Greater flexibility for unlicensed devices under new FCC rules
July 20, 2004
As reported in last week's RF Report, the FCC has modified its rules for unlicensed devices to allow greater flexibility for digital wireless devices. The Report and Order detailing the new rules was released last week. The new rules are focused on devices using spread spectrum digital modulation.
Under the new rules, systems using advanced antenna systems such as sectorized and adaptive array systems, will be allowed to operate with an aggregate output power transmitted simultaneously on all beams of up to 8 dB above (6.3 times) the limit for an individual beam, provided that the total effective radiated power (EIRP) on any beam may not exceed the EIRP limits for conventional point-to-point operation. If multiple beams overlap, the EIRP of the individual beams has to be reduced enough to ensure that the EIRP in the overlap area does not exceed the limit for a single beam.
Although the FCC had proposed restricting advanced antenna systems to a 120-degree beamwidth, that restriction was dropped in the Report and Order (R&O).
"We conclude that the EIRP limits, including the areas of overlap, will ensure that interference potential of the system is minimized, regardless of the beamwidth employed," the R&O stated.
Regarding the use of advanced antenna technologies, the R&O said they "will benefit service providers in both rural and high-density areas. In rural communities, these new regulations will allow service providers to use higher powers to reach distant customers. Conversely, in urban communities these new antenna systems will allow providers to re-use spectrum more efficiently and thereby serve multiple clients with minimal interference risk."
The FCC Report and Order also addressed replacement antennas for unlicensed devices. Commenters generally supported the use of replacement antennas. The FCC modified Sec. 15.204 to permit intentional radiators to be authorized with multiple antennas of similar in- and out-of-band gain and radiation pattern.
The R&O stated, "Compliance testing for the intentional radiator must be performed using the highest gain antenna that will be used with the device. The manufacturer must supply a list of other acceptable antennas in the literature delivered to the customer."
Commenters in the proceeding asked the FCC to eliminate the requirement for unique connectors for antennas used with these unlicensed devices.
The R&O stated, "They argue that the rule is ineffective because it has no impact on ordinary consumers, and does not deter those who want to modify unlicensed devices."
The FCC disagreed.
"We are not convinced, however, that the unique connector requirement should be eliminated," the R&O stated. "Thus, all replacement antennas authorized for use with an intentional radiator must incorporate a nonstandard connector, which uniquely couples with that intentional radiator. We remain concerned that removing this requirement could make it easier for parties to attach unauthorized high-gain antennas or linear amplifiers to unlicensed devices in violation of the rules. Of even greater importance, however, is our concern that removing this requirement might have the unintended consequence of allowing uninformed consumers to inadvertently attach an antenna, which causes the device to emit at levels in excess of the limits for human exposure to radio emissions. For these reasons, we will continue to require that unlicensed devices use nonstandard antenna connectors as currently required in Sec. 15.203."
The FCC did agree to allow the use of external power amplifiers with unlicensed wireless systems, but put restriction on them to prevent RF amplifiers from being combined with untested systems.
The R&O states, "Accordingly, we are adopting rules to allow external amplifiers to be marketed separately if they are designed in such a way that they can only be used with a specific system that is covered by an equipment authorization, such as through use of a unique connector or via an electronic handshake with a host device."
There are several other restrictions.
"The amplifiers must have a proprietary connection both into the amplifier and into the associated routers and access points with which they are FCC-approved to work, so that consumers with any other routers or access points cannot use them. The output power of such an amplifier must not exceed the maximum permitted output power of the system with which it is authorized. In addition, we are requiring that the amplifiers will be sold with a notice that they are to be used only in conjunction with the routers and access points for which they have been approved. A description or listing of the devices with which the amplifier can be used must appear on the outside packaging as well as in the user manual for the amplifier. The amplifiers must not be used to circumvent regulations regarding output power."
Other portions of the R&O deal with power and emission measurement procedures for digital modulation systems. The FCC did not establish a new limit for out-of-band emissions that fall over the satellite DARS band, as Sirius Satellite requested. The FCC said that it had already dealt with this issue in another rulemaking.
The FCC replaced the term "peak transmit power" in the U-NII rules with "maximum conducted output power." It defined this as, "the total transmit power delivered to all antennas and antenna elements averaged across all symbols in the signaling alphabet when the transmitter is operating at its maximum power control level."
The frequency hopping channel spacing requirements were also modified to allow operation of the next-generation of Bluetooth wireless devices. The FCC adopted a proposal by ITI to change a portion of Sec. 15.247(a)(1) to read "Frequency hopping systems shall have hopping channel carrier frequencies separated by a minimum of 25 kHz or the 20 dB bandwidth of the hopping channel, whichever is greater. Alternatively, frequency hopping systems operating in the 2400-2483.5 MHz band may have hopping channel carrier frequencies that are separated by 25 kHz or two-thirds of the 20 dB bandwidth of the hopping channel, whichever is greater, provided the systems operate with an output power no greater than 125 mW."
See the R&O for the complete rule.
The proceeding considered the possibility of requiring "spectrum etiquette" for unlicensed devices, which would establish a set of steps a device must follow before it can access the spectrum. Many commenters felt this would limit development of new technologies. The FCC declined to impose any form of spectrum etiquette for the Part 15 bands, because they are already heavily used. It did note that it could consider requirements for this when it contemplated making available additional spectrum for unlicensed devices.
For additional details, including the new rules, see the Report and Order FCC 04-165.