FCC Proposes 14.0-14.5 GHz for Air-to-Ground Broadband Services
The FCC is considering opening up some Ku-Band spectrum that’s currently reserved for satellite communications in order to provide broadband services for airline passengers. This 14.0 to 14.5 GHz segment has long been allocated on a primary basis for such operations as distribution of content to stations and relay of news stories via satellite from the field.
Last Thursday at the Commission’s open meeting, it adopted a Notice of Proposed Rulemaking (FCC 13-66 titled “Expanding Access to Broadband and Encouraging innovation through Establishment of an Air-Ground Mobile Broadband Secondary Service for Passengers Aboard Aircraft in the 14.0-14.5 GHz band,” which could lead to use of this satellite communications spectrum for airborne broadband connectivity on a secondary basis.
The FCC does not expect interference to be a problem for satellite operations as FSS Earth station antennas point south (towards the equator), while the AMS ground stations would be located with their antennas pointing north across a 120 degree arc. Aircraft antennas, while pointed south towards the AMS ground stations, would be aimed below the horizon, thus limiting power in the direction of the geostationary arc. Technical parameters are based on the Air-Ground service Qualcomm proposed in July 2011 in Petition for Rulemaking (RM-11640).
If the proposal is adopted, aircraft flying in Canadian airspace would have to terminate operations “until such time as Canada may authorized air-ground mobile broadband or authorize aircraft in Canadian airspace to use U.S. licensed air-ground broadband.” (Mexico would not be affected, as U.S. based ground antennas will always be pointed north.)
The technical parameters in Table 1 of the NPRM show indicate a base station (BS) equivalent isotropic radiated power of 39.5 dBW/50 MHz. Aircraft EIRP would be 3.00 dBW/2 MHz. There would be 150 to 250 base stations, each capable of carrying four beams. Qualcomm has stated that the aggregate EIRP from all air-ground mobile broadband equipped aircraft should be less than −47 dBW/Hz. The NPRM describes the Qualcomm analysis in detail and requests comment as to whether its assumptions and conclusions are valid. The NPRM considers allowing base stations to increase power up to 6 dB, but requests comment as to whether the number of beams should be reduced proportionate to the power increase. For example, if power were to be increased by 3 dB, then two beams, rather than four, would be allowed. If the power were to be increased by 6 dB, then only one beam would be allowed, in order to protect FSS operations.
The Qualcomm proposal said that if the FCC split the band into two 250 MHz segments, each segment could support an aggregate throughput of approximately 150 Gbps. The FCC requested comment on whether it should create two 250 MHz licenses or one 500 MHz block. The Qualcomm system would use time division duplexing. The NPRM asks, “would it be possible to deploy a FDD (frequency division duplexing) system to provide air-ground mobile broadband service that provides sufficient protection to existing licensees and services and, if so, are the proposed technical rules sufficiently robust to allow this?”
The Satellite Industry Association is likely to be commenting on the NPRM, as it has already questioned Qualcomm's analysis in its Dec. 11, 2012 ex-parte filing, noting that it is “vitally important for the Commission to consider the potential for interference in both directions, i.e. from the secondary into the primary service as well as from the primary into the secondary service.”
The SIA stressed: “There is an inherent risk to the Commission’s initial allocation decisions if a secondary service that is vulnerable to interference from primary services were to become widely deployed and then require interference protection at a later date.”
The FCC addressed this in the NPRM, stating:
“We recognize SIA’s concerns. However we believe that, even with its secondary regulatory status, there may be technical approaches that can be built into air-ground mobile broadband systems (frequency selection, amount of bandwidth, error correction, incremental redundancy protocols, ability to handoff, etc.) to mitigate any effects of interference that these systems may receive from primary systems in the band. Given the range of technical approaches, we believe that air-ground mobile broadband systems may be robust enough in the event that interference from a primary system is received such that there will not be any detrimental effect on users.”
The Commission did state that it welcomed further exploration of this issue, though.
“We seek comment on this analysis. Are there any mitigation techniques that air-ground mobile broadband providers should be required to use, or robustness requirements that air-ground mobile broadband providers should be required to meet, to maintain reliable links in the anticipated spectral environment?
“In sum, we propose a secondary allocation here, and do not contemplate any way to entertain a future request to elevate the status to primary, because co-primary status for air-ground mobile broadband would likely constrain the ability to blanket license FSS earth stations, and, for example, could prohibit satellite newsgathering trucks from changing locations to cover news events without prior coordination with neighboring co-primary air-ground mobile broadband base stations. We seek comment on this proposal.”
The FCC further noted that it was “aware that the addition of traditional terrestrial services, particularly mobile services, is likely not appropriate for the 14.0-14.5 GHz band due, for example, to potential interference and poor propagation for terrestrial mobile services at higher frequencies.” And the present use of that spectrum signaled that care is required when any new services were being considered, as “new users cannot go forward without ensuring the protection of primary FSS operations and first-in secondary operations, as well as accounting for permitted uses.”
(The 14.0-14.5 GHz band is also used for VSAT links transporting data to and from businesses and by the NASA Tracking and data Relay Satellite System . The 14.47-14.5 GHz portion of the band is shared with Radio Astronomy Service users.)
Broadcast SNG operators may want to file comments supporting maintaining the service as secondary.
Comments are due 45 days after the NPRM is published in the Federal Register, with the reply comment deadline 75 days after publication in the Federal Register.
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Doug Lung is one of America's foremost authorities on broadcast RF technology. He has been with NBC since 1985 and is currently vice president of broadcast technology for NBC/Telemundo stations.