Wi-Fi Technology

Wi-Fi is a brand originally licensed by the Wi-Fi Alliance to describe the underlying technology of wireless local area networks (WLAN) based on the IEEE 802.11 specifications. It was developed to be used for mobile computing devices, such as laptops, in LANs, but is now increasingly used for more services, including Internet and VoIP phone access, gaming, and basic connectivity of consumer electronics such as televisions and DVD players, or digital cameras. More standards are in development that will allow Wi-Fi to be used by cars in highways in support of an Intelligent Transportation System to increase safety, gather statistics, and enable mobile commerce (see IEEE 802.11p). Wi-Fi and the Wi-Fi CERTIFIED logo are registered trademarks of the Wi-Fi Alliance - the trade organization that tests and certifies equipment compliance with the 802.11x standards.

Uses

A person with a Wi-Fi enabled device such as a computer, cell phone or PDA can connect to the Internet when in proximity of an access point. The region covered by one or several access points is called a hotspot. Hotspots can range from a single room to many square miles of overlapping hotspots. Wi-Fi can also be used to create a mesh network. Both architectures are used in community networks.[citation needed]

Wi-Fi also allows connectivity in peer-to-peer (wireless ad-hoc network) mode, which enables devices to connect directly with each other. This connectivity mode is useful in consumer electronics and gaming applications.

When the technology was first commercialized there were many problems because consumers could not be sure that products from different vendors would work together. The Wi-Fi Alliance began as a community to solve this issue so as to address the needs of the end user and allow the technology to mature. The Alliance created the branding Wi-Fi CERTIFIED to show consumers that products are interoperable with other products displaying the same branding.

A term for certain types of wireless local area networks (WLAN) that use specifications conforming to IEEE

Wi-Fi At Home

Home Wi-Fi infrastructure devices typically fall into the category of a multifunction piece of networking equipment, with wireless being only one of many features. Home Wi-Fi clients come in many shapes and sizes, from stationary PCs to digital cameras. The trend today and into the future will be to enable wireless into every device where mobility is prudent.

Wi-Fi devices are often used in home or consumer-type environments in the following manner:

* Termination of a broadband connection into a single router which services both wired and wireless clients

* Ad-hoc mode for client to client connections

* Built into non-computer devices to enable simple wireless connectivity to other devices or the Internet

Wi-Fi in gaming

Some gaming consoles and handhelds make use of Wi-Fi technology to enhance the gaming experience:

* The Nintendo DS handheld is Wi-Fi compatible. The majority of its Wi-Fi compatible games use only WEP encryption.

* The PlayStation Portable is Wi-Fi compatible, and uses this for local multiplayer as well as connecting to wireless networks for online gameplay.

* The Xbox 360 can be made Wi-Fi compatible if the user purchases a separate wireless adapter.

* The PlayStation 3 Premium model features built-in Wi-Fi, while the Basic model can be upgraded with a separate wireless adapter.

* The Wii is Wi-Fi compatible.

Wi-Fi in Business

Business and industrial Wi-Fi has taken off, with the trends in implementation varying greatly over the years. Current technology trends in the corporate wireless world are:

* Dramatically increasing the number of Wi-Fi Access Points in an environment, in order to provide redundancy and smaller cells

* Designing for wireless voice applications (VoWLAN or WVOIP)

* Moving toward 'thin' Access Points, with all of the intelligence housed in a centralized network appliance; relagating individual Access Points to be simply 'dumb' radios

* Outdoor applications utilizing true mesh topologies

* A proactive, self-managed network that functions as a security gateway, firewall, DHCP server, intrusion detection system, and a myriad of other features not previously considered relavent to a wireless network.

Technical information

Wi-Fi: How it Works

A typical Wi-Fi setup contains one or more Access Points (APs) and one or more clients. An AP broadcasts its SSID (Service Set Identifier, "Network name") via packets that are called beacons, which are usually broadcast every 100 ms. The beacons are transmitted at 1 Mbit/s, and are of relatively short duration and therefore do not have a significant effect on performance. Since 1 Mbit/s is the lowest rate of Wi-Fi it assures that the client who receives the beacon can communicate at at least 1 Mbit/s. Based on the settings (e.g. the SSID), the client may decide whether to connect to an AP. If two APs of the same SSID are in range of the client, the client firmware might use signal strength to decide which of the two APs to make a connection to. The Wi-Fi standard leaves connection criteria and roaming totally open to the client. This is a strength of Wi-Fi, but also means that one wireless adapter may perform substantially better than another. Since Wi-Fi transmits in the air, it has the same properties as a non-switched wired Ethernet network, and therefore collisions can occur. Unlike a wired Ethernet, and like most packet radios, Wi-Fi cannot do collision detection, and instead uses a packet exchange (RTS/CTS used for Collision Avoidance or CA) to try to avoid collisions.'

Channels

Except for 802.11a, which operates at 5 GHz, Wi-Fi uses the spectrum near 2.4 GHz, which is standardized and unlicensed by international agreement, although the exact frequency allocations vary slightly in different parts of the world, as does maximum permitted power. However, channel numbers are standardized