References of "Piazza, Roberto 50002852"
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See detailMulti-gateway Data Predistortion for Non-linear Satellite Channels
Piazza, Roberto UL; Shankar, Bhavani UL; Ottersten, Björn UL

in IEEE Transactions on Communications (2015), 63(10), 3789-3802

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See detailGeneralized direct predistortion with adaptive crest factor reduction control
Piazza, Roberto UL; Bhavani Shankar, M. R.; Ottersten, Björn UL

in ICASSP, IEEE International Conference on Acoustics, Speech and Signal Processing - Proceedings (2015), 2015-August

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. © 2015 IEEE. [less ▲]

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See detailLow Complexity Predistortion and Equalization in Nonlinear Multicarrier Satellite Communications
Zenteno, Efrain; Piazza, Roberto UL; Shankar, Bhavani UL et al

in EURASIP Journal on Advances in Signal Processing (2015)

Aiming to reduce the power/mass requirements in satellite transponders and to reduce mission costs, joint amplification of multiple carriers using a single high-power amplifier (HPA) is being considered ... [more ▼]

Aiming to reduce the power/mass requirements in satellite transponders and to reduce mission costs, joint amplification of multiple carriers using a single high-power amplifier (HPA) is being considered. In this scenario, a careful investigation of the resulting power efficiency is essential as amplification is nonlinear, and multicarrier signals exhibit enlarged peak-to-average power ratio. Thus, operating the amplifier close to saturation vastly increases signal distortion resulting in a severe degradation of performance, especially for higher order modulations. This paper proposes a reduced-complexity digital predistortion (DPD) scheme at the transmitter and a corresponding equalizer (EQ) at the receiver to mitigate these nonlinear effects. Scenarios include both the forward as well as the return links. In particular, the paper exploits the MIMO Volterra representation and builds on a basis pursuit approach using a LASSO (least absolute shrinkage and selection operator) algorithm to achieve an efficient basis representation, avoiding large computational complexity, to describe the selection of predistorter/equalizer model. The work further compares and contrasts the two mitigation techniques taking various system aspects into consideration. The gains in performance and amplification efficiency demonstrated by the use of DPD/ EQ motivate their inclusion in next-generation satellite systems. [less ▲]

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See detailA MIMO Symbol Rate Signal Digital Predistorter for Nonlinear Multicarrier Satellite Channels
Zenteno, Efrain; Piazza, Roberto UL; Shankar, Bhavani UL et al

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 ▲]

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See detailData Predistortion for Multicarrier Satellite Channels Based on Direct Learning
Piazza, Roberto UL; Shankar, Bhavani UL; Ottersten, Björn UL

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 ▲]

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See detailPerformance Analysis of Fractionally Spaced Equalization in Non-linear Multicarrier Satellite Channels
Piazza, Roberto UL; Shankar, Bhavani UL; Berheide, Tobias et al

in Proceedings of 32nd AIAA International Communications Satellite Systems Conference (ICSSC), (2014, August 05)

Joint amplification of multiple carriers with a single wideband high power amplifier (HPA) has been considered towards reusing the satellite resources among multiple links to reduce the mission cost. The ... [more ▼]

Joint amplification of multiple carriers with a single wideband high power amplifier (HPA) has been considered towards reusing the satellite resources among multiple links to reduce the mission cost. The non-linear characteristic of the HPA, especially near saturation, coupled with the on-board IMUX/ OMUX filters result in non-linear adjacent carrier interference (ACI) and inter-symbol interference (ISI) during multicarrier power amplification. To benefit from the advantages of multicarrier transmissions, on-ground techniques to mitigate the non-linear distortions need to be devised. These techniques include predistortion at the transmitter and equalization at the receiver. Several works have considered the use of multicarrier predistortion along with single carrier equalization. A symbol synchronous equalizer, while being simple to implement, may not necessarily provide for the optimum linear filter. Towards improving the performance, fractionally spaced equalizers (FSE) have been considered. Such receivers are shown to provide enhanced performance by effectively compensating for the group delay distortions. The objective of this work is to consider the use of FSE in the context of multicarrier transmissions over non-linear channels and illustrate their performance enhancements [less ▲]

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See detailMulticarrier LUT-based data predistortion for non-linear satellite channels
Piazza, Roberto UL; Shankar, Bhavani UL; Ottersten, Björn UL

in Communications (ICC), 2014 IEEE International Conference on (2014, June)

Current satellite communication architectures can be potentially improved by applying multicarrier power amplification. Joint on-board amplification of multiple carriers reduces hardware and weight ... [more ▼]

Current satellite communication architectures can be potentially improved by applying multicarrier power amplification. Joint on-board amplification of multiple carriers reduces hardware and weight, enabling cost-efficient satellite architectures. However, on board power amplification is inherently a non-linear operation, whose distortion effects drastically increase when the high power amplifier (HPA) is operated in multiple carrier mode due to the generated inter-modulation products. In order to achieve the desired on-board power efficiency and to reduce the non-linear distortion, specific countermeasures need to be put in place. In this work we provide a novel data predistortion technique for multiple carriers satellite channel based on look up table (LUT) for high throughput applications. In contrast to known single carrier LUT techniques, the entries of the table are obtained by pursuing an analytical approach exploiting channel model and implementing recursive least squares techniques (RLS). A novel method to reduce the number of LUT entries based on LUT partitioning is proposed. Considerable performance gains over standard polynomial based predistortion are realized by the proposed technique. [less ▲]

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See detailCarrier Rate Optimization on the Return Link of Interactive Mobile Satellite Networks
Piazza, Roberto UL; Shankar, Bhavani UL; Ottersten, Björn UL

in European Wireless 2014; 20th European Wireless Conference; Proceedings of (2014, May)

Emerging interactive satellite applications demand highly efficient transmission schemes. Narrow-band satellite return channels for mobile users have peculiar characteristics that make the optimal user ... [more ▼]

Emerging interactive satellite applications demand highly efficient transmission schemes. Narrow-band satellite return channels for mobile users have peculiar characteristics that make the optimal user-rate determination a hard problem. Carrier rate enhancement can only be enabled by increasing the user bandwidth and by the application of highly efficient coding schemes. However, with the system bandwidth held constant, gains from increased user bandwidth can be offset by interference from an adjacent user channels. Additional interference is caused by spurious emissions from adjacent channels; these arise from the spectral regrowth caused by the user terminal power amplifier when operated in high-efficiency region. On the other hand, efficient amplification is mandatory to achieve the required signal to noise ratio at the receiver. In this work we propose a combination of transmitter and receiver techniques to improve the user-rate while controlling the user power efficiency. [less ▲]

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See detailData Predistortion for Multicarrier Satellite Channels using Orthogonal Memory polynomials
Piazza, Roberto UL; Shankar, Bhavani UL; Ottersten, Björn UL

in International Workshop on Signal Processing Advances for Wireless Communications (2013) (2013, June 16)

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See detailNon-parametric data predistortion for non-linear channels with memory
Piazza, Roberto UL; Shankar, Bhavani UL; Ottersten, Björn UL

in Acoustics, Speech and Signal Processing (ICASSP), 2013 IEEE International Conference on (2013, May 26)

With the growing application of high order modulation techniques, the mitigation of the non-linear distortions introduced by the power amplification, has become a major issue in telecommunication. More ... [more ▼]

With the growing application of high order modulation techniques, the mitigation of the non-linear distortions introduced by the power amplification, has become a major issue in telecommunication. More sophisticated techniques to counteract the strong generated interferences need to be investigated in order to achieve the desired power and spectral efficiency. This work proposes a novel approach for the definition of a transmitter technique (predistortion) that outperforms the standard methods with respect to both performance and efficiency. [less ▲]

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See detailSensitivity Analysis of Multicarrier Digital Pre-distortion/ Equalization Techniques for Non-linear Satellite Channels
Piazza, Roberto UL; Shankar, Bhavani UL; Zenteno, Efrain et al

in Proceedings of 31st AIAA International Communications Satellite Systems Conference (ICSSC), (2013)

On-board joint power amplification of multiple-carrier DVB-S2 signals using a single High-Power Amplifier (HPA) is an emerging configuration that aims to reduce flight hardware and weight. However ... [more ▼]

On-board joint power amplification of multiple-carrier DVB-S2 signals using a single High-Power Amplifier (HPA) is an emerging configuration that aims to reduce flight hardware and weight. However, effects specific to such a scenario degrade power and spectral efficiencies with increased Adjacent Channel Interference caused by non-linear characteristic of the HPA and power efficiency loss due to the increased Peak to Average Power Ratio (PAPR). The paper studies signal processing techniques that counteract for both aspects enabling efficient multicarrier on board amplification. Digital pre-distortion (DPD) at the gateway and equalization (EQ) at the User Terminal are the designed avenues of attack to mitigate the non-linear effects and improve power as well as spectral efficiencies. This paper builds on our initial work in Ref.1 that performed a survey on the adaptability of various compensation techniques to the considered scenario and short-listed the most favourable ones. Preliminary performance analysis of these techniques was undertaken with Signal to Interference Ratio (SINR) as the figure of merit. The contribution of this work over Ref. 1 includes : (a) a full DVB-S2 chain is simulated with the chosen techniques with Total Degradation (TD) as the figure of merit and (b) a sensitivity analysis is performed to study the dependence of the pre-distortion/ equalization performance ( measured as TD) on the channel parameters. [less ▲]

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See detailMulticarrier Digital Pre-distortion/ Equalization Techniques for Non-linear Satellite Channels
Piazza, Roberto UL; Shankar, Bhavani UL; E, Zenteno et al

in Proceedings of 30th AIAA International Communications Satellite Systems Conference (ICSSC), (2012)

Detailed reference viewed: 293 (16 UL)