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What are the latest advances to 802.11?

What are the latest advances to the 802 standards? Are there new standards for supporting 1000 mbps CSMA/CD or wireless LANs?

There are new 802.11 standards that increase WLAN capacity, but they do not even come close to reaching 1000 Mbps.

802.11a-1999 is a high-rate extension to the 802.11 WLAN standard that operates in the 5 GHz UNII band. It uses Orthogonal Frequency Division Multiplexing (OFDM) to encode more data within each channel, for a maximum data transfer rate of 54 Mbps. All 802.11a products must operate at 6, 12, and 24 Mbps; 36, 48, or 54 Mbps are optional. Some 802.11a products also offer a proprietary "turbo mode" to reach 108 Mbps.

These data rates do not represent actual throughput. Speed and distance are inversely related in wireless LANs. According to chipset manufacturer Atheros, at a typical distance of 65 feet, 802.11a throughput drops to 21 Mbps. However, 802.11a also defines more non-overlapping channels. If you were to deploy twelve 802.11a access points in the same location, the combined capacity of these APs would be 648 Mbps. Doing the math, you can see that actual combined throughput would probably average no more than 250 Mbps.

Another high rate standard, 802.11g, was recently approved by IEEE 802.11 task group G and is likely to become a formal standard by May 2003. Like 802.11a, 802.11g supports Orthogonal Frequency Division Multiplexing to reach 54 Mbps, but it does so using the 2.4Ghz range now occupied by 802.11b Wi-Fi. This lets the same AP supply higher bandwidth to new 802.11g stations while simultaneously supporting DSSS CCK for backwards compatibility with older 802.11b stations. However, like 802.11b, 802.11g can only use three non-overlapping channels. Therefore, the maximum capacity of three 802.11g access points deployed in the same spot will only be 162 Mbps.

This was last published in November 2002

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