The IEEE 802.11 is a communications protocol that defines the use of the two lower layers of the OSI model (physical layer and data link), specifying its rules of operation for a wireless network (WLAN). The key technology that contains the 802.11 standard is the Direct Sequence Spread Spectrum (DSSS). The DSSS applies to wireless devices operating within the range of 1-2 Mbps. A DSSS system can transmit up to 11 Mbps, but if operating above 2 Mbps are considered not compliant.
Also called 802.11b Wi-Fi or wireless high-speed and refers to DSSS systems operating at 1, 2, 5.5 and 11 Mbps 802.11b. All systems comply with the rule retrospectively, and which are also compatible with 802.11 data transmission speeds of 1 and 2 Mbps DSSS only. This backward compatibility is very important as it allows for wireless network upgrade without replacing the NIC or access points. 802.11b devices achieve higher rates of data transfer rate and using an encoding technique other than that of 802.11, allowing the transfer of a greater amount of data in the same amount of time. Most 802.11b devices have not yet reached transfer rates of 11 Mbps, usually working in a range of 2-4 Mbps.
Includes 802.11a WLAN devices operating in the transmission band of 5 GHz. The use of the range of 5 GHz does not allow interoperability of 802.11b devices as they operate within the 2.4 GHZ. 802.11a can provide a data transfer rate of 54 Mbps and a proprietary technology known as “double speed” has reached the 108 Mbps networks of production, the standard speed is 20 to 26 Mbps.
802.11g offers transfer rate of 802.11a but with backwards compatibility for 802.11b devices using modulation technology Orthogonal Frequency Division Multiplexing (OFDM). Cisco has developed an access point that allows 802.11b and 802.11a devices coexist on the same WLAN. The access point provides gateway services that enable these devices, which are otherwise incompatible to communicate.
802.11n, unlike other versions of Wi-Fi, 802.11n can operate in two frequency bands: 2.4 GHz (using the 802.11b and 802.11g) and 5GHz (which uses 802.11a). As a result, 802.11n is compatible with all devices based on earlier versions of Wi-Fi. In addition, it is useful to work in the 5 GHz band, since it is less congested and 802.11n achieves higher performance.