Mobile ad-hoc networks (MANETs) are formed spontaneously by wireless devices without any preexisting infrastructure. Nodes in a MANET are free to move randomly and organize themselves arbitrarily, so the network topology can change unpredictably. MANETs have advantages like decentralized administration and self-configuration, but also challenges like limited bandwidth, dynamic topology, and security threats. Applications of MANETs include personal devices like cell phones communicating directly, military environments, emergency response situations, and more.

1. Chapter 5
Mobile Ad-hoc Network &
Wireless Sensor Network
Marks 16

3. Manet
• Mobile ad hoc networks (MANETs) are envisioned to become key components in
the 4G architecture, and ad hoc networking capabilities are expected to become
an important part of overall next-generation wireless network functionalities.
• Mobile ad hoc networks are formed dynamically by an autonomous system of
mobile nodes that are connected via wireless links without using an existing
network infrastructure or centralized administration.
• The nodes are free to move randomly and organize themselves arbitrarily; thus,
the network’s wireless topology may change rapidly and unpredictably.
• Such a network may operate in a standalone fashion, or may be connected to the
larger Internet.
• Mobile ad hoc networks are infrastructure less networks since they do not
require any fixed infrastructure such as a base station for their operation.
• Routes between nodes in an ad hoc network may include multiple hops and,
hence, it is appropriate to call such networks ―multihop wireless ad hoc
networks.”

4. Manet Architecture

5. Advantages and Disadvantages of MANET
Advantages
• Separation from central network administration.
• Each nodes can play both the roles ie. of router and host showing
autonomous nature.
• Self configuring and self healing nodes, does not require human
intervention.
Disadvantages
• Resources are limited due to various constraints like noise, interference
conditions, etc.
• Lack of authorization facilities.
• More prone to attacks due to limited physical security.

6. Characteristics/ Properties of MANET
• Dynamic Topologies: Network topology which is typically multihops, may
change randomly and rapidly with time, it can form unidirectional or bi-
directional links.
• Bandwidth constrained, variable capacity links: Wireless links usually have
lower reliability, efficiency, stability and capacity as compared to wired
network. The throughput of wireless communication is even less than a radio’s
maximum transmission rate after dealing with the constraints like multiple
access, noise, interference conditions, etc.
• Autonomous Behaviour: Each nodes can act as a host and router, which shows
its autonomous behaviour.
• Energy Constrained Operation: As some or all the nodes rely on batteries or
other exhaustible means for their energy. Mobile nodes are characterized with
less memory, power and light weight features.
• Limited Security: Wireless network are more prone to security threats. A
centralized firewall is absent due to its distributed nature of operation for
security, routing and host configuration.
• Less Human Intervention: They require minimum human intervention to
configure the network, therefore they are dynamically autonomous in nature.

7. Types of MANET
• Vehicular Ad hoc Network (VANETs) –
Enable effective communication with another vehicle or with the roadside equipments.
Intelligent vehicular ad hoc networks(InVANETs) deals with another vehicle or with the
roadside equipment.
• Smart Phone Ad hoc Network (SPANC) –
To create peer-to-peer network without relying on cellular carrier networks, wireless
access points or traditional network infrastructure. Here peer can join or leave the
network without destroying it.
• Internet based Mobile Ad hoc Network (iMANETs) –
It supports internet protocols such as TCP/UDP and IP. To link mobile nodes and establish
routes distributed and automatically.
• Hub-Spoke MANET:
Multiple sub MANET’s may be connected in hub-spoke VPN to create a geographically
distributed MANET. Normal Ad-hoc routing algorithm does not apply directly.
• Military or Tactical MANETs –
This is used by the military units. Emphasis on data rate, real time demand, fast re-routing
during mobility, security, radio range, etc.
• Flying Ad hoc Network (FANETs) –
This is composed of unmanned aerial vehicle (commonly known as drone). Provides links
to remote areas and mobility.

8. Challenges in Manet
• Limited Bandwidth -The wireless networks have a limited bandwidth in comparison to the
wired networks. Wireless link has lower capacity as compare to infrastructure networks.
The effect of fading, multiple accesses, interference condition is very low in ADHOC
networks in comparison to maximum radio transmission rate.
• Dynamic topology - Due to dynamic topology the nodes has less truest between them. I
some settlement are found between the nodes then it also make trust level questionable.
• High Routing - In ADHOC networks due to dynamic topology some nodes changes their
position which affects the routing table.
• Problem of Hidden terminal -The Collision of the packets are held due to the transmission
of packets by those node which are not in the direct transmission range of sender side but
are in range of receiver side.
• Transmission error and packet loss -By increasing in collisions , hidden terminals,
interference, uni-directional links and by the mobility of nodes frequent path breaks a
higher packet loss has been faced by ADHOC networks.
• Mobility - Due to the dynamic behaviour and changes in the network topology by the
movement of the nodes .ADHOC networks faces path breaks and it also changes in the
route frequently.
• Security threats - New security challenges bring by Adhoc networks due to its wireless
nature. In Adhoc networks or wireless networks the trust management between the nodes
leads to the numerous security attacks.

9. Applications of Manet
• Personal area networking - cell phone, laptop, ear phone,
wristwatch
• Military environments- soldiers, tanks, planes
• Civilian environment- Car network meeting rooms
• Meeting rooms- sports stadiums, boats, small aircraft
• Emergency operations- search-and-rescue, policing and fire
fighting