A Novel Distributed Beamforming Scheme Based on Phase Adjustment and Dynamic Tracking for LEO Satellite Communications

Abstract

Among LEO satellites communications, satellite direct connectivity to User Equipment (UE) has drawn much attention for its ability of providing basic emergent services. However, the link budget shortage resulting from long propagation length limits the capacity of communications. Distributed beamforming is a solution that provides high power gain by utilizing multiple transmitters simultaneously. This work presents a novel distributed beamforming scheme for LEO satellites direct connectivity services that can provide high power gain for multiple ground UEs with arbitrary locations and numbers. Firstly, an algorithm is designed for static satellites. By selecting satellites from a set of available ones and optimizing the transmit phases of electromagnetic waves on satellites, all the ground UEs can receive power gains improvement. Furthermore, this work considers satellite motions by proposing a fast algorithm that adjusts phases according to changing satellite locations. Finally, a satellite re-selection process is designed to ensure stable power improvement when satellites become unavailable due to their motions. Simulation results demonstrate the effectiveness of our design. For four static satellites and 10 UEs, we examine 20 cases with different satellite and UE locations. Results show that UEs receive an average of at least 7 dB power gain in most cases. The condition of four moving satellites is also tested, and results demonstrate that all 10 UEs can have consistent receiving power gain as satellites move quickly.