10 Things You Should Know About 802.11n

802.11n can operate in either the 2.4GHz or 5GHz band-conferring more deployment flexibility by allowing implementers to get away from common sources of interference. IT buyers should be aware that almost all 802.11n clients based on CardBus or Expre

802.11n can operate using the standard 20MHz channels or with wide 40MHz channels that confer higher top-end throughput. Draft 2.0 of the specification recommends that 40MHz channels only be used in the 5GHz band-but many implementations will allow c

A key component of 802.11n, MIMO (multiple input, multiple output) uses spatial multiplexing to simultaneously transmit different chains of information at the same time on the same channel, leveraging multipath reflection to make sure everything gets to i

The most common antenna configurations currently are either three by three or two by three transmit/receive chains, but 802.11n will have plenty more options over time. Vendors will explore both the low end (single transmit/dual receive) for the budget-co

The current POE standard, 802.3af, may not supply enough juice to power access points with 3×3 or greater antenna configurations. A new POE standard, 802.3at, is in the works, but in the meantime administrators may need to get creative with the number of

With possible top-end wireless throughput in excess of 100M bps, wireless implementers need to look at upgrading the access points wired network connection to Gigabit Ethernet. Although this is probably not necessary immediately, growing usage of the wir

With each access points wireless link capable of pushing over 100M bps and a new Gigabit Ethernet infrastructure, the traffic bottleneck may move to the wireless controller. Wireless switches that perform traffic decryption or are otherwise in the middle

802.11n is designed to be backward-compatible with both 802.11b/g in the 2.4GHz band and 802.11a in the 5GHz band. For a long time to come, the majority of wireless clients on an 802.11n network will be legacy devices, so administrators must continue to p

While the traditional wireless LAN cell shape is roughly spherical (sans obstructions), MIMO and spatial multiplexing will make 802.11n cells spiky and less predictable depending on environmental factors. This may render traditional site sur

In summer 2007, the Wi-Fi Alliance started certifying devices for compliance with Version 2.0 of the 802.11n draft specification-essentially giving vendors (and customers) the go-ahead to start actively selling, or at least investigating, the technol

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