FCC Updates/Clarifies Shipboard Uplink Rules
July 27, 2012
For many people, Internet connectivity has become a necessity, even if they are on a ship in the middle of the ocean. Cruise ships, military vessels and other ships use satellite links for Internet connectivity. Keeping uplink dishes correctly aligned as the ship bounces around in the ocean requires complicated systems, not only to maintain dish position, but to protect adjacent satellites from interference if the system can't respond fast enough to stay locked on the correct satellite.
Last week the FCC adopted a Second Order on Reconsideration on procedures to govern the use of satellite Earth stations on board vessels operating on the conventional C-band and Ku-band frequencies. This Order resulted from requests from the Boeing Company and ViaSat requesting changes to FCC rules for Earth stations on vessels (ESVs). The revised rules specify technical requirements for variable power ESV systems using co-frequency transmitters operating simultaneously at varying data rates. The rules require variable power ESV systems operate 1 dB below the off-axis EIRP density limits, although ESV applicants can request a waiver of the reduction. A variable power ESV system must cease transmissions if it exceeds applicable power-density limits. The variable power rules are important for systems using CDMA (code division multiple access) technology rather than the simpler SCPC (single channel per carrier) method.
The FCC rejected Boeing's request to completely eliminate the 1 dB restriction, stating, "As we explained in the VMES Order, a dynamic or variable power system is complex--the system’s network control and monitoring center must manage a large number of factors and, as a result of operating commands through FSS satellites, there are inherent time delays in relaying commands and monitoring the co-frequency terminals. This complexity, combined with the fact that these are mobile applications operating in a fixed satellite frequency band, necessitates adoption of more cautionary measures, such as requiring the ESV system to reduce power-density by 1 dB."
The FCC acknowledged certain variable power ESV systems may be capable of operating without the 1 dB requirement while preventing interference and thus regain the system capacity lost with the reduction. It noted that as Boeing had stated, variable power networks have been operated experimentally in the United States for some time without generating interference complaints.
The Order states, "Pursuant to Section 1.3 of the Commission’s rules, the ESV operator may file a request to waive the 1 dB requirement. We require the waiver request to be accompanied by a report that demonstrates that the system has operated without providing unacceptable interference to adjacent satellites."
The FCC added that to make sure that such reports contain "sufficient technical information," it was encouraging ESV applicants to hold off on filing a request for waiver until its system "is operating at or above 50 percent of its capacity."
It noted that these reports would provide data needed to make a determination on waiver requests.
"We will place the waiver request and report on public notice seeking comment from the FSS satellite operators and other interested parties. As a result, variable power ESVs may demonstrate through the waiver process, as explained above, that they are capable of operating at the same power-density level as other ESV systems without causing harmful interference to the FSS."
The commission stated that variable power ESVs must "cease or reduce emissions automatically" within 100 milliseconds of detecting the violation. The waiver request must show how system will achieve this.
Under one scenario an individual transmitters must be self-monitoring and able to shut itself off. Under the second scenario, the shutdown or reduction command would come from the system's central control and monitoring station and the transmitter would have to react within 100 milliseconds of receiving the command.
The Second Order on Reconsideration has additional information on these requirements and the FCC's decisions on other requests from ViaSat and Boeing regarding ESV rules.