SkyBridge Satellite System Shares BAS Ku-Band Spectrum
July 26, 2005
The FCC has authorized SkyBridge LLC to launch and operate a non-geostationary orbit satellite. The frequencies authorized include the 12.75-13.25 GHz broadcast auxiliary services (BAS) band for Earth-to-space uplinks.
When completed, the SkyBridge system will consist of a constellation of 80 low-earth-orbit (LEO) satellites, in-orbit spares, a satellite control center, TT&C (tracking, telemetry and command) earth stations, a mission control center, gateway satellite earth stations and user terminals. User terminals will use the satellites for connection to terrestrial networks via the gateway earth stations. The transponders on the satellite will be configured to repeat the signals from the gateway and user-terminal earth stations, acting as a "bent pipe."
Frequencies in the 12.75-13.15 GHz and 13.2125-13.25 GHz Ku-band are authorized for transmissions from the gateway earth stations to the satellites. The 13.15-13.2125 GHz band can be used only in areas of the country outside a 50-km radius of the top 100 television markets. This band was carved out "in order to continue remote backup operations throughout the United States for incumbent BAS and CARS," according to the FCC.
SkyBridge LLC will be subject to the coordination procedures developed in the NGSO, FSS, BAS and CARS Coordination NPRM (FCC 03-318) (Notice of Proposed Rulemaking), which was released Dec. 23, 2003.
"We acknowledge that frequency coordination and spectrum sharing between FSS and BAS/CARS fixed and mobile operations will be challenging. Nevertheless, we believe that spectrum sharing between FSS earth stations (both GSO and NGSO) and BAS/CARS fixed and mobile operations is feasible because the number of new FSS earth stations should be relatively small, " the FCC stated. The FCC Order and Authorization DA 05-2037 said the SkyBridge system was expected to use approximately 200 gateways worldwide, 30-40 of which will serve the United States.
The NPRM for FSS operations in the BAS/CARS bands would maintain the existing coordination requirements. "NGSO and GSO FSS operators seeking to deploy new earth stations in these bands would continue to initiate coordination with mobile BAS and CARS operations using the coordination procedures in Sections 25.203, 25.251 and 101.103(d). Similarly, new mobile BAS and CARS operations initiating coordination in the 7 GHz and 13 GHz bands would continue to have the flexibility to use either the informal ad hoc local coordination procedures in Sections 74.638 and 78.36 or the coordination procedures in Section 101.103(d) to coordinate with FSS earth stations." For more information on coordination procedures, refer to the NGSO, FSS, BAS and CARS Coordination NPRM (FCC 03-318).
The SkyBridge system also was authorized to use the 13.75-14.5 GHz band for uplinks. Outside the United States, SkyBridge may use 17.3-17.8 GHz and 17.8-18.1 GHz for uplinks on a non-harmful interference basis. For downlinks, SkyBridge is authorized to use the 10.7-12.7 GHz band. Outside the western hemisphere, it may use the 12.7-12.75 GHz band. With this wide range of frequencies, BAS/CARS are not the only services affected by this authorization. The 12.2 to 12.7 GHz band is allocated on a primary basis to the broadcast satellite service (BSS) for DBS systems. SkyBridge shares the allocation with BSS operators on a co-primary basis, with limits on effective power flux density (EPFD), and must protect incumbent BSS operations.
The SkyBridge satellite system offers some advantages over geostationary satellite Internet service providers. The 80 satellites will orbit the earth at an altitude of 1,469.3 km, in 20 orbital planes with four equally spaced satellite per plane. The circular orbital planes will be inclined at 53 degrees from the equator and will be equally spaced around the equator, 18 degrees apart. The low altitude of the satellites should help mitigate the latency that makes geostationary satellite Internet service difficult to use for some applications, including voice-over-IP telephony (VoIP), virtual private networks (VPN) and online gaming. Coverage to very isolated areas may be problematic, however, as the gateway Earth station has to be within the 350 km radius spot beam cell. If the description of the system in the FCC authorization is correct, it is likely there will be no coverage of some isolated islands or in large, sparsely populated mainland areas.
For more information, refer to the FCC Order and Authorization DA 05-2037. Also see the Space and Tech - SkyBridge Summary page. Planning for this system started more than 10 years ago and a Google search showed little activity in the past three years. The Web site listed for the company, www.skybridgesatellite.com is now occupied by a directory and advertising page. Now that SkyBridge LLC has an authorization, will it be able to secure the funding to launch the 80 satellites?