Unit8 tgb

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UNIT 8:- Mobile Ad-Hoc Networks,
Wireless Sensor Networks
a Mobile Ad hoc NETwork (MANET) is one that comes together as needed, not necessarily with
any support from the existing infrastructure or any other kind of fixed stations. We can formalize this
statement by defining an ad hoc (ad-hoc or adhoc) network as an autonomous system of mobile hosts
(MHs) (also serving as routers) connected by wireless links, the union of which forms a
communication network modeled in the form of an arbitrary communication graph. This is in contrast
to the wellknown single hop cellular network model that supports the needs of wireless
communication by installing base stations (BSs) as access points. In these cellular networks,
communications between two mobile nodes completely rely on the wired backbone and the fixed
BSs. In a MANET, no such infrastructure exists and the network topology may dynamically change
in an unpredictable manner since nodes are free to move.
Important characteristics of a MANET Characteristics:
Dynamic Topologies Nodes are free to move arbitrarily with different speeds; thus,the network
topology may change randomly and at unpredictable times.
Energy-constrained Operation Some or all of the nodes in an ad hoc network may rely on batteries or
other exhaustible means for their energy. For these nodes, the most important system design
optimization criteria may be energy conservation.
Limited Bandwidth: Wireless links continue to have significantly lower capacity than infra
structured networks. In addition, the realized throughput of wireless communications - after
accounting for the effects of multiple access, fading, noise, and interference conditions, etc., is often
much less than a radio's maximum transmission rate
Security Threats : Mobile wireless networks are generally more prone to physical security threats than
fixed-cable nets. The increased possibility of eavesdropping, spoofing, and minimization of denial-of
service type attacks should be carefully considered.

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Applications of MANETs
Collaborative Work - For some business scenarios, the need for collaborative computing might be
more important outside office environments than inside a building. After all, it is often the case
where people do need to have outside meetings to cooperate and exchange information on a given
project;
• Crisis-management Applications - These arise, for example, as a result of natural disasters where
the entire communications infrastructure is in disarray (for example, Tsunamis, hurricanes, etc.).
Restoring communications quickly is essential. By using ad hoc networks, an infrastructure could be
set up in hours instead of days/weeks required for wire-line communications;
Personal Area Networking - A personal area network (PAN) is a short-range, localized network
where nodes are usually associated with a given person. These nodes could be attached to someone's
cell phone, pulse watch, belt, and so on. In these scenarios, mobilityis only a major consideration
when interaction among several PANs is necessary, illustrating the case where, for instance, people
meet in real life. Bluetooth [Haarstenl998] is an example of a technology aimed at, among other
things, supporting PANs by eliminating the need of wires between devices such as printers, cell
phones, PDAs, laptop computers, headsets, and so on, and is discussed later in this book. Other
standards under the IEEE 802.15 working group for wireless PANs are also described.
Classification of routing protocols
Ad-hoc Routing protocols can be categorized as table-driven or source initiated.
Table-driven or proactive ,routing protocols finds routes to all possible destinations ahead of
time. The routes are recorded in the nodes’ routing tables and are updated within the
predefined intervals. Proactive routing protocols are faster in decision making ,but cause
problems if the topology of the network continually changes.
These protocols require every node to maintain one or more tables to store updated
routing information from every node to all other nodes.
Source-initiated routing protocols:
Source-initiated, or reactive, routing protocols are on-demand procedures and create routes
only when requested to do so by source nodes. A route request initiates a route-discover
process in the network and is completed once a route is discovered. If it exists, at the time of
request, a route is maintained by a route-maintenance procedure until either the destination
node becomes irrelevant to the source or the route is no longer needed.
Control overhead of packets is smaller than of proactive protocols.

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Table driven / proactive
 Destination sequenced distance vector [DSDV]: The DSDV is table driven based
routing algorithm. DSDV is improved version of Bellman Ford routing algorithm.
 Each DSDV node maintain two routing tables: - table for forwarding packets, and table
for advertising incremental updates. The nodes will maintain a routing table that consists
of a sequence number. The routing table periodically exchanged so that every node will
have latest information.
 DSDV is suitable for small networks.
The algorithm works as follows
 A node or a mobile device will make an update in its routing table and send the
information to its neighbor upon receiving the updated information and make an update
in its own routing table.
 The update is made by comparing the sequence number received is greater than present
sequence number than the new one will be used.
 If there is a link failure in one of the node will change the metric value to infinity and
broadcast the message.
Cluster head gateway switch router [CGSR]
CGSR is also a table driven routing protocol. In this algorithm the mobile devices will be
grouped to form a cluster the grouping is based on the range and each cluster is controlled by
cluster head. All the mobile devices will maintain 2 tables cluster member table and routing
table.
The cluster member table will have the information about the cluster head for each
destination the routing table will have routing information. In this protocol the packet cannot
be directly sent to the destination instead cluster heads are used for routing.
CGSR routing involves cluster routing, where a node finds the best route over cluster heads
from the cluster member table.

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Wireless routing protocol [WRP]
WRP is also based on table driven approach this protocol makes use of 4 tables
1. Distance table :- Which contains information like destination, next hop, distance
2. Routing table: - Which contains routing information.
3. Link cost table:- Which contains cost information to each neighbor
4. Message retransmission list table: - this table provides sequence number of the message,
a retransmission counter, acknowledgements and list of updates sent in update message.
Whenever there is a change in the network an update will be made which will be broadcasted
to other nodes.
Other nodes upon receiving the updated information will make an update in their table.
If there is no update in the network a hello message should be sent.
Source initiated / reactive protocol
 Dynamic source routing [DSR]: DSR is a source initiated or on demand routing
protocol in which source finds unexpired route to the destination to send the packet. It is
used in the network where mobile nodes move with moderate speed.
 Overhead is significantly reduced, since nodes do not exchange routing table information
it has 2 phases.
1. Route discovery
2. Route maintenance
The source which wants to send the information to the destination will create a route request
message by adding its own identification number and broadcasts them in the network. The
intermediate nodes will continue the broadcast but adding their own identification number.
When the destination is reached a route reply message is generated which will be sent back
to the source. The source can receive multiple route replies indicating the presence of
multiple paths.
The source will pick up one of the path and will use for transmission. If there is a link failure
one of the node will detect and will create a route error message which will be sent back to
the source in this case the path has to be re-established for further transmission.

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Associated based routing [ABR]: ABR is an efficient on-demand or source initiated
routing protocol. In ABR, the destination node decides the best route, using node
associativity. ABR is suitable for small networks, as it provides fast route discovery and
creates shortest paths through associativity.
Each node keeps track of associativity information by sending messages periodically.
If the associativity value is more means nodes mobility is less.
If the associativity value is less means nodes mobility is
In ABR the source which wants to send the packet to the destination will create a query
packet and broadcast in the network. Query packet generation is required for discovering the
route.
The broadcast continues as long as destination is reached once the destination is reached it
creates the reply packet and sends back to the source.
The query packet will have the following information.
1. Source id
2. Destination id
3. All intermediate node id
4. Sequence number
5. CRC and
6. Time to live [TTL]
A node sends an update packet to the neighbors and waits for the reply if update is received
back, then associative tick will be incremented high then it means mobile device is still a part
of the network otherwise it might not be.
Adhoc on demand distance vector [AODV]
It is a source initiated routing protocol in mobile adhoc networks.
The algorithm consist of 2 phases
1. Route discovery phase
2. Route maintenance phase
In route discovery phase the path from source to destination is identified by broadcasting
route request packet [RREQ]. When the intermediate node receive RREQ they will create a
backward pointer and continue the broadcast when the route request packet reaches the
destination a route reply would be generated [RREP]. The route reply will have information
about the path that can be chosen for the packet transmission.

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The route request packet can have following information.
1. Source id
2. Destination id
3. Sequence number
4. Backward pointer information
5. CRC and
6. Time to live[TTL]
In the above network the RREQ will be broadcasted by the source node 1 to its neighbor and
neighbors will check whether RREQ is already processed. If it is already processed the
packet will be discarded.
If it is not processed a backward pointer is created and the broad cast continues.
When the packet is reached at destination a route reply is created [RREP] in the above
network the first RREP is sent to the source can have the path information as 1-2-4-6-8.
When the source receives this information it will be stored in the routing table. Mean
while the destination can create one more RREP which can have the information as 1-3-7-8
the destination will send this RREP to the source and will also ask the source to discard old
path as the new path is having minimum number of hops.
Route maintainence phase
The nodes in the network periodically exchange hello messages to inform that they
are still a part of network and the path is valid. Whenever there is a link failure detected. A
route error packet [RERR] will be sent to the source indicating the path is no more valid.
Temporary ordered routing algorithm [TORA]
It is also a source initiated routing algorithm, creates multiple routes for any source/
destination pair. The advantage of multiple routes is that route discovery is not required for
every alteration in the network topology.
TORA consists of three phases,
1. Route Creation/discovery
2. Route maintenance
3. Route erasure
TORA uses three types of packets: Query Packets for route creation, Update Packets for both
creation and maintenance

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The route will be discovered from the source to destination only when a request is made for
the transmission. In this algorithm the source will generate a query packet which will be
broadcasted in the network this continues as long as a node that is directly connected to the
destination is identified.
When the destination is identified an update packet will be generated and sent back to
the source. The update packet will have the path information if there are more than one
update packet received by the source, it means there are multiple paths to the destination, the
source has to choose best path available.
Security in adhoc networks
The following are the security threat in adhoc network.
1. Limited computational capabilities : the nodes in the mobile adhoc network are
modular, independent and will have limited computational capability.
It becomes a source of vulnerability when they handle public key cryptography.
2. Limited power supply : since nodes have limited power supply attacker can exhaust
batteries by giving excessive computations to be carried out.
3. Challenging key management : the key management becomes extremely difficult as the
mobile devices will be under movement.
Types of attack in adhoc network
The attack can be classified into 2 types
1. Passive 2. Active
In passive attack, the normal operation of routing protocol is not interrupted. The attacker
just tries to gather the information
In active attack, the attacker can insert some arbitrary packets and therefore might affect the
normal operation of network
Attack can also be one of the following types
1. Pin attack : with the pin attack, an unauthorized node pretends to have shortest path to
the destination
The attacker can listen to path setup phase and become the part of network.
2. Location disclosure attack : by knowing the locations of intermediate nodes, the
attacker can find out the location of target node
3. Routing table overflow : the attacker can create some routes whose destination do not
exist. It will have major impact on proactive based routing
4. Energy exhaustion attack : the attacker tries to forward unwanted packets or send
unwanted requests which can conserve the battery of the nodes

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Criteria for a secure routing protocol
The attack in adhoc network can be prevented by using a securing routing protocol. It should
have following properties
1. Authenticity: when a routing table is updated, it must verify whether updates were
provided by authenticated node.
2. Integrity of information : when a routing table is updated the information must be
verified whether it is modified or not
3. In order updates: sequence numbers or some mechanism must be used to maintain
updates in order.
4. Maximum update time: updates in routing table must be done as quickly as possible.
5. Authorization: only authorized nodes must be able to send update packets.
Wireless sensor network
WSNs, which can be considered as a special case of ad hoc networks with reduced or no mobility, are
expected to find increasing deployment in coming years, as they enable reliable monitoring and
analysis of unknown and untested environments. These networks are "data centric", i.e., unlike
traditional ad hoc networks where data is requested from a specific node, data is requested based on
certain attributes such as,"which area has temperature over 35°C or 95°F". Therefore a large
number of sensors need to be deployed to accurately reflect the physical attribute in a given area.
Routing protocol design for WSNs is heavily influenced by many challenging factors, which must be
overcome before efficient communication can be achieved. These challenges can be summarized as
follows:
Ad hoc deployment - Sensor nodes are randomly deployed which requires that the system be able to
cope up with the resultant distribution and form connections between the nodes. In addition, the
system should be adaptive to changes in network connectivity as a result of node failure.
• Computational capabilities - Sensor nodes have limited computing power and therefore may not
be able to run sophisticated network protocols leading to light weighted and simple versions of
routing protocols.

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• Energy consumption without losing accuracy - Sensor nodes can use up their limited energy
supply carrying out computations and transmitting information in a wireless environment. As such,
energyconserving forms of communication and computation are crucial as
the node lifetime shows a strong dependence on the battery lifetime. In a multi-hop WSN, nodes play
a dual role as data sender and data router. Therefore, malfunctioning of some sensor nodes due to
power failure can cause significant topological changes and might require rerouting of packets and
reorganization of the network.
Scalability - The number of sensor nodes deployed in the sensing area may be in the order of
hundreds, thousands, or more. Any routing scheme must be scalable enough to respond to events and
capable of operating with such large number of sensor nodes. Most of the sensors can remain in the
sleep state until an event occurs, with data from only a few remaining sensors providing a coarse
quality.
• Communication range - The bandwidth of the wireless links connecting sensor nodes is often
limited, hence constraining inter sensor communication. Moreover, limitations on energy forces
sensor nodes to have short transmission ranges. Therefore, it is likely that a path from a source to a
destination consists of multiple wireless hops
Fault tolerance - Some sensor nodes may fail or be blocked due to lack of power, physical damage,
or environmental interference. If many nodes fail, MAC and routing protocols must accommodate
formation of new links and routes to the data collection BSs. This may require actively adjusting
transmit powers and signaling rates on the existing links to reduce energy consumption, or rerouting
packets through regions of the network where more energy is available. Therefore, multiple levels of
redundancy may be needed in a fault tolerant WSN.
• Connectivity - High node density in sensor networks precludes them from being completely
isolated from each other. Therefore, sensor nodes are expected to be highly connected. This, however,
may not prevent the network topology from varying and the network size from shrinking due to
sensor nodes failures. In addition, connectivity depends on the, possibly random, distribution of
nodes.
Transmission media - In a multi-hop sensor network, communicating nodes are linked by a wireless
medium. Therefore, the traditional problems associated with a wireless channel (e.g., fading, high
error rate) also affect the operation of the sensor network. In general, bandwidth requirements of
sensor applications will be low, in the order of 1-100 kb/s. As we have seen in Chapters 4 and 5 and
in the previous section, the design of the MAC protocol is also critical in terms of conserving energy
in WSNs.
• QoS - In some applications (e.g., some military applications), the data should be delivered within a
certain period of time from the moment it is sensed, otherwise the data will be useless. Therefore,
bounded latency for data delivery is another condition for time constrained applications.

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• Control Overhead - When the number of retransmissions in wireless medium increases due to
collisions, the latency and energy consumption also increases. Hence, control packet overhead
increases linearly with the node density. As a result, tradeoffs between energy conservation, self-
configuration, and latency may exist.
• Security - Security is an important issue which does not mean physical security, but it implies that
both authentication and encryption should be feasible. But, with limited resources, implementation of
any complex algorithm needs to be avoided. Thus, a tradeoff exists between the security level and
energy consumption in a WSN.
Protocol stack for sensor network
The protocol stack of sensor network combines power efficiency and least cost path routing.
The architecture consist of
1. Physical layer
2. Data link layer
3. Network layer
4. Transport layer
5. Application layer
All these layers are backed by management plane, mobility management plane and task
management plane.
Physical layer is responsible for transmitting and receiving signals.
 The data link layer consists of medium access control [MAC] which is used to
prevent packet collision.
 The network layer is responsible for routing the packets
 The application layer is used for creation of packets by making use of software.
 The power management plane monitors the sensor’s power level among sensor node.

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Structure of a sensor node
Transceiver
Embedded
Processor
Sensor
Battery
Memory
Transceiver
Embedded
Processor
Sensor
Battery
Memory
1Kbps- 1Mbps
3m-300m
Lossy Transmission
8 bit, 10 MHz
Slow Computation
Limited Lifetime
Requires
Supervision
Multiple sensors
128Kb-1Mb
Limited Storage
The sensor node consist of a
1. sensing unit
2. processing unit
3. memory unit
4. self power unit
5. wireless transreceiver
 Sensing unit: it consists of a sensor and analog to digital converter [ADC]. the
analog signal produced by sensor is converted to digital and is fed into processing
unit. The sensing unit is responsible for collecting the data externally and interacts
with central processor
 Processing and memory unit: the processing unit is responsible for performing
some computations it executes some instructions which is responsible for setting up
the connection with another node. The memory unit is used for storing the data.
 Self power unit: it is responsible for powering the node and keeping it alive. The
main task of the sensor node is to identify events , to process data , and then to
transmit the data. The power of a node is consumed mainly in the transmitter and
receiver unit. The sensor node can be supplied by a self-power unit, self-power unit
battery, or solar cells.

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Communication energy model
IEEE standards as 802.11a, b, and g provide a wide range of data rates: 54,48,36,24,18,12,9
and 6 mb/s. this range reflects the trade off between the transmission range and data rate
intrinsic in a wireless communication channel. An accurate energy model is crucial for the
development of energy efficient clustering and routing protocols. The energy consumption, E
for all components of the watts is summarized as
E=theta+ηwdn
Where Ѳ is the distance independent term that accounts for the overhead of the radio
electronics and digital processing, and ηwd^n is the distance dependent term in which η
represents the amplifier inefficiency factor w is the free space path loss d is the distance and
n in the environmental factor. Based on an environmental condition, n can be any number
between 2 and 4 and η specifies the inefficiency of the transmitter when generating
maximum power wd^n at the antenna. Clearly the distance dependent portal of total energy
consumption depends on the real-world Tranreceiver parameters, Ѳ, η and the path
attenuation wd^n. if the value of Ѳ overshadows ηwd^n, the reduction in the transmission
distances through the use of multihop communication is not effective.
Clustering protocol
Decentralized energy efficient propagation protocol [DEEP]: DEEP is used for
identifying a head and the members.
The algorithm works as follows
1. Initialize: when network is created one of the node in the network will be made as cluster
head. The cluster head sends a signal known as cluster head declaration signal to all the
nodes which are in the range ’ .
This is used for identifying the members of the cluster. The cluster head sends cluster
head exploration to all the nodes which are in the range dr1 and dr2. This is done to
identify a new cluster head.
2. Repeat : even though many nodes receive the cluster head exploration only one node fro
which the equation ERC1 < ER < ERC2 can become the candidate of the cluster head.
‘ER’ is the energy of cluster head exploration and
‘ERC!’=Pout – ηwd 1
‘ERC2’=Pout–ηwd 2
η, w, n are dependent on environment factors.

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The new candidate sends cluster head declaration for all the nodes in the range dr. if a
node receives multiple cluster head declaration which ever signal is having higher energy
will be chosen as cluster head. The other candidates will be eliminated.
3. Conclusion: if there are not enough members in a cluster member exploration/search
signal will be generated atleast if a node does not receive any signal member exploration
or search signal will be generated.
Low energy adaptive clustering hierarchy protocol [LEACH]:
LEACH is a clustering protocol used for identifying the cluster head and the members. It
consist of 2 phases
1. Clustering phase
2. Steady state phase
Both these phases are repeated in round. The algorithm works as follows. A node will pick
up a number between 0 and 1 and compares the value with if is greater it
becomes the candidate for cluster head.
P is the ratio of cluster heads to total number of nodes
r-> is the round
g-> number of nodes who has not got during the first round will be equivalent to P and
node can become the cluster head.
Similarly when the value of ‘r’ reaches close to (1-p) will be equivalent to P and node
can become a cluster head
The cluster head candidates begin to send a signal to other nodes which ever candidate is
having a higher signal will become cluster head.
Routing protocol

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Routing protocol in sensor network: In sensor network the routing of information can
happen within a cluster or between nodes of different clusters.
If the routing is happening within a cluster. Then the protocol is called as intra cluster
routing.
If the routing is happening between the nodes of different clusters it is called as inter cluster
routing.
Intracluster routing
In intracluster routing, the packets are transmitter with in a cluster
It can be of two types.
1. Direct routing algorithm
2. Multihop routing algorithm
In direct routing, the cluster head as the destination for all cluster nodes. The cluster nodes
can communicate directly with cluster nodes.
In multihop the destination is reached through multiple hops. If there are many paths. Then
only the path which is energy efficient will be considered. In multihop routing, a node might
have to under go multiple hops before it reaches the destination. The sensor node will be at
different distances apart from other nodes. A packet from a node is routed to a neighbor node
that exhibits high energy. The number in the node indicates the remaining energy in the node
Inter cluster routing [ICR]: It is a destination initiated reactive routing algorithm. The
destination is called as local base station [LBS] it will start the route discovery by creating
interest signal and following them. ICR works in two phases, Route discovery and data
acquisition.
In Route Discovery Phase, the LBS initiates route discovery by sending an interest signal
within the range Ri,
1. All the nodes which are in the range Ri will receive the interest signal.
2. Upon receiving the interest signal it will be stored and flooding continues.

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3. If an intermediate node receive already processed interest signal it will be discarded
4. Before flooding the interest signal the cost value will be updated. The format of the
interest signal and the formula for the cost is as given below.
Interest signal
Type Period Source
Address
cost
The type field indicates message format. The period indicates how often interest signal has to
be sent. The source address field is used for sorting address of the source node. The cost field
indicates number of hops required to reach the source. In formula for the cost α and β are
normalization factor based on environment.
Cost=αh+β∑ Bm/Bri
Where, h is hop count
Bm = It is the maximum battery available in the node
Bri = it is the remaining battery in the node.
Write a note on Zigbee technology?
 ZigBee is one of the newest technologies enabling Wireless Personal Area Networks
(WPAN).
 ZigBee is an established set of specifications for wireless personal area networking
(WPAN), i.e. digital radio connections between computers and related devices.
 WPAN Low Rate or ZigBee provides specifications for devices that have low data rates,
consume very low power and are thus characterized by long battery life. ZigBee makes
possible completely networked homes where all devices are able to communicate and be
controlled by a single unit.
 The IEEE 802.15.4 standard and Zigbee wireless technology are designed to satisfy the
market's need for a low-cost, standard-based and flexible wireless network technology,
which offers low power consumption, reliability, interoperability and security for control
and monitoring applications with low to moderate data rates.
 The data which gets transmitted includes temperature reading on or off state of a switch
keystroke of a keyboard etc.
 The Bluetooth technology which is used in mobile phones, laptops, runs on zigbee.
Zigbee is an IEEE 802.15.4 standard. Zigbee operates in a frequency range 900MHz- 2.5
GHz.
 The technology can be used for transmitting the data within the range of 20mts.
 It can also be used for transmission of data within a range greater than 20mts. This is
possible through the intermediate nodes.