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CHAPTER 1

WIRELESS SENSOR NETWORKS

1.1 INTRODUCTION

Wireless Sensor Networks (WSNs) are highly distributed networks

of small, lightweight wireless nodes that monitor the environment or system

by measuring the physical parameters such as temperature and pressure. The

substantial blocks of WSNs are

Sensing unit

Processing unit

Communication unit

Power unit

Sensing unit is used to measure the physical conditions such as

temperature and pressure in the deployed environment. Processing unit

involves in collecting and processing signals. Communication unit is used for

transferring the signal from the sensor to the user. The power unit is used to

support all the previous units. The wireless communication unit is responsible

for transferring signals from the sensor to the user via the Base Station (BS).

The power unit supports all the previous units to provide the required energy

in order to carry out the required tasks. The distinctiveness of a sensor node

lies in its light weight and tiny size.

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1.2 APPLICATION OF WSN

Security applications

Industrial control

Environmental monitoring

Traffic control

1.2.1 Security Applications

WSNs may be used for infrastructure security and counter

applications. For potential, critical buildings and facilities such as power

plants, communication centers should be preserved. WSNs can also be used to

detect biological, chemical, and nuclear attacks. The data are sent to

computationally powerful nodes which are called the BS or the sinks in terms

of the network flow.

1.2.2 Industrial Control

Industrial sensors are mainly deployed to lower the cost and

improve the machine, user performances and maintainability. Optical sensors

can replace existing the instruments and perform material property and

composition measurements. Applications of WSNs are to enable multi point

sensing.

1.2.3 Environmental Monitoring

It can be used to study track and measure the population of animals,

vegetation response to climate trends and diseases.

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1.2.4 Traffic Control

Nowadays, WSNs are used for vehicle traffic monitoring and

control. Video cameras are frequently used to monitor road segments with

heavy traffic.

In the research of WSN, energy efficiency has been celebrated as

the most important issue. There is a great importance to design an energy

efficient routing protocol for WSN. Almost all of the routing protocols can be

classified into three types. There are, Flat routing, Hierarchical routing, and

location-based routing. In flat routing, each sensor node is involved in the

same role and sends the data to a sink node. In hierarchical routing, originally

proposed in wire line networks are well-known techniques with special

advantages related to scalability and efficient communication. It is an efficient

way to lower energy consumption within a cluster, performing data

aggregation and fusion in order to decrease the number of transmitted

messages to the Base station. The complete network is divided into several

clusters, in accordance with the distance between the nodes and the hop count.

For aggregation point called cluster heads, Location-based

protocols utilize the position information to relay the data to the desired

regions rather to the whole network. Cluster heads play an important role in

the operation of clustering. Besides data aggregation and transmission, the

selection of cluster heads also has substantial influence on energy efficiency

because a cluster head selection approach can determine the size, position and

number of clusters in the network.

Furthermore, these protocols can be classified into different types.

They are as follows,

Multipath-based

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Query-based

Negotiation-based

QOS-based

Coherent-based

1.2.5 Multipath-based

Multiple paths are applied rather than a single path in order to

develop network performance. For example the fault tolerance can be

increased by maintaining multiple paths between the source and destination.

1.2.6 Query-based

The objective nodes propagate a query for data from a node

through the network. A node with this data sends the data.

1.2.7 Negotiation-based

It is used to eliminate redundant data transmissions.

Communications based on the resources are made available.

1.2.8 QOS-based

Quality of Service requirements in the routing protocols for mixed

data reporting applications. Due to the dynamic nature of the network, the

existing QoS protocols for wired networks cannot be applied directly to

WSNs.

1.2.9 Coherent-based

The data is forwarded to aggregators after minimum processing.

The minimum processing typically includes tasks like time stamping,

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duplicate suppression, etc. To perform energy efficient routing, coherent

processing is normally selected

1.3 CHALLENGES IN WSNs

The efficient of WSNs are challenging and algorithmic, because of

the unique characteristics of these devices. WSN deal either real world

environments. Very few results exist to date regarding meeting real-time

requirements in WSN. Most protocols either ignore real-time attempt to

process as fast as possible or hope that this speed is sufficient to meet

deadlines. A sensor network requires the efficient and robust distributed

protocols and algorithms with properties such as

i. Scalability

ii. Efficiency

iii. Fault tolerance

1.3.1 Scalability

It is able to operate in extremely large networks composed of huge

number of nodes. A wireless sensor network usually consists of hundreds of

sensor nodes densely distributed in phenomena.

1.3.2 Efficiency

It is with respect to both energy and time.

1.3.3 Fault Tolerance

The network should be able to operate despite of the failure of any

nodes. Sensor nodes may fail or be blocked due to lack of power, or

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environmental interference. The failure of sensor nodes should not affect the

overall task of the sensor network.

The following inherent features of WSNs introduce unique

challenges for privacy preservation of data and prevent the existing

techniques.

1.3.3.1 Uncontrollable environment

Sensors may have to be deployed in an environment that is

uncontrollable by the defender. As a result, an adversary may retrieve private

keys used for secure communication.

1.3.3.2 Sensor node resource constraints

Sensor nodes generally have severe constraints on their ability to

store, process and sense data. As a result, the computational complexity and

resource consumption of public-key is usually unconsidered for WSNs.

1.3.3.3 Topological constraints

The limited communication range of sensor nodes in a WSN

requires multiple hops in order to transmit data from the source to the base

station.

One of the most crucial goals in designing efficient protocols for

WSNs is minimizing the energy consumption. This goal has various

prospects. These are, minimizing the total energy spent in the network,

minimizing the number of data transmission, combining energy efficiency and

fault tolerance by allowing redundant data transmission, maximizing the

number of ‘alive’ node overtime, balancing the energy dissipation among the

sensors in the network.

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1.4 ROUTING TECHNIQUE

Routing in WSNs is a hard challenge due to the inherent

characteristics that differentiate between these networks from wireless

networks. Due to the relatively large number of sensor nodes, it is not

possible to build a global addressing scheme for the deployment of a large

number of sensor nodes as the overhead of ID maintenance is high.

Routing algorithms are more capable and suitable than the flat

routing algorithms. Routing in WSNs is very demanding due to the inherent

characteristics that decide these networks from other wireless network. To

minimize energy consumption, routing techniques are proposed in the

literature. Data aggregation protocols are essential in Wireless Sensor

Networks (WSNs) to reduce the amount of network traffic which helps to

reduce energy consumption and reduces the number of message exchanges

between the nodes and the base station. Some important aspects are given

below.

Node deployment

Energy consumption without losing accuracy

Data reporting method

Scalability

Coverage

1.4.1 Node Deployment

It is application-dependent and can be either manual or randomized.

Position of sensor nodes is also important. Sensor node deployment usually

varies with application requirements and affects the performance of the

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routing protocol. Inter-sensor communication is normally within the short

transmission ranges due to energy and bandwidth.

1.4.2 Energy Consumption without Losing Accuracy

Sensor nodes are tightly controlled in terms of energy, storage, and

processing capacities. So they require careful resource management. The

lifetime of nodes is a critical issue. Sensor nodes can use maximum of their

limited supply of energy to perform computations and for transmitting the

information in a wireless environment.

1.4.3 Data Reporting Method

Data reporting in WSNs is application-dependent and also depends

on the time critically of the data. Data reporting method can be categorized as:

Time-driven

Query driven

Event-driven

1.4.3.1 Time-driven

The data is transmitted at constant periodic time intervals. Its

delivery method is suitable for applications that require periodic data

monitoring.

1.4.3.2 Query-driven

The sensor nodes respond to a query generated by the Base station

in the network. The routing protocol is high especially by the area reporting

method.

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1.4.3.3 Event-driven

Sensor nodes react immediately to sudden changes in the value of a

sensed attribute. The sensor nodes respond to the occurrence of a certain

event.

1.4.4 Scalability

Routing method must be able to work with a large number of

sensor nodes. In addition, routing protocols should be scalable enough to

respond to events in the environment. The network may be required to reduce

the quality of the results in order to reduce the energy dissipation in the nodes

and the total network lifetime. Therefore, sensor nodes are expected to be

highly connected.

1.4.5 Coverage

The environment is limited in both range and accuracy. It can only

cover a limited area of the environment. Hence, it is also an important design

parameter in sensor network.

1.5 CLUSTERING AND ROUTING IN WSN

The network structure is organized in such a way that cluster head

nodes are further classified into different levels, which achieves employing

the ring-based and substantial energy savings. The cluster head nodes in the

proposed scheme are deployed according to redeployment process before

deploying general sensor nodes. A cluster-based hierarchical routing

algorithm appears to be ideal for WSNs. This algorithm has several merits. It

ensures more energy-efficient routing in the manner of forming local clusters

and transmitting the information. In hierarchical routing, the complete

network is divided into several clusters, in accordance with the distance

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between the nodes and the hop count. For aggregating the data from various

sensor nodes, there is a requirement of aggregation point called cluster heads.

Hence, each cluster consists of some sensor nodes and a cluster head.

(Yuzhong Chen et al 2009).

Cluster head selection is performed in a greedy manner via the local

exchange of node energy states. Each cluster head determines when to

abandon this role and become a cluster member, depending only on its own

energy state. A cluster member transmits packets only to its cluster heads, but

a cluster head can transmit packets to any node that can route the packets to

the sink node. This routing algorithm further simplifies the clustering process

because gateway nodes for inter-cluster communication can be selected

independently from other clusters.

Efficient clustering algorithms for WSNs have to satisfy several

requirements:

Clustering overhead should be small.

Enough to be performed by low-performance processors.

Clusters should cover entire sensor fields.

Clustering is used to split data transmission into two types: There

are

Intra-cluster

Inter-cluster

1.5.1 Intra-cluster

Intra-cluster is communication within a cluster. This makes the

network to consume higher energy in data collection from cluster nodes to

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cluster head and in information dissemination from cluster head to cluster

nodes.

1.5.2 Inter-cluster

Inter-cluster is used for communication between cluster heads and

every cluster head and the sink.

Random-selected-CH protocols can bring more flexibility and

toleration. These approaches have two main disadvantages. First, the

randomly picked CH may have a higher communication overhead because it

has no knowledge of intra-cluster or inter-cluster communication. Second, the

periodic CH rotation or election needs extra energy to rebuild clusters.

1.5.3 Energy Efficiency

The energy-efficient data access mechanism such as clustering, in

which the data can be preprocessed before submission, is commonly accepted

as an option to increase scalability, reduce delay and prolong the network

lifetime for wireless sensor network. The energy efficient factor of clustering

includes the aggregation of Cluster heads and compress a large amount of

sensor data to reduce the number of data transmissions. Also Clustering can

reduce the amount of nodes responsible for long distance transmission, thus

saving energy consumption due to transmission. Moreover, the energy

efficiency in WSN is obtained by combining the nodes having maximum

residual energy.

1.5.4 Fault Tolerance

Fault tolerance is the ability of a system to deliver a desired level of

functionality in the presence of faults. It is a basic requirement in the design

of protocols and applications for Wireless sensor networks. It is designed for

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event-driven networks tend to be reactive. To better understand the behavior

of the protocols evaluated, it is important to understand how each protocol

deals with the failure situations. Security attacks can be avoided recovered

with the use of fault tolerance techniques. The fault tolerance techniques

avoid the denial of service attacks. Fault tolerance is one of the most

important research topics in WSNs. There are as follows

Interference attacks

Collision attacks

Sinkhole attacks

1.6 OPTIMIZATION FOR ROUTING IN WIRELESS SENSOR

NETWORK

Wireless sensor networks and their constraints have performed the

need for specific requirements to routing protocols. The algorithms in

wireless sensor networks usually realize the specifications. There are

Location based

Energy efficiency

Data aggregation

Multipath communication

Attribute-based

1.6.1 Location-based

When location-based technique is used, a node decides the

transmission route according to the localization of the final destination.

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1.6.2 Energy Efficiency

There are multiple routes of communication between a node and

the sink. The aim of these algorithms is to select those routes which are

expected to minimize the network lifetime.

1.6.3 Data Aggregation

A way to reduce energy consumption is data aggregation. It

consists of suppressing redundancy in different data messages.

1.6.4 Multipath Communication

This technique is used for multiple paths from an origin to a

destination in the network.

1.6.5 Attribute-based

In this technique, the sink sends queries to certain regions and waits

for the response from the sensors located in this area.

1.7 LOW ENERGY ADAPTIVE CLUSTERING HIERARCHY

It is an adaptive clustering-based protocol using randomized

rotation of cluster-heads to evenly distribute the energy load among the sensor

nodes in the network. The data will be collected by cluster heads from the

nodes in the cluster and after processing, the data aggregation forwards it to

base station.

Low Energy Adaptive Clustering Hierarchy (LEACH) is one of the

popular cluster-based structures, which has been commonly proposed in

wireless sensor network. It is divided into five clusters. Each cluster has a

black circle represents the first cluster node. The rest of the white circle

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indicates a non-cluster head node. Each cluster has a cluster head node,

protocol randomly selecting cluster head node cycle. The energy of the entire

network load is equally distributed to each sensor node. This protocol is

calculated for Low energy consumption in WSN.

LEACH protocol arranges the nodes into groups, in an order in

which each cluster has a cluster-head for a specific period for its own cluster.

This protocol specifies that nodes become cluster heads with a probability of

normal circumstances, a value which results in suboptimal operation in most

of the scenarios. It randomly elects the cluster-head in each round by which

the energy will be uniformly distributed. In nature, the base station is fixed

and other nodes are energy constrained.

The operation of LEACH is separated into two phases, namely the

setup phase and the steady state phase. In the setup phase, the clusters are

organized and Cluster heads are selected. In the steady state phase, the actual

data transfer to the Base station takes place. The duration of the steady state

phase is longer than the duration of the setup phase in order to minimize

overhead. During the steady state phase, the sensor nodes can begin sensing

and transmitting data to the Cluster Heads. The CH node, after receiving all

the data, aggregates it before sending it to the Base station. LEACH is an

adaptive and self-organized clustering protocol proposed by Lee et al (2006).

When the data is transferred to the sink node, the operation of LEACH is

separated into rounds, where each round actualizes with a setup phase for

cluster formation followed by a steady-state phase.

Although LEACH is able to increase the network lifetime, there are

still a number of issues about the assumptions used in this protocol. LEACH

assumes that all nodes can transmit with enough power to reach the Base

station if needed and that each node has computational, data that provides

new information which is transmitted to the CHs before being transmitted.

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Figure 1.1 LEACH routing protocol

In the current LEACH, several problems exist. One among them is

that LEACH is energy inefficient. Since cluster heads use more energy than

leaf nodes, it is quite important to reselect cluster heads periodically.

In LEACH, a sensor node is selected as the cluster head using distributed

probabilistic approach whereas the non-cluster nodes determine which cluster

to join, depending on the signal strength. This progress cannot declare that

cluster heads are equally distributed over the entire network. Likewise,

LEACH entails sourcing needs to send the data to cluster.

The Proposed Data Aggregation-Optimal LEACH (DAO-LEACH)

protocol is used to decrease the energy consumption compared to LEACH. It

is improved in terms of security and fault-tolerance based on Gracefully

Degraded Data Aggregation (GDDA) to ensure the integrity of data and

Hybrid Layer User Authentication (HLUA) to ensure the confidentiality of

data. Energy is preserved by Locality Sensitive Hashing (LSH) technique.

HLUA consists of a combination of Secret Key Cryptography

(SKC) method such as Message Authentication Code (MAC) algorithm and

Cluster

Base station

Sensor node Cluster head

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Public Key Cryptography (PKC) method such as Elliptic Curve Cryptography

(ECC). MAC algorithm is used to connect the cluster heads (CHs) and SNs

to complete lower power demand. ECC is applied for User Authentication

(UA) between CHs and Users. A user is allowed to access the SNs through

the CH, when it is authenticated to that CH. The HLUA is resistant to the

following attacks:

1.7.1 Replay Attacks

An intruder cannot re-use the former login message to hack the

WSN, because the timestamp produced by the user ensures that this message

cannot be used after some time.

1.7.2 Node Compromising Attacks

The nodes cannot be compromised due to the intrusion-resistant

hardware of CHs. Sensor nodes do not care important information to

compromise the entire Wireless Sensor Network. The secret keys between

each Sensor nodes and its associated Cluster head are updated at specific

periods.

Gracefully Degraded Data Aggregation method is able to detect the

false data in the sensed data and eliminate them. This ensures the fault-

tolerance in the Wireless Sensor Network. It is based on Locality Sensitivity

Hashing technique. LSH codes are generated by the Sensor Nodes to decrease

the amount of data transmitted. Its codes are used to define the sensor data

using less number of bits. Each Cluster Head requests the Sensor Nodes in its

cluster to transmit their LSH codes for data aggregation. The Sensor Nodes

append their unique IDs along with the LSH codes.

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The Proposed DAO-LEACH protocol is challenging to refuge

attacks such as replay attacks, node compromising attacks, and impersonation

attacks. It performs better in terms of energy consumption, number of live

nodes, End-to-End Delay (EED), and false data detection, compared to

Simple Cluster-based data Aggregation and Routing(SCAR), Energy-

Efficient Secure Path Algorithm (ESPA), Deterministic Key Management

based LEACH (DKS-LEACH), Secure and Efficient DATA Aggregation

protocol for WSNs (SEDAN) and Data Aggregation and Authentication

(DAA).

Cryptographic algorithm for authentication and encryption can be

implemented in two ways: using public key or private key. When using public

key, the key value of every node is public information. The source node

simply encrypts data using the public key of the sink node.

A public key cryptography employs a pair of different but

associated keys. One of these keys is released to the public while the other,

the private key, is known only to its owner. It is used for calculating a private

key from its associated public key.

Applications of wireless sensor network have many critical Quality

of Service requirements, among which meeting end-to-end delay constraints

are an important factor. Several WSN applications require an end-to-end

delay. A target tracking system may require sensors to collect and deliver

target information to sink nodes before the target leaves the surveillance field,

Even though the end-to-end delay is difficult to clear for event-driven sensor

networks due to their unpredictable traffic pattern.

The characteristics of sensor network are, a cluster-based

hierarchical routing algorithm appear to be ideal for WSNs. This algorithm

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has several merits. That is, it ensures more energy-efficient routing in the

manner of forming local clusters.

In Distributed Energy Efficient Clustering (DEEC), each node

expends energy uniformly by rotating the cluster-head role among all nodes.

In DEEC, the cluster-heads are elected by a probability based on the ratio

between the residual energy of each node and the average energy of the

network. It can prolong the network lifetime, especially the stability period.

An Energy-efficient Secure Path Algorithm (ESPA) for wireless

sensor networks aims at achieving authenticity and integrity on the actual

sensed data within an energy-efficient network communications. In ESPA, a

routing architecture is created as the topology of the network. Due to inherent

deployment nature and energy limitation constraint of the sensors, the energy

efficiency must be ensured together with the security of the sensed data.

Hybrid Energy-Efficient Distributed (HEED) Clustering is one type

of the cluster based approach. HEED, which periodically selects cluster heads

according to a hybrid of the node residual energy and a secondary parameter.

It can asymptotically almost surely guarantee connectivity of the clustered

networks. Assumptions of HEED’s links are symmetric, energy consumption

non-uniform for all nodes and processing and communication capability

similar. It uses using residual energy as primary parameter and network

topology are only used as secondary parameters to break the network between

cluster heads.

Power-Efficient GAthering in Sensor Information Systems (PEGASIS) is tree

based approach. LEACH and PEGASIS use the same constants for

calculating energy costs. PEGASIS achieves its energy savings by minimizing

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the number of transmissions and receives for each node. It would achieve

even greater savings compared to LEACH. The main idea in PEGASIS is for

each node to receive from and transmit to the Base station. The difference

from LEACH is to use multi-hop routing by forming chains and selecting

only one node to transmit to the base station instead of using multiple nodes.

The elimination of the overhead is caused by dynamic cluster

formation in LEACH through decreasing the number of transmissions and

reception by using data aggregation. To locate the closest neighbor node in

PEGASIS, each node uses the signal strength to measure the distance to all

neighboring nodes and then adjusts the signal strength so that only one node

can be heard. In PEGASIS, each data aggregation chain has a leader which is

responsible to transmit the aggregated data to the base station. In order to

evenly distribute the energy expenditure in the network, sensor nodes take

turns acting as the chain leader.

LEACH is a cluster-based protocol for sensor networks which

achieves energy-efficient, scalable routing and light media access for sensor

nodes. However, the election of a malicious or compromised sensor node at

the cluster head is one of the most important breaches in wireless sensor

network.

1.7.3 Data Aggregation

Data aggregation is defined as the method of aggregating the data

from multiple sensors to reduce redundant transmission and provide fused

information to the base station. It usually involves the fusion of data from

multiple sensors at intermediate nodes and transmission of the aggregated

data to the base station.

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Figure1.2Data aggregation in wireless sensor network

Data aggregation is used to refer to the process of data gathering.

This technique is used to avoid the redundancy and overlaying problems in

wireless sensor networks. Due to the low deployment cost requirement of

wireless sensor networks, sensor nodes have simple hardware and severe

resource constraints. Data aggregation protocols aim to combine data packets

of several sensor nodes so that the amount of data transmission is reduced.

Data aggregation in wireless sensor network should be competent enough in

terms of memory consumption, overhead, energy efficient, and secure.

In wireless sensor networks, the benefit of data aggregation

increases if the intermediate sensor nodes perform data aggregation

incrementally when data are being forwarded to the base station. However,

this continuous data aggregation operation improves the energy utilization.

A protocol is designed for the aggregation process with the

following operating and security requirements. Privacy-preserving, the

Sensor nodes

Dataaggregator Base

Station

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protocol can protect the private sensed value of a node from being disclosed

to any other sensor node and the sink of the network nodes. The protocol is

data-loss:-it will always compute an intended aggregation function over the

actual contributing data values.

1.8 SECURITY REQUIREMENTS OF WIRELESS SENSOR

NETWORK

Due to the unique properties of wireless sensor networks, it is a

difficult task to protect sensitive information transmitted by wireless sensor

networks. Security is an important issue for wireless sensor networks. The

requirements are,

Data Confidentiality

Data Integrity and Freshness

Source Authentication

Secure Data Aggregation

Figure 1.3 Interaction between wireless sensor networkand data aggregation

WirelessSensor

Network

Data Data Integrityand

SourceAuthentication

and

Availability ofdata

Aggregation ofencrypted

Alterations inaggregated

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1.8.1 Data Confidentiality

Ina wireless sensor network, data confidentiality ensures that

privacy of sensitive data is by no mean disclosed to unauthorized parties and

it is the most important concern in critical applications. The standard

approach for keeping sensitive data secret is to encrypt the data with a secret key only intended receivers possess, hence achieving confidentiality.

1.8.2 Data Integrity and Freshness

In a wireless sensor network, data integrity guarantees that a

message being transferred is never degraded. Thus, message authentication codes are used to prevent data integrity.

Even if data integrity is assured, it is also necessary to ensure the

freshness of each message. It suggests that the data is recent, and it ensures

that no old messages have been replayed.

1.8.3 Source Authentication

Source authentication enables a sensor node to ensure the identity of the peer node it is communicating with. Without source authentication, an

adversary could masquerade a node, thus gaining unauthorized access to resources and sensitive information and interfering with the operation of other

nodes. If only two nodes are communicating, and authentication can be

provided by symmetric key cryptography. The sender and the receiver share a secret key to compute the message authentication code for all transmitted

data.

1.8.4 Secure Data Aggregation

In a wireless sensor network, data aggregation protocols must

satisfy the security requirements. In this protocol, security and data

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aggregation are achieved together in a hop-by-hop fashion. That is, data

aggregators must decrypt every message they receive, aggregate the messages

according to the corresponding aggregation function, and encrypt the

aggregation result before forwarding it.

1.9 DESCRIPTION OF DAO-LEACH

The network deployment model is based on a 2D Gaussian

distribution. The coverage probability is derived with respect to the Gaussian

distribution. The formation of clusters in sensor network depends on time

duration for receiving the neighbor nodes message and the residual energy of

the neighbor node. Two nodes do not transmit data at the same time slot in

order to reduce the interference. Hop distance and hierarchy level plays a vital

role in the cluster formation. A sorting algorithm based on the residual energy

of the neighbor nodes is executed to obtain the list of neighbor nodes

regarding its hop distance.

CH performs data aggregation before transmitting the data to the

sink node. A cluster of nodes in a WSN is replaced with a single node without

changing the underlying joint employment of the network. Data ensemble

also takes place while aggregating the nodes. A macro node which is capable

of aggregation is determined. The conditional probability of the macro node

should be equal to the product of all component nodes’ conditional

probabilities. The conditional probability of a macro node’s successor is

equivalent to the conditional probability of the successor given the entire

component SNs in the macro node.

DAO-LEACH is a WSN routing protocol where the remaining

energy is considered in cluster formation and CH election. It involves a data

ensemble based optimal clustering scheme, where CH is termed as the

aggregated node which performs data accumulation from the received cluster

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member data. The non-cluster nodes choose its CH based on the residual

energy of the available CHs and the cluster size.

1.10 ISSUES OF WIRELESS SENSOR NETWORK

The major issues that affect the design and performance of a

wireless sensor network are, Quality of service, security, Data aggregation,

synchronization, localization and deployment. In sensor network, a sensor

node is mainly responsible for computation of the extracted data from the

local environment. Low power consumption in sensor networks is needed to

enable long operating lifetime by facilitating low duty. Energy consumption

of the sensing device should be minimized and sensor nodes should be energy

efficient since their limited energy resource determines their lifetime. Sensor

networks consist of hundreds of thousands of nodes.

SNs possess insecurity and limited energy. The sensed information

is aggregated at CHs to reduce the energy consumption by decreasing the

network traffic. But, data aggregation puts forward security challenges like

confidentiality and integrity of data. Also, this method is not optimized in

terms of memory consumption and overhead. The aggregated data is exposed

to intruders making the data insecure. Similarly an unauthorized user can

attach false data into the aggregated data and make the sink node accept false

data.

1.11 OBJECTIVE OF THE THESIS

The positioning of nodes in a sensor network has received a notable

attention in research. The localization and deployment are the fundamental

issues.

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To reduce the amount of transmitting data over the wireless

sensor network.

To provide secure data transmission.

To avoid implosion and overlaying problems.

To prevent a novel based security protocol called Data

Aggregation and Authentication protocol (DAA), to combine

false data detection with data aggregation and confidentiality.

DAO-LEACH is enhanced in terms of memory consumption, and

fault-tolerance based on Gracefully Degraded Data Aggregation (GDDA) to

ensure the integrity of the aggregated data and Hybrid Layer User

Authentication (HLUA) to ensure the confidentiality of the aggregated data.

DAO-LEACH protocol decreases consumption of higher memory.

Integrity protecting hierarchical Concealed Data Aggregation

protocol allows hierarchical aggregation of encrypted sensor data while

providing integrity and confidentiality. The proposed protocol employs a

privacy encryption and Message Authentication codes (MAC) to achieve

hierarchical data aggregation. It virtually partitions the network into several

regions and employs a different public key in each region. The encrypted data

of several regions can be hierarchically aggregated into a single piece of data

without violating data confidentiality.

In cluster-based wireless sensor network, the cluster head is one of

the most significant branches. Elliptic curve cryptography processors can be

designed in such a way to quality for lightweight applications suitable for

wireless sensor networks. Lightweight assumes low die size and low power

consumption. Therefore, a hardware processor supporting ECC which

features very low and low-power is proposed. ECC relies on a group structure

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induced on an elliptic curve. A set of points on an elliptic curve is combined

together with the point at infinity. The main operation of ECC is key-

exchange in the scalar multiplication.

The enhanced DAO-LEACH protocol is optimized to reduce the

bandwidth consumption, data transmission message size per packet, the

number of messages and overhead. The enhanced DAO-LEACH protocol for

Wireless sensor network is compared with various existing secure and energy-

efficient data aggregation schemes in Wireless sensor network.

1.12 ORGANIZATION OF THESIS:

The thesis is organized as follows:

Chapter 1: This chapter gives a brief overview of the wireless sensor

networks and the different routing algorithms which are used in wireless

sensor networks and the general introduction about the research work. The

research problem identification and purpose of the research are explained in

this chapter

Chapter 2: It also presents the literature review to provide necessary

background for a general understanding of the challenges related to routing

protocol in wireless sensor networks and discusses the solution methodology

for the problems.

Chapter 3: This Chapter explains LEACH with Newly proposed DAO-

LEACH in terms of throughput, energy utilization and packet delivery

analysis.

Chapters 4: This Chapter describes the Newly Enhanced DAO-LEACH in

terms of authentication, security, fault-tolerance based on Hybrid Layer User

Authentication (HLUA). It involves the performance evaluation and

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comparison of the enhanced DAO-LEACH with the existing techniques based

on Dynamic Data Aggregation with Privacy function (DyDAP), Integrity

Protecting Hierarchical Concealed Data Aggregation (IPHCDA) protocol,

SEDAN (Secure and Efficient Data Aggregation protocol for WSNs), and

DAA (Data Aggregation and Authentication).

Chapters 5: This Chapter describes the Newly Enhanced DAO-LEACH in

terms of energy-efficiency, memory overhead and aggregation accuracy based

on Gracefully Degraded Data Aggregation (GDDA). It involves the

performance evaluation and comparison of the enhanced DAO-LEACH with

the existing techniques based on SCAR (Simple cluster-based data

aggregation and routing), Energy-efficient Secure Path Algorithm (ESPA),

Deterministic key management based LEACH (DKS-LEACH), Secure and

Efficient Data Aggregation protocol for WSNs (SEDAN) and Perturbation-

based Efficient Confidentiality Preserving Protocol (PEC2P).

Chapter 6: This chapter provides a conclusion of the study by summarizing

the findings of the research. And it also reviews how well the aim and

objectives have been fulfilled. The chapter finally looks up to the possibilities

for future research and ends with some concluding statements.

1.13 CONCLUSION

While huge amount of research work is conducted in the field of

Wireless sensor networks, many of the topics related to routing, energy-

efficiency, security, and fault-tolerance have been studied by different

researchers with different ideas. At this juncture, it is necessary to organize

the contents in such a way that the importance of different research areas is

recognized and the next chapter concentrates on the literature reviews

presented by different research persons.