Precoding Design and User Selection for Multibeam Satellite Channels

in 16th IEEE International Workshop on Signal Processing Advances in Wireless Communications, SPAWC 2015 (2015, June 28)

Precoding for the downlink of a multibeam satellite system has been recently shown, under ideal conditions, to be promising technique towards employing aggressive frequency reuse gainfully. However, time ... [more ▼]

Precoding for the downlink of a multibeam satellite system has been recently shown, under ideal conditions, to be promising technique towards employing aggressive frequency reuse gainfully. However, time varying phase uncertainties imposed by the components and the channel, combined with delayed feedback perturbs the channel state information at the transmitter (CSIT). In this paper, we consider a power constrained robust formulation of the downlink precoding problem to counter the phase uncertainties. In particular it considers imposing conditions on the average signal to interference plus noise ratio (SINR), to deal with imperfect CSIT. In addition to the robust formulation, the primacy of user selection is highlighted and a new approach exploiting the satellite system design is proposed. Performance of the derived robust precoder in conjunction with the proposed location based user selection is then evaluated and the gains are tabulated. [less ▲]

On-board Signal Predistortion for Digital Transparent Satellites

in Proceedings on IEEE International Workshop on Signal Processing Advances in Wireless Communications (SPAWC) (2015, June)

On-board processing (OBP), a paradigm that allows for manipulation of the signal at the satellite transponder, is being embraced by a large section of the satellite community. Exploiting OBP can lead to ... [more ▼]

On-board processing (OBP), a paradigm that allows for manipulation of the signal at the satellite transponder, is being embraced by a large section of the satellite community. Exploiting OBP can lead to efficient implementation, bandwidth saving, lower redundancy, and better performance. Enabling processing aboard a satellite necessitates re-assessing the implementation of a number of signal processing techniques which, so far, have been ground-centric. In this work, we investigate the possibility of implementing signal predistortion (SPD) aboard a satellite having digital transparent processor (DTP). Such satellites employ transponders that allow for the implementation of limited functionalities in the digital domain. On-board predistortion can then be performed on the digitized data and can provide better performance compared to on-ground techniques. However, the conversion to the digital domain performed by an analog-to-digital converter (ADC) introduces different types of noise. Among these, the clock jitter requires the implementation of estimation and compensation algorithms. In this paper we propose a reduced-complexity on-board signal predistortion algorithm capable of post-compensating the jitter introduced by the ADC, and pre-compensating the distortion generated by the amplifier. [less ▲]

Generalized Direct Predistortion With Adaptive Crest Factor Reduction Control

in Proceedings of 40th IEEE International Conference on Acoustics, Speech and Signal Processing (ICASSP) 2015 (2015, April)

Efficient power amplification is inherently a non linear operation that introduces unwanted interference in the amplified signal. Strong inter-symbol interference is generated when the amplifier non ... [more ▼]

Efficient power amplification is inherently a non linear operation that introduces unwanted interference in the amplified signal. Strong inter-symbol interference is generated when the amplifier non linearity is combined with channel memory effects. Further, signals with very high peak to average power ratio, typical of multiple carrier systems, are even more sensitive to the non linearities resulting in severe distortion effects. Signal pre-clipping (crest factor reduction) and predistortion are conventional countermeasure techniques to reduce the generated non linear distortion and improve power and spectral efficiency. In this work, novel optimization methods for predistortion and pre-clipping are analytically derived for a general non-linear communication channel with memory. A combined architecture in which crest factor reduction is followed by signal predistortion is proposed and the parameters are estimated resorting to iterative algorithms based on least squares method. Performance evaluation of the estimation techniques shows the effectiveness of the derived algorithms and significant gain compared to previously known methods. [less ▲]

Feasibility Study of Full-duplex Relaying in Satellite Networks

in The 16th IEEE International Workshop on Signal Processing Advances in Wireless Communications, SPAWC 2015 (2015)

With the successful implementation of full-duplex radio prototypes, traditional orthogonal half-duplex communications is deemed to be inefficient in certain terrestrial applications. While full-duplex ... [more ▼]

With the successful implementation of full-duplex radio prototypes, traditional orthogonal half-duplex communications is deemed to be inefficient in certain terrestrial applications. While full-duplex techniques are gaining interest in terrestrial communications, thanks to the trend of short-distance and low-power transmissions, their application to satellite communications has drawn little attention. Motivated by this, the paper explores the use of the full-duplex relaying operation on-board the satellite in a DVB-S2 compliant network. Self-interference, whose management is the key component of a full-duplex communication, is the focus of study in this paper. Modelling the effects of self-interference and power amplifier nonlinearities on the quality of the received signal in undertaken. Subsequently, closed-form expressions for the various interference components are derived. The numerical evaluations of derived expressions rely on realistic link budgets and indicate substantial gains in spectral efficiency when self-interference can be well calibrated and measured. This confirms that the satellite full-duplex communications could be a promising solution for the efficient use of satellite spectrum, at least from a technical point of view. [less ▲]

Multiple Gateway Transmit Diversity in Q/V Band Feeder Links

in IEEE Transactions on Communications (2015)

Design of high bandwidth and reliable feeder links is central towards provisioning new services on the user link of a multibeam satellite communication (SatCom) system. Towards this, utilization of the Q ... [more ▼]

Design of high bandwidth and reliable feeder links is central towards provisioning new services on the user link of a multibeam satellite communication (SatCom) system. Towards this, utilization of the Q/V band and an exploitation of multiple gateways (GW) as a transmit diversity measure for overcoming severe propagation effects are being considered. In this context, this contribution deals with the design of a feeder link comprising N + P GWs (N active and P redundant GWs). Towards provisioning the desired availability, a novel switching scheme is analysed and practical aspects such as prediction based switching and switching rate are discussed. Unlike most relevant works, a dynamic rain attenuation model is used to derive analytically average outage probability in the fundamental 1 + 1 gateway case. Building on this result, an analysis for the N +P scenario leading to a quantification of the end􀀀to􀀀end performance is provided. This analysis aids system sizing by illustrating the interplay between the number of active and redundant gateways on the chosen metrics : average outage and average switching rate. [less ▲]

A MIMO Symbol Rate Signal Digital Predistorter for Nonlinear Multicarrier Satellite Channels

in IET Communications (2015), 9(15), 20532059

A digital predistortion (DPD) scheme is presented for non-linear distortion mitigation in multi-carrier satellite communication channels. The proposed DPD has a multiple-input multiple-output architecture ... [more ▼]

A digital predistortion (DPD) scheme is presented for non-linear distortion mitigation in multi-carrier satellite communication channels. The proposed DPD has a multiple-input multiple-output architecture similar to data DPD schemes. However, it enhances the mitigation performance of data DPDs using a multi-rate processing algorithm to achieve spectrum broadening of non-linear operators. Compared to single carrier (single-input single-output) signal (waveform) DPD schemes, the proposed DPD has lower digital processing rate reducing the required hardware cost of the predistorter. The proposed DPD outperforms, in total degradation, both data and signal DPD schemes. Further, it performs closest to a channel bound described by an ideally mitigated channel with limited maximum output power. [less ▲]

Pushing for higher rates and efficiency in Satcom: the different perspectives within SatNExIV

in Proceedings of the 11th International Symposium on Wireless Communication Systems (ISWCS 2015) (2015)

SatNEx IV project aims at studying medium and long term directions of satellite telecommunication systems for any of the commercial or institutional applications that can be considered appealing by key ... [more ▼]

SatNEx IV project aims at studying medium and long term directions of satellite telecommunication systems for any of the commercial or institutional applications that can be considered appealing by key players although still not mature enough for attracting industry or initiating dedicated ESA R&D activities. This paper summarizes the first year activities identified as very promising techniques for next generation satellite communication systems. Concretely, very high throughput satellite trunking, physical layer advances for fullduplex and multipolarization systems, network coding applications and multiple access schemes for information centric networking are briefly presented. For all the activities, we identify the scenarios under study so as the preliminary technical solutions to be further investigated. [less ▲]

Data Predistortion for Multicarrier Satellite Channels Based on Direct Learning

in IEEE Transactions on Signal Processing (2014), 62(22),

Satellite communication is facing the urgent need of improving data rate and efficiency to compete with the quality of service offered by terrestrial communication systems. An imminent gain, achievable ... [more ▼]

Satellite communication is facing the urgent need of improving data rate and efficiency to compete with the quality of service offered by terrestrial communication systems. An imminent gain, achievable without the need of upgrading current satellite technology, can be obtained by exploiting multicarrier operation at the transponder and using highly efficient modulation schemes. However, on-board multicarrier joint amplification of high order modulation schemes is a critical operation as it brings severe non-linear distortion effects. These distortions increase as the on-board High Power Amplifier (HPA) is operated to yield higher power efficiencies. In this work, we propose novel techniques to implement on ground predistortion that enable multicarrier transmission of highly efficient modulation schemes over satellite channels without impacting infrastructure on the downlink. [less ▲]

Applicability of MIMO to satellite communications

in International Journal of Satellite Communications and Networking (2014)

This paper presents achievements of an on-going activity where the applicability of MIMO to satellite communications with Digital Video Broadcasting – Satellite services to Handhelds as the key ... [more ▼]

This paper presents achievements of an on-going activity where the applicability of MIMO to satellite communications with Digital Video Broadcasting – Satellite services to Handhelds as the key application is studied. The potential satellite and hybrid satellite-terrestrial MIMO scenarios are described, and the applicable MIMO schemes for each scenario are selected. The performance of the MIMO schemes was studied by performing comprehensive computer simulations, and the main results are presented in this paper. [less ▲]

Enhanced List-Based Group-Wise Overloaded Receiver with Application to Satellite Reception

in Proceedings of IEEE ICC 2014 (2014, June)

The market trends towards the use of smaller dish antennas for TV satellite receivers, as well as the growing density of broadcasting satellites in orbit require the application of robust adjacent ... [more ▼]

The market trends towards the use of smaller dish antennas for TV satellite receivers, as well as the growing density of broadcasting satellites in orbit require the application of robust adjacent satellite interference (ASI) cancellation algorithms at the receivers. The wider beamwidth of a small size dish and the growing number of satellites in orbit impose an overloaded scenario, i.e., a scenario where the number of transmitting satellites exceeds the number of receiving antennas. For such a scenario, we present a two stage receiver to enhance signal detection from the satellite of interest, i.e., the satellite that the dish is pointing to, while reducing interference from neighboring satellites. Towards this objective, we propose an enhanced List-based Group-wise Search Detection (LGSD) receiver architecture that takes into account the spatially correlated additive noise and uses the signal-to-interference-plus-noise ratio (SINR) maximization criterion to improve detection performance. Simulations show that the proposed receiver structure enhances the performance of satellite systems in the presence of ASI when compared to existing methods. [less ▲]