LEACH CLUSTER-BASED ROUTING PROTOCOL

FOR WIRELESS SENSOR NETWORKS

WIRELESS SENSOR NETWORK

A Wireless Sensor Network (WSN) of spatially distributed autonomous sensors to monitor physical or environmental conditions, such as temperature, sound, pressure,humidity,wind direction and speed,vibration intensity,power-line voltage, etc. and to cooperatively pass their data through the network to a main location. Provide a bridge between the real physical and virtual worlds Allow the ability to observe the previously unobservable at a fine resolution over large spatio-temporal scales Applications in Disaster,Surveillance,Agriculture,etc

Direct communication with BS •Each sensor sends its data directly to

the base station. •Possibly optimal if either the base

station is close to the nodes, or the energy required to receive data is large.

Minimum energy multi-hop routing •Nodes route data destined ultimately for the base station through intermediate nodes. •The intermediate nodes are chosen such that the transmit amplifier energy is minimized. •Rather than just one (high-energy) transmit of the data, each data message must go through n (low-energy) transmits and n receives •Shorten system lifetime as the nodes closest to the base station are the ones to die out first since they are the ones most used as “routers” for other sensors’ data.

Clustering •Nodes are organized into clusters that communicate with a local base station, and these local base stations transmit the data to the global base station, where it is accessed by the end-user. •If the base station is an energy-constrained node, it would die quickly, as it is being heavily utilized.

LEACH •Low-Energy Adaptive Clustering Hierarchy •Clustering-based protocol •Select sensor nodes as CHs by rotation, so the high energy dissipation in communicating with the BS is distributed evenly to all sensor nodes in the network.

Figure: LEACH protocol

Assumption •The base station is fixed and located far

from the sensors. •All nodes in the network are

homogeneous and energy constrained.

Key Features •Localized coordination and control for

cluster set-up and operation. •Randomized rotation of the cluster

“base stations” or “cluster-heads” and the corresponding clusters.

•Local compression to reduce global communication.

LEACH •The nodes organize themselves into local clusters, with one node

acting as the local base station or cluster-head. •Cluster-head nodes broadcast their status to the other sensors in

the network. •Each sensor node determines to which cluster it wants to belong

by choosing the cluster-head. •Each cluster-head creates a schedule for the nodes in its cluster. • Once the cluster-head has all the data from the nodes in its

cluster, the cluster-head node aggregates the data and then transmits the compressed data to the base station.