Konstantinos P. Liolis

MIMO over Satellite: A Review

The present article carries out a review of MIMO-based 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.

Statistical Modeling of Dual-Polarized MIMO Land Mobile Satellite Channels

This Letter addresses the statistical modeling of dual-polarized MIMO-LMS fading channels. In the absence of accurate experimental results, a statistical model for the characterization of MIMO-LMS channels is proposed based on consolidation of available experimental results for SISO-LMS and MIMO wireless channels as well as on their extrapolation to the MIMO-LMS case of interest. Moreover, a step-by-step methodology for the simulation and time-series generation of the proposed MIMO-LMS channel model is provided, which is useful for the design and performance assessment of MIMO-LMS transmission systems. The proposed model incorporates the effects of all relevant critical channel aspects in a flexible and fully-parameterized way.

Multi-satellite MIMO communications at Ku-band and above: investigations on spatial multiplexing for capacity improvement and selection diversity for interference mitigation

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 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 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.

Full length article: MIMO channel modeling and transmission techniques for multi-satellite and hybrid satellite-terrestrial mobile networks

The Quality of Service (QoS) in land mobile satellite (LMS) communications drops drastically in the presence of shadowing and multipath fading. This paper studies two promising multiple-input multiple-output (MIMO) schemes, along with specific transmission techniques, aimed at overcoming this problem. First, specific proposals for a dual-satellite distributed MIMO scheme are studied based upon delay-tolerant and spectral-efficient schemes. As a second alternative, a hybrid satellite-terrestrial scheme is studied with specific proposals for MIMO processing. In order to carry out a performance assessment the paper addresses related MIMO satellite propagation channel modeling issues which lead to a new mathematical model to accommodate the multi-satellite transmission. In both cases, we quantify and conclude the MIMO gains in terms of bit error rate (BER) and spectral efficiency for urban and suburban environments. The transmitted air-interfaces in both proposed MIMO schemes are DVB-SH standard compatible. The analytical results have been validated by means of Monte Carlo simulations.

On 64-APSK constellation design optimization

This paper investigates the design of power and spectrally efficient coded modulations based on amplitude phase shift keying (APSK) with application to broadband satellite communications. Emphasis is put on 64APSK constellations. The APSK modulation has merits for digital transmission over nonlinear satellite channels due to its power and spectral efficiency combined with its inherent robustness against nonlinear distortion. This scheme has been adopted in the DVB-S2 Standard for satellite digital video broadcasting. Assuming an ideal rectangular transmission pulse, for which no nonlinear inter-symbol interference is present and perfect pre-compensation of the nonlinearity takes place, we optimize the 64APSK constellation design by employing an optimization criterion based on the mutual information. This method generates an optimum constellation for each operating SNR point, that is, for each spectral efficiency. Two separate cases of interest are particularly examined: (i) the equiprobable case, where all constellation points are equiprobable and (ii) the non-equiprobable case, where the constellation points on each ring are assumed to be equiprobable but the a priory symbol probability associated per ring is assumed different for each ring. Following the mutual information-based optimization approach in each case, detailed simulation results are obtained for the optimal 64APSK constellation settings as well as the achievable shaping gain.

On the Combination of Tropospheric and Local Environment Propagation Effects for Mobile Satellite Systems Above 10 GHz

Land mobile satellite (LMS) channels at the L (1/2 GHz) and S (2/4 GHz) frequency bands are mainly affected by propagation effects due to the local environment of a mobile terminal, such as multipath, shadowing, and blockage. Future systems for mobile satellite services (MSS) will operate at higher frequency bands, such as Ku (12/14 GHz) and Ka (20/30 GHz), where the tropospheric propagation effects also play an important role. Experimental campaigns conducted so far for Ku/Ka-band LMS channels have not considered any possible correlation between the tropospheric and local environment propagation effects. However, recent experimental work has indicated that these fading effects are not independent. As a first analytical approach to this open problem, a novel statistical analysis is presented in this paper. Emphasis is put on Ku/Ka-band LMS channels whose fading events can be modeled by the Ricean distribution with a relatively high K-factor. A novel analytical relationship between the Ricean K-factor and the rain attenuation effects is derived, and based on them, an analytical statistical prediction model for the distribution of the Ricean K-factor is derived. Particular attention is paid to the rainfall spatial inhomogeneity, as well as to the different effects of the climatic area of interest (temperate versus tropical) on the Ricean K-factor statistics. Thus, the presented analysis considers both spatially correlated bivariate lognormal and gamma statistics for the accurate characterization of rain attenuation. The proposed models are flexible and incorporate the impact of several critical operational, climatic, and geometrical parameters of an LMS channel on its multipath behavior under rainfall conditions. Useful numerical results are provided, specific future planned work is outlined, and the need for further experimental verification data is also pointed out.

Railway satellite channel at Ku band and above: Composite dynamic modeling for the design of fade mitigation techniques

SUMMARY Past studies on the railway satellite channel (RSC) at Ku band and above consider exclusively the attenuation coming from the metal power arches (PAs) along the railway route, producing significant though deterministic periodical fast fading. Nevertheless, limited attention has been given to model tropospheric effects on the RSC. The present paper takes a more comprehensive view of the RSC by introducing a novel stochastic dynamic model of rain fading in mobile satellite systems on top of the diffraction because of PAs. The proposed approach builds upon well-established research on rain attenuation time series synthesizers employing stochastic differential equations. It is shown that this propagation tool may provide significant aid, in general, in mobile satellite system simulations and in the design of fade mitigation techniques (FMTs), particularly aiming at the railway scenario. The tool enables the generation of fade events, fade duration statistics, rain attenuation power spectrum and predicting the necessary FMT control loop margin. This is particularly useful for the RSC because most of the proposed FMTs focusing on PAs are not appropriate for compensating atmospheric fading. Copyright

On the applicability of MIMO principle to 10-66GHz BFWA networks: capacity enhancement through spatial multiplexing and interference reduction through selection diversity

This paper investigates the applicability of multiple-input-multiple-output (MIMO) technology to broadband fixed wireless access (BFWA) systems operating in the 10-66 GHz frequency range. In order to employ the MIMO principle at these frequencies, the spatial channel benefits that may arise from the rainfall spatial inhomogeneity are more relevant since multipath is insignificant. Therefore, a special MIMO/BFWA channel may be implemented if every subscriber is equipped with multiple antennas and communicates with multiple base stations. The exact relationship between conventional MIMO and the proposed 10-66 GHz MIMO/BFWA channels is established. Then, emphasis is put on two different topics from the field of MIMO applications: (i) capacity enhancement for spatial multiplexed MIMO/BFWA systems; and (ii) interference reduction for MIMO/BFWA diversity systems employing receive antenna selection. More specifically, in the first case, a communication-oriented single-user capacity analysis of a 2 times 2 MIMO/BFWA spatial multiplexing system is presented, the relevant optimal power allocation policy is explored and useful analytical expressions are derived for the outage capacity achieved in the asymptotically low and high SNR regions. The effect of feedback on the capacity is investigated and quantified through Monte Carlo simulations. In the second case, a 2 times 2 MIMO/BFWA diversity system with receive selection combining is considered and its efficiency to mitigate intrasystem/intersystem cochannel interference over the downstream channel is studied from a propagation point of view. A general analytical prediction model for the interference reduction obtained by such a 2times2 MIMO/BFWA diversity system is presented along with a numerical validation.

Amplitude Phase Shift Keying Constellation Design and its Applications to Satellite Digital Video Broadcasting

Konstantinos P. Liolis1, Riccardo De Gaudenzi2, Nader Alagha3, Alfonso Martinez4, and Albert Guillen i Fabregas5 1Space Hellas S.A., R&D and Applications Division, 312 Messogion Ave., 153 41, Athens, Greece 2,3European Space Agency (ESA/ESTEC), Keplerlaan 1, P.O. Box 299, 2200 AG, Noordwijk, The Netherlands 4Centrum Wiskunde & Informatica (CWI), Science Park 123, 1098 XG, Amsterdam, The Netherlands 5University of Cambridge, Department of Engineering, Trumpington Street, CB2 1PZ, Cambridge, UK

On the Relation between Mobility and Rainfall Effects in Ku/Ka-band Line-of-Sight Land Mobile Satellite Channels: An Analytical Statistical Approach

The candidate frequency bands for the extension of the DVB-S2/RCS broadband satellite systems to fully support mobility are the Ku (12/14 GHz) and Ka (20/30 GHz). At these frequencies, rainfall is a significant propagation impairment which has to be taken into account together with other propagation effects due to mobility, such as multipath, shadowing and blockage. Experimental measurement campaigns conducted so far for Ku/Ka-band land mobile satellite (LMS) channels have mainly focused on the characterization of the mobility effects and have not considered any possible relation between the mobility and rainfall effects. However, recent limited work has indicated that these two fading sources are not independent. The present analysis represents a first approximation addressing this open problem. Emphasis is put on the line-of-sight (LOS) state of a Ku/Ka-band LMS channel, which can be modeled by the Ricean distribution and a high K-factor. A novel analytical model relating the Ricean K-factor with the rain fading effects is presented based on which, an analytical prediction model for the distribution of the Ricean K-factor is derived. The proposed analysis is flexible, can be applied on a global scale and incorporate the impact of several important operational, climatic and geometrical parameters of a mobile satellite system on its channel multipath behavior. Useful numerical results are provided, the need for further experimental verification data is pointed out and specific future planned work is also mentioned.