http://en.wikipedia.org/wiki/Ad_hoc
ad hoc
ad hoc is a Latin phrase meaning "for this". It generally signifies a solution designed for a specific problem or task, non-generalizable, and not intended to be able to be adapted to other purposes. Common examples are organizations, committees, and commissions created at the national or international level for a specific task. In other fields the term may refer, for example, to a military unit created under special circumstances, a tailor-made suit, a handcraftednetwork protocol, or a purpose-specific equation. ad hoc can also mean makeshift solutions, shifting contexts to create new meanings, inadequate planning, or improvised events.
ad hoc networking[edit]
Main article: Wireless ad hoc network
The term ad hoc networking typically refers to a system of network elements that combine to form a network requiring little or no planning.
ad-hoc mode
http://www.webopedia.com/TERM/A/ad_hoc_mode.html
An 802.11 networking framework in which devices or stations communicate directly with each other, without the use of an access point (AP). Ad-hoc mode is also referred to as peer-to-peer mode or an Independent Basic Service Set (IBSS). Ad-hoc mode is useful for establishing a network where wireless infrastructure does not exist or where services are not required.
Wireless ad hoc network
http://en.wikipedia.org/wiki/Wireless_ad_hoc_network
A wireless ad hoc network (WANET) is a decentralized type of wireless network.[1][2] The network is ad hoc because it does not rely on a pre existing 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, so the determination of which nodes forward data is made dynamically on the basis of network connectivity. In addition to the classic routing, ad hoc networks can use flooding for forwarding data.
An ad hoc network typically refers to any set of networks where all devices have equal status on a network and are free to associate with any other ad hoc network device in link range. Ad hoc network often refers to a mode of operation of IEEE 802.11 wireless networks.
It also refers to a network device‘s ability to maintain link status information for any number of devices in a 1-link (aka "hop") range, and thus, this is most often a Layer 2 activity. Because this is only a Layer 2 activity, ad hoc networks alone may not support a routeable IP network environment without additionalLayer 2 or Layer 3 capabilities.
Wi-Fi Direct
http://en.wikipedia.org/wiki/Wi-Fi_Direct
The widespread adoption of Wi-Fi in new classes of smaller devices made the need for ad hoc networking much more important. Even without a central Wi-Fi hub or router, it would be useful for a laptop computer to be able to wirelessly connect to a local printer. Although the ad hoc mode was created to address this sort of need, the lack of additional information for discovery makes it difficult to use in practice.