Multi-Satellite MIMO Communications at Ku-Band and Above: Investigations on Spatial Multiplexing for Capacity Improvement and Selection Diversity for Interference Mitigation

Abstract

This paper investigates the applicability of multiple-input multiple-output (MIMO) technology to satellite communications at the Ku-band and above. After introducing the possible diversity sources to form a MIMO matrix channel in a satellite environment, particular emphasis is put on satellite diversity. Two specific different topics from the field of MIMO technology applications to satellite communications at these frequencies are further analyzed: (i) capacity improvement achieved by MIMO spatial multiplexing systems and (ii) interference mitigation achieved by MIMO diversity systems employing receive antenna selection. In the first case, a single-user capacity analysis of a satellite 2 × 2 MIMO spatial multiplexing system is presented and a useful analytical closed form expression is derived for the outage capacity achieved. In the second case, a satellite 2 × 2 MIMO diversity system with receive antenna selection is considered, adjacent satellite cochannel interference on its forward link is studied and an analytical model predicting the interference mitigation achieved is presented. In both cases, an appropriate physical MIMO channel model is assumed which takes into account the propagation phenomena related to the frequencies of interest, such as clear line-of-sight operation, high antenna directivity, the effect of rain fading, and the slant path lengths difference. Useful numerical results obtained through the analytical expressions derived are presented to compare the performance of multi-satellite MIMO systems to relevant single-input single-output (SISO) ones.

MIMO Channel Modelling for Satellite Communications

“…The application of MIMO systems for satellite communications at Ku frequency band (12-18 GHz) and above has been discussed in (Liolis et al, 2007). In this model, two features of MIMO technology are presented: (i) a 2x2 MIMO spatial multiplexing system is used to achieve capacity improvements and a closed form expression for the outage capacity is derived (ii) MIMO spatial diversity scheme with receive antenna selection is applied in order to reduce interference in LMS communication links.…”

“…A dualsatellite MIMO communication channel at Ku-band and above is shown in Fig. 1 in (Liolis et al, 2007). The terminal station is equipped with two highly directive collocated antennas to communicate with two satellites S1 and S2.…”

“…The separation, ,   between the antennas is kept large enough so that the spatial correlation due to rain along the relevant paths is as low as possible. Considering the clear LOS between the terminal station and each satellite and that each terminal station antenna is at bore-sight with the corresponding satellite, the total path loss along each link can be written as follows (Liolis et al, 2007): The convective raincell model using Crane's assumptions is employed for the description of vertical variation of the rain fall structure using the same approach as in (Panagopoulos & Kanellopoulis, 2002). Based on these suppositions if   is sufficiently large, the spatial correlation between random variables Ri A representing channel coefficients is low and a decorrelated (ideal) MIMO satellite channel model is obtained.…”

“…The capacity of the dual satellite MIMO channel based on the standard MIMO theory, taking into the account above assumptions, can be written as follows: . Complete mathematical details about these variables can be found in (Liolis et al, 2007) This model is applicable over a large range of SNR values and shows significant capacity gains of the MIMO systems over the SISO systems for moderate and high SNR levels.…”

“…A satellite 2x2 MIMO diversity system based on receive antenna selection to mitigate the cochannel interference problem on the forward link due to differential rain attenuation from adjacent satellites is presented in (Liolis et al, 2007). In addition an analytical model is provided for interference mitigation based on satellite 2x2 MIMO diversity systems.…”