Data Aggregation in Wireless Sensor

NetworkPresented By

P.Praveen Kumar(09751A0581)B.TECH (CSE),SITAMS.

Abstract :

Sensor networks are collection of sensor nodes which co-operatively send sensed data to base station. As sensor nodes are battery driven, an efficient utilization of power is essential in order to use networks for long duration hence it is needed to reduce data traffic inside sensor networks, reduce amount of data that need to send to base station. The main goal of data aggregation algorithms is to gather and aggregate data in an energy efficient manner so that network lifetime is enhanced. Wireless sensor networks (WSN) offer an increasingly Sensor nodes need less power for processing as compared to transmitting data. It is preferable to do in network processing inside network and reduce packet size.

Data Aggregation Overview

Data aggregation is a process of aggregating the sensor data using aggregation approaches.

The algorithm uses the sensor data from the

sensor node and then aggregates the data by using some aggregation algorithms such as centralized approach, LEACH(low energy adaptive clustering hierarchy),TAG(Tiny Aggregation) etc.

This aggregated data is transfer to the sink node by selecting the efficient path.

DATA AGGREGATION: AN OVERVIEW

This is an address centric approach where each node sends data to a central

node via the shortest possible route using a multi-hop wireless protocol.

The sensor nodes simply send the data packets to a leader, which is the powerful node. The leader aggregates the data which can be queried.

Centralized Approach:

In-network aggregation is the Global process of gathering and routing

information through a multi-hop network, processing data at intermediate nodes with the objective of reducing resource consumption (in particular energy), thereby increasing network lifetime.

There are two approaches for in-network aggregation: with size reduction and without size reduction.

In-Network Aggregation

Tree based approach

In the tree-based approach perform Aggregation by constructing an

aggregation tree, which could be a minimum spanning tree, rooted at sink and source nodes are considered as leaves.

Each node has a parent node to forward its data.

Flow of data starts from leaves nodes up to the sink and therein the aggregation done by parent nodes.

Tree-Based Approach

In cluster-based approach, whole

Network is divided in to several clusters. Each cluster has a cluster-head which is selected among cluster members.

Cluster heads do the role of aggregator which aggregate data received from cluster members locally and then transmit the result to sink.

Cluster-Based Approach

We have plenty of simulation tools orsimulators for simulating wireless networks

The simulators which are most popular areTOSSIM, NS-2, OPNET, OMNet++, J-Sim,GlomoSim, and Qualnet and so on. TOSSIMis a discrete event simulator for TinyOS (TinyOSis a popular sensor network operating system)sensor networks.

SIMULATION AND EXPERIMENTALANALYSIS

1) Simple Queries These are aggregate queries. Eg. "SELECT temperature FROM sensor

WHERE node = z". These are generally mapped into broadcast

or point to point quires

1) Simple Queries

Simulation run

They may contain sub queries. Eg. "SELECT temperature FROM sensor

WHERE room = (SELECT room WHERE floor = ’3’)"

2) Complex Queries

Simulation run

These are the continuous query that returns the values periodically at specified time intervals.

Eg: “SELECT AVG (temperature) FROM sensor where node =“Z”

Event Driven Queries

With aggregation query: SELECT MAX (temp), AVG (light) FROM

SENSORS SAMPLE PERIOD 2048 Without aggregation query: SELECT light FROM sensors SAMPLE PERIOD

2048 With aggregation and with clustering query: SELECT AVG(light) FROM SENSORS GROUP BY NODEID % 2SAMPLE PERIOD 2048.

Simulation results and comparison

Simulation results and comparison

Enhance robustness and accuracy of information

Reduce traffic load &conserve energy of sensors

ADVANTAGES

Malicious attacker

Cannot ensure correctness

Increase power consumption

DISAVANTAGES

CONCLUSION

In this work we have studied the two most important parts of data communication in sensor networks- query processing, data aggregation and realized how communication in sensor networks is different from other wireless networks. Wireless sensor networks are energy constrained network. Since most of the energy consumed for transmitting and receiving data, the process of data aggregation becomes an important issue and optimization is needed. Efficient data aggregations not only provide energy conservation but also remove redundancy data and hence provide useful data only.

Thank you