Spectrum Efficiency and Rapid Deployment are Focus of FCC's Wireless Backhaul Proposals

Following up on our post from last week, the FCC’s NPRM and NOI on ways to improve regulation of microwave wireless spectrum used for the “backhaul” transport of network traffic focuses in many parts on the need to balance efficient use of the wireless spectrum with measures to ensure facilities can be deployed quickly. Last Thursday’s FCC action begins implementation of one of the spectrum initiatives set forth in the National Broadband Plan. This initiative aims to remove regulatory barriers to the deployment of wireless backhaul links, which constitute a critical piece of the system architecture of broadband networks. Among other uses, backhaul can be used for linking wireless cell towers to the wired broadband networks.

The NPRM proposes three rule changes: removing spectrum use restrictions, altering technical rules, and changing licensing requirements. First, the FCC proposes to eliminate the service-specific restrictions on certain microwave frequency bands used for the Cable TV Relay Service (CARS) and Broadcast Auxiliary Service (BAS). This includes a proposal to open up the largest current CARS band – the 500 MHz allocation at 12.7 to 13.2 GHz – for alternative uses. While the CARS and BAS bands are currently designated for the transport of video programming by cable television system and broadcast stations, the proposed change would allow any parties to apply for FCC licenses in those spectrum bands for microwave backhaul of any kind of traffic. Similarly, the FCC proposes to eliminate a rule which prohibits broadcasters from using general fixed microwave spectrum to deliver video to studios when BAS frequencies are available.

In proposing these changes, the FCC emphasized that no existing CARS or BAS license would be altered, and that any new users would be required to coordinate with existing licensees in these bands. The FCC asked for comment on a variety of aspects of this proposal, including whether opening up these bands would have an adverse impact on cable operators’ future use of CARS spectrum. Next, the FCC proposes a minor change to allow for “adaptive modulation” technology, which can reduce signal fading and allow microwave signals to propagate further. The use of adaptive modulation requires temporary departures from the minimum payload capacity requirement for wireless traffic delivery, a rule designed to ensure microwave spectrum is being fully utilized. Under the proposal, the minimum payload thresholds need not be met while signal fading is occurring to allow parties to take advantage of the modulation technique.

Finally the FCC proposes a set of rule changes to allow the addition of “auxiliary stations” to existing microwave authorizations. Under the current rules, microwave applicants must provide specific site-based information to the FCC to obtain a license, and the FCC will issue authorizations only for the applied-for paths, frequencies, and antennas. Under the proposed rule, a holder of a microwave license for a given path and set of frequencies would be allowed to add multiple new antenna sites to an existing authorization, either on a conditional authority or blanket authority basis. This would allow license holders to “re-use” their authorized frequencies with additional antennas surrounding the licensed link, similarly to how mobile wireless licensees currently re-use spectrum within an area by transmitting signals from multiple base station antennas simultaneously.

Proponents of the rule changes claim it will allow for more efficient microwave spectrum use, while opponents have expressed concerns that the changes could lead to congestion in the microwave bands and unacceptable interference to existing users. In the NOI the FCC asks whether rural broadband service deployments in particular could be accelerated by eliminating or revising certain microwave spectrum efficiency standards and antenna design requirements. The FCC noted that it often gives waivers of the capacity requirements for rural microwave systems to allow them to provide better service at lower cost through less efficient transmission standards, which would be impractical in heavily-trafficked urban environments but are acceptable where spectrum demand is lower. Along the same lines, the FCC asks whether it could revise its technical standards for microwave frequency usage (at least in certain bands or areas) so that smaller and more inexpensive antennas could be used without creating interference problems that would offset any gains from accelerated network deployments.

Comments and reply comments are due 60 and 90 days after publication of the item in the Federal Register.