FCC Authorizes Additional 100 MHz of Unlicensed Spectrum in 5 GHz Band (Part 2: Key Takeaways from the Report and Order)
The FCC’s order takes several significant steps to help alleviate crowding in the 5 GHz unlicensed spectrum band to address the growing demand for spectrum to support wireless data traffic. For example, Cisco estimates that Wi-Fi traffic accounted for 47% of total domestic Internet traffic in 2012, and that mobile data traffic grew 62% in 2012.1 To meet this demand the FCC is revising its rules to expand available spectrum for Wi-Fi devices in what is known as the Unlicensed National Information Infrastructure (U-NII) band. The order also increases the amount of unlicensed spectrum available in the U-NII band. These changes present the opportunity for service providers to deliver Gigabit Wi-Fi services in excess of 1 gigabit per second using the new 802.11ac standard.
The most significant change in the 5 GHz order is to the rules governing devices operating in the U-NII-1 band. Devices operating in this band were limited to a relatively insignificant 50 milliwatts of transmitter power and were restricted to indoor use (i.e., prohibited from outdoor operations). These constraints were put in place to limit interference with satellite operators that use the spectrum, which made the band less useful for Wi-Fi devices. The order eliminates the prohibition on outdoor operations in the band and also increases permissible transmitting power levels in the band—effectively doubling the amount of unlicensed spectrum in the U-NII band available for use by Wi-Fi providers. The FCC also took measures to protect satellite services by placing technical limits on the amount of energy that can be directed up toward satellites.
In addition, service providers deploying more than 1,000 access points in the U-NII-1 band must notify the FCC and “acknowledge” that, if harmful interference to licensed services in the band occurs, the submitting party will be required to take corrective action to mitigate the interference. Such “corrective action”, the FCC explained, may include reducing power, turning off devices, changing frequency bands, and/or further reducing power in the vertical direction. The intent here is to provide the FCC a means to identify the largest deployments of U-NII access points and, in the unlikely event that the access points generate an aggregate noise level that does cause harmful interference to satellite services, take action to address such problems.
The order also extends the upper edge of the U-NII-3 band to 5.85 GHz, an increase of 25 MHz, and harmonizes the rules for operation in the band (which currently includes separate rules for U-NII-3 devices and other unlicensed “digital modulation” devices). A contentious issue in the proceeding centered around whether to keep the U-NII-3 rule that limited operation at a maximum EIRP of 200 watts for narrowly focused antennas.2 Narrowly focusing the antennas allows for fixed point-to-point wireless communications at long distances, which is why the U-NII-3 band is used by wireless ISPs to serve suburban and rural areas. But in harmonizing the rules for this spectrum, the FCC decided to keep the digital modulation rule that allowed operation of antennas at 1 watt of power no matter how narrowly focused and with no limit on the resulting EIRP, which allows for wireless systems to cover even longer distances in one hop. Because there were no harmful interference cases caused by compliant high gain point-to-point systems, the FCC believes that its enhanced security requirements (discussed below) are sufficient to prevent harmful interference by these devices.
The FCC also improved interference protection for incumbent systems operating in the U-NII bands by requiring manufacturers to secure their devices against illegal modification, which could cause interference to incumbent users. The exact methods used to secure the device software are left to the manufacturer, but must be documented in the application for equipment authorization to the FCC. The FCC did note, however, that more detailed security requirements may be necessary later as software-defined radio technology develops. The FCC also declined to implement rules that would force manufacturers to render a device inoperable if unauthorized modifications were made.
Twelve months after the effective date of the order, applications for certification of U-NII devices must meet the new and modified rules adopted.
Notably, the Commission did not address pending proposals to modify other portions of the U-NII bands. Those proposals, generally more controversial than the issues addressed in this order, remain pending.
2 EIRP stands for Effective Isotropic Radiated Power and is a measure of the output power when a signal is concentrated into a smaller area by the antenna. In other words, when antenna is focused to operate in a narrow space, such as with fixed point-to-point antennas, the power is effectively increased.