The most critical issue affecting WLAN demand has been limited throughput.
The data rates supported by the original 802.11 standards are too slow to support most general business requirements and slowed the adoption of WLANs.
Recognizing the critical need to support higher data-transmission rates, the IEEE ratified the 802.11b standard (also known as 802.11 High Rate) for transmissions of up to 11 Mbps.
After 802.11b one more standard 802.11a has been ratified and in January 2002 the draft specification of another 802.11g has been approved. 802.11g is expected to be ratified till early 2003.
The letters after the number "802.11" tell us the order in which the standards were first proposed . This means that the "new" 802.11a is actually older than the currently used 802.11b, which just happened to be ready first because it was based on relatively simple technology-Direct Sequence Spread Spectrum (DSSS), as opposed to 802.11a's Orthogonal Frequency Division Multiplexing (OFDM). The more complex technology provides a higher data rate: 802.11b can reach 11Mbits/sec, while 802.11a can reach 54Mbits/sec.