SNR urges FCC to consider 'negative implications' of Ligado proposal on AWS-3 licensees

While Ligado Networks, as the former LightSquared, worked through plenty of opposition in the GPS community, its proposal to conduct terrestrial mobile downlink operations in the 1675-1680 MHz band is triggering opposition from the AWS-3 spectrum community.

In short, Ligado's proposal "has serious and negative consequences for the efficient use of the AWS-3 spectrum," according to SNR Wireless in an ex parte filing with the FCC. Such limitations were not contemplated by Auction 97 bidders like SNR, but if they had been, "there likely would have been less demand for the spectrum and less auction revenue as well," the company said.

SNR Wireless is one of two Dish Network (NASDAQ: DISH) designated entities that bid in the AWS-3 auction last year but were deemed ineligible for discounts because they were effectively controlled by Dish. SNR Wireless now holds 244 licenses acquired in Auction 97. Some 150 of those licenses authorize SNR to conduct mobile uplink operations in the 1695 – 1710 MHz band (AWS-3 uplink band).

In 2012, Ligado petitioned the FCC for a rulemaking to allow terrestrial mobile use of the 1675-1680 MHz band. More recently, after negotiating settlement agreements with GPS manufacturers, Ligado has proposed license modifications consistent with those agreements and asked that the commission move forward with reallocation and auction of the 1675-1680 MHz band, including license conditions that will permit the licensee to use that spectrum on a shared basis and in ways that accommodate the concerns of the National Oceanic and Atmospheric Association (NOAA), the SNR filing states.

As part of its "comprehensive proposal," Ligado states that it would voluntarily relinquish the right to conduct terrestrial downlink operations at 1545 – 1555 MHz. In exchange, Ligado would use the 1675 – 1680 MHz band for terrestrial downlink operations in combination with the 1670 – 1675 MHz band, which is already allocated for terrestrial mobile use. Ligado also would deploy terrestrially in the 1526 – 1536 MHz downlink band with lower power limits than currently allowed, according to SNR's filing.

SNR says Ligado's proposal presents several difficult interference issues for AWS-3 licensees in the 1695 – 1710 MHz band that have not been considered by the commission or any other authority. SNR spells out a number of problems with the proposal, including base station-to-base station interference.

Ligado's base station transmissions at 1675 – 1680 MHz would cause interference to AWS-3 base station receivers at 1695 – 1710 MHz in many common deployment scenarios, according to SNR. That raises siting issues and could impose debilitating constraints on AWS-3 deployments. For example, co-location of Ligado and AWS-3 base stations on the same tower or rooftop would require adequate vertical separation in order to prevent interference. If the required vertical separation were not possible, the only solution would be to install external filters at the victim AWS-3 base stations, adding cost to and reducing performance of AWS-3 operations.

"Similarly, and worse, the location of each provider on sites in close proximity to one another would pose problems for AWS-3 licensees," SNR states. "Any potential interference from AWS-3 licensees in which Ligado would be the victim would be probabilistic and transient in nature, whereas the base-to-base interference in which AWS-3 licensees would be the victim would be deterministic. The interference experienced by the AWS-3 licensees would, therefore, be more critical to AWS-3 operations than any experienced by Ligado."

For more:
- see this SNR filing

Related articles:
LightSquared rebrands as Ligado Networks but spectrum plans remain cloudy
FCC approves LightSquared's request to transfer spectrum licenses
LightSquared wants FCC to solicit comments on spectrum sharing proposal

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