WiFi (or WLAN, as it is commonly called) is fast becoming the preferred mode of connecting to the internet. WiFi derives its name from a certification called Wireless Fidelity given to networks operating under 802.11 standards. WiFi makes it possible for computers, PDAs and other devices to link to a broadband connection in a wireless mode. The 802.11 standard defines the wireless communication operating via electromagnetic waves. While reading the descriptions and explanations related to WiFi, one should remember there are different modes for wirelessnetworks like Infrastructure mode and Ad-Hoc mode that can be used for different criteria.
Wi-Fi (WLAN, WiFi or WLAN) technology is a computer network technology that was designed originally to operate as an internal network and has since become a means of access to the Internet (broadband).
The IEEE 802.11 (ISO/CEI 8802-11) is an international standard describing the characteristics of a wireless local network (WLAN). The name WiFi (short for Wireless Fidelity) is originally the name given to the certification granted by the WECA (Wireless Ethernet Compatibility Alliance), the institution responsible for maintaining interoperability between devices under the 802.11 standard. By abuse of language (and for marketing reasons) the name of the standard is the same as the name of the certification. De facto a WiFi network is actually a network operating under the 802.11 standard.
WiFi allows us to create wireless local area networks at high speed. In practice, the WiFi can connect laptops, desktops, PDAs or other devices (printers, game consoles) to a broadband connection (300 Mbps) over a radius of several meters indoors (usually between 20 and 50 meters). In an open environment, the range can reach over several hundred of meters in optimal conditions.
ISPs are starting to equip areas with high concentrations of internet users (stations, airports, hotels, trains, etc.) with wireless internet access.
These access areas are called "hot spots".
The 802.11 standard defines the lower layers of the OSI model for wireless communication using electromagnetic waves, that is to say:
The physical layer offering three types of information coding;
The data link layer, composed of two sub-layers:
The Logical Link Control, or LLC.
The Media Access Control or MAC.
The physical layer defines the modulation of radio waves and the characteristics of the signal for transmission of data, while the data link layer defines the interface between the bus of the machine and the physical layer, including a method access similar to the one used for a standard Ethernet network and the communication rules between the different stations. 802.11 actually proposes three physical layers, defining alternative modes of transmission:
It is possible to use any protocol over a wireless WiFi network as well as an Ethernet network.
Infrastructure mode allows you to connect computers equipped with a wireless network adapter with each other via one or more access points (AP), which will assume the role of a hub.
This mode is mainly used in the business environment. The establishment of such a network requires the setting up of terminals (AP) at regular intervals over the area to be covered by the network. The terminals and the machines must be configured with the same SSID (network name) in order to communicate.
The advantage of this mode is that it allows you to check out who enters the network (Connection trough AP is compulsory). The cons: the network can only be expanded by installing new terminals.
The Ad-Hoc mode is used to connect (directly) computers equipped with a wireless network card (without using a third-party hardware such as an access point (AP)) to the internet. This mode is ideal for connecting machines together quickly without additional hardware (eg: file sharing between phones, sharing Internet access).
The establishment of such a network needs you to configure the machines in Ad-Hoc mode (instead of infrastructure mode), selecting channel (frequency) and SSID (network name) common to all and the job is done. The advantage of this mode is to avoid costly third-party hardware and it is easier to implement. With the addition of a simple dynamic routing software (Ex: OLSR, AODV...) the network grows naturally (enabling the connection of new machines).