  Low Earth orbit (LEO) satellite networks (SatNets) are envisioned to play a
crucial role in providing global and ubiquitous connectivity efficiently.
Accordingly, in the coming years, thousands of LEO satellites will be launched
to create ultradense LEO mega-constellations, and the Third Generation
Partnership Project (3GPP) is working on evolving fifth-generation (5G) systems
to support such non-terrestrial networks (NTN). However, many challenges are
associated with the deployment of LEOs from communications and networking
perspectives. In this paper, we propose a novel cell-free massive
multiple-input multiple-output (CF-mMIMO) based architecture for future
ultra-dense LEO SatNets. We discuss various aspects of network design, such as
duplexing mode, pilot assignment, beamforming, and handover management. In
addition, we propose a joint optimization framework for the power allocation
and handover management processes to maximize the network throughput and
minimize the handover rate while ensuring quality-of-service (QoS) satisfaction
for users. To the best of our knowledge, this is the first work to introduce
and study CF-mMIMO-based LEO SatNets. Extensive simulation results demonstrate
the superior performance of the proposed architecture and solutions compared to
those of conventional single-satellite connectivity and handover techniques
from the literature.
