Since the inception of wireless networking there have been two types of wireless networks: the infrastructure network, including some local area networks (LANs), and the ad hoc network. Ad hoc is Latin meaning "for this purpose." Ad hoc networks therefore refer to networks created for a particular purpose. They are often created on-the-fly and for one-time or temporary use. Often, ad hoc networks are comprised of a group of workstations or other wireless devices which communicate directly with each other to exchange information. Think of these connections as spontaneous networks, available to whomever is in a given area.
An ad hoc network is one where there are no access points passing information between participants. Infrastructure networks pass information through a central information hub which can be a hardware device or software on a computer. Office networks, for example, generally use a server to which company workstations connect to receive their information. Ad hoc networks, on the other hand, do not go through a central information hub.
Ad hoc networks are common for portable video game systems like the Sony PSP or the Nintendo DS because they allow players to link to each other to play video games wirelessly. Some retail stores even create networks within them to allow customers to obtain new game demos via the store's own ad hoc network.
A wireless ad hoc network is a decentralized wireless network.[1] The network is ad hoc because it does not rely on a preexisting infrastructure, such as routers in wired networks or access points in managed (infrastructure) wireless networks. Instead, each node participates in routing by forwarding data for other nodes, and so the determination of which nodes forward data is made dynamically based on the network connectivity.
The earliest wireless ad hoc networks were the "packet radio" networks (PRNETs) from the 1970s, sponsored by DARPA after the ALOHAnet project.
The decentralized nature of wireless ad hoc networks makes them suitable for a variety of applications where central nodes can't be relied on, and may improve the scalability of wireless ad hoc networks compared to wireless managed networks, though theoretical[2] and practical[3] limits to the overall capacity of such networks have been identified.
Minimal configuration and quick deployment make ad hoc networks suitable for emergency situations like natural disasters or military conflicts. The presence of a dynamic and adaptive routing protocol will enable ad hoc networks to be formed quickly.
Wireless ad hoc networks can be further classified by their application:
· mobile ad hoc networks (MANETs)
· wireless mesh networks
· wireless sensor networks.
· Technical requirements
· An ad hoc network is made up of multiple “nodes” connected by “links”.
· Links are influenced by the node's resources (e.g. available energy supply, transmitter power, computing power and memory) and by behavioral properties (reliability, and trustworthiness), as well as by link properties (e.g. line-of-sight interference, length-of-link and signal loss, interference and noise). Since new and old links can be connected or disconnected at any time, a functioning network must be able to cope with this dynamic restructuring, preferably in a way that is timely, efficient, reliable, robust and scalable.
· The network must allow any two nodes to communicate, often via other nodes that relay the information. A “path” is a series of links that connects two nodes. Often there are multiple paths between any two nodes. Nodes are often limited by transmitter power (transmission range) and available energy resources. Transmitter power often consumes the most energy in the node. According to the inverse square law, it is more energy efficient to relay information across a network via multiple nodes. [4]
Mobile ad hoc network
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"MANET" redirects here. For other uses, see Manet (disambiguation).
A mobile ad hoc network (MANET), sometimes called a mobile mesh network, is a self-configuring network of mobile devices connected by wireless links.[1]
Each device in a MANET is free to move independently in any direction, and will therefore change its links to other devices frequently. Each must forward traffic unrelated to its own use, and therefore be a router. The primary challenge in building a MANET is equipping each device to continuously maintain the information required to properly route traffic.
Such networks may operate by themselves or may be connected to the larger Internet.
MANETs are a kind of wireless ad hoc networks that usually has a routeable networking environment on top of a Link Layer ad hoc network. They are also a type of mesh network, but many mesh networks are not mobile or not wireless.
The growth of laptops and 802.11/Wi-Fi wireless networking have made MANETs a popular research topic since the mid- to late 1990s. Many academic papers evaluate protocols and abilities assuming varying degrees of mobility within a bounded space, usually with all nodes within a few hops of each other and usually with nodes sending data at a constant rate. Different protocols are then evaluated based on the packet drop rate, the overhead introduced by the routing protocol, and other measures.
Types of MANET
· Vehicular Ad Hoc Networks (VANETs) are used for communication among vehicles and between vehicles and roadside equipment.
· Intelligent vehicular ad hoc networks (InVANETs) are a kind of artificial intelligence that helps vehicles to behave in intelligent manners during vehicle-to-vehicle collisions, accidents, drunken driving etc.
· Internet Based Mobile Ad hoc Networks (iMANET) are ad hoc networks that link mobile nodes and fixed Internet-gateway nodes. In such type of networks normal ad hoc routing algorithms don't apply directly.