The purpose of this paper is investigating behaviors of Ad Hoc protocols in Agent-based simulation environments. First we bring brief introduction about agents and Ad Hoc networks. We introduce some agent-based simulation tools like NS-2. Then we focus on two protocols, which are Ad Hoc On-demand Multipath Distance Vector (AODV) and Destination Sequenced Distance Vector (DSDV). At the end, we bring simulation results and discuss about their reasons.
An agent is an animate entity that is capable of doing something on purpose. That definition is broad enough to include humans and other animals, the subjects of verbs that express actions, and the computerized robots and soft bots. But it depends on other words whose meanings are just as problematical: animate, capable, doing, and purpose. The task of defining those words raises questions that involve almost every other aspect of ontology.
• Animate. Literally, an animate entity is one that has an anima or soul. But anima is the Latin translation of Aristotle’s word psychê, which had a much broader meaning than the English word soul. Aristotle defined a hierarchy ranging from a vegetative psyche for plants to a rational psyche for humans. The first question is whether Aristotle’s hierarchy of psyches can accommodate the modern robots and soft bots.
• Capable. The agent of a verb plays that role only as long as the action persists, but an entity can also be considered an agent if it has the power to perform some action whether or not it actually does. Formalizing that notion of power raises questions about modality, potentiality, dispositions, and counterfactuals that have been discussed in philosophy for centuries.
• Doing. The verb do sounds as simple as two other little verbs be and have. But like those verbs, its dictionary entry has one of the largest number of senses of any word in the English language. A common feature of all those senses is causality and purpose: some agent for some purpose causes some process to occur. This feature not only creates a cyclic dependency of doing on agent, it also introduces the notions of causality, process, and occurrence.
• Purpose. In the top-level ontology, purpose is defined as an intention of some agent that determines the interaction of entities in a situation. That is consistent with the definition of an agent as an entity that does something on purpose, but the circularity makes it impossible to give a closed-form definition of either term.
The term “Ad Hoc” implies that this network is a network established for a s pecial, often extemporaneous service customized to applications. So, the typical Ad Hoc network is set up for a limited period of time. The protocols are tuned to the particular application (e.g., send a video stream across the battlefield; find out if a fire has started in the forest; establish a videoconference among 3 teams engaged in a rescue effort). The application may be mobile and the environment may change dynamically. Consequently, the Ad Hoc protocols must self-configure to adjust to environment, traffic and mission changes.
What emerges from these characteristics if the vision of an extremely flexible, malleable and yet robust and formidable network architecture. An architecture that can be used to monitor the habits of birds in their natural habitat, and which, in other circumstances, can be structured to launch deadly attacks onto unsuspecting enemies.
The complexity of mobile Ad Hoc network designs has challenged generations of researchers since the 70’s, Thanks in part to the advances in radio technology, major success have been reported in military as well as civilian applications on this front (eg, battlefield, disaster recovery, homeland defense, etc). At first look, these applications are mutually exclusive with the notion of “infrastructure networks and the Internet” on which most commercial applications rely. This is in part the reason why the Ad Hoc network technology has had a hard time transitioning to commercial scenarios and touching people’s everyday lives.
This may soon change, however. An emerging concept that will reverse this trend is the notion of “opportunistic Ad Hoc networking”. An opportunistic Ad Hoc subnet connects to the Internet via “wireless infrastructure” links like 802.11 or 2.5/3G, extending the reach and flexibility of such links. This could be beneficial, for example, in indoor environments to interconnect out of reach devices; in urban environments to establish public wireless meshes which include not only fixed access point but also vehicles and pedestrians, and; in Campus environments to interconnect groups of roaming students and researchers via the Internet. It appear thus that after more than 30 years of independent evolution, Ad Hoc networking will get a new spin and wired Internet and Ad Hoc networks will finally come together to produce viable commercial applications.
Developing support for routing is one of the most significant challenges in Ad Hoc networks and is critical for the basic network operations. Certain unique combinations of characteristics make routing in Ad Hoc networks interesting. First, nodes in an Ad Hoc network are allowed to move in an uncontrolled manner. Such node mobility results in a highly dynamic network with rapid topological changes causing frequent route failures. A good routing protocol for this network environment has to dynamically adapt to the chan
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