8/3/2019 Sensor New

1/21

8/3/2019 Sensor New

2/21

Wireless Sensor Networks

Sensor: a small, lightweight device which measures the

environment of physical parameters such as temperature,

pressure, relative humidity,

Sensor Networks: are highly distributed networks of wireless

sensor nodes, deployed in large numbers to monitor the

environment or system.

Sensor Node : consists of sensing, computing, communication,

actuation, and power components.

8/3/2019 Sensor New

3/21

Sensor networks VS ad hoc networks

y The number of nodes in a sensor network can be several orders ofmagnitude higher than the nodes in an ad hoc network.

y Sensor nodes are densely deployed.

y Sensor nodes are limited in power, computational capacities and memory.

y Sensor nodes are prone to failures.

y The topology of a sensor network changes frequently.

y Sensor nodes mainly use broadcast, most ad hoc networks are based on p2p.

y Sensor nodes may not have global ID.

8/3/2019 Sensor New

4/21

Factors Influencing Sensor Network Designy Fault tolerance

y Scalability

y Operating environment

y Sensor network topology

y Transmission media

y Power consumption

8/3/2019 Sensor New

5/21

Application Of Wireless Sensor Networks

y Environmental Data Collection

y Security Monitoring

y Node Tracking Scenarios

y The military applications

yThe Medical Application

y Home and Other Commercial Application

8/3/2019 Sensor New

6/21

TYPES OFATTACKS ON WSN

y In many applications, the data obtained by the sensing nodes needs to be

kept confidential and it has to be authentic

y In the absence of security a false or malicious node could intercept private

information, or could send false messages to nodes in the network.

y

The major attacks are:Denial of Service (DOS),

Worm hole attack,

Sinkhole attack,

Sybil attack,

SelectiveF

orwarding attack,Passive information gathering,

Node capturing,

False or malicious node,

Hello flood attack

8/3/2019 Sensor New

7/21

Denial of Service (DoS)

y The simplest DoS attack tries to exhaust the resources available to

the victim node, by sending extra unnecessary packets and thus

prevents legitimate network users from accessing services or

resources to which they are entitled

y

DoS attack is meant not only for the adversary's attempt to subvert,disrupt, or destroy a network, but also for any event that diminishes a

network's capability to provide a service

The Sybil attack

y In this attack, a single node i.e. a malicious node will appear to be a set of

nodes and will send incorrect information to a node in the network.y Authentication and encryption techniques can prevent an outsider to launch

a Sybil attack on the sensor network. However, an insider cannot be

prevented from participating in the network, but he should only be able to

do so using the identities of the nodes he has compromised.

8/3/2019 Sensor New

8/21

Selective Forwarding attack

y It is a situation when certain nodes do not forward many of the messages

they receive.

y The sensor networks depend on repeated forwarding by broadcast for

messages to propagate throughout the network.

Sinkhole attacks

y In a sinkhole attack, the adversary's aim is to lure nearly all the traffic from

a particular area through a compromised node, creating a sinkhole with the

adversary at the center

y Sinkhole attacks typically work by making a compromised node lookespecially attractive to surrounding nodes with respect to the routing

algorithm.

8/3/2019 Sensor New

9/21

Passive Information Gathering

y An intruder with an appropriately powerful receiver and well designed

antenna can easily pick off the data stream.

y Interception of the messages containing the physical locations of sensor

nodes allows an attacker to locate the nodes and destroy them

y

Besides the locations of sensor nodes, an adversary can observe theapplication specific content of messages including message IDs, timestamps

and other fields.

False or Malicious Node

y Most of the attacks against security in wireless sensor networks are caused

by the insertion of false information by the compromised nodes within thenetwork

8/3/2019 Sensor New

10/21

8/3/2019 Sensor New

11/21

Sensor NetworkArchitecture

LayeredArchitecture

yThe sensor nodes, which are notnear enough to the base station,

communicate over nodes of

neighboring layers.

y

Example UNPF: Unified networkprotocol framework

8/3/2019 Sensor New

12/21

Clustered Architecture

y Sensor nodes are organized in

clusters

y Each cluster has a cluster-head,y Cluster formation must be an

autonomous process.

y Example: Low-Energy Adaptive

Clustering Hierarchy (LEACH)

8/3/2019 Sensor New

13/21

Data Handling Data dissemination is the process by which

queries for data are routed in the sensornetwork

Consists of a two-step process of interestpropagation and data propagation

First, the node that is interested in someevents, like temperature or air humidity,broadcasts its interests to its neighborsperiodically. Interests are then propagatedthrough the whole sensor network

In the second step, nodes that have requesteddata, send back data after receiving the

request. Intermediate nodes in the sensornetwork also keep a cache of receivedinterests and data.

8/3/2019 Sensor New

14/21

Flooding

each node which receives a packet broadcasts it if the maximum hop-count of the packet is not reached and the node is not the destination

of the packet.

y Advantages: easy to implement and maintenance

y Disadvantages: Implosion (duplicate messages are sent to the same

node), Overlap (overlapping regions of sensor coverage), Resource

blindness (many redundant transmissions, reduced network lifetime)

Gossiping

y modified version of flooding, nodes do not broadcast a packet, but send it to

a randomly selected neighbor.y Advantages: easy to implement and maintenance, lower overhead than

flooding

y Disadvantages: need a long time for a message to propagate throughout the

network, does not guarantee that all nodes will receive the message!

8/3/2019 Sensor New

15/21

Sensor Protocols For Information via Negotiation( SPIN)

SPIN uses three types of messages: ADV, REQ, and DATA

The sensor node that has collected some data sends an ADV message

containing meta-data describing the actual data.

If some of node's neighbors is interested in the data, the neighbor sends a

REQmessage back.

After receiving the REQ message, the sensor node sends the actual DATA.

The neighbor also sends ADV message forward to its neighbors, thus data isdisseminated through the network

8/3/2019 Sensor New

16/21

Cost FieldApproach

Considers the problem of setting up paths to a sink

y Two-phase process:

The first phase set up the cost field at all sensor nodes (based on metrics

such as delay,)

The second phase uses the cost for data dissemination

The cost at each node is the minimum cost from the node to the sink, which

occurs on the optimal path.

8/3/2019 Sensor New

17/21

Geographic Hash Table(GHT)

y Inspired by Internet-scale

distributed hash table (DHT)

y stores a pair (key, value)

y The data is stored distributed acrossall sensors not routed to a central

storage.

y More effective in large sensor

networks where a large number of

events are detected but not all are

queried.

8/3/2019 Sensor New

18/21

Data gathering model

y Data gathering algorithms try to maximize

the number of rounds of communication

before the nodes die and the network

becomes inoperable.

y Conflicting requirements:

Minimum delay and minimum energy

consumption

8/3/2019 Sensor New

19/21

DirectTransmission

y Every node sends the collected data

directly to the base station.

y high energy consumption, and delays

8/3/2019 Sensor New

20/21

PowerEfficient Gathering for Sensor Information System

y PEGASIS aims to minimize the transmission

distances over the whole sensor network,

minimize the broadcast overhead, minimize

the amount of messages that are sent to the

base stationy In PEGASIS a chain of sensor nodes is

constructed using a greedy algorithm starting

from the node farthest from the base station.

y During the data transmission, nodes

aggregate the data and only one message isforwarded to the next node.

y The node that is selected as a leader then

transmits all the data to the base station in a

single message.

8/3/2019 Sensor New

21/21

Binary Scheme

Also chain based algorithm like PEGASIS which classifies nodes intodifferent levels.

Levels: all nodes which receive a message rise to the next level. The

number of nodes is halved from a level to the next.

y An example of the binary scheme is shown in Figure below. Nodes s1,

s3, s5 and s7 receive messages on the first level and thus theyy rise to the next level. On the second level nodes s3 and s7 receive

messages and finally node s7 forwards all data to the base station.