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This paper discusses the advanced Space Based Network (SBN) built by Boeing for LightSquared, Virginia, USA. The first SBN has been accepted by LightSquared in early 2011, and is getting ready to begin the 4G broadband network services for mobile applications in North America. This hybrid SBN has several elements; like, LightSquared patented Ancillary Terrestrial Component (ATC) technology, advanced geo-mobile satellite with 22m L-band reflector with an on-board channelizer, feederlink gateways and Ground Based Beam Former (GBBF) that interfaces to the Satellite Base Station Subsystem (SBSS). The system is capable of beam forming up to 1500 L-band spot cells, 500 spot cells with adaptive interference cancellation in the return path and support 30MHz L-band spectrum with four gateways. The SBN has unique features like L-band reflector thermal deformation compensation, electronic beam steering and the ability to generate spot cells, regional or shaped beams. The in-orbit tests including the beam cuts show the performance that meets the needs of advanced 4G mobile network commercial services. In addition, several necessary functional threads that support and enhance the ground based beam forming such as, service band inter channel amplitude and group delay equalization, Doppler compensation, uplink power control, high power management, relative calibration and pointing Beacon, are discussed. The material presented here demonstrates the leadingedge communications solution that draw on Boeing’s proven performance on large-scale integration programs. |
