MIMO over Satellite: A Review

Abstract

The present article carries out a review of MIMObased techniques that have been recently proposed for satellite communications. Due to the plethora of MIMO interpretations in terrestrial systems and the particularities of satellite communications, this review is built on two pillars, namely fixed satellite and mobile satellite. Special attention is given to the characteristics of the satellite channel, which will ultimately determine the viability of MIMO over satellite. Finally, some future research directions are identified.

Four-dimensional constellations for dual-polarized satellite communications

“…This means that each of the eight symbols belonging to a projected 2D constellation (8-QAM or 8-PSK) can be associated to any other symbol belonging to an identical constellation on the other polarization to form a 4D symbol (i.e., the 2D projected constellations are independent). These constellations are equivalent to the traditional spatial multiplexing in dual-polar MIMO [3]. We denote the resulting 4D constellations respectively by 8×8-QAM and 8×8-PSK.…”

“…Exploiting dual polarizations to incorporate the MIMO paradigm has been studied in a number of works including [3]- [5]. Spatial multiplexing has been seen as a predominant candidate for satellite-only S-band applications [4].…”

“…In this perspective, much effort has been dedicated to investigate many different diversity techniques, leading, for example, to space-time codes (STC) [1] and massive multipleinput multiple-output (MIMO) systems [2]. In satellite scenarios, time diversity may be an unpractical solution for applications with time constraints, while the spatial diversity required by MIMO systems sometimes cannot be provided by the satellite link [3]. On the other hand, polarization diversity has been regarded as an effective replacement for spatial diversity in satellite applications, where the number of antennas and their sizes are limiting features of the satellite transponder and the user terminal [3].…”

“…In satellite scenarios, time diversity may be an unpractical solution for applications with time constraints, while the spatial diversity required by MIMO systems sometimes cannot be provided by the satellite link [3]. On the other hand, polarization diversity has been regarded as an effective replacement for spatial diversity in satellite applications, where the number of antennas and their sizes are limiting features of the satellite transponder and the user terminal [3]. Several works have considered exploiting dual polarization in the S-band, e.g., [4] and [5].…”

“…In the following, we assess the performance of 4D constellations obtained in three different ways: as Cartesian product of standard 2D constellations (which is equivalent to transmitting independently over the two polarizations or performing spatial multiplexing [3]), as Cartesian product of numerically optimized 2D constellations (as in [18]), and by means of an optimization performed directly in 4D (as in [17]). For all the considered constellations, we investigate the performance over different channels commonly used in satellite communications.…”