Wi-Fi is the trademark of Wi-Fi Alliance covering the functionality defined by the set of IEEE 802.11 standards. This set of standards defines so-called Wireless Local Area Network (WLAN) operation principles. This name comes from the idea that Wi-Fi should provide LAN-like functionality over the air. It concerns frequency bands used, possible supported data rates, data and management frame formats etc.
Wi-Fi is now the most popular technology for providing the wireless connectivity between devices, used by over 700 million people. It allows for direct connection between two devices, but the most important use case is now to provide the wireless connection to Internet.
- Ad-hoc mode
Ad-hoc mode allows Wi-Fi devices to directly communicate with each other. It was popular in the beginning of Wi-Fi era. This mode implies serious limitations on the wireless connection to be established (e. g. WPA security cannot be used) and is considered obsolete. However, some gaming devices still use it.
- Infrastructure mode
This mode is the most commonly used one at the moment. It creates an infrastructure for connecting Wi-Fi devices to other networks, e. g. wired Ethernet LAN or global network such as Internet. The infrastructure mode defines 2 roles for wireless connectivity devices: station and Access Point (AP). AP acts like a server, cabled to the wired network to allow wireless clients access other networks. Stations are then the clients of the respective AP.
- Peer-to-Peer (P2P) mode
P2P Wi-Fi mode, also known as Wi-Fi Direct is the emerging standard where two wireless devices are to negotiate which one will act as a station and which will effectively become an Access Point. The latter one will then be called a Group owner and will allow other P2P-enabled wireless devices to connect to it.
Wi-Fi in Embedded
Used primarily by laptops in the beginning, it is becoming increasingly popular on embedded devices. One can hardly imagine now a smartphone or a tablet without Wi-Fi. It is also implemented in modern TVs and set-top boxes. Being a crucial feature for certain types of embedded devices, Wi-Fi brings the challenge of significant power consumption increase for those. Please refer to the following presentation done at ELC-E 2011 for more details on this issue: Saving power with Wi-Fi.