Environment-Aware Coverage Optimization for Space-Ground Integrated Maritime Communications

To satisfy the growing demand for broadband maritime communications, space-ground integrated maritime communication networks (MCNs) arise, which are envisioned to take full advantage of both satellites and terrestrial shore-based networks. In practice, due to the frequent beam hopping of satellites and the limited number of geographically available onshore base-station sites, the space-ground integrated MCN usually presents a highly non-cellular network structure, leading to both challenging blind zones and coverage areas with severe interference. In this paper, we optimize the coverage performance by exploiting the marine environment information. Particularly, the transmit antenna correlation is estimated using the location and mobility information of scatterers on the sea, such as lighthouses, reefs, islands, and vessels. The position and attitude information of satellites are also utilized for interference estimation. Based on that, we optimize the input covariance and precoding matrix to maximize the ergodic sum capacity for all mobile terminals within the coverage. It is a complicated non-convex problem, especially because the ergodic sum capacity is difficult to be expressed straightly without the expectation operator. We introduce an upper bound of the ergodic sum capacity using the path loss and the transmit antenna correlation estimated from the environment information, and then propose an iterative algorithm to solve the problem by solving a set of convex subproblems. The proposed environment-aware scheme is evaluated using the real-world geographic information of a coastal area of China. Simulation results demonstrate that the proposed scheme can greatly improve the ergodic sum capacity and the energy efficiency compared with existing approaches, and achieve dynamic coverage to match the non-cellular network structure.