The nearly finished IEEE 802.11y could make Wi-Fi more practical over longer distances: Wi-Fi is a compromise. In the unlicensed bands in which it operates, it has to deal with interference from noise sources and other networks, while using very low power, and trying not to make a pest of itself. It’s done very well. In the 2.4 GHz band and parts of 5 GHz, the maximum power from the radio is 1 watt (W), and the effective power (EIRP) is 4 W on an omnidirectional antenna. (You can push far more power if you narrow the antenna’s beam. And parts of the 5 GHz band restrict radio power below 1 W. I wrote a long rundown of 5 GHz issues back in Jan-2007.)
But there’s this lovely new segment of lightly licensed spectrum in the U.S., the 3.65 GHz band. It’s a non-exclusive licensed band available only in parts of the country that don’t have pre-existing ground-to-satellite or radar uses that overlap. This omits most of the eastern seaboard and most major cities; Seattle is one exception.
The licensing mechanism allows any number of operators to obtain inexpensive licenses, and register the base stations they use by location. If interference arises among base stations, operators are required to work out the problems themselves. I wrote extensively about this band and its rules on 9-May-2008 in profiling Azulstar, formerly a metro-scale Wi-Fi firm, but now a big proponent of WiMax in 3.65 GHz. I also went over the rules for the band on 11-June-2007 when the FCC announced the arrangement.
Several firms offer base station and customer premises equipment for this band now, so close to the 3.5 GHz band more commonly exclusively licensed in Europe and elsewhere. WiMax equipment is available because the 3.65 GHz band can be used with WiMax without any modifications to that protocol, although limited to just 25 MHz of the 50 MHz that the FCC set aside.
Equipment that conforms to a more stringent set of rules about contention and other factors can use the whole 50 MHz, and that’s where 802.11y comes in. It’s an extension of Wi-Fi to cope with the specific needs—and to open Wi-Fi technology up to 20 W EIRP, a vastly higher power output. This could allow connections over 5 km, the group says.
The Wikipedia entry on 802.11y, clearly written by someone involved with the specification, notes that three specific additions are needed: a tweak to support the way in which the FCC wants contention among competing devices to work; a method for an access point to tell a station (a connecting radio) that it’s about to switch its channel or its channel’s bandwidth, and the station should do likewise; and a mechanism to handle a base station allowing or revoking permission to use the spectrum without uniquely identifying the user’s system or broadcasting its precise GPS-based location.
The standard is near completion and initial approval. I don’t have any knowledge about whether any mainstream Wi-Fi equipment makers or metro-scale equipment makers are looking into building 802.11y into their gear.
The fact is that this could be a great technology for the mostly sub-metropolitan markets that 3.65 GHz is available in, although it has the same pain as WiMax: all new gear on the towers and all new adapters for customers.
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