Cell-Free MIMO in Space: Cooperative Satellite Transmission with Multi-Antenna Ground Users
Parisa Ramezani, Emil Björnson
TL;DR
This work addresses downlink cell-free MIMO for distributed LEO satellites serving multi-antenna ground users, formulating a sum-rate maximization problem under per-satellite and per-antenna power constraints. It introduces a tractable approximate rate expression based on statistical CSI and reduces the problem to a WMMSE framework, enabling efficient precoder design. The authors extend the design to per-antenna constraints via a multi-dimensional Lagrangian approach and show through simulations that joint satellite transmission yields per-user multi-stream gains and superior interference management compared to traditional benchmarks. Overall, the paper demonstrates the feasibility and performance benefits of cooperative, multi-antenna ground-user communication in space-based cell-free MIMO systems with realistic hardware constraints.
Abstract
This paper develops a multi-user downlink communication framework for distributed low Earth orbit satellite networks serving ground users equipped with multiple antennas. Building upon the concept of cell-free multiple-input multiple-output in terrestrial networks, we propose a coordinated transmission scheme where multiple satellites jointly transmit spatially multiplexed data streams to each user. Using a new approximate achievable rate expression, we formulate a sum rate maximization problem under per-satellite and per-antenna power constraints and use the classical equivalence between sum rate maximization and mean square error minimization to optimize the satellites' precoding matrices using statistical channel state information. We numerically examine the performance of the proposed scheme in different settings and validate its effectiveness by comparing it against traditional precoding designs.