The Ad-hoc networks came in to existence in 1972 when DoD-sponsored Packet Radio Network (PRNET) emerged to Survivable Adaptive Radio Networks (SURAN) program in the early 1980s l.The ian objective of this program was to provide a packet switched network in battlefield to mobile elements in an infrastructure less environment.The concept of infrastructure less collection of nodes was first given in the conference papers 2,3 followed by IEEE 802.
11 subcommittee adopting the term the term “ad hoc networks.”The Channel access technology being used was CSMA/CA and TDMA along with several other novel routing and topology schemes were being developed.Stimulated by the growing importance and interest towards ad hoc networking, a number of commercial standards evolved in the mid to late 1990s. the Mobile Ad Hoc Networking (MANET) working group was born within the IETF, and worked on standardizing the routing protocols for ad hoc networks. The development of routing within the working group of MANET and the larger community branched into reactive ( on demand routes ) and proactive ( ready-to-use routes ) routing protocols 141.
The IEEE 802.1 1 subcommittee standardized a medium access protocol Which was based on collision avoidance and tolerated hidden terminals and made it usable, if not optimal, in order to build mobile ad hoc network prototypes.other standards that addressed and benefited the ad hoc networking were HIPERLAN and Bluetooth. One of the issue in ad hoc network was of scalability ,the ability of the network to provide acceptable level of service in presence of large number of network nodes.In proactive networks the scalability is accomplished by introducing location based routing hierarchy in the network6,7 while in reactive ad hoc network this was achieved by dynamically limiting the route request and local repair scopes to broken routes .
Another issue which was faced by the ad hoc network was of energy efficiency due to the presence of an infrastructure less network.In order to overcome this issue one solution at the MAC level and above it to set the receiver to sleep mode or by utilizing a variable output power and by choosing routes with shorer hops instead of fewer longer hops8.When we reflect on the multi-layered architecture of the network numerous attempts have been made in order to improve the Quality of service QoS from the service contacts for the MAC layer9.This can be done by Reflecting the multi-layer nature of ad hoc networks, there are numerous attempts to improve the QoS problems from the service contracts 9 to the MAC layer. A promising method for satisfying QoS requirements is a more unified approach of cross-layer or vertical-layer integration.
The idea is to violate many of the traditional layering styles to allow different parts of the stack to adapt to the environment in a way that takes into account the adaptation and available information at other layers. Security is another issue which concerns the network10,the networks which share the radio medium in an insecure environment are open to security attacks which are difficult to track down when compared to the wired network.The network is also susceptible to other attacks like injection of fake network traffic and Denial of service attacks DoS which will result in depleting the battery .