Advantages Of Ad Hoc Network

Chapter 1
Introduction
1.1. Introduction An ad hoc network is a collection of nodes that communicate with one another without any fixed networking infrastructure. This is viewed as suitable system which can support some specific applications as virtual classrooms, military communications, emergency search and rescue operation, data acquisition in hostile environments communication set up in exhibitions, conference and meetings, in battle field soldiers to co ordinate defense or attack , at airport terminals for workers to share files etc. In ad hoc networks nodes can change position quite frequently. The nodes in the ad hoc network can be laptops, PDA etc. These are often limited in resources such as such as storage capacity, CPU capacity,

Advantages of ad hoc network
. Rapidly deployable and self configuring.
. No need for existing infrastructure.
. Wireless links.
. A MANET can be standalone network or it can be connected to external networks.
. Data must be routed via intermediate nodes.
. Scalability incorporates the addition of more nodes.
. Flexible ad hoc network can be temporarily setup at any time in any place.
. Lower getting started costs due to decentralized administration. . The nodes in ad hoc network need to rely on any hardware and software. So, it can be connected and communicated quickly.

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Why ad hoc network?
. Setting up of fixed access points and backbone infrastructure is not always viable.
. Infrastructure may not be present in a disaster area or war zone.
. Infrastructure may not be practical for short range radios.
. Are easy to deploy.
1.3. Minimum hardware requirements
. Pentium-IV based PC
. 512 MB RAM
. Super VGA monitor
. Mouse
. Keyboard
1.4. Software requirements
. MATLAB 7.6
. Operating System: Windows XP Service pack 3 or Windows 7
1.5. Problem

Useful when number of traffic session is much lower than the number of nodes.
. No routing structure created a priori.
Two key methods for route discovery:
. Source routing
. Backward routing
. Introduce delay.
Examples: AODV
Ad hoc on demand distance vector routing
Route Discovery Process
. Source node initiates path discoverer process by broadcasting RREQ. . RREQ is forwarded until it reaches an intermediate node that has recent route information about the destination or till it reaches the destination.
. The RREQ uses sequence numbers to ensure that the routes are loop free and reply contains latest information only.

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Route Reply Process . When a node forwards a route request packet to its neighbor; it also records in the table the node from which the first copy of the request came.
. This table is used to construct the reverse path for the RREQ.
. As the RREQ traverses back to the source, the nodes along the path enter the forward route into their tables.
. If one of the intermediate nodes move then the moved nodes neighbor realizes the link failure and sends a link failure notification to its upstream neighbors and so on till it reaches the source.
. Route Error Packets are used to erase broken