Adaptive Beamforming for Mobile Satellite Systems Based on User Location/Waveform

An individual-user-optimized, adaptive beamforming method for a mobile satellite system (MSS) is presented. The system creates a 'beam for each user', referred to as 'user beam'. The user beam is optimized based either on known user locations or the waveforms received from all cochannel users. The system operates in an environment of significant frequency reuse among the cochannel users. Knowledge of user locations is transferred to the S-BSS (Satellite Base Station Subsystem) by the return link or is derived at the S-BSS from estimation of the spatial signature of the return link signals and knowledge of pilot signals in the return link waveform. The user beam maximizes the signal-to-interference-and-noise ratio (SINR) relative to the desired user, both in the forward and return links. The optimization process considers the spatial distribution of all cochannel users in the footprint of the satellite. The user beam adapts to the user's location and co-channel interference environment. By simulation, the performance of the beamforming system is compared with an existing, fixed beamforming system, represented by a major GEO MSS covering the Continental United States (CONUS) and Canada. The simulation results show that user-optimized adaptive beamforming offers significant capacity advantages over the legacy beamforming, measured by aggregate system throughput.