Sensor networks

Sensor networks

1. 1.wireless sensor networks are

   • low power
   • small size
   • low cost
   • sensors to monitor the
     • the system or enviroment
       • by sensing of physical characteristics such as
         • pressure
         • temperature
         • and humidity

2. 2.the sensor node consist of

   • radio front end
   • microcontroller
   • power supply
   • and sensor

3. Transducers

   • Measures
     • Physical parameters such as
       • pressure
       • temperature
       • velocity
       • acceleration

4. An embedded processor

   • An embedded processor is used for local processing
   • The processor provides bidirectional communication at kbps

5. Memory Unit

   • This unit stores data

6. Transceivers

   • The wireless transceivers are used to send or receive data

7. Battery

   • The battery supply is the required energy to run all the devices

8. Design issues and challenges

   • 1.Ease of development
     • The wireless sensor nodes can be placed or dropped from a plane at desired location
     • once placed the sensors do not need any human intervention thus reducing the installation cost and time
   • 2.Coverage area
     • 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.Energy consumption
     • The life of sensor nodes strongly depends on battery life
       • In many cases it is impossible to recharge or replace the battery
     • Hence designer has to consider available energy and design power aware protocol and algorithm
   • 4.Hardware constraints
     • the prime requrements to design hardware for sensor is to consider energy efficiency
     • As size maybe few cublic mm
       • ,it has to fit into tight modules of size 2*5*1 or even less as 1*1*1 cm
   • 5. Environment
     • Sensor nodes should be able to communicate with each other in a completely distributed manner because
       • sensor nodes may be placed or dropped from a plane , or widely scattered.
     • This gives rises to challenging management of data from all sensor nodes
   • 6.Cost of sensor node
     • The cost of each sensor node should be kept as low as possible for global acceptance
       • currently cost of sensor based on blue tooth is $10
   • 7.Transmission channels
     • the sensor nodes are connected by wireless links
       • These wireless links operate in in the optical range or infrared waves.
         • Some low energy consuming sensors use single RF channel transceiver
           • that operates on 916 MHz
     • To facilitate global operations of these sensor nodes
       • the transmission channel selected must be available for all users.
   • 8.Connectivity and Network topology
     • Thousands of sensor nodes are placed or deployed in interested area in close proximity
     • The density of nodes maybe as large as 27 nodes- m cube
       • To remain connected with all of these nodes
         • many protocols and
         • algorithms are required
   • 9. Scalability
     • As thousands of nodes or more are installed in bounded area
       • routing area must be scalable to respond to events
         • and enough capable to work with such high number of sensor nodes
   • 10.Fault Tolerance
     • Some sensor nodes may fail due to jamming,physical damage, damage of battery and so on.
       • if this happens to many nodes and they stop to operate , MAC protocols and routing protocols update
         • and accomodate formation of new wireless links and route accordingly to collect the data