Red Flags Raised Over Various FCC Wireless Backhaul Proposals

Verizon and Verizon Wireless supported efforts to make more spectrum available for fixed service operations. “But the Commission should make sure it does not sacrifice policies designed to increase efficiency and to minimize interference and potential for misuse of available spectrum in the course of those efforts,” Verizon said. One of the key proposals, the carrier said, was to modify the adaptive modulation rule to let licensees avoid the rule’s capacity and loading requirements during “anomalous signal fading” as long as such modulations are needed to adjust to a modulation that allows them to maintain communications. If the FCC takes this step, it should impose “clear, enforceable protections” against misuse, Verizon said. “Without such minimum performance requirements, fixed wireless applicants could occupy large bandwidth channels to deliver low capacity payloads. Such inefficient use would limit the amount of spectrum available for future users of the band.”

The National Spectrum Managers Association agreed more spectrum should be allocated to fixed services and that more sharing should be allowed. “However, we see some significant issues with the proposal to allow Part 101 licensees to share the 6875-7125 MHz and 12700-13200 MHz bands with BAS and CARS licensees,” it said. “Specifically we believe that sharing spectrum between Temporary Fixed/Mobile licenses and Fixed Part 101 Fixed licenses using the present band structures would be difficult to accomplish without the risk of significant interference.”

NSMA said adaptive modulation might be workable, but can only be approved with safeguards. “For example, the link should be designed with good engineering practice to a high availability to assure expected operation at or above the minimum required payload except when a significant propagation anomaly occurs.” The group opposed a proposal to authorize “auxiliary” multipoint stations associated with a point-to-point link in bands where no point-to-multipoint service rules exist. “We believe deployment of these stations is not compatible with point-to-point operation, has the potential to cause harmful interference, is an inefficient use of the radio frequency spectrum and provides an incentive for point-to-multipoint operators to waste spectrum and interfere with other legitimate users of the point-to-point bands."

The Fixed Wireless Communications Coalition sees potential problems in sharing of spectrum by BAS, CARS and FS operators. Among the BAS users are “TV pickup operators, such as those covering news events, who must do frequency coordination quickly, often by phone,” the FWCC said. “We question whether Fixed Service operators can maintain their present levels of reliability -- often in excess of 99.9999 percent -- in an environment shared with TV pickup units.” The services also use different bandwidths, the group said. “Because the band edges do not line up, an operator coordinating in one service will typically block two channels in another service.” But adaptive modulation offers benefits, FWCC said. “The judicious use of adaptive modulation can improve overall data throughput, keep critical traffic flowing when the link would otherwise fail, maintain network synchronization, and raise spectrum efficiency overall.”

TIA supported more use of adaptive modulation and FCC efforts to make wireless backhaul “robust, efficient, and-cost effective.” The group opposed the Wireless Strategies proposal to allow FS licensees to coordinate primary and multiple auxiliary links. “Such an allowance will result in increased interference and congestion to longer point-to-point FS microwave links, particularly in the 6 GHz band and the 11 GHz band used by public safety,” TIA said.

T-Mobile was generally supportive of the proposals made by the commission to increase use of wireless backhaul. “Although future developments are sometimes difficult to predict, in this case the trends appear to be moving in the direction of progressively more data usage by consumers,” the carrier said. “Backhaul availability has become a key competitive factor in the wireless marketplace as carriers require additional backhaul facilities to carry the increased traffic."

The FCC’s efforts to enhance fixed services spectrum use for wireless backhaul and other services “cannot be considered in a vacuum,” the Satellite Industry Association said. The record lacks evidence showing a rule for accommodating auxiliary stations is in the public interest, it said. The proposal from Wireless Strategies on deploying multiple transmitting elements under one license is “technology in search of an application” and there’s no data on how the transmitters would actually be used, said SIA. Current coordination between fixed services and fixed-satellite service operations rely on the fact that both are point-to-point, it said. The auxiliary station proposal would move away from that approach, SIA said. Expansion of terrestrial services in the 6875-7125 MHz and 12700-13200 MHz bands must respect the co-primary status of satellite spectrum there, used by satellite radio and mobile satellite services, the group said.

Sirius XM also said the FCC must provide coordination procedures and interference protections for existing FSS operations. The company uses feeder links in the 6875-7125 band to uplink digital radio to its satellites, it said. The agency should promote the use of the 2.3 GHz band for fixed wireless backhaul, Sirius said. It has long fought against the use of the band for mobile wireless services, though the agency has ordered some changes in the band meant to make mobile service possible.