The FCC follows up on last summer’s overhaul by taking further steps to make life easier for Fixed Service wireless operators.
August must be unofficial “wireless backhaul” month over at the FCC. Following up on last summer’s “overall backhaul overhaul,” the FCC has now taken further steps to make life easier for Fixed Service wireless operators.
Fixed wireless is a low-profile yet indispensable component of the nation’s communications infrastructure, serving a wide variety of entities and industries. It helps to balance the electrical grid, coordinate the movements of railroad trains, and transmit emergency calls to local police and fire personnel. It moves business data for companies with dispersed locations, such as financial companies, chain stores, restaurants, hotels, airlines, and car rental companies.
Increasingly, fixed wireless links are used as “backhaul” for mobile communications, carrying signals between central network facilities and cell towers, particularly where wireline is impractical, as across rough terrain or dense urban buildup. In other words, wireless backhaul helps get that cat video to your smartphone or tablet. Anyone who doubts the ubiquity of fixed microwave need only note the vast numbers of sideways-facing dishes and domes on radio towers, water towers, and buildings.
As important as Fixed Service links are, however, we suspect that the technical minutiae of the FCC’s latest action is of interest to relatively few readers. Therefore, we are providing just the highlights. (If you want to know more, you can read all the details here.)
Basically, the FCC expands on last summer’s rule changes by authorizing smaller antennas and wider channels. It also updates microwave efficiency standards to reflect the current predominance of IP networks.
Smaller antennas. The Order establishes a new antenna category, “Category B2,” which allows smaller antennas at 6, 18, and 23 GHz. (The former Category B, now dubbed “Category B1,” has a different, alternative set of parameters.) The FCC’s rules do not actually dictate antenna size, but set various other technical parameters, like beamwidth and radiation suppression, that directly affect antenna size. Smaller antennas pose a regulatory dilemma: on the one hand, operators like them because they are cheaper to manufacture, install, and maintain; plus, they generate fewer zoning and aesthetic objections. On the other hand, a smaller antenna cannot create as focused a beam as a larger one, resulting in greater potential interference with other antennas and potentially less efficient use of the spectrum. Also, on the receive side, smaller antennas are more sensitive to interference from sources away from the centerline of the antenna.
The FCC has historically struck a compromise: if a smaller antenna causes interference to another operator, it must upgrade to meet a higher set of standards that provide for a tighter beam (“Category A”). The new rules apply the same solution to Category B2. But the FCC does not impose a set time period for interfering antennas to upgrade, an omission that can lead to squabbles among operators. In a Second Further Notice of Proposed Rulemaking (SFNPRM) included as part of its decision, the FCC asks whether it would make sense to require interfering smaller antennas to upgrade just enough to resolve the interference, rather than having to meet full Category A standards. While perhaps a temporary benefit to the interfering operator, this proposal risks making Category A a nullity, and could create multiple rounds of heel-dragging and negotiation in getting an interfering antenna to upgrade.
Wider channels in the 6 and 11 GHz bands. The FCC will now allow Fixed Service operators to “stack” two adjacent channels to create a wider channel in the 6 and 11 GHz bands. One advantage of a wider channel over a channel pair is less hardware: an operator only has to generate one radio signal. It also offers more efficient use of the channel. A radio signal can’t occupy the entire channel width, and must leave a space between two channels. A “double-wide” channel eliminates this unused center band.
Updated efficiency standards. Time was, all of the data transmitted on a radio link was “payload.” Communications were synchronized, so the receiver knew what to do with each bit coming from the transmitter. In a packet-switched world, however, each packet carries routing instructions and other network information in addition to its actual content. The link also transmits data used to establish and maintain the connection (such as forward error correction). Accordingly, the FCC has adopted a new definition of “payload capacity” as “the bit rate available for transmission of data over a radiocommunication system, excluding overhead data generated by the system” (emphasis added).
Similarly, the FCC has changed the existing minimum efficiency standards, which used to reflect the number of voice circuits a channel of given width must carry. The new rules incorporate efficiency standards based on bits per second per hertz. This approach is not only technology-neutral, but is scalable to any channel width.
Second Further Notice of Proposed Rulemaking. The SFNPRM seeks comment on (1) allowing smaller antennas in the 13 GHz band as well as at 6, 18, and 23 GHz; (2) clarifying the circumstances under which an 11 GHz licensee can reduce power instead of upgrading the antennas; and (3) allowing licensees to upgrade only to the extent needed to resolve interference, rather than being required to upgrade to full Category A standards as currently required.
Notice of Inquiry. In case these updates didn’t manage to completely catch the rules up to the technology, the Commission has indicated that it is prepared to step back and rethink its antenna regulations from the ground up. A Notice of Inquiry invites a “broad discussion of our microwave antenna standards” – in part to accommodate non-traditional technology, such as non-parabolic antennas.
The new rules will take effect 30 days after publication in the Federal Register. Watch this space for updates.