Doug Lung /
08.29.2013 03:06 PM
Comment Period Ends for 14-GHz Air-Ground ‘Broadband Plan’
Concerns expressed about possible interference to satellite users
The period for comments about the FCC’s Notice of Proposed Rule Making concerning the use of 14.0-14.5 GHz spectrum for aircraft passenger broadband service ended Monday, August 26, drawing 11 comments. The comments to the 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 (FCC 13-66) NPRM  are found in the FCC’s Comment Filing System.
 
None of the comments directly opposed the planned air-to-ground service (AMS in short), and most supported the concept (except perhaps the Utilities Telecom Council and Winchester Cator LLC whose proposal for a terrestrial service in the 14.0-14.5 GHz band was denied). However, several commenters raised concerns over potential interference to fixed satellite service (FSS) operations in the 14.0-14.5 GHz band and to new non-geostationary satellite services in the same band.
 
Comments from the Satellite Industry Association outlined several issues the FCC must address “in order to ensure that the new service would truly be secondary to the primary fixed-satellite service (FSS)” and stated that “As a secondary service, the AMS must fully protect the primary FSS in the band and must not constrain existing or future uses.”
 
SIA provided a Technical Annex with a detailed analysis showing “a considerable risk of unacceptable interference to primary FSS from AMS ground stations and aircraft terminals.”
 
Among the issues raised by SIA was the potential for interference to satellites from AMS ground terminals due to sidelobe or backlobe radiation from the AMS phased array antenna. SIA asked for more study of interference caused by rain scatter and possibly troposcatter effects from the main beam of the AMS ground station to FSS satellite receivers.
 
SIA warned that AMS operations using power levels low enough to protect FSS may not be able to avoid interference from VSAT (such as SNG operations) as the number of VSATs deployed increases. “For example, when a major news story occurs, dozens of satellite news gathering (“SNG”) trucks may be deployed to a single area, creating a high concentration of VSATs in a small geographic area, with a concomitant increase in potential interference to AMS operations,” SIA said.
 
SIA also raised issues with the technical parameters in Qualcomm's proposal that would allow the AMS to create up to a one percent rise in the thermal noise (Delta-T/T) noise floor. While this is the limit specified in ITU-R Recommendation S.1432, that limit applies to interference from all non-primary sources of interference into a primary FSS link. SIA said that limiting the increase to 0.33 percent was more appropriate as AMS is not the only non-primary source of interference.
 
The comments from Boeing Corp. are interesting, as Boeing is in the business of making sure communications systems on aircraft work as promised in addition to building satellites. Boeing expressed concern about interference to Earth Stations Aboard Aircraft (ESAA). ESAA operations are currently allowed under experimental licenses and are secondary until the FCC elevates them to full primary status. Boeing argued that ESAA should be given primary status before any new services are introduced in the “intensively used 14.0-14.5 GHz band.” Under the NPRM air-ground service would be “co-secondary” to ESAA and thus ESAA operators would have no claim of interference protection to their uplinks.
 
Boeing supported SIA's technical analysis showing the proposed rules are not sufficient to protect FSS from interference from AMS. In addition to support for SIA's recommendation to limit the delta-T/T increase in the noise floor to 0.33 percent, Boeing also agree with SIA's assertion that when calculating interference a FSS satellite receiver G/T of 6 dB/K should be used instead of 2 dB/K as proposed.
 
Boeing noted that Qualcomm's proposed “spatial diversity” “may still result in significant interference into FSS operations under various circumstances.” The company added that it uses the 14.0-14.5 GHz band for tracking, telemetry and command and testing during transfer orbits of its satellites when the satellites are in non-geostationary orbits.
 
Other commenters were concerned about the impact of AMS on non-geostationary satellite systems in the Ku-band.
 
In addition, Boeing was concerned the system wouldn't be reliable, explaining that, “as a manufacturer, Boeing seeks to ensure the reliable performance of its aircraft, including the components and communications systems that it installs in its aircraft. Boeing is very concerned that, as a result of this proceeding, it may be asked by its airline customers to equip aircraft with an air-ground mobile broadband system that may not work as claimed. The uncertainty created by a poorly-considered new service would negatively affect Boeing’s airline customers and their passengers as well as Boeing’s relationship with those customers.”
 
American, the only airline to file comments, said in its comments, “...U.S. air travelers expect anywhere/anytime broadband access, including when they are flying on an airplane above the continental United States. For these reasons, American supports the FCC in establishing the new Air-Ground Mobile Broadband Service at 14.0-14.5 GHz in accordance with the proposals set forth in the Notice of Proposed Rulemaking.”
 
The NAB agreed that “under certain conditions, the proposed service could be effectively deployed in the 14.0-14.5 GHz band.” The NAB cautioned, however, that the service would have to be “designated a secondary allocation in the band and its service rules must clear establish this secondary status” in order to prevent interference to primary and co-secondary incumbent users and services, which include fixed earth-to-space communications. NAB described how critical Ku-band SNG operations are to broadcasters and networks ability to cover news events, wherever they happen as well as to deliver programming to viewers.
 
As expected, Qualcomm strongly supports the NPRM. In addition to outlining the need for the service, the company agreed to secondary status, even with the newly created ESAA service. Backing up its technical analysis of the potential for interference, Qualcomm reiterated the FCC should use the one percent rise in delta-T/T noise floor, stating that the technical parameters in Table 1 of the NPRM would actually ensure the actual delta-T/T remains “well below one percent during typical operation.”
 
Qualcomm did not appear to be concerned about interference into the proposed system, stating: “Qualcomm strongly believes that the proposed Air-Ground Mobile Broadband Service will operate successfully in the presence of potential interference from primary FSS users as its detailed technical filings in RM-11640 demonstrate. The FCC need not impose any ‘robustness requirements’ upon Air-Ground Mobile Broadband Service licensees.”
Reply comments in this Proceeding are due in 30 days. It will be interesting to see how Qualcomm and SIA respond to the others comments and how the satellite operators that filed comments in the proceeding, Viasat and EchoStar Satellite Operating Corporation and Hughes Network Systems LLC, respond.


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