Sensor networks

1.wireless sensor networks are
1. low power
2. small size
3. low cost
4. sensors to monitor the
  1. the system or enviroment
    1. by sensing of physical characteristics such as
      1. pressure
      2. temperature
      3. and humidity
2.the sensor node consist of
1. radio front end
2. microcontroller
3. power supply
4. and sensor
Transducers
1. Measures
  1. Physical parameters such as
    1. pressure
    2. temperature
    3. velocity
    4. acceleration
An embedded processor
1. An embedded processor is used for local processing
2. The processor provides bidirectional communication at kbps
Memory Unit
1. This unit stores data
Transceivers
1. The wireless transceivers are used to send or receive data
Battery
1. The battery supply is the required energy to run all the devices
Design issues and challenges
1. 1.Ease of development
  1. The wireless sensor nodes can be placed or dropped from a plane at desired location
  2. once placed the sensors do not need any human intervention thus reducing the installation cost and time
2. 2.Coverage area
  1. AS there is no central admininstration or fixed BS in WSN all routing and maintenance algorithms need to be distributed among the various sensor nodes to communicate with each other
3. 3.Energy consumption
  1. The life of sensor nodes strongly depends on battery life
    1. In many cases it is impossible to recharge or replace the battery
  2. Hence designer has to consider available energy and design power aware protocol and algorithm
4. 4.Hardware constraints
  1. the prime requrements to design hardware for sensor is to consider energy efficiency
  2. As size maybe few cublic mm
    1. ,it has to fit into tight modules of size 2*5*1 or even less as 1*1*1 cm
5. 5. Environment
  1. Sensor nodes should be able to communicate with each other in a completely distributed manner because
    1. sensor nodes may be placed or dropped from a plane , or widely scattered.
  2. This gives rises to challenging management of data from all sensor nodes
6. 6.Cost of sensor node
  1. The cost of each sensor node should be kept as low as possible for global acceptance
    1. currently cost of sensor based on blue tooth is $10
7. 7.Transmission channels
  1. the sensor nodes are connected by wireless links
    1. These wireless links operate in in the optical range or infrared waves.
      1. Some low energy consuming sensors use single RF channel transceiver
        that operates on 916 MHz
  2. To facilitate global operations of these sensor nodes
    1. the transmission channel selected must be available for all users.
8. 8.Connectivity and Network topology
  1. Thousands of sensor nodes are placed or deployed in interested area in close proximity
  2. The density of nodes maybe as large as 27 nodes- m cube
    1. To remain connected with all of these nodes
      1. many protocols and
      2. algorithms are required
9. 9. Scalability
  1. As thousands of nodes or more are installed in bounded area
    1. routing area must be scalable to respond to events
      1. and enough capable to work with such high number of sensor nodes
10. 10.Fault Tolerance
  1. Some sensor nodes may fail due to jamming,physical damage, damage of battery and so on.
    1. if this happens to many nodes and they stop to operate , MAC protocols and routing protocols update
      1. and accomodate formation of new wireless links and route accordingly to collect the data

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Sensor networks

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