[http://standards.ieee.org/getieee802/download/802.11a-1999.pdf IEEE 802.11a] is a protocol based on the 5.8GHz ["UNII"] band (instead of the 2.4GHz IsmBand), this protocol can reach theoretical speeds of 52Mbs.

In typical outdoor usage it will have a shorter range (though it may be effected by water less) however it's use of OfdmModulation means it's better at dealing with MultiPathFading issues which are especially prevelant in warehouse / metropolitan area deployments due to reflections.

See also: ChannelFrequencyChart, ["802.11b"], ["802.11g"], AccessPointReviews

A recent posting by JimThompson to the PersonalTelco MailingList has more information:

{{{SamChurchill writes: > I thought 5 Ghz could deliver backbone services to multiple users 10 miles > away. Am I mistaken? > > A Multi-Point 5.8 Ghz tower on a hill reaching 10-15 miles might make a good > backbone for the Satellite Truck. But upon looking at the FCC part 15 rules > now I'm not so sure. The 5.8 Ghz band can go 20 or miles but only point to > point. Antenna gain limits EIRP for multipoint connections. Perhaps too much > to be useful. Am I wrong?}}}

( example of high sensitive card is the [http://www.diswire.com/SpecsSR5.pdf SR5] with -74dBm@54Mbps and -94dB@6Mbps on sale at [http://www.diswire.com/ Diswire]