Wireless Fidelity (Wi-Fi) refers to a type of Ethernet specified under the IEEE 802.11a and IEEE 802.11b Standards for LANs operating in the 5- and 2.4-GHz unlicensed frequency bands respectively. Wi-Fi is equally suited to residential users and businesses, and equipment is available that allows both bands to be used to support separate networks simultaneously.
The IEEE 802.11 Standard makes the wireless network a straightforward extension of the wired network. This has allowed for a very uncomplicated implementation of wireless communication with obvious benefits—they can be installed using the existing network infrastructure with minimal retraining or system changes. Notebook users can roam throughout their sites while remaining in contact with the network via strategically placed access points that are plugged into the wired network.
Wireless users can run the same network applications they use on an Ethernet LAN. Wireless adapter cards used on laptop and desktop systems support the same protocols as Ethernet adapter cards. For most users, there is no noticeable functional difference between a wired Ethernet desktop computer and a wireless computer equipped with a wireless adapter other than the added benefit of the ability to roam within the wireless cell.
Under many circumstances, it may be desirable for mobile network devices to link to a conventional Ethernet LAN in order to use servers, printers, or an Internet connection supplied through the wired LAN. A wireless access point (AP) is a device used to provide this link. The IEEE 802.11b Standard designates devices that operate in the 2.4-GHz band to provide a data rate of up to 11 Mbps at a range of up to 300 feet (100 meters) using directsequence spread-spectrum technology.
Some vendors have implemented proprietary extensions to the IEEE 802.11b Standard, allowing applications to burst beyond 11 Mbps to reach as much as 22 Mbps. Users can share files and applications, exchange e-mail, access printers, share access to the Internet, and perform any other task as if they were directly cabled to the network. The IEEE 802.11a Standard designates devices that operate in the 5-GHz band to provide a data rate of up to 54 Mbps at a range of up to 900 feet (300 meters).
Sometimes called “Wi-Fi5,” this amount of bandwidth allows users to transfer large files quickly or even watch a movie in MPEG format over the network without noticeable delays. This technology works by transmitting high-speed digital data over a radio wave using Orthogonal Frequency Division Multiplexing (OFDM) technology. OFDM works by splitting the radio signal into multiple smaller subsignals that are then transmitted simultaneously at different frequencies to the receiver.
OFDM reduces the amount of interference in signal transmissions, which results in a high-quality connection. Wi-Fi5 products automatically sense the best possible connection speed to ensure the greatest speed and range possible with the technology. Some vendors have implemented proprietary extensions to the IEEE 802.11a Standard allowing applications to burst beyond 54 Mbps to reach as much as 72 Mbps.
IEEE 802.11 wireless networks can be implemented in infrastructure mode or ad-hoc mode. In infrastructure mode—referred to in the IEEE specification as the “basic service set”—each wireless client computer associates with an AP via a radio link. The AP connects to the 10/100-Mbps Ethernet enterprise network using a standard Ethernet cable and provides the wireless client computer with access to the wired Ethernet network.
Ad-hoc mode is the peer-topeer network mode, which is suitable for very small instal lations. Ad-hoc mode is referred to in the IEEE 802.11b specification as the “independent basic service set.” Security for Wi-Fi networks is handled by the IEEE standard called Wired Equivalent Privacy (WEP), which is available in 64- and 128-bit versions. The more bits in the encryption key, the more difficult it is for hackers to decode the data.
It was originally believed that 128-bit encryption would be virtually impossible to break due to the large number of possible encryption keys. However, hackers have since developed methods to break 128-bit WEP without having to try each key combination, proving that this system is not totally secure. These methods are based on the ability to gather enough packets off the network using special eavesdropping equipment to then determine the encryption key.
Although WEP can be broken, it does take considerable effort and expertise to do so. To help thwart hackers, WEP should be enabled and the keys rotated on a frequent basis. The wireless LAN industry has recognized that WEP is not as secure as once thought and is responding by developing another standard, known as IEEE 802.11i, that will allow WEP to use the Advanced Encryption Algorithm (AES) to make the encryption key even more difficult to determine.
AES replaces the older 56-bit Digital Encryption Standard (DES), which had been in use since the 1970s. AES can be implemented in 128- , 192- , and 256-bit versions. Assuming a computer with enough processing power to test 255 keys per second, it would take 149 trillion years to crack AES.
Wi-Fi is a certification of interoperability for IEEE 802.11b systems awarded by the Wireless Ethernet Compatibility Alliance (WECA), now known as the Wi-Fi Alliance. The Wi- Fi seal indicates that a device has passed independent tests and will reliably interoperate with all other Wi-Fi certified equipment. Customers benefit from this standard by avoiding becoming locked into one vendor’s solution—they can purchase Wi-Fi certified access points and client devices from different vendors and still expect them to work together.