chapter 1 wireless sensor networks -...
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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.