  This paper presents a study of an integrated satellite-terrestrial network,
where Low-Earth-Orbit (LEO) satellites are used to provide the backhaul link
between base stations (BSs) and the core network. The mobility of LEO
satellites raises the challenge of determining the optimal association between
LEO satellites, BSs, and users (UEs). The goal is to satisfy the UE demand
while ensuring load balance and optimizing the capacity of the serving link
between the BS and the LEO satellite. To tackle this complex optimization
problem, which involves mixed-integer non-convex programming, we propose an
iterative algorithm that leverages approximation and relaxation methods. The
proposed solution aims to find the optimal two-tier satellite-BS-UE
association, sub-channel assignment, power and bandwidth allocation in the
shortest possible time, fulfilling the requirements of the integrated
satellite-terrestrial network.
