Abstract
This paper investigates uplink transmission from a single-antenna mobile
phone to a cluster of satellites, emphasizing the role of inter-satellite links
(ISLs) in facilitating cooperative signal detection. The study focuses on
non-ideal ISLs, examining both terahertz (THz) and free-space optical (FSO)
ISLs concerning their ergodic capacity. We present a practical scenario derived
from the recent 3GPP standard, specifying the frequency band, bandwidth, user
and satellite antenna gains, power levels, and channel characteristics in
alignment with the latest 3GPP for non-terrestrial networks (NTN).
Additionally, we propose a satellite selection method to identify the optimal
satellite as the master node (MN), responsible for signal processing. This
method takes into account both the user-satellite link and ISL channels. For
the THz ISL analysis, we derive a closed-form approximation for ergodic
capacity under two scenarios: one with instantaneous channel state information
(CSI) and another with only statistical CSI shared between satellites. For the
FSO ISL analysis, we present a closed-form approximate upper bound for ergodic
capacity, accounting for the impact of pointing error loss. Furthermore, we
evaluate the effects of different ISL frequencies and pointing errors on
spectral efficiency. Simulation results demonstrate that multi-satellite
multiple-input multiple-output (MIMO) satellite communication (SatCom)
significantly outperforms single-satellite SatCom in terms of spectral
efficiency. Additionally, our approximated upper bound for ergodic capacity
closely aligns with results obtained from Monte Carlo simulations.