Position-Based Transceiver Design for Multiple Satellite to VSAT Downlink

Abstract

We propose a novel approach for downlink transmission from a satellite swarm towards a very small aperture terminal (VSAT). These swarms have the benefit of much higher spatial separation in the transmit antennas than traditional satellites with antenna arrays, promising a massive increase in spectral efficiency. The resulting precoder and equalizer have only low demands on computational complexity, inter-satellite coordination and channel estimation. This is achieved by taking knowledge about the geometry between satellites and VSAT into account. Due to the position based transceiver design, only slowly changing long-term statistics of the channel coefficient are considered. The necessity of accurate positional information is further relaxed by considering stochastic knowledge about the relative positions between satellites and VSAT rather than exact knowledge. Specifically, each satellite needs only stochastic information about the VSATs’ relative positions to calculate its precoding vector. Similarly, the VSAT requires only stochastic knowledge of the satellites’ relative positions for equalization. Furthermore, we evaluate the impact the inter-satellite distance has on the achievable data rate. Based on that, an analytic approach to arrange the satellites in a satellite swarm to maximize the rate is provided. The combination of the low complexity transceiver with suitable inter-satellite distances is proven to be capacity achieving in specific scenarios. The simulation results provide evidence that the proposed inter-satellite distance in combination with the proposed transceiver enables close-to-optimal rates in practical applications.