Saturday, March 8, 2008

REPORT 1

AD HOC NETWORK

ABSTRACT

Ad hoc network is network architecture that can be rapidly deployed without pre-existance of any fixed communication infrastructure. Ad hoc network is useful in situations where fixed communication infrastructure does not exists or has been destroyed. In such situations it is very difficult to provide the necessary infrastructure but it is a challenging task to enable fast and reliable communication within such a network. Ad hoc network are multi-layer containing Physical Layer, Multiple Access Layer, Network Layer, Transport Layer, Application Layer.

Ad hoc network increases the flexibility and mobility. Ad hoc network could be more economical in some cases as they eliminate fixed infrastructure costs and power consumption at mobile nodes. Ad hoc network are more reliable than conventional network because their non-hierarchical distributed control and management mechanism. Because multi-hop support in an ad hoc network communication beyond Line Of Straight is possible at high frequencies.

1. Introduction:-
Computer network is interconnected collection of autonomous computers. Roughly speaking, networks can be divided into LANs, MANs, WANs and internetworks, each with their own characteristics, technologies, speeds, and functions. Cellular network is nothing but wireless WAN. It has predetermined infrastructure with static backbone.

2. Need Of Ad Hoc Networks:

Some times the situation occurs where a fixed communication infrastructure, wired or wireless, does not exist or has been destroyed. Then it is very difficult to provide the necessary infrastructure but it is a challenging task to enable fast and reliable communication within such a network. Ad hoc networks are required in these situations. Ad hoc networks are the network architecture that can be rapidly deployed, without preexistence of any fixed infrastructure.

3. What Is Ad Hoc Network?

An ad hoc network is a (possibly mobile) collection of communications devices (nodes) that wish to communicate, but have no fixed infrastructure available, and have no pre-determined organization of available links. Individual nodes are responsible for dynamically discovering which other nodes they can directly communicate with. A key assumption is that not all nodes can directly communicate with each other, so nodes are required to relay packets on behalf of other nodes in order to deliver data across the network. Thus the nodes in ad hoc form multi-hop radio network.

The nodes communicate with each other over wireless links. Each node in a wireless ad hoc network functions as both a host and a router, and the control of the network is distributed among the nodes. The network topology is in general dynamic, because the connectivity among the nodes may vary with time due to node departures, new node arrivals, and the possibility of having mobile nodes. There are no explicit links in an ad hoc network, and all communication is by broadcast.

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