possible sensors. The three basic parts of a sensor node have to be accompanied by power supply. This requires, high capacity batteries that last for long times. The counterpart to the basic hardware technologies is software..
- 16. APPLICATION TYPES Eventdetection Periodic measurements Function approximation and edge detection: Tracking: Deployment options
- 17. Single Node Architecture-Hardware components Application’s requirements play a decisive factor with regard mostly to size, costs, and energy consumption of the nodes – Communication and computation facilities as such are often considered to be of acceptable quality, The trade-offs between features and costs is crucial.
- 18. In someextreme cases, an entire sensor node should be smaller than 1 cc, weigh (considerably) less than 100 g, be substantially cheaper than US$1, and dissipate less than 100 µW. In even more extreme visions, the nodes are sometimes claimed to have to be reduced to the size of grains of dust. In more realistic applications, the mere size of a node is not so important; rather, convenience, simple power supply, and cost are more important
- 19. Hardware components Sensornode hardware overview Controller Memory Communication device Sensors and actuators Power supply of sensor nodes
- 20. Controller :It is the Central processing unit of the node It collects data from sensor and processes and decides when and where to send Its capable of executing arbitrary code. Example : General purpose processor, DSP and microcontollers Memory are used to store programs and intermediate data; usually, different types of memory are used for programs and data. RAM- for intermediate data ROM- for storing the program code Flash Memory- for storage of data if RAM gets affected
- 21. Sensors and actuators Sensors:The actual interface to the physical world: devices that can observe or control physical parameters of the environment Passive, Omindirectional sensor:- The Sensor measure the physical quantity without manipulating the environment and also obtain energy from environment to amplify their analog signal Passive narrow-beam sensor:- These are Passive Sensor and as well defined notion of direction of measurement Active Sensor:- There are quite specific and plays a special attention for sensing the shock waves from explosion. It requires external source of power Actuators: These are for wireless sensor network that convers Electrical signals into physical phenomenon
- 22. Communication device: Turning nodesinto a network requires a device for sending and receiving information over a wireless channel. Here it uses Radio frequencies Transceiver:- It is a device for both transmitting and receiving operations that convert bit stream coming from a micro controller and convert them to and from radio waves Usually, half-duplex operation is realized since transmitting and receiving at the same time on a wireless medium is impractical in most cases
- 23. Power Amplifier: ittakes signal from IF and amplifies them for Transmission over antenna Low noise amplifier: Amplifier incoming signals without reducing the signal to noise ratio Elements:- Local oscillator(or) Voltage Controlled Oscillator are used for freq conversion from RF to IF or Baseband
- 24. Transceiver Tasks andcharacteristics Service to upper Layer:- Receiver has to offer some services to the MAC layer Power consumption: power required to transmit single bit and receiving the same bit State change time and energy: operated in different modes and different power safe states Data rate: Carriers freq and bandwidth will determine the data rate Modulation: It supports On/OFF Keying, ASK, FSk or similar modulation Coding:- various coding schemes are used Noise figure: (S/N)i/(S/N)o Gain: Its is the ratio of output signal to input signal power Frequency Stability: Denotes the degree of variations from centre frequencies when temp/pressure changes Voltage range: It should operate reliably over a range of supply voltage
- 25. Power supply As usuallyno tethered power supply is available, some form of batteries are necessary to provide energy. Sometimes, some form of recharging by obtaining energy from the environment is available as well (e.g. solar cells). Energy Scavenging: The process of recharging the battery with energy gathered fromm the environment is called energy scavenging Photovoltaics:- Power obtained from solar cells Temperature gradient: Difference in temperature Vibrations : due to vehicles Pressure Vibrations Flow of liquid /air : in wind mills or turbines