Interference control is an essential part of effective use of unlicensed and shared communications spectrum, all might agree. But such rules also can have important ramifications. Consider the impact of proposed changes in rules regarding use of 5-GHz spectrum.
In a rulemaking, the Federal Communications Commission wants to amend Part 15 of FCC rules governing the operation of Unlicensed National Information Infrastructure (U-NII) devices in the 5 GHz band (5.15-5.35 GHz and 5.47-5.825 GHz), reducing maximum device power to provide greater protection against interference.
That is part of a broader change making available an additional 195 megahertz of spectrum in the 5.35-5.47 GHz and 5.85-5.925 GHz bands for U-NII use, vastly increasing the amount of spectrum available to unlicensed devices in the 5 GHz band by approximately 35 percent.
The issue, as the FCC sees it, is that unlicensed spectrum is designed to support devices operating over relatively short distances (think Wi-Fi rather than mobile services), at low power, and there has been some evidence of interference to other licensed users operating in parts of the affected spectrum.
The proceeding was prompted by interference with Federal Aviation Administration users in parts of the band, though only for parts of the bands the FCC wants to regulate more intensely for interference protection.
Another issue, the FCC argues, is that parts of the spectrum originally were seen as supporting indoor communications only, (Wi-Fi) but over time have become methods for outdoor communications as well (mobile or portable apps that require devices to operate at higher power).
As always, there are potential winners and losers. Broadly, the changes harmonize U.S. rules with global rules regarding Wi-Fi bands and enable use of some air interfaces over a wider footprint.
That would benefit suppliers and apps able to use the 5-GHZ band for unlicensed operations using Wi-Fi. Small cell applications would gain. Cable TV operators see themselves as winners.
But power-reduction measures for the 5.725 GHz - 5.85 GHz band would negatively affect U.S. wireless Internet service providers who use those bands for signal distribution over longer distances.
WISPA, the wireless ISP trade organization, notes that the new power reductions proposed for the 5.725 GHz to 5.85 GHz band will require WISPS to either reduce transmit power or antenna gain, which drastically reduces link distance (estimated to be 65 percent loss).
The impact is that link distances today spanning 10 miles will be reduced to 3.5 miles.
There are other implications, WISPA says. Manufacturers will need to install new filtering in all radios, possibly adding $300 in cost per radio, while reducing available spectrum by 80 MHz.
The loss of spectrum will mean customer broadband speeds necessarily are reduced, as bandwidth and top feasible speed are directly related.
WISPA argues an exception safely can be made for the point-to-point backhaul operations WISPs conduct in the 5.725 GHz to 5.85 GHz band.
As WISPs primarily serve Internet access customers in rural areas, those customers will suffer.
So WISPA is asking the FCC to reconsider those rule changes.
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