This work investigates the potentials of the multiple-input multiple-output (MIMO) technology to improve the throughput of geostationary satellite systems for fixed satellite services (FSS). The data rate performance of modern satellite systems, such as high-throughput satellites (HTSs) with multibeam antennas, is limited by interference between adjacent antenna beams rather than by thermal noise at the receiver. The distribution of multiple antennas in space, which is also known as spatial MIMO in the literature, provides a further degree of freedom. This additional degree of freedom can be exploited to address the interference issue and, in the optimal case, achieve a linear increase of the throughput with the minimum of the number of antennas on ground and in orbit. To achieve this gain, interference alignment is performed through a careful arrangement of the satellite and ground antennas. The geometrical lengths of the Line-of-Sight (LOS) propagation paths between all antennas must have a particular difference such that the MIMO signals at the receive antennas are combined with a distinct offset in phase. This requires a particular geometrical positioning of the satellite and ground antennas. The criterion of the Optimal Positioning of the MIMO Antennas (OPA) is derived that allows to optimally place the antennas on Earth and in orbit such that the maximum channel capacity is achieved. The spacing between the antennas is a key parameter in the design of a maximum-capacity MIMO satellite communication system. Based on the antenna spacing in orbit, basically three different categories of MIMO satellite scenarios are defined: The Single-Satellite Application, the Co-Located Satellites Application and the Multiple-Satellites Application. All relevant effects that possibly degrade the MIMO capacity of a geometrically optimized satellite system are identified, including atmospheric perturbations, antenna patterns and satellite motion in orbit. Their impact on the capacity is thoroughly analyzed and the necessary positioning accuracy of the antennas to achieve high capacity gains is presented. As a basic result, no practical constraints prohibit the application of MIMO to FSS. Simulation results of an HTS scenario with MIMO in the feeder link and full frequency reuse in a multiuser MIMO downlink show the data rate advantage compared to the state-of-the-art. Measurement results collected with a MIMO satellite testbed support the theory presented in this work. The presented approach provides the necessary fundamentals to practically achieve the capacity gains that are promised by spatial MIMO.     «

This work investigates the potentials of the multiple-input multiple-output (MIMO) technology to improve the throughput of geostationary satellite systems for fixed satellite services (FSS). The data rate performance of modern satellite systems, such as high-throughput satellites (HTSs) with multibeam antennas, is limited by interference between adjacent antenna beams rather than by thermal noise at the receiver. The distribution of multiple antennas in space, which is also known as spatial MIMO...     »